Article

Effects of equivolume isometric training programs comprising medium or high resistance on muscle size and strength

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Abstract

Isometric unilateral elbow extension training was conducted for 10 weeks (3 times per week) on 12 young adult men to investigate the effects of equivolume exercise programs with different combinations of intensity and duration on the morphological and functional aspects of the triceps brachii muscle. One group of 6 subjects trained by developing maximal voluntary contraction (MVC) for 6 s per set with 12 sets per session (100%G), while the other group of 6 subjects trained at 60% of MVC for 30 s per set with 4 sets per session (60%G). Training significantly increased the muscle volume (V m), fascicle pennation angle of the triceps brachii, and torque output during concentric and eccentric elbow extensions at three constant velocities of 0.52, 1.57, and 3.14 rad·s–1 as well as under the training condition, with no significant differences in the relative gains between the two programs. However, 100%G showed significantly greater V m than 60%G after training, when V m before training was normalized. Thus, only 60%G significantly increased the ratio of torque to V m developed in the eccentric actions at the three velocities and concentric action at 1.57 rad·s–1. The present results indicate that isometric training programs of medium resistance/long duration and high resistance/short duration produce different effects on V m and dynamic strength relative to V m, even if the training volume is equalized between the two protocols.

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... Several studies have determined that fast eccentric contractions cause greater muscle damage, soreness, and acute performance reductions, relative to slow velocities (54,65,66). Additionally, researchers have examined the effects of range of motion, and contraction duration with a consensus supporting longer time-under-tensions (164,344), and larger ranges of motion when aiming to improve muscle size and performance (310). Therefore, it is important to characterize the above biomechanical variables when examining new contractions, or altered loading parameters, including EQIs. ...
... As with any mode of resistance training, several variables can be manipulated to alter the stimulus. The most common isometric training variations include altering joint angles (9,35,188,205,231,250,251,289,335,353) and contraction intensity or duration (19,21,32,164,169,231,314,344,354). Less frequently researched variations include contraction intent (eg. ...
... Of the ten included studies, eight centred on the knee extensors (9,35,49,188,205,250,251,335), with two utilizing the elbow flexors (289,353). Six published articles examining the effect of contraction intensity (Table 2) fulfilled the inclusion criteria (19,21,164,169,344,396). Of these studies, three examined plantar flexors (19,21,396), one examined knee extensors (344), while single studies examined the elbow flexors (169) and extensors, respectively (164). ...
Thesis
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Muscle structure and function are important to quality of life and physical performance. With eccentric and isometric resistance training established for improving muscle size and strength, eccentric quasi-isometric (EQI) contractions, defined as “holding a position until isometric failure and maximally resisting the subsequent eccentric phase”, are the focus of this thesis. The primary aims were to answer the overarching research question: “What are the acute, and long-term effects of EQI loading on muscle form and function?”. Systematic and narrative reviews were conducted, followed by the evaluation and optimization of testing methods, culminating in acute and short-term experimental studies. Reviews of the literature established that isometric training at longer muscle lengths produced greater hypertrophy than volume-equated shorter muscle length training (0.1-1.0%·week-1, effect size (ES) = 0.05-0.2·week-1), and transferred better to full range of motion (ROM) performance. Ballistic intent resulted in greater increases in rate of torque development (RTD) and neuromuscular activation (-1.5-3.6%·week-1, ES = 0.03-0.28·week-1). Hypertrophy and strength improvements were not related to isometric training intensity, however, contractions ≥ 70% were likely required to improve tendon qualities. While there is a lack of studies directly examining EQIs, they may provide a practical means of increasing metabolic and hormonal factors, while safely applying large quantities of mechanical tension. EQI training appears to be effective for improving musculotendinous morphological and performance variables with low injury risk. To be confident in the primary findings of the PhD, it was important to test and determine an optimized assessment battery for the acute and long-term effects and adaptations to EQI loading. Repeated between-day testing determined that ultrasound derived muscle thickness (MT) and subcutaneous fat corrected echo intensity (EI) had low variability in all quadriceps muscles and regions. Pennation angle (PA) and extended field-of-view fascicle length (FL) could only be reliably assessed in the vastus lateralis. Concentric torque and impulse were reliable between 90-20° of knee-flexion. Maximal voluntary isometric torque (MVIT), and RTD and impulse from 0-200 ms can be confidently assessed regardless of joint angle. Correlational analysis revealed that the isometric length-tension relationship was minimally associated with regional architecture and that the middle and distal architecture were the strongest predictors of MVIT. When comparing impulse-equated bouts of EQI and isokinetic eccentric loading (ECC), physiological responses were similar in 21/56 variables. EQIs resulted in greater vastus intermedius swelling (7.1-8.8%, ES = 0.20-0.29), whereas ECC resulted in greater soreness at the distal and middle vastus lateralis and distal rectus femoris (16.5-30.4%, ES = 0.32-0.54) and larger echogenicity increases at the distal rectus femoris and lateral vastus intermedius (11.9-15.1%, ES = 0.26-0.54). Furthermore, ECC led to larger reductions in concentric (8.3-19.7%, ES = 0.45-0.62) and isometric (6.3-32.3%, ES = 0.18-0.70) torque and RTD at medium-long muscle lengths. There were substantial differences in the number of contractions required to impulse-match the conditions (ECC: 100.8 ± 54 vs EQI: 3.85 ± 1.1). Mean contraction velocity over four contractions was 1.34º·s-1 with most (62.5 ± 4.9%) impulse produced between 40-70º. Most between-contraction changes in total angular impulse, contraction velocity, and time-under-tension occurred between 30-50º (ES = 0.53 ± 0.31, 60 ± 52%), while kinetics and kinematics relatively constant between 50-100º (ES = 0.10 ± 0.26, 14.3 ± 24.6%). Findings suggest that EQI loading could be an alternative to traditional resistance-training, possibly for individuals suffering from, or susceptible to musculoskeletal injury. Practitioners could shift the loading distribution to longer muscle lengths by prescribing a greater number of contractions, reducing rest periods, or implementing EQI contractions towards the end of a traditional training session where fatigue may be present. Although extensive future research is required to understand underlying mechanisms and long-term adaptations, the thesis provided novel and original information on the biomechanics and physiological effects of EQI loading. With the benefits of time-efficiency and minimal negative effects, EQI training is likely best applied in rehabilitation, general preparatory, unloading, or transition periods of the periodized plan.
... The most common isometric training variations include altering joint angles [30][31][32][33][35][36][37][38][39][40] and contraction intensity or duration. 34,39,[41][42][43][44][45][46][47] Less frequently researched variations include contraction intent (eg, ramp vs ballistic) 43,47,48 and incorporating special methods such as blood flow restriction, 49,50 vibration, 51,52 and electrical stimulation. 53 Additionally, emerging research has demonstrated unique neuromuscular characteristics between "pushing" (ie, exerting force against an immovable object) and "holding" (ie, maintaining a joint position while resisting an external force) isometric contractions. ...
... 36,37 Six published articles examining the effect of contraction intensity (Table 2) fulfilled the inclusion criteria. 41,42,[44][45][46]65 Of these studies, three examined plantar flexors 41,42,65 and one examined knee extensors, 46 while single studies examined the elbow flexors 45 and extensors, respectively. 44 Training variations outside of joint position or contraction intensity were also included. ...
