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The acute and chronic effects of "NO LOAD" resistance training
... Co-contraction training has shown positive results in muscle recruitment level [7][8][9] , as well as in incrementing strength and hypertrophy 5,6,10 . Counts et al. 11 observed an average increase of 0.2 cm in muscle thickness of the anterior portion of the upper arm, corresponding to approximately 33% change from baseline. This result is similar to those obtained with conventional resistance training with high and low intensity, which increased the biceps crosssectional area by 20% 12 . ...
... This result is similar to those obtained with conventional resistance training with high and low intensity, which increased the biceps crosssectional area by 20% 12 . It has been suggested that muscle growth occurs regardless of external load, since training recruits (35 to 50% of maximum activation) and places most of the musculature under tension 11 . ...
... After review, reviewers agreed to include seven articles for data extraction Figure 1). Data from five studies [9][10][11]13,21 were estimated from the figures using ImageJ software 15 when possible and inserted in the quantitative analysis. ...
Co-contraction training has been proposed to improve muscle strength in the absence of external equipment, yet it is needed to elucidate the effects of co-contraction training and its applicability. Thus, we synthesized the effects of co-contraction training on elbow muscle strength, myoelectric activity, and muscle thickness. We searched papers from MEDLINE via PubMed, Web of Science, Scopus and Embase databases. The inclusion criteria were studies comprising adults between 18-64 years old; investigating chronic effects of co-contraction training on elbow muscles; comparing pre-and post-intervention or control values; presenting any of the outcomes; randomized, quasi-experimental, pre-and post-design; in English. Seven studies met the inclusion criteria. We performed a systematic review and meta-analysis following PRISMA recommendations. We used the revised RoB 2, ROBINS-I to verify the level of evidence. We also included a questionnaire for biomechanical studies and GRADE analysis. We extracted data independently by two investigators, considering the characteristics of study, participants and training, outcomes, and results. We calculated the effect sizes for each outcome. The analysis was carried out by combining and dividing flexors and extensors in a subgroup analysis. Comparing the experimental vs. control group, our results showed that co-contraction training increased isometric strength (SMD=0.51 [0.19, 0.83]) and agonist myoelectric activity (SMD=0.54 [0.25, 0.83]). Comparing pre-vs. post-training, co-contraction training also improved isometric strength (SMD=1.28 [0.75, 1.81]); concentric elbow extensor strength (SMD=0.64 [0.01, 1.26]); and myoelectric activity (SMD=0.46 [0.18, 0.73]). No effect was observed for muscle thickness. The co-contraction training improves muscle performance without morphological changes.
... In the past decade, there has been a considerable amount of research conducted that has aimed to find potential alternatives to traditional high load resistance training (i.e., ≥70% one-repetition maximum; 1RM) [1][2][3][4][5][6][7] . The results from these studies indicate that muscle growth adaptations are not limited to higher load training protocols, but rather appear to be driven by exercising with a high degree of voluntary effort (i.e., to or near task failure) 1,2,6,8 . ...
... The results from these studies indicate that muscle growth adaptations are not limited to higher load training protocols, but rather appear to be driven by exercising with a high degree of voluntary effort (i.e., to or near task failure) 1,2,6,8 . Counts et al. 1 , for example, demonstrated similar increases in muscle size between a "NO LOAD" training protocol (i.e., maximal effort elbow flexions without an external load) and a traditional high load training protocol (i.e., 4 sets of 8-12RM at 70% 1RM). Interestingly, however, the authors 1 observed greater variability with respect to increases in muscle size for the NO LOAD training protocol. ...
... Interestingly, however, the authors 1 observed greater variability with respect to increases in muscle size for the NO LOAD training protocol. Counts et al. 1 speculated that such findings may be related to each individual's ability to maximally contract the muscle throughout the full range of motion. If true, then this would seem to invite a search for alternative training techniques which are capable of augmenting muscle activation during situations of very low external tension (i.e., to provide a more homogenous stimulus for muscle growth). ...
Objectives
This study compared muscle growth in response to very low load resistance training with direct pulsed current (DPC) stimulation and traditional high load training.
Methods
Twenty-six resistance trained individuals had each leg assigned to one of two unilateral knee extension protocols: 1) 4 sets of 20 repetitions at ~10% one-repetition maximum (1RM) and inter-set rest periods of 30 s (DPC) and 2) 4 sets to muscular failure at ~70% 1RM (TRAD). Muscle thickness (MTH), 1RM strength, and local muscular endurance (LME) were measured before and after 8-weeks of training. An alpha level of 0.05 was used for all comparisons.
Results
MTH increased similarly between TRAD and DPC at the 50% (0.24 cm, 95%CI: 0.11-0.36), and the 60% anterior sites (0.25 cm, 95%CI: 0.10-.040), as well as the lateral (0.25 cm, 95%CI: 0.10-.040) and medial sites (0.21 cm, 95%CI: 0.10-0.31), but was greater for TRAD at the 40% anterior site (0.3 cm, 95%CI: 0.16-0.43). Changes in 1RM were greater for TRAD (10.2 kg, 95%CI: 5.8-14.4). LME increased similarly between protocols (5 repetitions, 95%CI: 3-7).
Conclusions
The current data suggest that very low load knee extension resistance training with DPC could be a viable training strategy for promoting skeletal muscle growth and local muscular endurance.
... We went through 16 different data sets with a total of 963 individuals (454 males and 509 females) (Abe et al., 2015;Bell et al., 2022;Buckner et al., 2017;Buckner et al., 2019;Buckner et al., 2020;Counts, Buckner, et al., 2016;Dankel et al., 2016;Dankel et al., 2017;Jessee et al., 2019;Song et al., 2021;Wong et al., 2020). Fifteen of the data sets have published papers associated with them, and one is from an investigation only recently completed and currently under review (primary outcome data not yet published but unrelated to the current study). ...
... As such, pair matching was not possible in four of the 16 data sets Buckner et al., 2020;Dankel et al., 2016;Dankel et al., 2017). Four other studies provided one additional pairing each (4 pairs) Counts, Buckner, et al., 2016;. Dankel (Song et al., 2021). ...
... Three of those five Jessee et al., 2019; included only trained individuals with the other 2 studies including a mix of both trained and untrained Wong et al., 2020). Five of the 12 data sets included individuals who were untrained (Bell et al., 2022;Counts, Buckner, et al., 2016;. The other two studies did not collect information on training status (Abe et al., 2015;Song et al., 2021). ...
... We went through 16 different data sets with a total of 963 individuals (454 males and 509 females) (Abe et al., 2015;Bell et al., 2022;Buckner et al., 2017;Buckner et al., 2019;Buckner et al., 2020;Counts, Buckner, et al., 2016;Dankel et al., 2016;Dankel et al., 2017;Jessee et al., 2019;Song et al., 2021;Wong et al., 2020). Fifteen of the data sets have published papers associated with them, and one is from an investigation only recently completed and currently under review (primary outcome data not yet published but unrelated to the current study). ...
... As such, pair matching was not possible in four of the 16 data sets Buckner et al., 2020;Dankel et al., 2016;Dankel et al., 2017). Four other studies provided one additional pairing each (4 pairs) Counts, Buckner, et al., 2016;. Dankel (Song et al., 2021). ...
... Three of those five Jessee et al., 2019; included only trained individuals with the other 2 studies including a mix of both trained and untrained Wong et al., 2020). Five of the 12 data sets included individuals who were untrained (Bell et al., 2022;Counts, Buckner, et al., 2016;. The other two studies did not collect information on training status (Abe et al., 2015;Song et al., 2021). ...
Objectives:
Concerns have been raised against the current two-sex binary category in sports competitions. The thesis states that if males and females were separated based on muscle size, it would negate the strength advantage between the sexes. We tested the possible sex differences in various strength outcomes when pair-matched for muscle thickness.
Methods:
A total of 16 different data sets (n = 963) were assessed to pair-match females with males who had a muscle thickness value within 2%. We further compared the competition performances of the smallest male weight class within the International Powerlifting Federation (IPF) to different weight classes in females.
Results:
Overall, 76%-88% of the strength assessments were greater in males than females with pair-matched muscle thickness, regardless of contraction types (i.e., isotonic, isometric, isokinetic). Additionally, males in the lightest weight division in the IPF largely outperformed females in heavier weight divisions.
Conclusions:
Our results would suggest that segregation based on muscle mass or surrogates of muscle mass (e.g., lean body mass) might not be an appropriate classification to create fair competition within strength sports. This is not to refute the concept of the desegregation of the two-sex binary category but to present data that raises important concerns about the potential sex-based differences in strength performance.
... The quest of examining alternatives to traditional resistance training has allowed scientists to demonstrate that an individual can achieve hypertrophy without the use of an external load 6 . Counts et al. 6 observed that voluntary maximal contractions of the biceps muscles throughout the range of motion (termed "NO LOAD" training) resulted in muscle growth similar to that of traditional high load resistance exercise. ...
... The quest of examining alternatives to traditional resistance training has allowed scientists to demonstrate that an individual can achieve hypertrophy without the use of an external load 6 . Counts et al. 6 observed that voluntary maximal contractions of the biceps muscles throughout the range of motion (termed "NO LOAD" training) resulted in muscle growth similar to that of traditional high load resistance exercise. Authors demonstrated that an external load is not necessary to produce maximal muscle growth if there is a high level of voluntary internal tension and effort 6 . ...
... Counts et al. 6 observed that voluntary maximal contractions of the biceps muscles throughout the range of motion (termed "NO LOAD" training) resulted in muscle growth similar to that of traditional high load resistance exercise. Authors demonstrated that an external load is not necessary to produce maximal muscle growth if there is a high level of voluntary internal tension and effort 6 . Thus, individuals who are unable to perform traditional resistance training (i.e., lifting a heavy weight around 8-12 reps for 3-4 sets) may achieve muscle growth by simply contracting their muscle as hard as possible throughout a range of motion. ...
... The quest of examining alternatives to traditional resistance training has allowed scientists to demonstrate that an individual can achieve hypertrophy without the use of an external load 6 . Counts et al. 6 observed that voluntary maximal contractions of the biceps muscles throughout the range of motion (termed "NO LOAD" training) resulted in muscle growth similar to that of traditional high load resistance exercise. ...
... The quest of examining alternatives to traditional resistance training has allowed scientists to demonstrate that an individual can achieve hypertrophy without the use of an external load 6 . Counts et al. 6 observed that voluntary maximal contractions of the biceps muscles throughout the range of motion (termed "NO LOAD" training) resulted in muscle growth similar to that of traditional high load resistance exercise. Authors demonstrated that an external load is not necessary to produce maximal muscle growth if there is a high level of voluntary internal tension and effort 6 . ...
... Counts et al. 6 observed that voluntary maximal contractions of the biceps muscles throughout the range of motion (termed "NO LOAD" training) resulted in muscle growth similar to that of traditional high load resistance exercise. Authors demonstrated that an external load is not necessary to produce maximal muscle growth if there is a high level of voluntary internal tension and effort 6 . Thus, individuals who are unable to perform traditional resistance training (i.e., lifting a heavy weight around 8-12 reps for 3-4 sets) may achieve muscle growth by simply contracting their muscle as hard as possible throughout a range of motion. ...
Objectives:
To examine changes in muscle thickness (MT), soreness (SOR), and isometric torque (ISO) following exercise with pulsed direct current (Neubie) or traditional high-load (TRAD) exercise.
Methods:
Thirty-two participants had SOR, MT, and ISO measured before, immediately after, and 24 and 48h following TRAD and Neubie. Rating of perceived exertion (RPE) and discomfort were also measured. Results are displayed as means(SD).
Results:
For MT, there was a condition x time interaction (p<0.001). For Neubie, MT increased pre [3.7(0.7)cm] to post [3.9(0.8) cm, p<0.001] and remained elevated at 24h. For TRAD, MT increased pre [3.7(0.6)cm] to post [4.0 (0.7)cm, p<0.001] and remained up to 48h. Greater values were observed for TRAD post-exercise. For ISO, both conditions decreased up to 48h. TRAD demonstrated a greater change post exercise (p<0.001). For SOR, both conditions increased up to 48h. Neubie demonstrated greater SOR at 48h (p=0.007). RPE was higher for all sets in TRAD [Mean across sets=16.0(1.9) vs. 13.5(2), p<0.001]. Discomfort was higher in all sets for Neubie [Mean across sets=5.8(1.5)vs. 4.5(2.0), p<0.05].
Conclusions:
Both conditions showed increased SOR, and decreased ISO for up to 48h, with MT increased for up to 24h. MT remained elevated in TRAD at 48h. Neubie training might be effective for individuals who are looking to experience lower RPE responses during exercise.
... In order to distinguish two different conditions, participants were cued to "squeeze the muscle" for internal focus and cued to "lift weight up" for external focus. A similar concept was examined by Counts et al., which compared maximal effort elbow flexion exercise with no external load (internal focus coined "NO LOAD") to traditional high-load (70% 1RM) resistance training in the elbow flexor exercise (6). The authors observed no difference between conditions for changes in muscle thickness. ...
... Similar acute muscle swelling has been noted in response to resistance exercise in the upper body (2,6,38), as well as across a variety of protocols in the lower body (15). Notably, this acute response is highly repeatable and, in line with the hypotheses of Haussinger et al., is believed to International Journal of Exercise Science http://www.intjexersci.com ...
... Interestingly, Counts et al. compared EMG amplitude between NO LOAD and traditional high load resistance exercise, finding that high load training produced greater EMG amplitudes during the last three repetitions of exercise (87% MVC) compared to NO LOAD training (52% MVC) (6). Despite this, the authors observed similar decreases in isometric torque from pre to post-exercise. ...
Changes in muscle thickness (MT), isometric torque, and arterial occlusion pressure (AOP) were examined following four sets of twenty unilateral elbow flexion exercise. Participants performed four sets of maximal voluntary contractions with no external load
throughout a full range of motion of a bicep curl with and without the application of blood flow restriction (BFR). For torque there was an interaction (p = 0.012). The BFR condition had lower torque following exercise (56.07 ± 17.78 Nm) compared to the control condition (58.67 ± 19.06 Nm). For MT, there was a main effect for time (p < 0.001). MT increased from pre (3.52 ± .78cm) to post (3.68 ± 81cm) exercise and remained increased above baseline 15 min post-exercise. For AOP, there was an interaction (p = 0.027). The change in AOP was greater in the BFR condition (16.6 ± 13.42mmHg) compared to the control (11.1 ± 11.84 mmHg). NO LOAD exercise with BFR let to greater reductions in torque and an exaggerated cardiovascular response compared to exercise alone. There were no differences in swelling. These results suggest that the application of BFR to NO LOAD exercise may result in greater fatigue.
... This effort based approach opens the possibility of performing resistance training using non-traditional approaches and have the same results as during traditional resistance training (TRT) such as elastic bands [12][13][14], body weight exercises [15,16] and even some training models traditionally associated with aerobic activities such as cycling [9,17,18]. This evidence raised the suggestion that effort, rather than external load, might be a key determinant of training adaptations [8,10,19,20]. ...
... In agreement with this suggestion, Counts et al. [20] found similar gains in muscle size when comparing two distinct training protocols in young men. The study involved a contralateral design in which one arm performed traditional resistance training (TRT) with 70% of 1 RM, while the other trained without external load but tried to maximally contract the muscles during the full range of motion. ...
... Our findings are in agreement with previous studies that reported high levels of muscle activation during no load resistance training [21,27] for the arm muscles in many different situations. Counts et al. [20] reported high levels of biceps brachii muscle activation during NL-VF in untrained men and women. Later, Gentil et al. [26] reported that no load resistance training promoted high levels of muscle activation in young men independent of training status (trained vs. untrained), movement velocity, visual feedback and muscles analyzed (biceps and triceps brachii). ...