... 41,42,[44][45][46]65 Of these studies, three examined plantar flexors 41,42,65 and one examined knee extensors, 46 while single studies examined the elbow flexors 45 and extensors, respectively. 44 Training variations outside of joint position or contraction intensity were also included. These variations include the following: (a) intent of contraction which included "progressive" vs "rapid" 48,66 and "explosive" vs "sustained" 43,47,67 contractions (Table 3); (b) total volume 39 ; (c) contraction duration 13,34 ; (d) rest period duration 68 ; and (e) periodization schemes 69 (Table 4). ...
Article
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Isometric training is used in the rehabilitation and physical preparation of athletes, special populations and the general public. However, little consensus exists regarding training guidelines for a variety of desired outcomes. Understanding the adaptive response to specific loading parameters would be of benefit to practitioners. The objective of this systematic review, therefore, was to detail the medium to long‐term adaptations of different types of isometric training on morphological, neurological and performance variables. Exploration of the relevant subject matter was performed through MEDLINE, PubMed, SPORTDiscus and CINAHL databases. English, full‐text, peer‐reviewed journal articles and unpublished doctoral dissertations investigating medium to long‐term (≥3 weeks) adaptations to isometric training in humans were identified. These studies were evaluated further for methodological quality. Twenty‐six research outputs were reviewed. Isometric training at longer muscle lengths (0.86‐1.69%/week, ES = 0.03‐0.09/week) produced greater muscular hypertrophy when compared to equal volumes of shorter muscle length training (0.08‐0.83%/week, ES = ‐0.003‐0.07/week). Ballistic intent resulted in greater neuromuscular activation (1.04‐10.5%/week, ES = 0.02‐0.31/week vs. 1.64‐5.53%/week, ES = 0.03‐0.20/week) and rapid force production (1.2‐13.4%/week, ES = 0.05‐0.61/week vs. 1.01‐8.13%/week, ES = 0.06‐0.22/week). Substantial improvements in muscular hypertrophy and maximal force production were reported regardless of training intensity. High‐intensity (≥ 70%) contractions are required for improving tendon structure and function. Additionally, long muscle length training results in greater transference to dynamic performance. Despite relatively few studies meeting the inclusion criteria, this review provides practitioners with insight into which isometric training variables (e.g. joint angle, intensity, intent) to manipulate to achieve desired morphological and neuromuscular adaptations.
... Several studies have explored training to failure hut have not directly equated several important training variables within the experimental design, such as volume (3 sets of 10 repetitions not to failure vs. 1 set of 8-12 repetitions to failure) (21), duration of the training period (about 4 vs. more than 20 minutes) (11), or training intensities (60 vs. 100% maximal voluntary contraction IMVCI) (20). Other studies used only untrained subjects (2,26) or single-joint movements and isokinetic or isometric machines (11,19,20,27), which may not he directly relevant for most sporting applications that involve coordinating several joints for movements (2,26). ...
... Several studies have explored training to failure hut have not directly equated several important training variables within the experimental design, such as volume (3 sets of 10 repetitions not to failure vs. 1 set of 8-12 repetitions to failure) (21), duration of the training period (about 4 vs. more than 20 minutes) (11), or training intensities (60 vs. 100% maximal voluntary contraction IMVCI) (20). Other studies used only untrained subjects (2,26) or single-joint movements and isokinetic or isometric machines (11,19,20,27), which may not he directly relevant for most sporting applications that involve coordinating several joints for movements (2,26). Therefore, a protocol that equates volume, time, and intensity of training in noncontact team sport athletes undertaking multiple-joint, free-weight training could elucidate valuable information about including training that leads to repetition failure into larger periodized programs. ...
... The need for training leading to repetition failure to enhance strength is not universally accepted (11,27), though it does have support. Several studies have demonstrated strength gains by using light weights (about 15-60% MVC) with multiple repetitions to train to failure (7,8,20,25). Although it seems intuitive that equating the work volume and intensity would elicit equal strength gains, Rooney et al. (27) showed that suhjects who per-formed biceps curls until repetition failure attained significantly greater 1 repetition maximum (IRM) gains than subjects training without assistance but permitted short rest intervals hetween repetitions. ...
... Several studies have explored training to failure but have not directly equated several important training variables within the experimental design, such as volume (3 sets of 10 repetitions not to failure vs. 1 set of 8-12 repetitions to failure) (21), duration of the training period (about 4 vs. more than 20 minutes) (11), or training intensities (60 vs. 100% maximal voluntary contraction [MVC]) (20). Other studies used only untrained subjects (2,26) or single-joint movements and isokinetic or isometric machines (11,19,20,27), which may not be directly relevant for most sporting applications that involve coordinating several joints for movements (2,26). ...
... Several studies have explored training to failure but have not directly equated several important training variables within the experimental design, such as volume (3 sets of 10 repetitions not to failure vs. 1 set of 8-12 repetitions to failure) (21), duration of the training period (about 4 vs. more than 20 minutes) (11), or training intensities (60 vs. 100% maximal voluntary contraction [MVC]) (20). Other studies used only untrained subjects (2,26) or single-joint movements and isokinetic or isometric machines (11,19,20,27), which may not be directly relevant for most sporting applications that involve coordinating several joints for movements (2,26). Therefore, a protocol that equates volume, time, and intensity of training in noncontact team sport athletes undertaking multiple-joint, free-weight training could elucidate valuable information about including training that leads to repetition failure into larger periodized programs. ...
... The need for training leading to repetition failure to enhance strength is not universally accepted (11,27), though it does have support. Several studies have demonstrated strength gains by using light weights (about 15-60% MVC) with multiple repetitions to train to failure (7,8,20,25). Although it seems intuitive that equating the work volume and intensity would elicit equal strength gains, Rooney et al. (27) showed that subjects who per-formed biceps curls until repetition failure attained significantly greater 1 repetition maximum (1RM) gains than subjects training without assistance but permitted short rest intervals between repetitions. ...
Article
Drinkwater, E.J., T.W. Lawton, R.P. Lindsell, D.B. Pyne, P.H. Hunt, and M.J. McKenna. Training leading to repetition failure contributes to bench press strength gains in elite junior athletes. J. Strength Cond. Res. 19(2):382-388. 2005. The purpose of this study was to investigate the importance of training leading to repetition failure in the performance of 2 different tests: 6 repetition maximum (6RM) bench press strength and 40-kg bench throw power in elite junior athletes. Subjects were 26 elite junior male basketball players (n 12; age = 18.6 +/- 0.3 years; height = 202.0 +/- 11.6 cm; mass = 97.0 +/- 12.9 kg; mean SD) and soccer players (n = 14; age = 17.4 +/- 0.5 years; height = 179.0 +/- 7.0 cm; mass = 75.0 +/- 7.1 kg) with a history of greater than 6 months' strength training. Subjects were initially tested twice for 6RM bench press mass and 40-kg Smith machine bench throw power output (in watts) to establish retest reliability. Subjects then undertook bench press training with 3 sessions per week for 6 weeks, using equal volume programs (24 repetitions X 80-105% 6RM in 13 minutes 20 seconds). Subjects were assigned to one of two experimental groups designed either to elicit repetition failure with 4 sets of 6 repetitions every 260 seconds (RF4x6) or allow all repetitions to be completed with 8 sets of 3 repetitions every 113 seconds (NF8x3). The RF4X6 treatment elicited substantial increases in strength (7.3 +/- 2.4 kg, + 9.5%, p < 0.001) and power (40.8 +/- 24.1 W, + 10.6%, p < 0.001), while the NF8X3 group elicited 3.6 +/- 3.0 kg (+ 5.0%, p < 0.005) and 25 +/- 19.0 W increases (+ 6.8%, p < 0.001). The improvements in the RF4x6 group were greater than those in the repetition rest group for both strength (p < 0.005) and power (p < 0.05). Bench press training that leads to repetition failure induces greater strength gains than nonfailure training in the bench press exercise for elite junior team sport athletes.
... Exercise intensities during maximal voluntary co-contraction training of elbow flexors and extensors, expressed as the value relative to its maximum (e.g. % EMgmax or % MVc), have been shown to be 40-60 % and 60-75 %, respectively (Maeo et al. 2013;Serrau et al. 2011;tyler and Hutton 1986). Kanehisa et al. (2002) reported that 10-week isometric elbow extension training with 60 % MVc induced a significant gain in the volume of the triceps brachii muscle. taking this into account together with Fig. 1 A picture of the subject performing maximal voluntary cocontraction in elbow flexors and extensors. ...
... these values are similar to those (+6 to +28 % for elbow flexion and +9 to +22 % for elbow extension) in previous studies that involved voluntary co-contraction training (Driss et al. 2013;Mac-Kenzie et al. 2010) or traditional resistance training such as isometric (Barry et al. 2005;Davies et al. 1988Davies et al. ), isokinetic (colson et al. 1999, or weight training (Bemben and Murphy 2001) for 2-7 weeks. the corresponding values at 12 weeks, +15 % for elbow flexion and +46 % for elbow extension from Pre, are also comparable to those (+9 to Values are means ± SDs 1 3 +36 % for elbow flexion and +13 to +61 % for elbow extension) reported in previous studies that adopted a traditional resistance training regimen for 8-12 weeks (Kanehisa et al. 2002;Matta et al. 2011;Moore et al. 2012;Moritani and deVries 1979). taking these findings together, it is considered that the training modality with maximal voluntary co-contraction is as effective as traditional resistance training methods to produce muscle strength gain. ...
... Using high [≥70 % one repetition maximum (1rM) or MVc] intensity is often recommended as the optimal way to maximize muscle hypertrophy with resistance training (AcSM 2009). However, several studies (Holm et al. 2008Kanehisa et al. 2002;Mitchell et al. 2012) have shown that resistance training with light-to-medium intensity (15.5-60 % 1rM or MVc) can also trigger structural adaptations if the training volume is sufficient. For example, Holm et al. (2008) andMitchell et al. (2012) reported that resistance training using low intensity (15.5 and 30 % 1rM, respectively) produced 3-7 % increase in muscle size. ...
Article
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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.
... To ensure a comparable training volume between the two training modalities we matched the contraction intensity and duration for the EMS and VOL groups. Although higher voluntary exercise loads are recommended to promote muscle hypertrophy and strength gains [40], significant strength gains could be achieved even when using medium loads (50-60% MVC) [25,[41][42][43][44]. In fact, Szeto et al. [44] demonstrated a 31% increase in MVC following isometric VOL training at 50% MVC, while Filipovic et al. [24] reported gains in maximum strength of 32.6 ± 17.6% in trained subjects and of 32 ± 15.6% in elite athletes following isometric EMS. ...
... In fact, Szeto et al. [44] demonstrated a 31% increase in MVC following isometric VOL training at 50% MVC, while Filipovic et al. [24] reported gains in maximum strength of 32.6 ± 17.6% in trained subjects and of 32 ± 15.6% in elite athletes following isometric EMS. Nonetheless, the results obtained in the current study are in line with those reported previously [24,25,[42][43][44] and show no substantial difference in MVC torque gains between VOL and EMS training modalities. ...
Article
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This study explored the changes in the rate of torque development scaling factor (RTD-SF) and maximum voluntary isometric contraction (MVC) variables following six weeks of unilateral isometric electromyostimulation (EMS) and voluntary (VOL) exercises. Twenty-six physically active participants were randomly assigned to EMS (n = 13) or a VOL group. MVC and RTD-SF of the quadriceps femoris of both legs were assessed before and after training. EMS and VOL exercises had identical frequency (three sessions/week), intensity (60% MVC), volume (40 contractions), and work-to-rest ratio (18 min: 6.25 s of work/20 s of rest). There were no between-group differences for the trained leg with overall increases in maximal torque (Tmax) of ~29% (d = 2.11–2.12), ~13% for RTDmax (d = 0.92–1.10); ~23% for Intercept (d = 0.72–0.78), and reduction in RTD-SF by ~15% (d = 1.01–1.10). In the non-trained leg, significant moderate change was only observed after EMS for RTD-SF which decreased by 12.5% (d = 0.76). Both EMS and VOL training applied at equivalent workloads positively impact on Tmax, RTDmax, and Intercept, but they negatively affect the quickness with which muscle contracts across a wide range of submaximal forces. Using a moderate training intensity in regularly physically active participants could explain the absence of cross-education in the VOL group.
... Additionally, a systematic review (Oranchuk et al., 2019) has shown that the total training volume is more important than training intensity to gain strength improvement. In previous studies, training volume, such as percentage of maximal voluntary contraction (MVC) × duration of contraction per set × number of sets per session (Kanehisa et al., 2002) and/or total impulse (areas under the force-time training curve) (Young et al., 1985), were controlled using different training intensity protocols. For example, a group showed a 60.3% increase in MVC torque induced by isometric training at 100% of MVC (6 s × 12 sets), whereas another group demonstrated a 61.0% ...
... For example, a group showed a 60.3% increase in MVC torque induced by isometric training at 100% of MVC (6 s × 12 sets), whereas another group demonstrated a 61.0% increase at 60% of MVC (30 s × 4 sets) (Kanehisa et al., 2002). In addition, Tillin and Folland (2014) compared two types of isometric training (force exertion over 1 s, up to 75% of MVC, hold for 3 s vs. contraction as fast and hard as possible up to 90% of MVC for −1 s). ...
Article
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This study aimed to examine the association between interindividual variability in strength changes and in training volume. A total of 26 untrained men completed 4-weeks of isometric knee extension (KE group, n = 12) and hip flexion (HF group, n = 14) training. Each training session comprised four sets of ten isometric contractions, 3-s contractions every 20 s. Training volume, which was defined as impulse during contractions, and maximal voluntary contraction (MVC) torque during KE and HF were evaluated. Based on the magnitude of MVC torque changes, the participants were divided into the high and low responders (n = 13; KE = 6 and HF = 7 per responders). The MVC torque changes (KE, 20.8%; HF, 22.4%) and total training volume did not significantly differ between the two groups. A higher training volume was demonstrated in the low responders than the high responders. The total training volume was positively associated with the MVC torque changes in low responders (r = 0.869%, 95% confidence interval [0.610, 0.960], p < 0.001), but not in high responders [r = 0.229, 95% confidence interval (−0.368, 0.693), p = 0.451], KE or HF group. Results showed that training volume was an important factor in determining the magnitude of strength gains in low responders, and MVC torque could improve by approximately 20% with the use of the study protocol regardless of joint actions involved during training.
... The training group then followed a 12-week ankle-specific block progression program including isometric, DCER, AEL, and plyometric training modalities while the control group continued dancing normally. Our contention was that dancers (whom already train 6+ h per week) may benefit from the previously described adaptations in each block progression for ankle-specific movements (Kanehisa et al., 2002;Haff and Nimphius, 2012;Suchomel et al., 2018). Block 1 (isometrics) was intended to enhance joint-specific strength at critical ranges of motion (Kanehisa et al., 2002;Kubo et al., 2006) and neuromuscular control. ...
... Our contention was that dancers (whom already train 6+ h per week) may benefit from the previously described adaptations in each block progression for ankle-specific movements (Kanehisa et al., 2002;Haff and Nimphius, 2012;Suchomel et al., 2018). Block 1 (isometrics) was intended to enhance joint-specific strength at critical ranges of motion (Kanehisa et al., 2002;Kubo et al., 2006) and neuromuscular control. Block 2 (DCER) projected to continue strength enhancements with full range of motion dynamic exercises containing low-to-moderate repetition ranges. ...