The present article aims to compare electromyographic (EMG) activity of the knee extensors during traditional resistance training (TRT) and no load resistance training with or without visual feedback (NL-VF and NL-NF). Sixteen healthy men (age: 25.2 ± 3.6) volunteered to participate in the study. Participants visited the laboratory on three occasions involving: (1) a 10 repetition maximum test (10 RM test), (2) familiarization and (3) performance of knee extensions using TRT, NL-VF and NL-NF in a random order, with 10 min of rest between them. TRT involved the performance of a set to momentary muscle failure using the 10 RM load. NL-NF involved the performance of 10 repetitions with no external load, but with the intention to maximally contract the muscles during the whole set. NL-VF involved the same procedure as NL-NF, but a monitor was positioned in front of the participants to provide visual feedback on the EMG activity. Peak and mean EMG activity were evaluated on the vastus medialis (VM), vastus lateralis (VL) and rectus femoris (RF). Results: there were no significant differences in VM and VL peak EMG activity among different situations. There was a significant difference for peak EMG activity for RF, where TRT resulted in higher values than NL-VF and NL-NF (p < 0.05). Higher values of mean EMG activity were found for VM, VL and RF during TRT in comparison with both NL-VF and NL-NF. Conclusions: resistance training with no external load produced high levels of peak muscle activation, independent of visual feedback, but mean activation was higher during TRT. These results suggest that training with no external load might be used as a strategy for stimulating the knee extensors when there is limited access to specialized equipment. Although the clinical applications of no load resistance training are promising, it is important to perform long-term studies to test if these acute results will reflect in muscle morphological and functional changes.
... In order to distinguish two different conditions, participants were cued to "squeeze the muscle" for internal focus and cued to "lift weight up" for external focus. A similar concept was examined by Counts et al., which compared maximal effort elbow flexion exercise with no external load (internal focus coined "NO LOAD") to traditional high-load (70% 1RM) resistance training in the elbow flexor exercise (6). The authors observed no difference between conditions for changes in muscle thickness. ...
... Similar acute muscle swelling has been noted in response to resistance exercise in the upper body (2,6,38), as well as across a variety of protocols in the lower body (15). Notably, this acute response is highly repeatable and, in line with the hypotheses of Haussinger et al., is believed to International Journal of Exercise Science http://www.intjexersci.com ...
... Interestingly, Counts et al. compared EMG amplitude between NO LOAD and traditional high load resistance exercise, finding that high load training produced greater EMG amplitudes during the last three repetitions of exercise (87% MVC) compared to NO LOAD training (52% MVC) (6). Despite this, the authors observed similar decreases in isometric torque from pre to post-exercise. ...
... NLRT is a relatively novel resistance training strategy that consists of repeatedly contracting a muscle or muscle group as hard as possible through a full range of motion without the use of an external load (Counts et al., 2016;Gentil et al., 2017). It can be easily performed by any individual, including hospitalized patients (Barbalho et al., 2017). ...
... It can be easily performed by any individual, including hospitalized patients (Barbalho et al., 2017). A typical NLRT session consists of 4 sets of 20 repetitions with 30 s of rest between sets (Counts et al., 2016) for several exercises (e.g., squats, and arm press or push exercises). A recent study reported that this training strategy resulted in an increase in muscle size, measured by ultrasound, similar to traditional high load resistance training (Counts et al., 2016). ...
... A typical NLRT session consists of 4 sets of 20 repetitions with 30 s of rest between sets (Counts et al., 2016) for several exercises (e.g., squats, and arm press or push exercises). A recent study reported that this training strategy resulted in an increase in muscle size, measured by ultrasound, similar to traditional high load resistance training (Counts et al., 2016). Strength gains were also reported, although at lower levels when compared to traditional high load resistance training. ...
The coronavirus disease 2019 (COVID-19) has spread to at least 115 countries and caused an alarming number of deaths. The current outbreak has lead authorities from many countries to adopt several protective measures, including lockdown and social distancing. Although being a reasonable measure to counteract the COVID-19 contamination, the restrictive measures have limited individual's ability to perform exercise outdoors or in gyms and similar facilities, thus raising the risks for chronic health conditions related to a sedentary lifestyle. The recent exercise recommendations to counteract the potential deleterious effects of COVID-19-related lockdown have not fully addressed resistance exercise interventions as potential home-based exercise strategies. Additionally, the following questions have been constantly raised: (1) Is training status capable of protecting an individual from COVID-19 infection?; and (2) Can a single endurance or resistance exercise session acutely increase the risks for COVID-19 infection? Therefore, the current mini review aimed to focus on these two concerns, as well as to discuss the potential use of practical blood flow restriction and no load resistance training as possible resistance exercise strategies that could be performed during the current COVID-19 pandemic.
... Based on the results from related studies, it can be hypothesized that this strategy might be beneficial for enhancing these adaptations. In a withinsubject study design by Counts et al. (2016), 13 untrained participants completed 18 sessions of the unilateral elbow flexion exercise. Each participant trained the elbow flexor of one arm for four sets with 20 repetitions without any external load (i.e., no-load training). ...
... While the results of Maeo et al. (2014) and Counts et al. (2016) provide evidence that no-load training per se can promote muscular adaptations in untrained individuals, neither study examined if combining iso-holds with traditional RT may have an additive effect that further augments strength and hypertrophy compared to resistance exercise conducted with passive inter-set rest. Moreover, the effects of no-load contractions in individuals with previous RT experience remain unclear. ...
... Given the current gaps in the literature, the present study aimed to compare the effects of traditional RT combined with isoholds during the inter-set period versus RT that involves passive inter-set rest on muscular strength, muscular hypertrophy, and muscular endurance in resistance-trained men. Based on the previously discussed observations (Maeo et al., 2014;Counts et al., 2016), we hypothesized that the group performing isoholds during the inter-set period (as compared to the group training with passive inter-set rest periods) would achieve greater increases in muscle size, strength, and endurance. ...
We aimed to investigate the effects of resistance training (RT) combined with no-load isometric actions (iso-holds) during the inter-set recovery period versus RT that involves passive inter-set rest on muscular strength, muscular hypertrophy, and muscular endurance in resistance-trained men. Twenty-seven resistance-trained male volunteers were randomly assigned to either a traditional group (TRAD) that performed a hypertrophy-oriented RT routine with the rest intervals spent passively (n = 13) or to a group that supplemented traditional RT with iso-holds (ISO) for the working muscle group between each set (n = 14). Training for both routines consisted of three weekly sessions performed for 8 weeks. Three sets of 8–12 repetitions were performed per exercise. A 2-min rest interval was afforded between sets; the ISO group performed iso-holds for the first 30 s of each rest interval and then recovered for the final 90 s. Maximal strength was assessed using the one repetition maximum (1RM) tests in the leg press and bench press. Upper-body muscle endurance was assessed by performing the bench press to failure at 50% of 1RM. Muscle thickness (MT) of the elbow flexors, elbow extensors, mid-thigh, and lateral thigh was assessed using B-mode ultrasound. Results indicated a favorable effect of ISO on MT in the mid-thigh. Alternatively, there was a possible detrimental effect for ISO on leg press strength. No other notable differences were seen between conditions. In conclusion, the use of inter-set iso-holds may be a time-efficient strategy to enhance development of the quadriceps femoris; conversely, it may be detrimental to maximizing lower body strength.
... [16][17][18] Elastic bands have gained popularity because of their low cost, simplicity, versatility, and portability. 19 Another promising low cost alternative is "NO LOAD" RT (NLRT) that has been shown to promote high levels of muscle activation, 20 and similar gains in muscle size as traditional RT. 21 In summary, during NLRT the participants are instructed to perform maximal muscle contractions over the range of motion without any external load. Based on previous studies, 20,21 NLRT might be a viable strategy to implement in environments that do not have equipment, such as intensive care units. ...
... Our findings may be supported by the study by Rudroff, Staudenmann and Enoka, 24 which indicate that high levels of motor units activation produced by repeated contractions may provide stimuli for muscular adaptations. Considering the high levels of activation reported in NLRT exercises, 20,21 this might, at least in part, explain the results. 26 Therefore, the fact that our participants increased muscle mass and functionality seem to be of clinical importance. ...
... Muscle thickness and functional performance pre and post the training period study involved hospitalized patients in an intensive care unit, which might present a lower adaptive threshold. Another point is the test used, Counts et al.21 used the 1RM tests, that is a more specific and similar to traditional RT, while we used an endurance-oriented functional performance test. Considering that increases in performance might be specific,25 this might have influenced the results. ...
The aim of the present study was to compare the effects of resistance training performed with no external load (NLRT) versus resistance training performed with elastic bands (RTEB) on muscle hypertrophy and functional performance in hospitalized patients. Twenty hospitalized females (age, 59.05±3.2 years; height 163.6±2.5 cm; body mass 70.2±3.6 kgs) were randomly assigned to RTEB or NLRT. Both groups trained three times a week for five weeks. RTEB was performed with elastic bands, while NLRT involved maximum voluntary contractions with no external loads. Biceps brachii, triceps brachii and pectoralis muscle thickness (MT) were measured by ultrasound. Functional performance was measured by the 30s elbow flexion test. MT significantly increased in all muscles tested for both groups, with no differences between groups. Changes ranged from 14 to 38%. Functional performance significantly improved by 42.7% for NLRT and 52.1% for RTEB, with no difference between them. The present results suggest that NLRT might be an efficient, feasible and low-cost strategy to promote morphological and functional benefits in the upper limb of hospitalized patients.
... 2.1 Load. RET-induced increases in 1RM are optimized when performing RET with nearer-tomaximal loads (e.g., >85 %1RM) [1][2][3][4][5]**. However, when muscular strength is evaluated using an unpracticed test (i.e., an outcome that is not performed in the RET protocol: isometric dynamometry), RET of any form is effective at increasing strength and heavier loads are not superior [2,3,[5][6][7][8]**/**. ...
... RET-induced increases in 1RM are optimized when performing RET with nearer-tomaximal loads (e.g., >85 %1RM) [1][2][3][4][5]**. However, when muscular strength is evaluated using an unpracticed test (i.e., an outcome that is not performed in the RET protocol: isometric dynamometry), RET of any form is effective at increasing strength and heavier loads are not superior [2,3,[5][6][7][8]**/**. Moreover, periodic practice/training of a 1RM test nullifies, or at least diminishes, the difference in RET-induced 1RM strength between heavier-and lighter-load RET indicating that a large part of the strength differences is practice-related, which may be facilitated by various neuromuscular adaptations [9]. ...
... RET-induced changes in muscular strength are primarily mediated by load [1][2][3][4][5]** and training specificity [4,7]**. Accordingly, as recommended by both the American College of Sports Medicine (ACSM) [40] and National Strength and Conditioning Association (NSCA) [41], recent evidence suggests that RET-induced changes in 1RM strength are greater when participants perform regular strength assessments with near-maximal loads (>85 %1RM) [1-5]**. ...
Resistance exercise training (RET)-induced increases in voluntary 1RM strength are greater with higher loads and training by replicating (or close) the strength test. In contrast, RET-induced muscular hypertrophy is primarily mediated by intensity of effort, which is achieved by performing RET to volitional fatigue and with an internal focus on contracting a muscle throughout the exercise range of motion. In addition, RET-induced muscular hypertrophy is augmented by increasing training volume, but with diminishing returns. Other training variables such as volume-load, inter-set rest, and time under tension have negligible effects on RET-induced changes in muscle size or strength. We conclude that an uncomplicated, evidence-based approach to optimizing RET-induced changes in muscle size and strength follows the FITT principle: frequency, intensity (effort), type, and time.
... Therefore, a possible explanation for this is that the exposure to the clinical practice overcame the negative neuromuscular adaptations associated with neck pain, allowing a similar muscular response to clinical training exposure. Despite our knowledge that higher loads promote greater changes in muscle architecture and function [56], several studies have reported that exposure to high levels of localized and sustained muscle activation produced from repeated contractions can provide sufficient stimulation of skeletal muscle to induce muscle changes both in size and function [57,58]. Hence, the engagement in a new activity seems to have promoted muscular adaptations independent of the previously reported neck pain, confirming that robust muscle changes can occur independent of an external load provided [57]. ...
... Despite our knowledge that higher loads promote greater changes in muscle architecture and function [56], several studies have reported that exposure to high levels of localized and sustained muscle activation produced from repeated contractions can provide sufficient stimulation of skeletal muscle to induce muscle changes both in size and function [57,58]. Hence, the engagement in a new activity seems to have promoted muscular adaptations independent of the previously reported neck pain, confirming that robust muscle changes can occur independent of an external load provided [57]. A possible interpretation for our findings could be the pain's multidimensionality, which includes physical, psychological, and social aspects [19,20] such as anxiety, stress, quality of life, or kinesiophobia. ...
Neck pain can induce specific motor responses and alterations in muscle strength. Therefore, this study aimed to investigate and compare the progression of cervical muscle strength within and between students with and without neck pain over the course of their first semester of clinical training. We used an online Nordic Musculoskeletal Questionnaire for group allocation, and neck strength in flexion, extension, and lateral flexion on both sides was measured using the KForce Bubble Pro hand-held dynamometer. Forty-four students were divided into neck pain (n = 21) and asymptomatic (n = 23) groups. Both groups increased neck strength by the end of the semester in flexion, extension, and left and right lateral flexion (p < 0.001). Students experiencing neck pain showed a significantly lesser degree of improvement (p = 0.036) in right lateral flexion. The agonist/antagonist ratios revealed an enhanced role of neck extensors across both groups. Dental students showed overall increased cervical strength in their first semester of clinical training. Those with neck pain exhibited a diminished rate of strength gain in right lateral flexion when compared with students without pain by the semester’s end, suggesting different neuromuscular adjustments to clinical practice in students experiencing pain, which may lead to functional impairments in later training stages.
... For example, measurements such as muscle swelling (e.g. acute change in muscle thickness) and decrements in isometric strength post-exercise have been used throughout the literature as a means to gauge the effectiveness of resistance training protocols (Yasuda et al 2012, Counts et al 2016a, Buckner et al 2019. In addition, when performing BFR exercise there is some concern regarding cardiovascular disturbances (e.g. ...
... Within the resistance training literature, acute changes in muscle thickness (i.e. muscle swelling) are often used to characterize the effectiveness of a training stimulus (Counts et al 2016a, Freitas et al 2017, Buckner et al 2019, Vasenina et al 2022. In the present study, we observed significant increases in muscle thickness following BFR exercise with both SMARTCUFF and HOKANSON devices, with no differences between cuff types for either 40% and 80% LOP. ...
Objective:
To compare the acute psychophysiological responses to blood flow restriction (BFR) exercise using a traditional research device or novel, automated system.
Methods:
Forty-four resistance trained individuals performed four sets of unilateral elbow flexion exercise [30% one-repetition maximum (1RM)] to volitional failure using two distinct restrictive devices [SmartCuffs PRO BFR Model (SMARTCUFF), Hokanson E20 Rapid Inflation device (HOKANSON)] and with two levels of BFR [40% limb occlusion pressure (LOP), 80% LOP]. Blood pressure (BP), muscle thickness (MT), and isometric strength (ISO) were assessed prior to and following exercise. Perceptual responses [ratings of perceived exertion (RPE), discomfort] were assessed prior to exercise and following each exercise set.