Article
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The purpose of this study was to investigate the effect of a 12-week ankle-specific block progression training program on saut de chat leaping performance [leap height, peak power (PP), joint kinetics and kinematics], maximal voluntary isometric plantar flexion (MVIP) strength, and Achilles tendon (AT) stiffness. Dancers (training group n = 7, control group n = 7) performed MVIP at plantarflexed (10◦) and neutral ankle positions (0◦) followed by ramping isometric contractions equipped with ultrasound to assess strength and AT stiffness, respectively. Dancers also performed saut de chat leaps surrounded by 3-D motion capture atop force platforms to determine center of mass and joint kinematics and kinetics. The training group then followed a 12-week ankle-focused program including isometric, dynamic constant external resistance, accentuated eccentric loading, and plyometric training modalities, while the control group continued dancing normally. We found that the training group's saut de chat ankle PP (59.8%), braking ankle stiffness (69.6%), center of mass PP (11.4%), and leap height (12.1%) significantly increased following training. We further found that the training group's MVIP significantly increased at 10◦ (17.0%) and 0◦ (12.2%) along with AT stiffness (29.6%), while aesthetic leaping measures were unchanged (peak split angle, mean trunk angle, trunk angle range). Ankle-specific block progression training appears to benefit saut de chat leaping performance, PP output, ankle-joint kinetics, maximal strength, and AT stiffness, while not affecting kinematic aesthetic measures. We speculate that the combined training blocks elicited physiological changes and enhanced neuromuscular synchronization for increased saut de chat leaping performance in this cohort of dancers.
... performed with varying periodization (Ullrich et al., 2015). Similarly, increased volume of the triceps brachii (+12.4%) was reported after 10 weeks of high-intensity IT (Kanehisa et al., 2002). Noteworthy, explosively performed IT did not result in significant changes in quadriceps muscle volume (Balshaw et al., 2016). ...
... In contrast, Alegre et al. (2014) did not find changes in fascicle lengths after IT at LML and other muscles than the VL. Significant increases (+11.7%) in VL PA were only found after IT at LML (Noorkõiv et al., 2014) and in the long head of the triceps brachii (~15.5%) after high-and low-intensity IT (Kanehisa et al., 2002). No change in PA was observed after training at SML (Noorkõiv et al., 2014) and in the study of Ullrich et al. (2015). ...
Article
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Treatment strategies and training regimens, which induce longitudinal muscle growth and increase the muscles’ length range of active force exertion, are important to improve muscle function and to reduce muscle strain injuries in clinical populations and in athletes with limited muscle extensibility. Animal studies have shown several specific loading strategies resulting in longitudinal muscle fiber growth by addition of sarcomeres in series. Currently, such strategies are also applied to humans in order to induce similar adaptations. However, there is no clear scientific evidence that specific strategies result in longitudinal growth of human muscles. Therefore, the question remains what triggers longitudinal muscle growth in humans. The aim of this review was to identify strategies that induce longitudinal human muscle growth. For this purpose, literature was reviewed and summarized with regard to the following topics: (1) Key determinants of typical muscle length and the length range of active force exertion; (2) Information on typical muscle growth and the effects of mechanical loading on growth and adaptation of muscle and tendinous tissues in healthy animals and humans; (3) The current knowledge and research gaps on the regulation of longitudinal muscle growth; and (4) Potential strategies to induce longitudinal muscle growth. The following potential strategies and important aspects that may positively affect longitudinal muscle growth were deduced: (1) Muscle length at which the loading is performed seems to be decisive, i.e., greater elongations after active or passive mechanical loading at long muscle length are expected; (2) Concentric, isometric and eccentric exercises may induce longitudinal muscle growth by stimulating different muscular adaptations (i.e., increases in fiber cross-sectional area and/or fiber length). Mechanical loading intensity also plays an important role. All three training strategies may increase tendon stiffness, but whether and how these changes may influence muscle growth remains to be elucidated. (3) The approach to combine stretching with activation seems promising (e.g., static stretching and electrical stimulation, loaded inter-set stretching) and warrants further research. Finally, our work shows the need for detailed investigation of the mechanisms of growth of pennate muscles, as those may longitudinally grow by both trophy and addition of sarcomeres in series.
... It has been shown that 42-100 days of IST training resulted in 5.4-23 % increase in muscle cross-sectional area accompanied by up to 91.7 % increase in strength [5,14,20,25,26,28,35,50,51,58]. The magnitude of muscle hypertrophy from each study was associated with the duration of the intervention training, with a longer intervention period showing higher magnitude of muscle hypertrophy. ...
... The finding of this study suggested that exercising at or near maximal intensity was superior in inducing maximal strength improvement while exercising at submaximal load with increased time under tension was more beneficial in improving muscular endurance. This was supported by Khouw and Herbert [29], who also showed greater increase in strength after performing IST at nearer to maximal intensity, but not supported by others [5,28,65]. In another study, Hagberg et al. [22] compared a 4 × 2 min (20-30 % MVC) and 10 × 5 s (MVC) isometric shoulder flexion protocol and noted higher strength improvement (5.28 vs. 2.66 Nm) after training at maximal intensity as compared to low intensity but no difference in improvement in muscular endurance. ...
Article
This review used a narrative summary of findings from studies that focused on isometric strength training (IST), covering the training considerations that affect strength adaptations and its effects on sports related dynamic performances. IST has been shown to induce less fatigue and resulted in superior joint angle specific strength than dynamic strength training, and benefited sports related dynamic performances such as running, jumping and cycling. IST may be included into athletes’ training regime to avoid getting overly fatigue while still acquiring positive neuromuscular adaptations; to improve the strength at a biomechanically disadvantaged joint position of a specific movement; to improve sports specific movements that require mainly isometric contraction; and when athletes have limited mobility due to injuries. To increase muscle hypertrophy, IST should be performed at 70–75% of maximum voluntary contraction (MVC) with sustained contraction of 3–30 s per repetition, and total contraction duration of>80–150 s per session for>36 sessions. To increase maximum strength, IST should be performed at 80–100% MVC with sustained contraction of 1–5 s, and total contraction time of 30–90 s per session, while adopting multiple joint angles or targeted joint angle. Performing IST in a ballistic manner can maximize the improvement of rate of force development.
... Muscle architectural adaptations to resistance exercise depend on several factors such as training status, intensity–volume relationship and muscle activation (Folland & Williams, 2007). These resistance-training-induced muscle architectural changes have been commonly quantified through the application of imaging techniques (Kawakami et al., 1995; Kanehisa et al., 2002; Blazevich et al., 2006). In this scenario, ultrasonography constitutes a safe, relatively low-cost and reliable technique (Lima et al., 2012), which has been validated through comparisons to 'gold standard' methods such as magnetic resonance imaging (MRI) and computerized axial tomography (Bemben, 2002; Noorkoiv et al., 2010). ...
... Although the long-term impact of resistance training on the muscle architecture has already been described (Kanehisa et al., 2002; Blazevich et al., 2006), there is no information on the magnitude of these adaptations on different sites of a muscle group. This investigation was then based on the premises that any different resistance exercise training regimens would induce heterogenic architectural adaptations on RF muscle and their magnitude would be site dependent. ...