Main Results:
Data are displayed as means (SD). Immediately following exercise with 40% LOP, there were no statistical differences between devices for BP, MT, and ISO. However, only following Set 1 of exercise, RPE was greater with SMARTCUFF compared to HOKANSON (p < 0.05). In addition, only following Set 2 of exercise, discomfort was greater with HOKANSON compared to SMARTCUFF (p < 0.001). Immediately following exercise with 80% LOP, there were no statistical differences between devices for BP, MT, and ISO. However, only following Set 4 of exercise, RPE was greater with HOKANSON compared to SMARTCUFF (p < 0.05). In addition, following all exercise sets, discomfort was greater with HOKANSON compared to SMARTCUFF (p < 0.001). Significance: The present study provides valuable insight into the efficacy of a novel, automated BFR system (SMARTCUFF) eliciting comparable acute physiological responses to BFR exercise and in some cases favorable psychological responses when compared to a traditional research device (HOKANSON).
... Through comparison of the work by Blangsted et al (2005) and Sjøgaard et al (1986) against that of Miyamoto et al (2013) and Tanimoto and Ishii (2006), it is reasonable to argue that a high external load is the catalyst towards attaining significant exerciseinduced metabolic stress. Yet this assumption can be challenged by examining a recent study by Counts et al (2016). The authors compared within-subject, between-arm changes to brachial muscle thickness and strength after completing eighteen sessions of elbow flexion exercises performed using either a high-load (70% 1RM) or no load. ...
... Longitudinally, cellular signalling pathways responsible for the development of muscular strength and hypertrophy may have been stimulated in similar ways between biceps exercised at 'no-load' and 70-80% 1RM. Within Counts et al (2016), the superiority of the 'high-load' training in terms of muscle strength and endurance may be linked to between-arm differences in exercise parameters. The 'no-load' arms were exercised for four sets of 20 repetitions, with 30 seconds of rest between sets. ...
... Several recent studies help to clarify this topic. In a within-subject design, Counts et al. [77] allocated untrained men and women to perform elbow flexion using a load of 70% 1RM in one arm while the other arm trained without using an external load (i.e., "no-load" group). The no-load condition required participants to contract their working muscle as hard as possible throughout the full range of motion of each repetition. ...
... Despite the curious findings of Counts et al. [77] showing marked hypertrophy with no-load training (at least over a 6-week intervention), there does appear to be a minimum threshold for loading below which hypertrophic gains are compromised. Given the evidence that training with 30% 1RM produces comparable hypertrophy to that with heavy loads [73], it can be inferred that the minimum threshold is somewhere in the range of 30% 1RM. ...
Loading recommendations for resistance training are typically prescribed along what has come to be known as the “repetition continuum”, which proposes that the number of repetitions performed at a given magnitude of load will result in specific adaptations. Specifically, the theory postulates that heavy load training optimizes increases maximal strength, moderate load training optimizes increases muscle hypertrophy, and low-load training optimizes increases local muscular endurance. However, despite the widespread acceptance of this theory, current research fails to support some of its underlying presumptions. Based on the emerging evidence, we propose a new paradigm whereby muscular adaptations can be obtained, and in some cases optimized, across a wide spectrum of loading zones. The nuances and implications of this paradigm are discussed herein.
... 7 No-load (no external load) resistance training can be performed anywhere and requires no equipment. In 2016, Counts et al. 8 were the first to investigate the effects of no-load resistance training and traditional high-load (70% of one repetition maximum) resistance training on muscle strength and muscle size in healthy young adults. The authors reported that both no-load and highload training programs elicited increases in elbow flexor muscle strength, although the degree of increase was greater for the high-load condition. ...
... 10 The no-load training exercise is defined as a maximum voluntary contraction of muscle through the full range of motion in selected movements. 8,9 No-load can also be combined with bodyweight exercise. By combining both, it is possible to maintain a high muscle activity level at all times regardless of the muscle strength level by performing voluntary maximum contractions during bodyweight exercise. ...
... Some studies suggest that activation might be important for muscle adaptations [30], since mechanotransduction is likely to occur only in muscle fibers activated during exercise [31]. This suggests that high levels of muscle activation produced from repeated contractions can provide stimulation to the muscle, especially when combined with other factors, such as mechanical and metabolic stress, muscle swelling, etc. [31][32][33][34][35]. Therefore, considering that electromyographic (EMG) activity may reflect greater challenges to the musculoskeletal system, the investigation of plantar flexors muscle activity during MJ and SJ exercise using EMG analysis might contribute to close the gap regarding this topic. ...
... However, it has been suggested that mechanotransduction is likely to occur only in muscle fibers activated during exercise [31]. This suggests that high levels of muscle activation produced from repeated contractions can provide stimulation to the muscle, especially when combined with other factors, such as mechanical and metabolic stress, muscle swelling, etc. [31][32][33][34][35]. Therefore, the present study can provide a rationale for further studies aimed at comparing the long-term effects of MJ and SJ in plantar flexors' function and morphology. ...
The present study aimed to compare soleus, lateral, and medial gastrocnemius muscles activation during leg press and calf raise exercises in trained men. The study involved 22 trained men (27.1 ± 3.6 years, 82.7 ± 6.6 kg, 177.5 ± 5.2 cm, 3.6 ± 1.4 experience years) who performed one set of each exercise using a 10-repetition maximum (10RM) load in a counterbalanced randomized order and separated by 10 min of rest. The electromyographic signal was measured for the three major plantar flexors: soleus, medial, and lateral gastrocnemius. A comparison between exercises showed that the mean adjusted by peak values during the leg press were 49.20% for the gastrocnemius lateralis, 51.31% for the gastrocnemius medialis, and 50.76% for the soleus. Values for calf raise were 50.70%, 52.19%, and 51.34% for the lateral, medial gastrocnemius, and soleus, respectively. There were no significant differences between exercises for any muscle (lateral gastrocnemius (p = 0.230), medial gastrocnemius (p = 0.668), and soleus (p = 0.535)). The present findings suggest that both leg press and calf raises can be used with the purpose to recruit triceps surae muscles. This bring the suggestion that one can chose between exercises based on personal preferences and practical aspects, without any negative impact on muscle activation.
... All these previous studies used VI focusing internally, in which attention was directed to body segments during exercises (Marchant et al., 2009;Wulf & Prinz, 2001). Since the cocontraction training has demonstrated similar activation levels compared to the conventional strength training (Counts et al., 2016), it is likely that verbal instructions might also benefit co-contraction sets and possibly change past differential muscle improvements by emphasizing specific EMG activity of targeted muscles. ...
... Succeeding, they performed three maximal voluntary isometric contractions (MVIC) of five seconds (De Luca, 1984;Gentil et al., 2017; with 90-seconds rest (Serrau et al., 2012) Cedral, São Paulo, Brazil). On the same equipment, we measured the MVIC for the TB muscle at an elbow joint angle of 90-degrees in the triceps pushdown exercise (Counts et al., 2016;Singla et al., 2018). ...
Co-contraction training has demonstrated similar electromyographic (EMG) activity levels compared to conventional strength training. Since verbal instructions can increase EMG activity on target muscles during conventional exercises, the same should occur during co-contraction. In this study we analyzed whether different verbal instructions would alter the EMG activity of target muscles - biceps brachii (BB) and triceps brachii lateral head (TB) - during co-contraction training for the elbow joint. Seventeen males with experience in strength training performed a co-contraction set in two verbal instruction conditions to emphasize either elbow flexion or elbow extension. Surface electrodes were fixed over biceps brachii and triceps brachii lateral head muscles. We measured EMG mean amplitude and analyzed data with 2-way ANOVA. We found a significant interaction between muscle and verbal instruction (p = 0.002). Post hoc tests indicated that verbal instructions (p = 0.001) influenced the BB EMG activity (elbow flexion: M = 68.74, SD = 17.96%; elbow extension: M = 53.47, SD = 16.13%); and also showed difference (p = 0.006) in the EMG activity between BB and TB with verbal instruction emphasizing the elbow extension (BB: M = 53.47, SD = 16.13%; TB: M = 69.18, SD = 21.79%). There was a difference in the EMG ratio of BB/TB (p = 0.001) when focusing on elbow flexion (M = 1.09, SD = 0.30) versus elbow extension (M = 0.81, SD = 0.25). As verbal instruction modified the magnitude of muscle recruitment during co-contractions for elbow joint muscles, there is a clear mind-muscle connection of importance to this method of training. Also, of importance to trainers, verbal instructions seemed to affect individuals differentially.
... For example, acute studies verified high levels of motor units recruitment when performing NEL muscle contractions with the intention to maximally contract the muscles . Some studies showed muscle strength and mass gains after NEL-RT programs (Counts et al., 2016;Barbalho et al., 2019). In young men and women, after a contralateral training design, equivalent gains in the arm muscle size was observed after traditional RT and NEL-RT (Counts et al., 2016). ...
... Some studies showed muscle strength and mass gains after NEL-RT programs (Counts et al., 2016;Barbalho et al., 2019). In young men and women, after a contralateral training design, equivalent gains in the arm muscle size was observed after traditional RT and NEL-RT (Counts et al., 2016). This hypothesis was also confirmed in rehabilitation setting, with positive outcomes in terms of hypertrophy and functionality . ...
Resistance training (RT) is a popular exercise mode and is considered an essential part of an exercise program. In current pandemic times due to the coronavirus (i.e. COVID-19) outbreak, RT practice has been strongly threatened. However, such threat might not be an inherent problem to RT, but rather to misconceptions related to RT. In the current opinion article, we provide insights to better understand RT. When analyzing current scientific evidence, it seems that RT can be performed in a safe, time-efficient and uncomplicated manner, in many different places and with few resources, which makes it fully feasible within measures adopted to control coronavirus dissemination. RT should not be sacrificed due to consequences of the coronavirus pandemic. However, it might be necessary to sacrifice some old-fashioned thoughts, rooted in beliefs that have already been overturned by science. It would be counter-productive for population health (and countries economy) to avoid RT due to the misconception that specialized equipment, fashioned programs, or resources are needed for effective programs implementation. Therefore, RT can be easily adapted to the new time and logistical challenges brought by the coronavirus outbreak. From a practical standpoint, RT could be performed using body weight, accessible materials (e.g. elastic bands, lights dumbbells and barbell) or even without external load at home or at public spaces and still result in important health benefits.
... elbow flexors and extensors) without the need for an external loading apparatus (Fujita et al., 2021;Mackenzie et al., 2010;Zbidi et al., 2017). Previous studies have indicated that co-contraction training promotes strength gain (Mackenzie et al., 2010;Villalba et al., 2024) and hypertrophy (Counts et al., 2016), and could serve as an alternative to conventional resistance training, especially in settings like hospitals where weights and resistance equipment are typically unavailable. Novel insights gained from the investigation of underlying neural mechanisms mediating co-contraction behaviours are likely to shed light on applying these types of muscle contraction for adaptations in both health and disease. ...
Motoneuronal persistent inward currents (PICs) are facilitated by neuromodulatory inputs but are highly sensitive to local inhibitory circuits. Estimates of PICs are reduced by group Ia reciprocal inhibition, and increased with the diffuse actions of neuromodulators released during remote muscle contraction. However, it remains unknown how motoneurons function in the presence of simultaneous excitatory and inhibitory commands. To probe this topic, we investigated motor unit discharge patterns and estimated PICs during voluntary co‐contraction of ankle muscles, which simultaneously demands the contraction of agonist–antagonist pairs. Twenty participants performed triangular ramps of both co‐contraction (simultaneous dorsiflexion and plantar flexion) and isometric dorsiflexion to a peak of 30% of their maximum muscle activity from a maximal voluntary contraction. Motor unit spike trains were decomposed from high‐density surface EMG activity recorded from tibialis anterior using blind source separation algorithms. Voluntary co‐contraction altered motor unit discharge rate characteristics. Discharge rate at recruitment and peak discharge rate were modestly reduced (∼6% change; P < 0.001; d = 0.22) and increased (∼2% change; P = 0.001, d = −0.19), respectively, in the entire dataset but no changes were observed when motor units were tracked across conditions. The largest effects during co‐contraction were that estimates of PICs (ΔF) were reduced by ∼20% (4.47 vs. 5.57 pulses per second during isometric dorsiflexion; P < 0.001, d = 0.641). These findings suggest that, during voluntary co‐contraction, the inhibitory input from the antagonist muscle overcomes the additional excitatory and neuromodulatory drive that may occur due to the co‐contraction of the antagonist muscle, which constrains PIC behaviour. image
Key points
Voluntary co‐contraction is a unique motor behaviour that concurrently provides excitatory and inhibitory synaptic input to motoneurons.
Co‐contraction of agonist–antagonist pairs alters agonist motor unit discharge characteristics, consistent with reductions in persistent inward current magnitude.
... While different studies have shown the benefits of co-contraction training with promising results for gains in strength [15][16][17][18] and hypertrophy 17,18 , most have primarily relied on EMG activity for assessing external load 20,34 . Moreover, only two studies used RPE to assess internal load during co-contraction 34,35 . Furthermore, no study sought to correlate the RPE with EMG activity to check whether the RPE would be a possible measure of training intensity for the co-contraction modality. ...
BACKGROUND: Evaluating exercise intensity is crucial for designing effective training programs and monitoring progress. The Rating of Perceived Exertion (RPE) scale, a subjective measure of effort, is commonly used for estimating exercise intensity. However, its applicability in specific conditions and populations, particularly in co-contraction training and older individuals, warrants further investigation. AIM: Our main aim was to analyze the correlation between RPE and electromyographic (EMG) activity in co-contraction and conventional resistance training. We also compared muscle activity and RPE across training methods. METHOD: Twenty-three older adults were allocated and divided into conventional resistance training (CRT) and co-contraction training (CCT). EMG activity and RPE were recorded for knee extension and flexion movement and knee co-contraction during training sets and correlated before and after eight weeks of training. RESULTS: The results indicated no significant correlation between EMG activity and RPE for either training method. Additionally, EMG analysis showed higher EMG activity in the CRT than in the CCT. On the other hand, CCT demonstrated an increase in EMG activity after eight weeks of training. CONCLUSION: In conclusion, RPE did not correlate with EMG activity, highlighting the need for finding accessible tools to assess exercise intensity, particularly in older people, and alternative training methods, such as co-contraction training.
... 23 Brittany R. Counts,et al. states that muscle contractions alone could activate the muscle enough to stimulate growth of the muscle like High Load training. 24 Scott K. Lynn,et al.stated that training the IFM had no effect on the results of the navicular height and static balancing tests. 25 Therefore, our study states the HLST is effective for managing Plantar fasciitis symptoms. ...
Background: Plantar fasciitis is a common condition characterized by pain and inflammation in the plantar fascia,a thick band of tissue that runs along the bottom of the feet, connecting the heel to the toes. It is particularlyprevalent among athletes who engage in activities that involve repetitive impact, such as running, jumping.Athletes with plantar fasciitis often undergo a structured rehabilitation program that incorporates high loadresistance training alongside other interventions such as stretching, massage, orthotic devices, and modificationsin training and footwear.Purpose: To compare the effectiveness of High Load Plantar Fascia Resistance Training with ultrasound andIntrinsic Muscle strengthening with ultrasound among athletes with Plantar Fasciitis.Materials and Methods: Total of 60 subjects were selected from Sri Sai Ortho General Clinic based on the selectioncriteria and randomly divided into two groups; High load plantar fascia resistance training (HLST) with ultrasound(n=30) and Intrinsic muscle strengthening with ultrasound (n=30). The subjects were assessed for pain intensityusing NPRS and using LEFS, for pre and post-test values. The interventions were given for 2 weeks. Study period: November 2022 to March 2023Result: The result of the study revealed that both exercises are effective but (HLST) with ultrasound was moreeffective and significant in terms of decreasing pain and improving functional mobility.Conclusion: Hence the study concludes that HLST was more effective in managing plantar fasciitis in terms ofboth relieving pain as well as functional mobility among athletes with plantar fasciitis.
... Third, forceful muscle contractions through a full ROM without an external load (e.g., voluntary co-contraction of agonists and antagonists during a movement) can increase strength over time (noteworthy, we consider this a low-load intervention because, although it does not involve an external load, it does involve forceful muscle contractions). A single study found that performing forceful muscle contractions in the absence of an external load produces small yet significant changes in strength, at least in untrained subjects (18). Whether this approach can maintain strength in individuals with RE experience or be used to facilitate rehabilitation remains to be determined. ...
Traditional heavy resistance exercise (RE) training increases maximal strength, a valuable adaptation in many situations. That stated, some populations seek new opportunities for pushing the upper limits of strength gains (e.g., athletes and military personnel). Alternatively, other populations strive to increase or maintain strength but cannot perform heavy RE (e.g., during at-home exercise, during deployment, or after injury or illness). Therefore, the purpose of this narrative review is to (a) identify the known stimuli that trigger gains in strength; (b) identify the known factors that mediate the long-term effectiveness of these stimuli; (c) discuss (and in some cases, speculate on) potential opportunities for maximizing strength gains beyond current limits (d) discuss practical applications for increasing or maintaining strength when traditional heavy RE cannot be performed. First, by conceptually deconstructing traditional heavy RE, we identify that strength gains are stimulated through a sequence of events, namely: giving maximal mental effort, leading to maximal neural activation of muscle to produce forceful contractions, involving lifting and lowering movements, training through a full range of motion, and (potentially) inducing muscular metabolic stress. Second, we identify factors that mediate the long-term effectiveness of these RE stimuli, namely: optimizing the dose of RE within a session, beginning each set of RE in a minimally fatigued state, optimizing recovery between training sessions, and (potentially) periodizing the training stimulus over time. Equipped with these insights, we identify potential opportunities for further maximizing strength gains. Finally, we identify opportunities for increasing or maintaining strength when traditional heavy RE cannot be performed. © 2023 NSCA National Strength and Conditioning Association. All rights reserved.
... Acute changes in muscle thickness following an exercise protocol may indicate a fluid shift into the muscle cell (Yasuda, et al., 2012) and possibly signal the mammalian target of rapamycin pathway (Loenneke et al., 2012b). It remains unclear whether acute muscle swelling is a mechanism for muscle growth, although acute muscle swelling is often observed within protocols that typically elicit muscle growth adaptations (Counts et al., 2016;Kim et al., 2017). In the present study, we observed a similar acute pressures (15% 1RM with either 0%, 40%, or 80% AOP) . ...
Purpose:
To examine the acute muscular and cardiovascular responses to applying blood flow restriction (BFR) prior to high-load training.
Methods:
40 trained individuals visited the lab on 3 occasions. On visit 1, participants completed paperwork and performed strength assessments. During Visits 2 and 3 participants completed 4 exercise conditions (one in each arm during each visit): 1) Traditional resistance training (TRAD), 2) Low load training with BFR (LLBFR), 3) Low repetition high load training with pre-exercise BFR (PreBFR), 4) Low repetition traditional training (LRTRAD). Blood pressure, muscle thickness (MT), and isometric torque (ISO) were measured before and after exercise.
Results:
Data is displayed as means (SD). Immediately following exercise, MT in TRAD was greater compared to PreBFR [mean difference = 0.18(0.30)cm, p<0.001] and LRTRAD [mean difference =0.28(0.30)cm, p<0.001]. In addition, LLBFR demonstrated greater MT compared to PreBFR [mean difference =0.24(0.30) cm,p< 0.001]. Immediately following exercise, ISO was lower in TRAD compared to PreBFR [mean difference = 33.8(46.9)N,p<0.001] and the LRTRAD condition [mean difference = 32.8(50.4)N,p<0.001]. In addition, ISO was lower in LLBFR compared to PreBFR [mean difference = 43.9 (47.4)N,p< 0.001] and LRTRAD [mean difference = 42.9 (43.8)N, p < 0.001]. Immediately following exercise, systolic blood pressure was greater in TRAD compared to PreBFR and LRTRAD.
Conclusion:
The application of BFR prior to engaging in high-load training does not seem to augment the muscular responses to exercise when compared to traditional high loads alone; however, it may pose less demand on the cardiovascular system. This article is protected by copyright. All rights reserved.
... The r value for the pre-post correlation used for leg extension was 0.923, based on a previous report [19]. We used 0.9 as the pre-post correlation for all other estimations, since this correlation on strength tests would be expected to be large (previous studies have noted pre to post correlations from 0.85 to 0.99 [7,[19][20][21][22][23][24]). Although we provide evidence that the correlation between pre-and post-values is large, we ran sensitivity analysis with r = 0.8 and r = 0.7. ...
Background
Isotonic exercise is the most common mode of strength training. Isotonic strength is often measured in the movement that was exercised, but isometric and isokinetic movements are also commonly used to quantify changes in muscular strength. Previous research suggests that increasing strength in one movement may not lead to an increase in strength in a different movement. Quantifying the increase in strength in a movement not trained may be important for understanding strength training adaptations and making recommendations for resistance exercise and rehabilitation programs.Objective
To quantify changes in non-specific strength relative to a control.DesignA systematic review and random effects meta-analysis was conducted investigating the effects of isotonic strength training on isotonic and isokinetic/isometric strength.Search and InclusionThis systematic review was conducted in Google scholar, PubMed, Academic Search Premier, and MENDELEY. To be included in this review paper the article needed to meet the following criteria: (1) report sufficient data for our variables of interest (i.e., changes in isotonic strength and changes in isokinetic or isometric strength); (2) include a time-matched non-exercise control; (3) be written in English; (4) include healthy human participants over the age of 18 years; (5) the participants had to train and test isotonically; (6) the participants had to be tested isokinetically or isometrically on a device different from that they trained on; (7) the non-specific strength task had to test a muscle involved in the training (i.e., could not have trained chest press and test handgrip strength); and (8) the control group and the experimental group had to perform the same number of strength tests.ResultsWe completed two separate searches. In the original search a total of 880 papers were screened and nine papers met the inclusion criteria. In the secondary search a total of 2594 papers were screened and three additional papers were added (total of 12 studies). The overall effect of resistance training on changes in strength within a movement that was not directly trained was 0.8 (Cohen’s d) with a standard error of 0.286. This overall effect was significant (t = 2.821, p = 0.01) and the 95% confidence interval (CI) is 0.22–1.4. The overall effect of resistance training on strength changes within a movement that was directly trained was 1.84 (Cohen’s d) with a standard error of 0.296. This overall effect was significant (t = 6.221, p < 0.001) and the 95% CI is 1.23–2.4.Conclusion
The results of our meta-analysis suggest that strength increases in both the specific and non-specific strength tests. However, the smaller effect size associated with non-specific strength suggests that it will be difficult for a single study to meaningfully investigate the transfer of strength training adaptions.
... Nonetheless, results from PNF should be analyzed with caution because they were driven by heterogeneous responses among the few studies available (I 2 5 61%, k 5 3). In addition, the slightly greater effect of PNF over static and dynamic models could be attributed to the active contraction phase performed during PNF and not to stretching-specific neuromuscular mechanisms (14,77). Studies from Barbosa et al. (3) and LaRoche et al. (49) were the only ones who directly compared the effects of dynamic vs. static stretching, and both reported no benefit on strength for any condition, as well as no significant difference between the conditions. ...
Background Evidence regarding chronic stretching training is limited. This study aimed to review studies that performed stretching training and evaluated the effects on muscular strength.
Methods Literature search was performed using three databases. Studies were included if compared the effects on strength following stretching training versus a non-training control group or stretching training combined with resistance training (RT) versus an RT-only group, following at least 4 weeks of intervention. The quality of the studies was assessed with the Downs & Black checklist. The meta-analyses were performed using a random-effects model with Hedges’ g effect size (ES).
Results A total of 35 studies (n=1179), predominantly of medium and high quality, were included in the review. The interventions were carried out over a mean period of 8 weeks (4–24 weeks), 3 to 4 days per week, applying ⁓4 sets of stretching of ~1-minute duration. The meta-analysis for the stretching vs. non-training control group showed a significant small effect on improving dynamic (k=14; ES=0.33; p=0.007) but not isometric strength (k=8; ES=0.10; p=0.377), following static stretching programs (k=17; ES=0.28; p=0.006). When stretching was added to RT interventions, the main analysis indicated no significant effect (k=17; ES=-0.15; p=0.136); however, the meta-regression revealed a significant negative association with study length, whereby the longer the intervention the greater was the impairing effect of the stretching exercises on RT-induced strength gains (β=-0.100; p=0.004).
Conclusions Chronic static stretching programs may increase dynamic muscular strength to a small magnitude. Performing stretching before RT and for a prolonged time (>8 weeks) may blunt the strength gains to a small-to-moderate magnitude. Performing stretching in sessions distant from RT sessions may be a strategy to not hinder strength development.
... An assessment was performed to determine the maximum load or maximum repetition (1RM) [25]. With this estimate, intensity can be measured as low intensity where loads are used at 20-30 % of 1RM, moderate-intensity with loads of 40-70 % of 1RM, and high intensity with loads >70 % of 1RM [26]. Some modalities combine resistance and strength exercises in the same physical training session and are known as combined or mixed exercises [27]. ...
MicroRNAs (miRNAs) control RNA translation and are a class of small, tissue-specific, non-protein-coding RNAs that maintain cellular homeostasis through negative gene regulation. Maintenance of the physiological environment depends on the proper control of miRNA expression, as these molecules influence almost all genetic pathways, from the cell cycle checkpoint to cell proliferation and apoptosis, with a wide range of target genes. Dysregulation of the expression of miRNAs is correlated with several types of diseases, acting as regulators of cardiovascular functions, myogenesis, adipogenesis, osteogenesis, hepatic lipogenesis, and important brain functions. miRNAs can be modulated by environmental factors or external stimuli, such as physical exercise, and can eventually induce specific and adjusted changes in the transcriptional response. Physical exercise is used as a preventive and non-pharmacological treatment for many diseases. It is well established that physical exercise promotes various benefits in the human body such as muscle hypertrophy, mental health improvement, cellular apoptosis, weight loss, and inhibition of cell proliferation. This review highlights the current knowledge on the main miRNAs altered by exercise in the skeletal muscle, cardiac muscle, bone, adipose tissue, liver, brain, and body fluids. In addition, knowing the modifications induced by miRNAs and relating them to the results of prescribed physical exercise with different protocols and intensities can serve as markers of physical adaptation to training and responses to the effects of physical exercise for some types of chronic diseases. This narrative review consists of randomized exercise training experiments with humans and/or animals, combined with analyses of miRNA modulation.
... In this regard, previous studies reported high levels of muscle activation when performing RT with the intention to maximally contract the muscles and no external load (Gentil et al., 2017a;Alves et al., 2020). A previous study reported equivalent gains in arm muscle hypertrophy after traditional and no external load RT in young men and women, using a contralateral training design (Counts et al., 2016). Positive outcomes in terms of hypertrophy and functionality have also been reported in intensive care units patients (Barbalho et al., 2019). ...
The second volume of the Research Topic entitled “Precision Physical Activity and Exercise Prescriptions for Disease Prevention: The Effect of Interindividual Variability Under Different Training Approaches” has been successfully completed, as expected. As stated in the preface to the first volume, this Research Topic was initially intended to address a challenge in this field, but this topic is becoming, over time, an important cornerstone for scientists who are exploring the fascinating subject of “Precision Physical Activity and Exercise Prescriptions for Disease Prevention” (Ramírez-Vélez et al., 2017). This Research Topic consists of 10 articles, of which seven contain original data, one is a systematic review with meta-analysis and two are opinion/hypothesis articles.
... If one decides to avoid exercise facilities, RT can be adapted to be performed in many different situations, even with limited space and equipment, and it can easily be adapted to an individual's characteristics and health status [61]. For example, previous studies have shown that bodyweight exercises [66][67][68], stationary bike training [69], plyometric training [70], elastic band training [71][72][73], and even exercises with no external load [74][75][76] promote similar responses to traditional RT. These exercises might be performed as basic multi-joint exercises (i.e., squats, pushups, pullups, rows, etc.) as this has been shown to be sufficient to promote gains in muscle strength and size in most muscles involved [77][78][79][80][81]; the addition of isolated exercises, in general, does not seem to bring benefits [80,82,83]. ...
By the end of 2019 a severe acute respiratory syndrome caused by the SARS-CoV-2 started a pandemic, leading to millions of deaths and many important political and social changes. Even in the absence of contamination, the mobility reduction, social distancing and closing of exercise facilities negatively affected physical activity and conditioning, which is associated to muscle atrophy, loss of muscle strength and reductions in functional capacity. In case of infection, it has been shown that increased physical capacity is associated with decreased hospitalization and mortality risk. Although millions of people died from COVID-19, most contaminated individu-als survived from the infection, but carried different sequelae, like severe loss of physical func-tion and reduced quality of life. Among different physical exercise models that might help to prevent and treat COVID-19 outcomes, resistance training (RT) might be particularly relevant. Among its benefits, RT can be adapted to be performed in many different situations, even with limited space and equipment, and it is easily adapted to individual characteristics and health status. The current narrative review aims to provide insights on how RT can be used in different scenarios to counteract the negative effects of COVID-19. By this, the authors expect to provide insights do deal with the current pandemic and also in case the World has to deal with similar events in the future.
... In this regard, previous studies reported high levels of muscle activation when performing RT with the intention to maximally contract the muscles and no external load (Gentil et al., 2017a;Alves et al., 2020). A previous study reported equivalent gains in arm muscle hypertrophy after traditional and no external load RT in young men and women, using a contralateral training design (Counts et al., 2016). Positive outcomes in terms of hypertrophy and functionality have also been reported in intensive care units patients (Barbalho et al., 2019). ...
The novel coronavirus disease (COVID-19) has emerged at the end of 2019 and caused
a global pandemic. The disease predominantly affects the respiratory system; however,
there is evidence that it is a multisystem disease that also impacts the cardiovascular
system. Although the long-term consequences of COVID-19 are not well-known,
evidence from similar diseases alerts for the possibility of long-term impaired physical
function and reduced quality of life, especially in those requiring critical care. Therefore,
rehabilitation strategies are needed to improve outcomes in COVID-19 survivors. Among
the possible strategies, resistance training (RT) might be particularly interesting, since it
has been shown to increase functional capacity both in acute and chronic respiratory
conditions and in cardiac patients. The present article aims to propose evidence-based
and practical suggestions for RT prescription for people who have been diagnosed with
COVID-19 with a special focus on immune, respiratory, and cardiovascular systems.
Based on the current literature, we present RT as a possible safe and feasible activity
that can be time-efficient and easy to be implemented in different settings.
... In a study, trying to remove the influence of an external load and to determine if muscle growth can be stimulated by solely maximally voluntary contracting the muscle through a full range of motion (ROM), Counts et al. (2016), subjected 13 participants to 18 sessions of unilateral elbow flexion exercise. Each arm was assigned to either the no load or high load (70% 1-RM) condition in a counterbalanced design. ...
Skeletal muscle is one of the most important tissues of the human body. It comprises up to 40% of the body mass and is crucial to survival. Hence, the maintenance of skeletal muscle mass and strength is pivotal. It is well-established that resistance exercise provides a potent anabolic stimulus to increase muscle mass and strength in men and women of all ages. Resistance exercise consists of mechano-biological descriptors, such as load, muscle action, number of repetitions, repetition duration, number of sets, rest interval between sets, frequency, volitional muscular failure, and range of motion, which can be manipulated. Herein, we discuss the evidence-based contribution of these mechano-biological descriptors to muscle mass and strength.
... These findings also extend to exercises whereby the influence of bodyweight loading is minimal. For example, in an interesting proof-of-concept study, comparable improvements in muscle mass (albeit lower strength gains) were evident with RT of the elbow flexors incorporating no external loading (only forceful muscle contraction throughout the range of motion) compared to high-load (70% 1RM) RT [76]. Since access to equipment and facilities presents a significant barrier to engagement with RT [20], these observations highlight the potential benefits of 'exercise snacking' approaches for engagement in resistance exercise compared with traditional approaches. ...