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One of the fundamental adaptations observed with resistance training (RT) is muscle hypertrophy. Conventional and isokinetic machines provide different forms of mechanical stress, and it is possible that these two training modes could promote differing degrees of hypertrophic adaptations. There is a lack of data comparing the selective hypertrophy of the quadriceps musculature after training with a conventional knee extension machine versus an isokinetic machine. The purpose of this study was to evaluate the selective hypertrophy of the quadriceps musculature and knee extension maximal isometric torque after 14 weeks of conventional versus isokinetic RT. Thirty-five men were assigned to three groups: control group and training groups (conventional and isokinetic) performed three sets of unilateral knee extensions per session with a progressive loading scheme twice a week. Prior to and following the intervention, maximal isometric knee extensor torque was measured using an isokinetic dynamometer, and muscle thickness (MT) of quadriceps femoris muscles was assessed via ultrasound. The results indicated non-uniform changes in MT between the muscles that comprise the quadriceps femoris group. For the conventional group, significantly greater increases in rectus femoris thickness were evident versus all other quadriceps muscles (14%). For the isokinetic group, increases in RF thickness (11%) were significantly greater in comparison with the vastus intermedius only. Although the muscle thickness did not increase for all the quadriceps femoris muscles, the relative rectus femoris adaptation suggested a selective hypertrophy favouring this portion. © 2015 Scandinavian Society of Clinical Physiology and Nuclear Medicine. Published by John Wiley & Sons Ltd.
... As muscle force is primarily determined by the number of sarcomeres arranged in parallel, which is represented by the PCSA (Close, 1972;Powell et al., 1984), it is important to know how resistance training affects PCSA in order to ascertain a complete overview of the variable response of human muscle to overload. Previous studies have used whole muscle volume (Kanehisa et al., 2002;Charbonneau et al., 2008) or ACSA (Tracy et al., 1999;Ferri et al., 2003;Hubal et al., 2005) to determine the effect of resistance training on muscle size. However, unlike PCSA, neither of these two indices of muscle size represents the CSA of the total number of fibres at right angles to their axes in pennate muscles. ...
... An alternative solution to the problem might have resided in the method used to determine the extent of muscle hypertrophy, which has previously been defined as the change in muscle volume (Kanehisa et al., 2002;Charbonneau et al., 2008) or ACSA (Davies et al., 1988;Tracy et al., 1999;Ferri et al., 2003) but neither of those indices of muscle size represent the CSA of the total number of muscle fibres perpendicular to their long axes. This is represented by the muscle PCSA, which largely determines the maximum force produced by a muscle (Powell et al., 1984). ...
... As principais mudanças na arquitetura muscular decorrentes do envelhecimento envolvem alterações na espessura, no comprimento do fascículo e no ângulo de penação 6,8,9 . O comprimento do fascículo está relacionado com a velocidade de contração muscular enquanto o ângulo de penação está associado com a capacidade de produzir elevados níveis de força [9][10][11][12] . ...
... Nenhum estudo anterior avaliou os efeitos do método Isostretching sobre a arquitetura muscular. No entanto, a especificidade das adaptações musculares decorrentes do treinamento pelo isostretching é consistente com estudos anteriores que observaram os efeitos do treinamento isométrico em jovens e idosos 11,18,19 . Portanto, estes achados confirmam que programas que utilizam contações isométricas leves a moderadas podem prover importantes alterações nos parâmetros morfológicos musculares que influenciam a capacidade contrátil muscular. ...
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O treinamento resistido de intensidade leve e moderada parece eficaz em prover importantes melhorias sobre a força, o equilíbrio e a funcionalidade em idosos. O objetivo do presente estudo foi analisar os efeitos de 12 semanas de treinamento do Método Isostretching sobre a capacidade funcional e arquitetura muscular em idosas. A amostra foi de 25 voluntárias (n=25), divididas em um grupo controle (GC; n=11; 62,3 ± 1,9 anos; 1,58 ± 0,06m; 73,4 ± 1,4kg) que prosseguiu suas atividades físicas habituais e um grupo experimental (GE; n=14; 64,2 ± 4,3anos; 1,56 ± 0,05 m; 74,2 ± 1,6kg) que realizou um programa de exercícios de isostretching. As avaliações compreenderam Timed Up and Go –TUG, avaliação de Tinetti e avaliação dos parâmetros morfológicos por meio da Ultrassonagrafia. Os resultados mostraram que o GE apresentou uma melhora (p<0,05) tanto no TUG quanto no Tinetti. Nos parâmetros morfológicos do vasto lateral no grupo GE observou-se: aumento médio de 3.6 mm do comprimento do fascículo em relaxamento (p<0,05; ES=1,15), em contração isométrica aumento de 4,9 mm (p<0.05; ES=1,94); no ângulo de penação na condição relaxada, um aumento de 16% (p<0.05; ES=0,70), em contração isométrica, aumento de 12% (p<0,05; ES=0,50); já na espessura (p<0,05; ES=0,52) aumento de 8% relaxado, em contração isométrica (p<0,05; ES=0,43) de 9%. O GC não apresentou alterações significativas. O treinamento isométrico por meio do isostretching promoveu alterações nos parâmetros morfológicos musculares e melhorou as capacidades funcionais em idosas.
... In this regard, Lum et al. (2019) suggest, for isometric strength training, a total contraction time of 30 to 90 seconds per session, while Fleck and Kraemer (2017) recommend a frequency of at least three sessions per week. Kanehisa et al. (2002) observed significant improvements in muscle volume, fascicular pennation angle, and torque production in elbow extensions after ten weeks of isometric training with sets of the same duration as in the present study (6s). However, these authors conducted 12 sets per session (totaling 72s of contraction), and the frequency was three sessions per week. ...
Article
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Shooting represents a fundamental skill in handball. Among other factors, its effectiveness requires a significant development of explosive strength. Isometric training may provide a powerful neuromuscular stimulus for its enhancement. Despite its importance and practicality, few studies have addressed the effect of this type of training on shooting speed in women's handball. Twenty female players were divided into two groups: isometric training (GI, n=10) and dynamic training (GD, n=10). Over nine weeks, twice a week, both groups completed an upper limb pushing resistance training: GI performed maximum isometric strength, and GD performed dynamic strength at 80% of one maximum repetition (1MR). In both cases, the effort was followed by medicine ball throws. The loads for both groups were equated in terms of sets and duration. Pre- and post-intervention, the 1MR of each player was estimated through a load progression test in bench press exercise. Additionally, the shooting speed with and without aiming at a target was measured from seven and nine meters using a radar. The findings showed a trend towards improvement in both groups (slightly higher in GI); however, only the not-targeted shooting speed from 9 meters in GI reached statistical significance (p < .05). The correlation between 1MR and shooting speed was low to moderate. In summary, both types of training yielded similar results. Given the practical advantages of isometric training, it could be suggested that this training could serve as an effective and practical alternative for enhancing strength and shooting speed in handball. Keywords: Handball, handball shooting, isometric strength training, women's sport.
... In this regard, Lum et al. (2019) suggest, for isometric strength training, a total contraction time of 30 to 90 seconds per session, while Fleck and Kraemer (2017) recommend a frequency of at least three sessions per week. Kanehisa et al. (2002) observed significant improvements in muscle volume, fascicular pennation angle, and torque production in elbow extensions after ten weeks of isometric training with sets of the same duration as in the present study (6s). However, these authors conducted 12 sets per session (totaling 72s of contraction), and the frequency was three sessions per week. ...