Resistance training (RT) is the only non-pharmacological intervention known to consistently improve, and therefore offset age-related declines in, skeletal muscle mass, strength, and power. RT is also associated with various health benefits that are underappreciated compared with the perceived benefits of aerobic-based exercise. For example, RT participation is associated with reduced all-cause and cancer-related mortality and reduced incidence of cardiovascular disease, hypertension, and symptoms of both anxiety and depression. Despite these benefits, participation in RT remains low, likely due to numerous factors including time constraints, a high-perceived difficulty, and limited access to facilities and equipment. Identification of RT strategies that limit barriers to participation may increase engagement in RT and subsequently improve population health outcomes. Across the lifespan, declines in strength and power occur up to eight times faster than the loss of muscle mass, and are more strongly associated with functional impairments and risks of morbidity and mortality. Strategies to maximise healthspan should therefore arguably focus more on improving or maintaining muscle strength and power than on increasing muscle mass per se. Accumulating evidence suggests that minimal doses of RT, characterised by lower session volumes than in traditional RT guidelines, together with either (1) higher training intensities/loads performed at lower frequencies (i.e. low-volume, high-load RT) or (2) lower training intensities/loads performed at higher frequencies and with minimal-to-no equipment (i.e. resistance ‘exercise snacking’), can improve strength and functional ability in younger and older adults. Such minimal-dose approaches to RT have the potential to minimise various barriers to participation, and may have positive implications for the feasibility and scalability of RT. In addition, brief but frequent minimal-dose RT approaches (i.e. resistance ‘exercise snacking’) may provide additional benefits for interrupting sedentary behaviour patterns associated with increased cardiometabolic risk. Compared to traditional approaches, minimal-dose RT may also limit negative affective responses, such as increased discomfort and lowered enjoyment, both of which are associated with higher training volumes and may negatively influence exercise adherence. A number of practical factors, including the selection of exercises that target major muscle groups and challenge both balance and the stabilising musculature, may influence the effectiveness of minimal-dose RT on outcomes such as improved independence and quality-of-life in older adults. This narrative review aims to summarise the evidence for minimal-dose RT as a strategy for preserving muscle strength and functional ability across the lifespan, and to discuss practical models and considerations for the application of minimal-dose RT approaches.
... Similar conclusions can be drawn from a large sample of males and females using two distinct protocols over a longer training duration to elicit differential growth responses, but resulting in similar strength outcomes [13]. Comparisons of various other training protocols from within [40,41] and outside [42] of our laboratory have observed that similar increases in muscle size do not necessarily translate into similar changes in muscle strength. For example, Mitchell et al. [42] observed that both low-load training and high-load training to volitional failure results in similar hypertrophy; however, the increases in one-repetition maximum are greater following high-load training, a disparity, as shown by Morton et al. [43], to be diminished when allowing the low-load training protocol to perform the strength testing (i.e., practice) more often. ...
Objective
To investigate the role of muscle thickness changes on changes in strength following 6 weeks of unaccustomed resistance training, via retrospective analysis.Methods151 participants completed 6 weeks of no intervention (CONTROL), one-repetition maximum training (1RM-TRAIN), or traditional resistance training (TRAD-TRAIN). Groups were assigned by covariate adaptive randomization. 1RM-TRAIN and TRAD-TRAIN performed elbow flexion exercise on the dominant arm 3 times/week. One-repetition maximum strength and muscle thickness (B-mode ultrasound at 50, 60, and 70% of the anterior upper arm) were assessed pre- and post-training. Direct and indirect effects on strength via each training modality were quantified relative to CONTROL using indicator-coded, change-score mediation analyses for each muscle thickness site. Values are presented as regression coefficients (95% CI).ResultsThe effect of 1RM-TRAIN on muscle thickness was greater than CONTROL for 60% [0.09 (0.01, 0.17) cm] and 70% [0.09 (0.01,0.18) cm] models. All muscle thickness changes for TRAD-TRAIN were greater than CONTROL: 50% [0.24 (0.16, 0.33) cm], 60% [0.25 (0.17, 0.33) cm], 70% [0.23 (0.14, 0.32) cm]. All direct effects on strength were greater for 1RM-TRAIN versus CONTROL: 50% [1.90 (1.21, 2.58) kg], 60% [1.89 (1.19, 2.58) kg], 70% [1.81 (1.12, 2.51) kg]; and TRAD-TRAIN versus CONTROL: 50% [2.04 (1.29, 2.80) kg], 60% [1.98 (1.22, 2.75) kg], 70% [1.79 (1.05, 2.53) kg]. Compared to CONTROL, there was no indication of an effect of 1RM-TRAIN on strength through muscle thickness (i.e., indirect effect) for 50% [− 0.03 (− 0.17, 0.10)], 60% [− 0.01 (− 0.17, 0.17)], or 70% [0.07 (− 0.09, 0.28)] sites, nor of TRAD-TRAIN for 50% [− 0.11 (− 0.48,0.29)], 60% [− 0.04 (− 0.42, 0.40)], and 70% sites [0.17 (− 0.23,0.58)].Conclusion
Training-induced changes in muscle thickness do not appear to appreciably mediate training-induced changes in the strength of untrained individuals during the first 6 weeks of training.
... In this regard, previous studies reported high levels of muscle activation when performing RT with the intention to maximally contract the muscles and no external load (Alves et al., 2020;Gentil et al., 2017a). A previous study reported equivalent gains in arm muscle hypertrophy after traditional and no external load RT in young men and women, using a contralateral training design (Counts et al., 2016). Positive outcomes in terms of hypertrophy and functionality have also been reported in intensive care units patients (Barbalho et al., 2019). ...
The novel coronavirus disease (COVID-19) has emerged at the end of 2019 and caused a global pandemic. The disease predominantly affects the respiratory system; however, there is evidence that it is a multisystem disease that also impacts the cardiovascular system. Although the long-term consequences of COVID-19 are not well-known, evidence from similar diseases alerts for the possibility of long-term impaired physical function and reduced quality of life, especially in those requiring critical care. Therefore, rehabilitation strategies are needed to improve outcomes in COVID-19 survivors. Among the possible strategies, resistance training (RT) might be particularly interesting, since it has been shown to increase functional capacity both in acute and chronic respiratory conditions and in cardiac patients. The present article aims to propose evidence-based and practical suggestions for RT prescription for people who have been diagnosed with COVID-19 with a special focus on immune, respiratory, and cardiovascular systems. Based on the current literature, we present RT as a possible safe and feasible activity that can be time-efficient and easy to be implemented in different settings.
... The WHO recommends 150 min of PE for asymptomatic people, which can be distributed throughout the week, and for those people with comorbidities who do not present symptoms the recommendation is to continue with active habits (40) From a practical standpoint, PE can be performed with numerous possibilities. It is possible to adapt materials, use body weight exercises, elastic bands, exercise with no external loads, calisthenics and others (41)(42)(43)(44)(45)(46)(47)(48)(49). ...
Objective: To evaluate the levels of anxiety, depression, and stress associated with the practice of physical exercise (PE) during pandemic by COVID-19.
Methods: This study has a cross-sectional characteristic and was carried out between May 12 and 14, 2020. An online questionnaire was applied with questions to assess sociodemographic characteristics and physical exercise during the CoVID-19 pandemic, in addition to depression, anxiety, and stress analysis. The study was approved by the local ethics committee (CAAE: 31521720.8.0000.5082).
Results: One thousand one hundred and fifty four answered the questionnaire (69.84% female). During the isolation period, the number of participants who declared not to exercise was 54.16%. Women generaly presented higher levels of anxiety, depression, and stress when compared to men (p < 0.0001 for all domains). The risk of having increased anxiety were 118% higher (OR = 2.183; 95% CI = 1.717–2.775), the risk of depression was 152% higher (OR = 2.525; 95% CI = 1.991–3.205), and the risk of stress symptoms increased 75.1% (OR = 1.751; 95% CI = 1.386–2.213) in the participants who did not perform PE when compared to those who maintain regular PE.
Conclusion: People who was not involved with PE during the COVID-19 pandemic had higher anxiety, depression, and stress scores. Based on this, it seems important to advise people to continue PE, following all the recommendations of preventive measures of the pertinent health organizations.
... Recent findings indicate that hypertrophy-oriented training with a wide range of loads performed to failure elicits similar muscle growth (Counts et al., 2016;Fink, Kikuchi, & Nakazato, 2018;Fink, Kikuchi, Yoshida, 2016;Jenkins et al., 2016;Lasevicius et al., 2019;Morton et al., 2016;. However, when volume load (sets x reps x weight) is equalized, protocols with higher loads may induce greater muscle growth and strength gains than those with lower loads (Holm et al., 2008). ...
Although used by resistance-trained individuals, it is unknown if increasing muscle strength prior to hypertrophy training leads to greater muscle growth and strength gains. We investigated muscle thickness and maximum strength in 26 resistance-trained men who were randomly assigned to either: STHT, consisted in a 3-week strength-oriented training period (4x1-3 repetition maximum [RM]) prior to a 5-week hypertrophy-oriented period (4x8-12RM), or HT, which comprised an 8-week hypertrophy-oriented training period. Vastus lateralis muscle thickness, and back squat and leg-press 1-RM were assessed at pre, third week, and after 8 weeks of training. When pre-to-post changes are compared, STHT induced greater muscle growth (p = 0.049; 95%CI = 0.15-3.2%; d = 0.81) and strength gains in the back squat (p = 0.015; 95%CI = 1.5-13%; d = 1.05) and leg-press 45° (p = 0.044; 95%CI = 0.16-9.9%; d = 0.79) compared to HT. Our results support the use of a period to increase muscle strength prior to an HT to increase muscle thickness and maximum strength in resistance-trained men.
... Several studies have shown that bodyweight-based RT, such as push-ups approaching momentary muscular failure, performed consistently over 4-6 weeks can significantly increase muscle strength [32] and thickness [33,34]. Similarly, other studies have shown that maximal isometric cocontraction, absent any external resistance, can elicit gains in strength and hypertrophy [35][36][37][38]. In terms of the relative amount of RT needed to increase strength, the current U.S. Physical Activity Guidelines acknowledge the fact that "one set... of each exercise is effective" when performed twice per week with significant effort [39]. ...
Background:
Resistance-training (RT) provides significant health benefits. However, roughly 3/4 of adults in the United States do not meet current Physical Activity Guidelines in this regard. There has been a call for research examining the effectiveness of interventions to increase participation in physical activity and to better understand the dose response relationship upon health outcomes. Studies are needed that assess the effectiveness of RT programs that are time-efficient and simple to perform. This fully-powered, randomized controlled study will assess a habit-based RT program consisting of one set of push-ups, angled-rows, and bodyweight-squats performed every weekday for 12-24 weeks in untrained individuals.
Methods:
Forty-60 untrained osteopathic medical students and college/university employees who work in an office setting will be recruited and randomized (1:1) to an intervention or waitlist control group. After 12-week follow-up assessment, the intervention group will continue the program and the control group will initiate the program for 12 weeks. In addition to the equipment and training needed to safely perform the exercises, all participants will receive training in the Tiny Habits® Method (THM) and digital coaching for the duration of the study. Participants will complete weekly assessments regarding the program during their initial 12-week intervention phase. The primary outcome is the change from baseline to 12 weeks in the intervention group versus the control group, in the combined number of repetitions performed in one set of each of the three exercises (composite repetitions) under a standardized protocol. Secondary outcomes include adherence to and satisfaction with the program, and change from baseline to 12- and 24-week follow-up in blood pressure, fasting lipid panel, hemoglobin A1c, body mass index, anthropometry, body composition, mid-thigh muscle thickness, and habit strength.
Discussion:
This study will evaluate a simple, habit-based RT intervention in untrained individuals. The approach is unique in that it utilizes brief but frequent bodyweight exercises and, via the THM, focuses on consistency and habit formation first, with effort being increased as participants are motivated and able. If effective, the program can be easily scaled for wider adoption.
Trial registration:
This study was prospectively registered at ClinicalTrials.gov, identifier NCT04207567 , on December 23rd, 2019.
... While typically assessed in response to resistance exercise, experimental studies have used the acute muscular response elicited by various protocols to make inferences about long-term adaptations Counts et al., 2016;Dankel et al., 2017;. ...
Purpose
To compare the acute effects of passive movement combined with blood flow restriction (PM+BFR) to passive movement (PM) or blood flow restriction alone (BFR).
Methods
20 healthy participants completed: time control (TC), PM, BFR, and PM+BFR (one per leg, over 2 days; randomized). For PM, a dynamometer moved the leg through 3 sets of 15 knee extensions/flexions (90° at 45°/second). For BFR, a cuff was inflated to 80% arterial occlusion pressure on the upper leg. Measurements consisted of: anterior muscle thickness at 60% and 70% of the upper leg before and after (‐0, ‐5, and ‐10 minutes) conditions, ratings of perceived effort and discomfort before conditions and after each set, and of the vastus lateralis during conditions. Data, presented as mean (SD), were compared using Bayesian RMANOVA, except for perceived effort and discomfort, which were compared using a Friedman’s Test (non‐parametric).
Results
60% [∆cm before‐after‐0: TC=0.04 (0.09), PM=‐0.01 (0.15), BFR=0.00 (0.11), PM+BFR=0.01 (0.22)] and 70% [∆cm before‐after‐0: TC=0.01 (0.09), PM=‐0.01 (0.15), BFR=0.02 (0.11), PM+BFR=‐0.03 (0.22)] muscle thickness did not change. Perceived effort was greater than TC following PM (p=0.05) and PM+BFR (p=.001). Perceived discomfort was greater following BFR and PM+BFR compared to TC (all p≤0.002) and PM (all p≤0.010). Changes in deoxygenation [e.g. channel 1; ∆μM start set 1‐end set 3: TC=0.9 (1.2), PM=‐1.2 (1.9), BFR=10.3 (2.7), PM+BFR=10.3 (3.0)] were generally greater with BFR and PM+BFR (BFinclusion=1.210e+13).
Conclusion
Acute muscular responses to PM+BFR are not augmented over the effect of BFR alone.
... Juneau and Tafur highlight that loads may have a lower threshold where decreasing %1RM further results in inferior hypertrophy compared to higher loads. Although we reference examples [4,5] of hypertrophy with very low or even no load training with high effort, we acknowledge that lower loads may result in less hypertrophy, but do result in hypertrophy nonetheless. As stated in our paper, ' . . . ...
... This being said, early work has suggested that adaptations to contractile kinetics may differ between isometric and concentric resistance training (Duchateau and Hainaut, 1984) and so perhaps a combination of the two may be best. Other examinations of "no load" resistance training have been reported showing that dynamic movement coupled with maximal voluntary effort to activate the muscle involved produces high electromyographical activity independent of training status, limb dominance, movement velocity, or the use of visual feedback , and such training has been shown to produce similar increases in muscle size and strength compared to traditional dynamic free weight training (Counts et al., 2016). In addition, there are more simple approaches to providing external resistance for dynamic resistance training compared to those primarily used in current μG environments. ...
Prolonged periods in microgravity (μG) environments result in deconditioning of numerous physiological systems, particularly muscle at molecular, single fiber, and whole muscle levels. This deconditioning leads to loss of strength and cardiorespiratory fitness. Loading muscle produces mechanical tension with resultant mechanotransduction initiating molecular signaling that stimulates adaptations in muscle. Exercise can reverse deconditioning resultant from phases of detraining, de-loading, or immobilization. On Earth, applications of loading using exercise models are common, as well as in μG settings as countermeasures to deconditioning. The primary modalities include, but are not limited to, aerobic training (or “cardio”) and resistance training, and have historically been dichotomized; the former primarily thought to improve cardiorespiratory fitness, and the latter primarily improving strength and muscle size. However, recent work questions this dichotomy, suggesting adaptations to loading through exercise are affected by intensity of effort independent of modality. Furthermore, similar adaptations may occur where sufficient intensity of effort is used. Traditional countermeasures for μG-induced deconditioning have focused upon engineering-based solutions to enable application of traditional models of exercise. Yet, contemporary developments in understanding of the applications, and subsequent adaptations, to exercise induced muscular loading in terrestrial settings have advanced such in recent years that it may be appropriate to revisit the evidence to inform how exercise can used in μG. With the planned decommissioning of the International Space Station as early as 2024 and future goals of manned moon and Mars missions, efficiency of resources must be prioritized. Engineering-based solutions to apply exercise modalities inevitably present issues relating to devices mass, size, energy use, heat production, and ultimately cost. It is necessary to identify exercise countermeasures to combat deconditioning while limiting these issues. As such, this brief narrative review considers recent developments in our understanding of skeletal muscle adaptation to loading through exercise from studies conducted in terrestrial settings, and their applications in μG environments. We consider the role of intensity of effort, comparisons of exercise modalities, the need for concurrent exercise approaches, and other issues often not considered in terrestrial exercise studies but are of concern in μG environments (i.e., O2 consumption, CO2 production, and energy costs of exercise).
... O crescimento muscular pode ocorrer sem o uso necessariamente de uma carga externa, levando-se em consideração o argumento que altos níveis de ativação muscular produzida a partir de contrações repetidas, podem fornecer estimulação suficiente das vias hipertróficas do músculo esquelético, sem que haja obrigatoriamente a aplicação de uma carga elevada ( Counts et al., 2016). (2016), destacando que o treinamento de carga baixa a moderada é mais adequada para objetivos relacionados à hipertrofia, quando um número igual de séries é realizado entre os grupamentos musculares. ...
Introdução: Vem sendo cada vez mais comum, pessoas recorrerem às salas de musculação com o intuito de estarem atingindo objetivos relacionados tanto a saúde quanto a estética, onde por sua vez, a hipertrofia destaca-se como objetivo mais almejado. Objetivo: analisar, através de uma revisão integrativa, a eficácia de diferentes métodos de treinamento resistido na hipertrofia muscular. Métodos: Trata-se de um estudo de revisão integrativa da literatura realizada nas bases de dados MedLine via
PubMed; Lílacs via BVS e Web of Science. Resultados: Foram analisados 18 estudos, que atenderam aos critérios de inclusão estabelecidos, todos tendo como amostra seres humanos de ambos os sexos, especificando em suas metodologias, diferentes métodos
de treinamento resistido voltados à hipertrofia muscular. Dentre os resultados alcançados o mais relevante foi o de que o método de treinamento resistido com baixa carga vem a ser um dos mais eficazes para gerar hipertrofia, levando em consideração o aperfeiçoamento de execução da técnica, biomecânica, bem como o volume e intensidade do treinamento. Conclusão: os diferentes métodos de treinamento aqui analisados são eficazes para gerar hipertrofia muscular esquelética, já que estará fornecendo estimulação suficiente das vias hipertróficas (neuromusculares e
fisiológicas) nos diferentes agrupamentos musculares.
Motoneuronal persistent inward currents (PICs) are both facilitated by neuromodulatory inputs and highly sensitive to local inhibitory circuits (e.g., Ia reciprocal inhibition). Methods aimed to increase group Ia reciprocal inhibition from the antagonistic muscle have been successful in decreasing PICs, and the diffuse actions of neuromodulators released during activation of remote muscles have increased PICs. However, it remains unknown how motoneurons function in the presence of simultaneous excitatory and inhibitory commands. To probe this topic, we investigated motor unit (MU) discharge patterns and estimated PICs during voluntary co-contraction of ankle muscles, which simultaneously demands the contraction of agonist-antagonist pairs. Twenty young adults randomly performed triangular ramps (10s up and down) of both co-contraction (simultaneous dorsiflexion and plantarflexion) and isometric dorsiflexion to a peak of 30% of their maximum muscle activity from a maximal voluntary contraction. Motor unit spike trains were decomposed from high-density surface electromyography recorded over the tibialis anterior (TA) using blind source separation algorithms. Voluntary co-contraction altered motor unit discharge rate characteristics, decreasing estimates of PICs by 20% (4.47 pulses per second (pps) vs 5.57 pps during isometric dorsiflexion). These findings suggest that, during voluntary co-contraction, the inhibitory input from the antagonist muscle overcomes the additional excitatory and neuromodulatory drive that may occur due to the co-contraction of the antagonist muscle, which constrains PIC behavior.
KEY POINTS
Voluntary co-contraction is a unique motor behavior that concurrently provides increases in excitatory and inhibitory inputs to motoneurons.
During co-contraction of agonist-antagonist pairs, agonist motor unit discharge characteristics are altered, consistent with reductions in persistent inward current magnitude.
Reciprocal inhibition from the antagonist likely becomes proportional to the increase in neural drive to the agonist, dampening the magnitude of persistent inward currents.
In recent years, electrical muscle stimulation (EMS) devices have been developed as a complementary training technique that is novel, attractive, and time-saving for physical fitness and rehabilitation. While it is known that EMS training can improve muscle mass and strength, most studies have focused on the elderly or specific patient populations. The aim of this study was to investigate the effects of frequency-specific EMS combined with resistance exercise training for 8 weeks on muscle mass, strength, power, body composition, and parameters related to exercise fatigue. Additionally, we aimed to evaluate the feasibility and safety of EMS as an exercise aid to improve body composition. We recruited 14 male and 14 female subjects who were randomly assigned to two groups with gender parity (seven male and seven female/group): (1) no EMS group (age: 21.6 ± 1.7; height: 168.8 ± 11.8 cm; weight: 64.2 ± 14.4 kg) and (2) daily EMS group (age: 21.8 ± 2.0; height: 167.8 ± 9.9 cm; weight: 68.5 ± 15.5 kg). The two groups of subjects were very similar with no significant difference. Blood biochemical routine analysis was performed every 4 weeks from pre-intervention to post-intervention, and body composition, muscle strength, and explosive power were evaluated 8 weeks before and after the intervention. We also performed an exercise challenge analysis of fatigue biochemical indicators after 8 weeks of intervention. Our results showed that resistance exercise training combined with daily EMS significantly improved muscle mass ( p = 0.002) and strength (left, p = 0.007; right, p = 0.002) and significantly reduced body fat ( p < 0.001) than the no EMS group. However, there was no significant advantage for biochemical parameters of fatigue and lower body power. In summary, our study demonstrates that 8 weeks of continuous resistance training combined with daily upper body, lower body, and abdominal EMS training can significantly improve muscle mass and upper body muscle strength performance, as well as significantly reduce body fat percentage in healthy subjects.
The purpose of this study was to determine if muscle growth mediates increases in a strength task which was not directly trained. One hundred fifty‐one participants were randomized into control, one‐repetition maximum training (1RM‐TRAIN), or traditional training (TRAD‐TRAIN). Training groups performed isotonic elbow flexion 3x/week for six weeks. Anterior muscle thickness at 50, 60, and 70% upper arm length, and maximal isokinetic torque at 60°/sec were assessed pre‐ and post‐training. Change‐score mediation models (adjusted for sex, pre‐muscle thickness, and pre‐strength) were constructed for each muscle thickness site. The effects of each training group were evaluated relative to the control. Data is presented as coefficient (95% CI). There were no significant relative direct effects on non‐specific strength for either training group outside of the 60% model [1.7 (0.13, 3.27) Nm]. The relative effect of 1RM‐TRAIN on muscle thickness was greater in 60% [0.09 (0.01, 0.17) cm] and 70% [0.09 (0.00,0.17) cm] models; while TRAD‐TRAIN was greater in all three: [50% = 0.24 (0.15, 0.32); 60% = 0.24 (0.16, 0.33); 70% = 0.22 (0.14, 0.31) cm]. The effect of muscle thickness on non‐specific strength was only significant for the 60% [‐3.06 (‐5.7, ‐0.35) Nm] model. The relative indirect effect on non‐specific strength was not significant for the 1RM‐TRAIN or TRAD‐TRAIN. Similar to previous findings on specific strength, we did not find evidence for a mediating effect of muscle growth on training induced increases in non‐specific strength. The importance of muscle growth for changes in non‐specifically trained strength may need to be reconsidered. This article is protected by copyright. All rights reserved.
Purpose:
The purpose of this study was to examine the changes in muscle size and strength throughout the menstrual cycle in females and to compare these values to a control group of time-matched males.
Methods:
12 males and 16 females visited the laboratory on four occasions. Measures of muscle thickness (MTH), isometric strength and body water were taken during the menstrual phase, ovulation phase and luteal phase of the menstrual cycle. Males scheduled their visits based on a mock menstrual cycle. In addition, participants were asked to complete 4 sets of biceps curls to volitional failure in one arm to examine swelling during each visit.
Results:
For MTH there was no interaction (p = .73); however, there was a main effect for sex with males having higher MTH values compared to females [4.07 (0.67) versus. 2.73 (0.42) cm, (p < .001)] at all time points. For changes in MTH (swelling) there was no interaction (p = .28). However, there was a main effect for sex, with males demonstrating greater changes in MTH compared to females [0.53(0.11) versus. 0.40 (0.10) cm, (p < .001)]. Similarly, for total body water, there was no interaction (p = .66). However, males had greater total body water compared to females [49.6 (6.8) versus. 32.3(3.9) kg, p < .001)] at all time points. Finally, for isometric strength, there was no interaction (p = .23). However, there was a main effect for sex. Males had higher isometric strength values compared to females [285 (42) versus. 156(36) N (p < .001)].
Conclusions:
Phase of the menstrual cycle does not appear to influence MTH, isometric strength or total body water.
Franco, CMdC, Carneiro, MAdS, Alves, LTH, Jú nior, GNdO, de Sousa, JdFR, and Orsatti, FL. Lower-load is more effective than higher-load resistance training in increasing muscle mass in young women. J Strength Cond Res XX(X): 000-000, 2019-This study was designed to investigate the impact of load (higher vs. lower) performed until or close to volitional fatigue on muscle strength (MS) and fat and bone-free lean mass (FBFM) in young women. To do this, 32 women performed resistance training (RT) in 1 of 2 conditions: lower-load RT (LL; n = 14, age = 24.3 6 4.8 years and body mass index [BMI] = 23.3 6 2.8 kgm 22). Leg FBFM (DXA) and MS (1 repetition maximum-unilateral leg extension [LE]) were evaluated before and after 9 weeks (the first week was used for familiarization) of RT. Both groups performed 3 unilateral exercises (LE, leg curl, and leg press), 3 sets per exercise, 60-90 seconds of rest between sets, 2 days per week. In the LL group, the loads used in the exercises were the loads necessary to perform 30-35 repetitions in the first set. For the HL group, the loads used were the loads necessary to perform 8-10 repetitions in the first set. The LL group showed higher RT volume than the HL. Both groups showed leg muscle mass gains (p , 0.05). However, the LL group was better [p = 0.032 and effect size (eta 2 = 0.14 [large]) than the HL group in leg FBFM gains (LL = 0.3 kg [IC 95%: 0.4 kg; 0.2 kg] and HL = 0.1 kg [IC 95%: 0.2 kg; 0.0 kg]). Both groups showed MS gains, without any difference between them (LL = 3.4 kg [IC 95%: 4.4 kg; 2.5 kg] and HL = 4.2 kg [IC 95%: 5.1 kg; 3.3 kg]; p = 0.239). Thus, lower-load RT is more effective than higher-load RT in increasing FBFM, but not MS in novice young women.
Low-load exercise performed to or near task failure appears to result in similar skeletal muscle adaptations as low-load exercise with the addition of blood flow restriction (BFR). However, there may be a point where the training load becomes too low to stimulate an anabolic response without BFR. This study examined skeletal muscle adaptions to very low-load resistance exercise with and without BFR. Changes in muscle thickness (MTH), strength, and endurance were examined following 8-weeks of training with a traditional high-load [70% 1RM,(7000)], low-load [15% 1RM,(1500)], low-load with moderate BFR [15%1RM + 40%BFR(1540)], or low-load with greater BFR [15% 1RM + 80%BFR(1580)]. 1RM strength changes were greater in the 7000 condition [2.09 (95% CI = 1.35-2.83) kg] compared to all low-load conditions. For isometric and isokinetic strength, there were no changes. For endurance, there was a main effect for time [mean pre to post change = 7.9 (4.3–11.6) repetitions]. At the 50% site, the mean change in MTH in the 7000 condition [0.16 (0.10-0.22) cm] was greater than all low-load conditions. For the 60% site, the mean change in MTH [0.15 (0.08-0.22)] was greater than all low-load conditions. For the 70% site there was a main effect for time [mean pre to post change = 0.09 (0.05–0.14 cm]. All groups increased muscle size; however, this response was less in all very low training conditions compared to high-load training. 1RM strength increased in the 7000 condition only, with no other changes in strength observed.
Skeletal muscle hypertrophy commonly occurs with repeated bouts of resistance exercise as well as following the administration of exogenous drugs. This increase in muscle size is thought to be mechanistically important for the increase in muscle function. However, at present, there is no experimental evidence that would support any paradigm in which muscle hypertrophy is a mechanism for increasing strength with exercise. Therefore, it seems reasonable to also question the importance of changes in muscle size for changes in muscle strength (function) following exogenous drugs as well as aging, where both muscle size and strength decrease. The purpose of this paper is to discuss whether changes in muscle size contribute to changes in voluntary strength following exercise, pharmaceutical interventions, and aging. We also aim to provide potential mechanisms (central and peripheral) for the change in strength as well as outline study designs to better address this question. Herein, we suggest that there are dissociations between changes in muscle size and strength following exercise, anabolic drug administration, and aging (to a point). These dissociations occur throughout the literature, suggesting that these changes may be completely separate phenomena. We are not dismissing the potential importance of maintaining muscle mass, particularly in clinical populations. What we are suggesting, however, is that muscle function may not necessarily be improved by these exercise or pharmacological induced increases in muscle size. Exploring mechanisms and explanations beyond just changes in muscle size may improve therapy targeted at improving muscle function.
Blood flow restriction (BFR) training has been shown to increase muscle size and strength when combined with low-load [20-30 % one-repetition maximum (1RM)] resistance training in the lower body. Fewer studies have examined low-load BFR training in combination with upper body exercise, which may differ as some musculature cannot be directly restricted by the BFR stimulus (chest, shoulders). The objective of this study was to examine muscle adaptations occurring in the upper body in response to low-load BFR training. Google Scholar, PubMed, and SPORTDiscus were searched through July 2015 using the key phrases 'blood flow restriction training', 'occlusion resistance training', and 'KAATSU'. Upper body training studies implementing the BFR stimulus and providing a pre and post measure of muscle size and/or strength were included. A total of 19 articles met the inclusion criteria for this review. The effectiveness of low-load BFR training appears to be minimally impacted by alterations to the intensity and restrictive pressures used; however, the ability to quantitatively analyze our results was limited by unstandardized protocols. Low-load BFR training increased muscle size and strength in limbs located proximal (chest, shoulders) and distal (biceps, triceps) to the restrictive stimulus; while volume-matched exercise in the absence of BFR did not elicit beneficial muscle adaptations. Some of the musculature in the upper body cannot be directly restricted by the application of BFR. Despite this, increases in muscle size and strength were observed in muscles placed under direct and indirect BFR.