Article
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Shooting represents a fundamental skill in handball. Among other factors, its effectiveness requires a significant development of explosive strength. Isometric training may provide a powerful neuromuscular stimulus for its enhancement. Despite its importance and practicality, few studies have addressed the effect of this type of training on shooting speed in women's handball. Twenty female players were divided into two groups: isometric training (IG, n=10) and dynamic training (DG, n=10). Over nine weeks, twice a week, both groups completed an upper limb pushing resistance training: IG performed maximum isometric strength, and DG performed dynamic strength at 80% of one maximum repetition (1MR). In both cases, the effort was followed by medicine ball throws. The loads for both groups were equated in terms of sets and duration. Pre-and post-intervention, the 1MR of each player was estimated through a load progression test in bench press exercise. Additionally, the shooting speed with and without aiming at a target was measured from seven and nine meters using a radar. The findings showed a trend towards improvement in both groups (slightly higher in IG); however, only the not-targeted shooting speed from 9 meters in IG reached statistical significance (p < .05). The correlation between 1MR and shooting speed was low to moderate. In summary, both types of training yielded similar results. Given the practical advantages of isometric training, it could be suggested that this training could serve as an effective and practical alternative for enhancing strength and shooting speed in handball. Keywords: Handball, handball shooting, isometric strength training, women's sport. Resumen. El lanzamiento a portería constituye una habilidad fundamental en balonmano. Su efectividad requiere, entre otros factores, un desarrollo significativo de la fuerza explosiva. El entrenamiento isométrico puede proporcionar un potente estímulo neu-romuscular para su incremento. A pesar de su importancia y practicidad, pocos estudios han abordado el efecto de este tipo de entre-namiento sobre la velocidad del lanzamiento en balonmano femenino. En el presente trabajo, 20 jugadoras fueron divididas en dos grupos: entrenamiento isométrico (GI, n=10) y entrenamiento dinámico (GD, n=10). Durante nueve semanas, dos veces a la semana, ambos grupos entrenaron fuerza de empuje de miembros superiores: GI realizó fuerza isométrica máxima y GD fuerza dinámica al 80% de una máxima repetición (1RM). En ambos casos el esfuerzo fue seguido por lanzamientos de balones medicinales. Las cargas de ambos grupos fueron equiparadas en términos de series y duración. Pre y post intervención se estimó el 1RM de cada jugadora mediante una prueba de progresión de cargas en el ejercicio de press de banca. También se midió, mediante un radar, la velocidad de lanzamiento con y sin puntería a un blanco desde una distancia de siete y de nueve metros. Los resultados mostraron tendencia a la mejora en ambos grupos (ligeramente mayor en GI); pero únicamente la velocidad de lanzamiento sin puntería desde los 9 metros en GI alcanzó significancia estadística (p < 0,05). La correlación entre el 1RM estimado y la velocidad de lanzamiento fue baja a moderada. En suma, ambos tipos de entrenamiento mostraron resultados similares. Dada las ventajas prácticas que ofrece el entrenamiento isométrico, los hallazgos sugieren que dicho entrenamiento podría constituirse en una alternativa eficaz y práctica para la mejora de la fuerza y velocidad de lanzamiento en balonmano. Palabras claves: Balonmano, lanzamiento en balonmano; entrenamiento isométrico de fuerza, deporte femenino.
... Speci cally, among anaerobic exercises, resistance training including squats, lunges, and knee-ups can be easily performed indoors 6 . This type of exercise targets speci c muscles and can enhance both muscle strength and endurance through precise movement and repetition 7 . There has been a growing demand for a variety of user-friendly resistance training programs or devices to help exercise that are easily accessible indoors. ...
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Guidelines encouraging social distancing, limited outings, and remote work due to COVID-19 have increased sedentary periods and reduced levels of physical activity. These habits increase the risk of metabolic diseases, obesity, cardiovascular disease, and diabetes mellitus. The World Health Organization recommends muscle-strengthening exercises as well as regular physical activity to promote overall health. This study investigates the effect of a wearable hip exoskeleton on muscle activity and heart rate during anaerobic exercise in 40 healthy adults (mean age of 40.00 ± 11.51 years; n = 20 females). Bot Fit, a wearable hip-type robotic exoskeleton, was developed by Samsung Electronics Co., Ltd. (Suwon, Republic of Korea) to enhance the effects of both aerobic and anaerobic exercise. All study participants performed a fitness exercise protocol, including knee-ups, good mornings, squats, mountain climbs, kick-backs, reverse lunges, and split jacks, with and without a Bot Fit. To evaluate the effect of anaerobic exercise with the Bot Fit, muscle activity and heart rate were measured during the performance of fitness exercises with and without a Bot Fit. Measured muscles included the rectus abdominis (RA), erector spinae (ES), rectus femoris (RF), vastus lateralis (VL), vastus medialis (VM), biceps femoris (BF), tibialis anterior (TA), gastrocnemius medialis (GCM), and gluteus maximus (GM). During anaerobic exercises with the Bot Fit, there was a significant increase in muscle activity compared to exercising without the Bot Fit. Muscle activity increased significantly in the RA, RF, VL, BF and TA muscles during knee-ups; in the ES, BF, and GM during good mornings; in the RF, VL, VM, BF, and GM during squats; in RA, RF, VL, VM, and GM during mountain climbs; in the RA and BF during kick-backs; in the RF, BF, and GCM during reverse lunges; and in the RF and VL during split jacks ( p < 0.05). Heart rates showed a statistically significant increase during good mornings, mountain climbs, and reverse lunge exercises while wearing the Bot Fit ( p < 0.05). This study demonstrated that anaerobic exercises by healthy adults using a Bot Fit led to enhanced activation of abdominal and lower-limb muscles as well as an improved heart rate, maximizing the effect of anaerobic exercise compared with the same exercise protocol without a Bot Fit. This suggests that use of a Bot Fit can increase the effectiveness of anaerobic exercise in healthy adults.
... Moreover, studies, in which the training is isometric and unilateral, provide a natural way to study the influence of training by comparing the trained limb with the contralateral limb. There exists a number of studies on unilateral training of the upper extremities (e.g., Rasch and Morehouse, 1957;Meyers, 1967;Coleman, 1969;Ikai and Fukunaga, 1970;Knapik et al., 1983;McDonagh et al., 1983;Davies et al., 1988;Thepaut-Mathieu et al., 1988;Kitai and Sale, 1989;Herbert et al., 1998;Macaluso et al., 2000;Ebersole et al., 2002;Kanehisa et al., 2002;Colson et al., 2009;Lee et al., 2009;Driss et al., 2014) and the lower ones (e.g., Young et al., 1985;Alway et al., 1989;Behm and Sale, 1993;Burgess et al., 2007;Del Balso and Cafarelli, 2007) as well as the hand (e.g., Darcus and Salter, 1955;Duchateau and Hainaut, 1984;Cannon and Cafarelli, 1987;Davies et al., 1988;Yue and Cole, 1992;Patten et al., 2001;Carroll et al., 2002;Manca et al., 2016). Most unilateral isometric knee extension (UIKEE) studies focus on neuromechanical changes by analysing EMG data (e.g., Lewis et al., 1984;Carolan and Cafarelli, 1992;Garfinkel and Cafarelli, 1992;Bandy and Hanten, 1993;Weir et al., 1994Weir et al., , 1995Rich and Cafarelli, 2000;Balshaw et al., 2016Balshaw et al., , 2017Ema et al., 2017), morphological changes through monitoring muscle mass/cross-sectional area/volume (e.g., Lewis et al., 1984;Jones and Rutherford, 1987;Garfinkel and Cafarelli, 1992;Kubo et al., 2001;Balshaw et al., 2016Balshaw et al., , 2017, comparison of the training effect of UIKEE with non-isometric modes of training (e.g., Bonde Petersen, 1960;Parker, 1985;Rutherford and Jones, 1986;Jones and Rutherford, 1987;Folland et al., 2000Folland et al., , 2005Lee et al., 2018), changes in co-activation of the synergistic muscles (e.g., Carolan and Cafarelli, 1992;Tillin et al., 2011), cross-education (e.g., Lewis et al., 1984;Weir et al., 1995), comparison of externally stimulated and voluntary exercises on the training outcome (e.g., Mohr et al., 1985;Hartsell, 1986;Kubiak et al., 1987;Baskan et al., 2011), specificity of the joint angle and it's influence at the trained as well as non-trained angles (e.g., Bandy and Hanten, 1993;Weir et al., 1994Weir et al., , 1995, and metabolic changes (e.g., Grimby et al., 1973;Komi et al., 1978;Lewis et al., 1984). ...