This study investigated the hypertrophic potential of load-matched blood-flow restricted resistance training (BFR) vs free-flow traditional resistance training (low-load TRT) performed to fatigue. Ten healthy young subjects performed unilateral BFR and contralateral low-load TRT elbow flexor dumbbell curl with 40% of one repetition maximum until volitional concentric failure 3 days per week for 6 weeks. Prior to and at 3 (post-3) and 10 (post-10) days post-training, magnetic resonance imaging (MRI) was used to estimate elbow flexor muscle volume and muscle water content accumulation through training. Acute changes in muscle thickness following an early vs a late exercise bout were measured with ultrasound to determine muscle swelling during the immediate 0-48 h post-exercise. Total work was threefold lower for BFR compared with low-load TRT (P < 0.001). Both BRF and low-load TRT increased muscle volume by approximately 12% at post-3 and post-10 (P < 0.01) with no changes in MRI-determined water content. Training increased muscle thickness during the immediate 48 h post-exercise (P < 0.001) and to greater extent with BRF (P < 0.05) in the early training phase. In conclusion, BFR and low-load TRT, when performed to fatigue, produce equal muscle hypertrophy, which may partly rely on transient exercise-induced increases in muscle water content.
© 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.
The present study examined neuromuscular adaptations following 12-week maximal voluntary co-contraction training.
Sixteen young men were allocated to training (TG, n = 9) or control (CG, n = 7) group. TG conducted a training program (3 days/week), which consisted of 4-s maximal voluntary contractions of elbow flexors and extensors by simultaneously contracting both muscle groups at 90° of the elbow joint, followed by 4-s muscle relaxation (10 repetitions/set, 5 sets/day) for 12 weeks. In addition to the muscle thicknesses of elbow flexors and extensors, the torque and electromyograms (EMGs) of the two muscle groups during isometric maximal voluntary contraction (MVC) were determined before (Pre), after 4 weeks, and 12 weeks of intervention.
After intervention, CG showed no significant changes in all measured variables. In TG, MVC torque significantly increased in both elbow flexors (+13 % at 4 weeks and +15 % at 12 weeks) and extensors (+27 % at 4 weeks and +46 % at 12 weeks) from Pre. Muscle thickness also significantly increased in both elbow flexors (+4 %) and extensors (+4 %) at 12 weeks. Agonist EMG activities during MVC significantly increased in both elbow flexors (+31 % at 4 weeks and +44 % at 12 weeks) and extensors (+27 % at 4 weeks and +40 % at 12 weeks), without changes in antagonist involuntary coactivation level in both muscle groups.
These results indicate that maximal voluntary co-contraction is applicable as a training modality for increasing the size and strength of antagonistic muscle pairs without increasing involuntary coactivation level.
The purpose of this study was to determine whether the training responses observed with low-load resistance exercise to volitional fatigue translates into significant muscle hypertrophy, and compare that response to high-load resistance training. Nine previously untrained men (aged 25 [SD 3] years at the beginning of the study, standing height 1.73 [SD 0.07] m, body mass 68.9 [SD 8.1] kg) completed 6-week of high load-resistance training (HL-RT) (75% of one repetition maximal [1RM], 3-sets, 3x/wk) followed by 12 months of detraining. Following this, subjects completed 6 weeks of low load-resistance training (LL-RT) to volitional fatigue (30% 1 RM, 4 sets, 3x/wk). Increases (p < 0.05) in magnetic resonance imaging-measured triceps brachii and pectorals major muscle cross-sectional areas were similar for both HL-RT (11.9% and 17.6%, respectively) and LL-RT (9.8% and 21.1%, respectively). In addition, both groups increased (p < 0.05) 1RM and maximal elbow extension strength following training; however, the percent increases in 1RM (8.6% vs. 21.0%) and elbow extension strength (6.5% vs. 13.9%) were significantly (p < 0.05) lower with LL-RT. Both protocols elicited similar increases in muscle cross-sectional area, however differences were observed in strength. An explanation of the smaller relative increases in strength may be due to the fact that detraining after HL-RT did not cause strength values to return to baseline levels thereby producing smaller changes in strength. In addition, the results may also suggest that the consistent practice of lifting a heavy load is necessary to maximize gains in muscular strength of the trained movement. These results demonstrate that significant muscle hypertrophy can occur without high-load resistance training and suggests that the focus on percentage of external load as the important deciding factor on muscle hypertrophy is too simplistic and inappropriate.
We investigated the acute and chronic effects of low-intensity concentric or eccentric resistance training with blood flow restriction (BFR) on muscle size and strength. Ten young men performed 30% of concentric one repetition maximal dumbbell curl exercise (four sets, total 75 reps) 3 days/week for 6 weeks. One arm was randomly chosen for concentric BFR (CON-BFR) exercise only and the other arm performed eccentric BFR (ECC-BFR) exercise only at the same exercise load. During the exercise session, iEMG for biceps brachii muscles increased progressively during CON-BFR, which was greater (p<0.05) than that of the ECC-BFR. Immediately after the exercise, muscle thickness (MTH) of the elbow flexors acutely increased (p<0.01) with both CON-BFR and ECC-BFR, but was greater with CON-BFR (11.7%) (p<0.01) than ECC-BFR (3.9%) at 10-cm above the elbow joint. Following 6-weeks of training, MRI-measured muscle cross-sectional area (CSA) at 10-cm position and mid-upper arm (12.0% and 10.6%, respectively) as well as muscle volume (12.5%) of the elbow flexors were increased (p<0.01) with CON-BFR. Increases in muscle CSA and volume were lower in ECC-BFR (5.1%, 0.8% and 2.9%, respectively) than in the CON-BFR and only muscle CSA at 10-cm position increased significantly (p<0.05) after the training. Maximal voluntary isometric strength of elbow flexors was increased (p<0.05) in CON-BFR (8.6%), but not in ECC (3.8%). These results suggest that CON-BFR training leads to pronounced acute changes in muscle size, an index of muscle cell swelling, the response to which may be an important factor for promoting muscle hypertrophy with BFR resistance training.
The primary objective of this investigation was to quantitatively identify which training variables result in the greatest strength and hypertrophy outcomes with lower body low intensity training with blood flow restriction (LI-BFR). Searches were performed for published studies with certain criteria. First, the primary focus of the study must have compared the effects of low intensity endurance or resistance training alone to low intensity exercise with some form of blood flow restriction. Second, subject populations had to have similar baseline characteristics so that valid outcome measures could be made. Finally, outcome measures had to include at least one measure of muscle hypertrophy. All studies included in the analysis utilized MRI except for two which reported changes via ultrasound. The mean overall effect size (ES) for muscle strength for LI-BFR was 0.58 [95% CI: 0.40, 0.76], and 0.00 [95% CI: -0.18, 0.17] for low intensity training. The mean overall ES for muscle hypertrophy for LI-BFR training was 0.39 [95% CI: 0.35, 0.43], and -0.01 [95% CI: -0.05, 0.03] for low intensity training. Blood flow restriction resulted in significantly greater gains in strength and hypertrophy when performed with resistance training than with walking. In addition, performing LI-BFR 2-3 days per week resulted in the greatest ES compared to 4-5 days per week. Significant correlations were found between ES for strength development and weeks of duration, but not for muscle hypertrophy. This meta-analysis provides insight into the impact of different variables on muscular strength and hypertrophy to LI-BFR training.
We investigated the combined effect of low-intensity blood flow restriction and high-intensity resistance training on muscle adaptation. Forty young men (aged 22-32 years) were randomly divided into four groups of ten subjects each: high-intensity resistance training (HI-RT, 75% of one repetition maximum [1-RM]), low-intensity resistance training with blood flow restriction (LI-BFR, 30% 1-RM), combined HI-RT and LI-BFR (CB-RT, twice-weekly LI-BFR and once-weekly HI-RT), and nontraining control (CON). Three training groups performed bench press exercises 3 days/week for 6 weeks. During LI-BFR training sessions, subjects wore pressure cuffs on both arms that were inflated to 100-160 mmHg. Increases in 1-RM were similar in the HI-RT (19.9%) and CB-RT (15.3%) groups and lower in the LI-BFR group (8.7%, p < 0.05). Maximal isometric elbow extension (MVC) increased in the HI-RT (11.3%) and CB-RT (6.6%) groups; there was no change in the LI-BFR group (-0.2%). The cross-sectional area (CSA) of the triceps brachii (TB) increased (p < 0.05) in the HI-RT (8.6%), CB-RT (7.2%), and LI-BFR (4.4%) groups. The change in relative isometric strength (MVC divided by TB CSA) was greater (p < 0.05) in the HI-RT group (3.3%) than in the LI-BFR (-3.5%) and CON (-0.1%) groups. Following training, relative dynamic strength (1-RM divided by TB CSA) was increased (p < 0.05) by 10.5% in the HI-RT group and 6.7% in the CB-RT group. None of the variables in the CON group changed. Our results show that low-intensity resistance training with BFR-induced functional muscle adaptations is improved by combining it with HI-RT.
Muscle-fiber pennation angles were measured in vivo with the use of ultrasonography to investigate the relationship between fiber pennation and muscle size for 32 male subjects (from untrained subjects to highly trained bodybuilders). From the image of a B-mode ultrasonogram, fiber pennation angles and thickness of triceps brachii were determined, the former as angles between echoes from the interspaces of fascicles and from the aponeurosis of long and medial heads of triceps and the latter as the distance between the fat-muscle and muscle-bone interfaces. The pennation angles were in the range of 15 and 53 degrees for the long head and 9 to 26 degrees for the medial head, which were similar to or greater than the published and the present data on human cadavers. Significant differences were observed between normal subjects and bodybuilders in muscle thickness and pennation angles (P < 0.01), and there were significant correlations between muscle thickness and pennation angles for both long (r = 0.884) and medial (r = 0.833) heads of triceps, suggesting that muscle hypertrophy involves an increase in fiber pennation angles.
This study assessed variability in muscle size and strength changes in a large cohort of men and women after a unilateral resistance training program in the elbow flexors. A secondary purpose was to assess sex differences in size and strength changes after training.
Five hundred eighty-five subjects (342 women, 243 men) were tested at one of eight study centers. Isometric (MVC) and dynamic strength (one-repetition maximum (1RM)) of the elbow flexor muscles of each arm and magnetic resonance imaging (MRI) of the biceps brachii (to determine cross-sectional area (CSA)) were assessed before and after 12 wk of progressive dynamic resistance training of the nondominant arm.
Size changes ranged from -2 to +59% (-0.4 to +13.6 cm), 1RM strength gains ranged from 0 to +250% (0 to +10.2 kg), and MVC changes ranged from -32 to +149% (-15.9 to +52.6 kg). Coefficients of variation were 0.48 and 0.51 for changes in CSA (P = 0.44), 1.07 and 0.89 for changes in MVC (P < 0.01), and 0.55 and 0.59 for changes in CSA (P < 0.01) in men and women, respectively. Men experienced 2.5% greater gains for CSA (P < 0.01) compared with women. Despite greater absolute gains in men, relative increases in strength measures were greater in women versus men (P < 0.05).
Men and women exhibit wide ranges of response to resistance training, with some subjects showing little to no gain, and others showing profound changes, increasing size by over 10 cm and doubling their strength. Men had only a slight advantage in relative size gains compared with women, whereas women outpaced men considerably in relative gains in strength.
The aim of the present study was to compare the changes in voluntary strength (isometric, concentric, and eccentric) and functional mobility in response to maximal isokinetic eccentric-only resistance training to those elicited by maximal isometric-only or maximal isokinetic concentric-only resistance training in older adults.
Twelve women (73 +/- 7 years) and 18 men (73 +/- 5 years) completed a 12-week training program (three times per week) using a Biodex System 3 dynamometer. Primary outcome measures included peak isometric and isokinetic (concentric and eccentric) knee extensor strength, concentric work, concentric power, stair ascent and descent, and gait speed. Participants were randomly assigned to one of three training groups: isometric-only, isokinetic concentric-only, or isokinetic eccentric-only.
All three training groups demonstrated an increase in peak isometric and isokinetic concentric and eccentric strength following 12 weeks of training (p <.01). Step time was positively influenced (p <.03) by all three training modes; however, gait speed was unchanged following 12 weeks of training. All three training groups experienced a significant increase in peak concentric work and concentric power (p <.01) with the concentric training group demonstrating the largest increases in both peak concentric work and concentric power when compared to the isometric and eccentric training groups.
It was clear that all three resistance training programs (isometric, concentric, and eccentric) in older adults were effective in increasing strength, concentric work, and concentric power over the 12-week training period. Furthermore, 12 weeks of resistance training resulted in improved stair ascent and descent performance.
The study compared changes in intramuscular and surface recordings of EMG amplitude with ultrasound measures of muscle architecture of the elbow flexors during a submaximal isometric contraction. Ten subjects performed a fatiguing contraction to task failure at 20% of maximal voluntary contraction force. EMG activity was recorded in biceps brachii, brachialis, and brachioradialis muscles using intramuscular and surface electrodes. The rates of increase in the amplitude of the surface EMG for the long and short heads of biceps brachii and brachioradialis were greater than those for the intramuscular recordings measured at different depths. The amplitude of the intramuscular recordings from three muscles increased at a similar rate (P = 0.13), as did the amplitude of the three surface recordings from two muscles (P = 0.83). The increases in brachialis thickness (27.7 +/- 5.7 to 30.9 +/- 3.5 mm; P < 0.05) and pennation angle (10.9 +/- 3.5 to 16.5 +/- 4.8 degrees ; P = 0.003) were not associated with the increase in intramuscular EMG amplitude (P > 0.58). The increase in brachioradialis thickness (22.8 +/- 4.8 to 25.5 +/- 3.4 mm; P = 0.0075) was associated with the increase in the amplitude for one of two intramuscular EMG signals (P = 0.007, r = 0.79). The time to failure was more strongly associated with the rate of increase in the amplitude of the surface EMG than that for the intramuscular EMG, which suggests that the surface measurement provides a more appropriate measure of the change in muscle activation during a fatiguing contraction.
We reported, using a unilateral resistance training (RT) model, that training with high or low loads (mass per repetition) resulted in similar muscle hypertrophy and strength improvements in RT-naïve subjects. Here we aimed to determine whether the same was true in men with previous RT experience using a whole-body RT program and whether post-exercise systemic hormone concentrations were related to changes in hypertrophy and strength. Forty-nine resistance-trained men (mean ± SEM, 23 ± 1 y) performed 12 wk of whole-body RT. Subjects were randomly allocated into a higher-repetition (HR) group who lifted loads of ~30-50% of their maximal strength (1RM) for 20-25 repetitions/set (n=24) or a lower-repetition (LR) group (~75-90% 1RM, 8-12 repetitions/set, n=25), with all sets being performed to volitional failure. Skeletal muscle biopsies, strength testing, DXA scans, and acute changes in systemic hormone concentrations were examined pre- and post-training. In response to RT, 1RM strength increased for all exercises in both groups (p < 0.01), with only the change in bench press being significantly different between groups (HR: 9 ± 1 vs. LR: 14 ±1 kg, p = 0.012). Fat- and bone-free (lean) body mass, type I and type II muscle fibre cross sectional area increased following training (p < 0.01) with no significant differences between groups. No significant correlations between the acute post-exercise rise in any purported anabolic hormone and the change in strength or hypertrophy were found. In congruence with our previous work, acute post-exercise systemic hormonal rises are not related to or in any way indicative of RT-mediated gains in muscle mass or strength. Our data show that in resistance-trained individuals load, when exercises are performed to volitional failure, does not dictate hypertrophy or, for the most part, strength gains.
To investigate the acute and chronic skeletal muscle response to differing levels of blood flow restriction (BFR) pressure.
Fourteen participants completed elbow flexion exercise with pressures from 40% to 90% of arterial occlusion. Pre/Post torque measurements and EMG amplitude of each set were quantified for each condition. This was followed by a separate 8 week training study of the effect of high (90% arterial occlusion) and low (40% arterial occlusion) pressure on muscle size and function.
For the acute study, decreases in torque were similar between pressures [-15.5 (5.9) Nm P=0.344]. For amplitude of the first 3 and last 3 reps there was a time effect. Following training, increases in muscle size (10%), peak isotonic strength (18%), peak isokinetic torque (180 degrees/sec=23%, 60 degrees/sec=11%), and muscular endurance (62%) changed similarly between pressures.
We suggest that higher relative pressures may not be necessary when exercising under BFR. This article is protected by copyright. All rights reserved.
© 2015 Wiley Periodicals, Inc.
IntroductionAn unresolved question in resistance training combined with blood flow restriction (BFR) is what percentage of estimated arterial occlusion pressure provides the most robust acute muscular response.Methods
Forty participants were assigned to Experiments 1, 2, or 3. Each experiment completed exercise protocols differing by pressure, exercise load, and/or volume. Torque was measured pre- and postexercise, and muscle activation was measured pre- and during each set.ResultsPressure and load did not affect torque greatly. Muscle activation increased in all conditions (P < 0.05) and was higher with 30% 1RM compared with 20% 1RM. Pressure appeared to increase muscle activation from 40% to 50% arterial occlusion [66% vs. 87% maximal voluntary contraction (30% 1RM)] but was not further increased with higher pressure.Conclusion
Different levels of BFR may alter the acute muscular response to a degree, although higher pressures do not appear to augment these changes. Muscle Nerve 51:713-721, 2015
SUMMARY In order to stimulate further adaptation toward specific training goals, progressive resistance training (RT) protocols are necessary. The optimal characteristics of strength-specific programs include the use of concentric (CON), eccentric (ECC), and isometric muscle actions and the performance of bilateral and unilateral single- and multiple-joint exercises. In addition, it is recommended that strength programs sequence exercises to optimize the preservation of exercise intensity (large before small muscle group exercises, multiple-joint exercises before single-joint exercises, and higher-intensity before lower-intensity exercises). For novice (untrained individuals with no RT experience or who have not trained for several years) training, it is recommended that loads correspond to a repetition range of an 8-12 repetition maximum (RM). For intermediate (individuals with approximately 6 months of consistent RT experience) to advanced (individuals with years of RT experience) training, it is recommended that individuals use a wider loading range from 1 to 12 RM in a periodized fashion with eventual emphasis on heavy loading (1-6 RM) using 3- to 5-min rest periods between sets performed at a moderate contraction velocity (1-2 s CON; 1-2 s ECC). When training at a specific RM load, it is recommended that 2-10% increase in load be applied when the individual can perform the current workload for one to two repetitions over the desired number. The recommendation for training frequency is 2-3 dIwkj1 for novice training, 3-4 dIwkj1 for intermediate training, and 4-5 dIwkj1 for advanced training. Similar program designs are recom- mended for hypertrophy training with respect to exercise selection and frequency. For loading, it is recommended that loads corresponding to 1-12 RM be used in periodized fashion with emphasis on the 6-12 RM zone using 1- to 2-min rest periods between sets at a moderate velocity. Higher volume, multiple-set programs are recommended for maximizing hypertrophy. Progression in power training entails two general loading strategies: 1) strength training and 2) use of light loads (0-60% of 1 RM for lower body exercises; 30-60% of 1 RM for upper body exercises) performed at a fast contraction velocity with 3-5 min of rest between sets for multiple sets per exercise (three to five sets). It is also recommended that emphasis be placed on multiple-joint exercises especially those involving the total body. For local muscular endurance training, it is recommended that light to moderate loads (40-60% of 1 RM) be performed for high repetitions (915) using short rest periods (G90 s). In the interpretation of this position stand as with prior ones, recommendations should be applied in context and should be contingent upon an individual's target goals, physical capacity, and training
A total of 117 Japanese subjects (62 men and 55 women) volunteered for the study. Subcutaneous adipose tissue (AT) and muscle thicknesses were measured by B-mode ultrasonography at nine sites of the body. Body density (BD) was determined the hydrodensitometry. Reproducibility of thickness measurements by ultrasonography was high (r = 0.96–0.99). Correlations between AT thickness and BD ranged from −0.46 (gastrocnemius) to −0.87 (abdomen) for males and −0.46 (gastrocnemius) to −0.84 (abdomen) for females. A higher negative correlation (r = −0.89) was observed for the sum of AT thicknesses (forearm, biceps, triceps, abdomen, subscapula, quadriceps, hamstrings, gastrocnemius, and tibialis anterior) both in males and in females. Slightly lower coefficients were observed between muscle thickness and LBM (r = 0.36 to r = 0.70 for males and r = 0.44 to r = 0.55 for females). Prediction equations for BD and LBM from AT and muscle thickness were obtained by multiple regression analysis. Cross-validation on a separate sample (33 men and 44 women) showed an accurate prediction for BD. The present findings suggest that B-mode ultrasonography can be applied in clinical assessment and field surveys. © 1994 Wiley-Liss, Inc.
We have reported that the acute postexercise increases in muscle protein synthesis rates, with differing nutritional support, are predictive of longer-term training-induced muscle hypertrophy. Here, we aimed to test whether the same was true with acute exercise-mediated changes in muscle protein synthesis. Eighteen men (21 ± 1 yr, 22.6 ± 2.1 kg/m(2); means ± SE) had their legs randomly assigned to two of three training conditions that differed in contraction intensity [% of maximal strength (1 repetition maximum)] or contraction volume (1 or 3 sets of repetitions): 30%-3, 80%-1, and 80%-3. Subjects trained each leg with their assigned regime for a period of 10 wk, 3 times/wk. We made pre- and posttraining measures of strength, muscle volume by magnetic resonance (MR) scans, as well as pre- and posttraining biopsies of the vastus lateralis, and a single postexercise (1 h) biopsy following the first bout of exercise, to measure signaling proteins. Training-induced increases in MR-measured muscle volume were significant (P < 0.01), with no difference between groups: 30%-3 = 6.8 ± 1.8%, 80%-1 = 3.2 ± 0.8%, and 80%-3= 7.2 ± 1.9%, P = 0.18. Isotonic maximal strength gains were not different between 80%-1 and 80%-3, but were greater than 30%-3 (P = 0.04), whereas training-induced isometric strength gains were significant but not different between conditions (P = 0.92). Biopsies taken 1 h following the initial resistance exercise bout showed increased phosphorylation (P < 0.05) of p70S6K only in the 80%-1 and 80%-3 conditions. There was no correlation between phosphorylation of any signaling protein and hypertrophy. In accordance with our previous acute measurements of muscle protein synthetic rates a lower load lifted to failure resulted in similar hypertrophy as a heavy load lifted to failure.
The differences in changes in strength, body composition, anthropometric measurements and selected motor performance tasks, between groups, trained isotonically and isokinetically were compared. Thirty-six male volunteers were randomly assigned to one of four groups: isotonic; isokinetic low speed contraction; isokinetic high speed contraction; and control. Strength training was conducted three days per week, 40 minutes per day for eight weeks. The results demonstrated a clear superiority of the isokinetic training procedures over the isotonic procedures relative to strength, antrhopometric measures and motor performance tasks. The three training groups exhibited similar changes in body composition. The isokinetic high speed group demonstrated the greatest gains overall. The significance of these results is discussed.
We used ultrasonography to measure muscles in the arms and thighs of 16 children with malignant diseases. Thicknesses of transverse sections of the brachial biceps muscle and the femoral quadriceps muscle were measured by ultrasound at the midpoint of the right arm and thigh. These two measures had a linear correlation (r = 0.76). The ultrasound measurements did not differ from those obtained by the CT scan which was used as a reference standard. The reproducibility of the measurements was good; the coefficient of variation was 2.4% for the midarm muscles and 2.8% for the midthigh muscles. We conclude that the ultrasound method combined with simple anthropometric measurements is helpful in the assessment of nutritional status of children with potential malnutrition.
The purpose of this study was to determine whether the rate of muscle glycogen storage could be enhanced during the initial 4-h period postexercise by substantially increasing the amount of the carbohydrate consumed. Eight subjects cycled for 2 h on three separate occasions to deplete their muscle glycogen stores. Immediately and 2 h after exercise they consumed either 0 (P), 1.5 (L), or 3.0 g glucose/kg body wt (H) from a 50% glucose polymer solution. Blood samples were drawn from an antecubital vein before exercise, during exercise, and throughout recovery. Muscle biopsies were taken from the vastus lateralis immediately, 2 h, and 4 h after exercise. Blood glucose and insulin declined significantly during exercise in each of the three treatments. They remained below the preexercise concentrations during recovery in the P treatment but increased significantly above the preexercise concentrations during the L and H treatments. By the end of the 4 h-recovery period, blood glucose and insulin were still significantly above the preexercise concentrations in both treatments. Muscle glycogen storage was significantly increased above the basal rate (P, 0.5 mumol.g wet wt-1.h-1) after ingestion of either glucose polymer supplement. The rates of muscle glycogen storage, however, were not different between the L and H treatments during the first 2 h (L, 5.2 +/- 0.9 vs. H, 5.8 +/- 0.7 mumol.g wet wt-1.h-1) or the second 2 h of recovery (L, 4.0 +/- 0.9 vs. H, 4.5 +/- 0.6 mumol.g wet wt-1. h-1).(ABSTRACT TRUNCATED AT 250 WORDS)
To study the effects of resistance training on muscle strength and size in older people, we enrolled 8 men and 17 women (mean age 68.2 +/- 1 SEM) into a one-year exercise trial.
Subjects were randomly assigned to exercise or control groups. Muscle biopsies were obtained from 11 subjects (8 exercisers/3 controls) at baseline and after 15 weeks; exercisers underwent another biopsy at 30 weeks. After testing maximum strength using the 1-RM method, the exercisers began a 12-exercise circuit (3 sets of 8 repetitions at 75% of 1-RM), 3 times a week. The controls repeated the strength testing every 15 weeks. They were asked to continue usual activities and not to start any exercise program.
With exercise, muscle strength increased, average increases ranging from 30% (hip extensors) to 97% (hip flexors). Strength increased rapidly over 3 months, then plateaued for the duration of the experiment. No strength changes were observed in sedentary controls. Cross-sectional area of type 1 muscle fibers increased in exercisers by 15 weeks (29.4 +/- 1%, p < .02) and after 30 weeks (58.5 +/- 13.7%, p < .002) compared to baseline. Type 2 fiber area did not change at 15 weeks, but increased by 30 weeks of training (66.6 +/- 9.5%, p < .0002).
These results suggest that prolonged moderate to high intensity resistance training may be carried out by healthy older adults with reasonable compliance, and that such training leads to sustained increases in muscle strength. These improvements are rapidly achieved and are accompanied by hypertrophy of both type 1 and type 2 muscle fibers.
The knowledge of surface electromyography (SEMG) and the number of applications have increased considerably during the past ten years. However, most methodological developments have taken place locally, resulting in different methodologies among the different groups of users.A specific objective of the European concerted action SENIAM (surface EMG for a non-invasive assessment of muscles) was, besides creating more collaboration among the various European groups, to develop recommendations on sensors, sensor placement, signal processing and modeling. This paper will present the process and the results of the development of the recommendations for the SEMG sensors and sensor placement procedures. Execution of the SENIAM sensor tasks, in the period 1996-1999, has been handled in a number of partly parallel and partly sequential activities. A literature scan was carried out on the use of sensors and sensor placement procedures in European laboratories. In total, 144 peer-reviewed papers were scanned on the applied SEMG sensor properties and sensor placement procedures. This showed a large variability of methodology as well as a rather insufficient description. A special workshop provided an overview on the scientific and clinical knowledge of the effects of sensor properties and sensor placement procedures on the SEMG characteristics. Based on the inventory, the results of the topical workshop and generally accepted state-of-the-art knowledge, a first proposal for sensors and sensor placement procedures was defined. Besides containing a general procedure and recommendations for sensor placement, this was worked out in detail for 27 different muscles. This proposal was evaluated in several European laboratories with respect to technical and practical aspects and also sent to all members of the SENIAM club (>100 members) together with a questionnaire to obtain their comments. Based on this evaluation the final recommendations of SENIAM were made and published (SENIAM 8: European recommendations for surface electromyography, 1999), both as a booklet and as a CD-ROM. In this way a common body of knowledge has been created on SEMG sensors and sensor placement properties as well as practical guidelines for the proper use of SEMG.
We investigated the feasibility of using real-time sonography to measure muscle thickness. Clinically, this technique would be used to measure the thickness of human muscles in which intramuscular microstimulators have been implanted to treat or prevent disuse atrophy.
Porcine muscles were implanted with microstimulators and imaged with sonography, MRI, and CT to assess image artifacts created by the microstimulators and to design protocols for image alignment between methods. Sonography and MRI were then used to image the deltoid and supraspinatus muscles of 6 healthy human subjects.
Microstimulators could be imaged with all 3 methods, producing only small imaging artifacts. Muscle-thickness measurements agreed well between methods, particularly when external markers were used to precisely align the imaging planes. The correlation coefficients for sonographic and MRI measurements were 0.96 for the supraspinatus and 0.97 for the deltoid muscle. Repeated sonographic measurements had a low coefficient of variation: 2.3% for the supraspinatus and 3.1% for the deltoid muscle.
Real-time sonography is a relatively simple and inexpensive method of accurately measuring muscle thickness as long as the operator adheres to a strict imaging protocol and avoids excessive pressure with the transducer.
This review is divided into two parts, the first dealing with the cell and molecular biology of muscle in terms of growth and wasting and the second being an account of current knowledge of physiological mechanisms involved in the alteration of size of the human muscle mass. Wherever possible, attempts have been made to interrelate the information in each part and to provide the most likely explanation for phenomena that are currently only partially understood. The review should be of interest to cell and molecular biologists who know little of human muscle physiology and to physicians, physiotherapists, and kinesiologists who may be familiar with the gross behavior of human muscle but wish to understand more about the underlying mechanisms of change.
Maximum voluntary contraction (MVC) and cross-sectional area (CSA) of fast and slow twitch fibers are reduced in the lower limb muscles of elderly subjects. Isokinetic training at medium and high velocities has been widely used to improve muscle performance and force in young as well as elderly subjects. EMG and mechanomyogram (MMG) are compound signals in which the electrical and mechanical activities of recruited motor units (MUs) are summated. The aim of the present study was to verify the hypothesis that isokinetic training in the elderly induces changes in EMG and MMG parameters, compatible with a functional retrieval of fast twitch fiber MUs. In ten sedentary males (62-78 years), the surface EMG and MMG were recorded from the vastus lateralis muscle during isometric contractions at 20, 40, 60, 80 and 100% of the MVC, before and after 12 weeks of isokinetic training (six series of ten repetitions, each at an angular velocity of 2.09 rad s(-1) and 4.19 rad s(-1), two times a week). With training: (a) MVC and CSA increased by about 35+/-5% and 8+/-1%, respectively (P<0.05); (b) the ratio MVC/CSA increased significantly in all subjects by 25+/-5%; (c) the EMG root mean square and MMG spectral mean frequency increased significantly at the highest workloads. In conclusion, our data indicate that isokinetic training in the elderly improved muscle size and performance significantly. The EMG and MMG changes suggest that these results may be due to a retrieval of the fast twitch fiber MUs, contributing to muscle action.
A study on training effect on strength per unit cross-sectional area of muscle by means of ultrasound measurement
- Ikae
M. Ikae, T. Fukunanaga, A study on training effect on strength per unit cross-sectional area of muscle by means of ultrasound measurement, Int. Z. Angew. Physiol. 28
(1970) 173-180.