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The aim of the study was to investigate the time-dependent increase in the knee extensors' isometric strength as a response to voluntary, unilateral, isometric knee extension exercise (UIKEE). To do so, a systematic review was carried out to obtain data for a Bayesian longitudinal model-based meta-analysis (BLMBMA). For the systematic review, PubMed, Web of Science, SCOPUS, Chochrane Library were used as databases. The systematic review included only studies that reported on healthy, young individuals performing UIKEE. Studies utilizing a bilateral training protocol were excluded as the focus of this review lied on unilateral training. Out of the 3,870 studies, which were reviewed, 20 studies fulfilled the selected inclusion criteria. These 20 studies were included in the BLMBMA to investigate the time-dependent effects of UIKEE. If compared to the baseline strength of the trained limb, these data reveal that UKIEE can increase the isometric strength by up to 46%. A meta-analysis based on the last time-point of each available study was employed to support further investigations into UIKEE-induced strength increase. A sensitivity analysis showed that intensity of training (%MVC), fraction of male subjects and the average age of the subject had no significant influence on the strength gain. Convergence of BLMBMA revealed that the peak strength increase is reached after ~4 weeks of UIKEE training.
... The present study analysed participants with similar basic characteristics: young males (18-30 years) who had practised resistance training for at least one year. Resistance training tends to increase the cross-section area, with a corresponding increase in the maximum strength of the muscle subjected to high mechanical tension (Campos et al., 2002;Kanehisa et al., 2002). Studies analysing the relation between strength and muscular development observe concomitant adaptive progression in these variables (Bonganha, Botelho, Conceição, Chacon-Mikahil, & Madruga, 2010;Okano et al., 2008). ...
Article
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It was our objective to analyse the correlation of the total, adipose, and muscular cross-section areas of the arm with the maximum voluntary strength performance of upper segments in practitioners of resistance training. A cross-sectional study was carried out with 32 healthy male subjects, right-handed and aged between 18 and 30 years at a fitness centre in the city of Fortaleza, Brazil. The maximum voluntary strength was measured by the maximal repetition test (1-MR) in unilateral exercises. A linear correlation was analysed using the Spearman test. Student's t-test was used for the quantitative analysis. A high correlation was obtained of the total cross-section area of the arm with the maximum voluntary biceps force (r= 0.72, p= 0.00) and the sum of loads (r= 0.73, p= 0.00). The muscle cross-section area of the arm showed moderate correlation with the maximum voluntary biceps force (r = 0.57, p= 0.00), triceps (r= 0.53, p= 0.00) and sum of loads (r= 0.59, p= 0.00). A low correlation was observed between the adipose cross-section area of the arm and the variables under analysis. In practitioners of resistance training, the increase in the total and muscle cross-section areas of the arm determines the increase in maximum voluntary strength in the upper segments.
... The present study analysed participants with similar basic characteristics: young males (18-30 years) who had practised resistance training for at least one year. Resistance training tends to increase the cross-section area, with a corresponding increase in the maximum strength of the muscle subjected to high mechanical tension (Campos et al., 2002;Kanehisa et al., 2002). Studies analysing the relation between strength and muscular development observe concomitant adaptive progression in these variables (Bonganha, Botelho, Conceição, Chacon-Mikahil, & Madruga, 2010;Okano et al., 2008). ...
Article
Full-text available
It was our objective to analyse the correlation of the total, adipose, and muscular cross-section areas of the arm with the maximum voluntary strength performance of upper segments in practitioners of resistance training. A cross-sectional study was carried out with 32 healthy male subjects, right-handed and aged between 18 and 30 years at a fitness centre in the city of Fortaleza, Brazil. The maximum voluntary strength was measured by the maximal repetition test (1-MR) in unilateral exercises. A linear correlation was analysed using the Spearman test. Student's t-test was used for the quantitative analysis. A high correlation was obtained of the total cross-section area of the arm with the maximum voluntary biceps force (r= 0.72, p= 0.00) and the sum of loads (r= 0.73, p= 0.00). The muscle cross-section area of the arm showed moderate correlation with the maximum voluntary biceps force (r = 0.57, p= 0.00), triceps (r= 0.53, p= 0.00) and sum of loads (r= 0.59, p= 0.00). A low correlation was observed between the adipose cross-section area of the arm and the variables under analysis. In practitioners of resistance training, the increase in the total and muscle cross-section areas of the arm determines the increase in maximum voluntary strength in the upper segments.
... Although musculo-tendinous stiffness has been reported to be lower in children compared with adults in some (Lambertz et al. 2003) but not all studies (Cornu & Goubel 2001), the effect of RT on tendinous stiffness in children and adolescents has not been investigated. Finally, recent studies in adults have provided strong evidence for an increase in the angle of pennation following RT (Aagaard et al. 2001;Kanehisa et al. 2002;Kawakami et al. 1995;Reeves et al. 2004), allowing for more myofibrillar packing and effectively increasing the physiological cross sectional area. An increase in the angle of pennation by itself is not necessarily advantageous. ...
... • type d'entraînement (l'hypertrophie augmente l'angle de pennation) [68][69][70][71] ; ...
Article
Le cause di debolezza muscolare sono molteplici: immobilizzazione prolungata, lesione muscoloaponeurotica, tendinopatia e frattura consolidata o in corso di consolidazione. Il muscolo non è sempre la principale causa dell’invalidità e saranno applicati diversi protocolli di trattamento a seconda dell’origine del deficit. Per identificare l’origine di questo deficit, è essenziale la valutazione della forza muscolare. Essa è svolta in un momento dato e in certe condizioni psicologiche, affettive (mattina-sera, a digiuno-durante la digestione, euforia-stanchezza, caldo-freddo, nervosismo, stress, ferite, problemi personali) e con diversi tipi di metodiche di valutazione. Questi sono altrettanti parametri che, sovrapposti al morfotipo, influenzeranno i risultati della valutazione. Si misura, quindi, il potenziale muscolare in un momento specifico della vita dell’atleta, che permette di definire la strategia terapeutica per migliorarlo. Il rinforzo, mirato e calibrato, porterà i cambiamenti anatomofisiopatologici ricercati, permettendo, così, un miglioramento delle prestazioni. Esso tiene conto del tipo di muscolo, quindi della sua fisiologia nel gesto atletico nonché del livello dell’atleta prima della sua lesione. Così, i principi del rinforzo muscolare nell’atleta in rieducazione devono tenere conto al tempo stesso della lesione e del livello iniziale dello sportivo per costruire un programma adeguato di rinforzo muscolare per l’atleta infortunato. Tutto questo lavoro ha l’obiettivo di presentare alcune tra le principali lesioni riscontrate negli atleti e i principi generali di rinforzo muscolare adeguato a queste lesioni, in particolare partendo da alcuni esempi di gestione.
... Despite the 3.1% gain in lean muscle mass due to isometric training, this gain was too small to add any extra functional gain. Kanehisa et al. (2002) found only a marginal hypertrophy induced by isometric training without any improvement in dynamic task performance. This may be explained by task specificity, such as static versus dynamic exercise (Jones et al., 1989). ...
Article
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Introduction: Several studies have been developed to determine which type of muscular action (isometric, isotonic and isokinetic) elicits more gains in functional strength and muscle mass. The comparisons between training outcomes are inconclusive due to lack of exercise standardization. Objective: To compare muscle strength, mass, and functional performance in response to isometric, isotonic, and isokinetic contractions, when training loads (volume and intensity) are equated. Method: Data were derived from a university community-recruited sample (n = 31 men). Interventions: Untrained men were assigned to isotonic (IT), isometric (IM), or isokinetic (IK) group, and trained their dominant quadriceps muscle 3 sessions/week for 8 weeks with a dynamometer. Muscle strength was assessed using Cybex 6000 dynamometer; the triple-hop-distance test was used to assess functional performance, and dual energy x-ray absorptiometry to assess lean muscle mass. Results: After training, muscle lean muscle mass increased in isometric (+3.1%, p < 0.01) and isotonic groups (+3.9%, p < 0.01); only the isokinetic group showed a significant improvement in the triple-hop-distance test (4.84%, p < 0.01). Conclusion: Clinicians should consider isometric training as an alternative for isotonic training to gain muscle mass, and isokinetic training to improve functional performance of daily activities and/or sports.
... Bezüglich der Muskeldickenänderungen werden die drei grundlegenden Mechanismen Hypertrophie, Hyperplasie und eine Vermehrung des interstitiellen Bindegewebes diskutiert ( Abernethy, et al., 1994;MacDougall, 2003) Gewebes zugrunde ( Goldspink, 1971;Goldspink & Harridge, 2003;Marx, et al., 2001;McCall, et al., 1996;Stone, et al., 1998) Ausschöpfung der im Muskel eingelagerten energiereichen Phosphate ( Kanehisa, et al., 2002;Saltin & Gollnick, 1983;Schott, et al., 1995;Holm, et al., 2008). Der genaue Anpassungsmechanismus der Hypertrophie ist allerdings nicht final aufgeklärt ( Vierck, et al., 2000). ...
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Das Anforderungsprofil des Fußballspieles zeigt, dass Maximal- und Schnellkraftleis-tungen einen leistungsdeterminierenden Faktor in dieser Sportart einnehmen. Krafttrai-ningsinterventionen im Kindes- und Jugendalter bis hin zum Erwachsenenalter führen zu Leistungsverbesserungen in Maximal- und Schnellkraftparametern. Ziel dieser Untersuchung ist es daher zu klären, ob und wie sich eine zweijährige Krafttrainingsintervention auf Maximal- und Schnellkraftleistungen jugendlicher Athleten aus dem Nachwuchsleistungssport auswirkt. An der zweijährigen Untersuchung nahmen 114 Probanden aus zwei Vereinen teil, die durch den Deutschen Fußball Bund e.V. mit dem Prädikat eines Leistungszentrums ausgezeichnet sind. Die Fußballer wurden in zwei Gruppen unterteilt. Die Fußballer wurden zusätzlich jeweils in Subgruppen nach Alter (unter 14 Jahren [U14], unter 16 Jahren [U16] und unter 18 Jahren [U18]) zugeordnet. Die eine Gruppe (KT) führte zweimal wöchentlich zusätzlich zum regulären Fußballtraining ein Krafttraining durch, die andere Gruppe (KG) absolvierte ausschließlich das reguläre Fußballtraining. Es wurde die Leistungsfähigkeit im Squat- (SJ), Countermovement- (CMJ) und Drop Jump (DJ) aus unterschiedlichen Höhen (16 bis 40 Zentimeter), sowie Maximalkraftleistungen im Ei-ner-Wiederholungs-Maximum (1RM) der Front- und Nackenkniebeuge vor, nach einem Jahr und nach der zweijährigen Trainingsphase erfasst. Zur Kontrolle des Einflussfak-tors Wachstum wurden in diesem Forschungsprojekt Querschnittsdaten im SJ, CMJ und DJ von insgesamt 426 Schülern (männlich) im Alter zwischen 12 und 19 Jahren analog zu den Fußballern erhoben. Die Schüler wurden in Altersklassen (U13 bis U19) eingeteilt. Für die Analyse der Leistungsentwicklung innerhalb einer Gruppe und die paarweisen Vergleiche zwischen zwei Gruppen wurde eine zweifaktorielle Varianzanalyse mit Messwiederholung mit den Faktoren Gruppe und Zeit durchgeführt. Im Falle signifikan-ter F-Werte wurde eine Post-hoc-Analyse (Scheffe) durchgeführt, um die Lokalisation der signifikanten Veränderungen zu errechnen. Die Analyse der Querschnittsdaten er-folgte über die einfaktorielle Varianzanalyse. Die Post-hoc-Analyse (Scheffe) zeigte statistisch signifikante Leistungsunterschiede zwischen den Altersklassen auf (paarwei-se Vergleiche zwischen zwei Altersstufen). Zur Ermittlung von Zusammenhängen zwi-schen verschiedenen Parametern wurde die Produkt-Moment-Korrelation nach Pearson berechnet. Das Signifikanzniveau wurde für alle statistischen Verfahren auf p < 0,05 festgelegt. Im Vergleich der Fußballer schnitt die Krafttrainingsgruppe nach der zweijährigen Untersuchungsdauer in den Maximalkraftleistungen der Front- und Nackenkniebeuge in allen Altersklassen signifikant besser ab. Die Ergebnisse der KG zeigen in der U18 für die Maximalleistungen bei den Kniebeugen über zwei Jahre Steigerungen im Mittel von 9,3 ± 13,1 bis 37,1 ± 21,4%, in der U16 von 48,3 ± 39,7 bis 62,1 ± 53,3% und in der U14 von 84,4 ± 26,1 bis 94 ± 39,8%. Die Leistungssteigerungen der KT in den Maxi-malkraftparametern übersteigen die Zunahmen der KG bei Weitem. In der U14 finden sich je nach Parameter zwischen 290,9 ± 107,7 bis 312,6 ± 118,6% Leistungssteigerung über zwei Jahre. Die U16 weist 112,4 ± 32,7 bis 121,4 ± 39,4% Leistungssteigerung auf und die U18 zwischen 104,0 ± 45,6 bis 106,0 ± 34,4% Leistungssteigerung je nach Pa-rameter über zwei Jahre. Im Squat Jump zeigte die KT ebenfalls signifikant bessere Leistungen (U18: 26,1 ± 13,9%, U16: 29,7 ± 16,7%, U14: 30,9 ± 13,8%), als die Gruppe, die kein Krafttraining absolvierte (U18: 1,0 ± 8,7%, U16: 10,4 ± 11,8%, U14: 8,1 ± 9,9%). Ähnliche signifikante Steigerungsraten wurden beim Countermovement Jump (U18: 20,3 ± 14,0% vs. 1,2 ± 6,9%, U16: 21,2 ± 14,4% vs. 11,1 ± 10,5%, U14: 21,6 ± 14,4% vs. 9,9 ± 7,7%) zugunsten der KG ermittelt. Die U18 der KT weist im Mittel Steigerungen des Drop Jump in den jeweiligen Höhen von 6,6 ± 16,9 bis 14,8 ± 21,3% auf. Es wurden keine signifikanten Unterschiede zur KG analysiert (Steigerungen: 0,0 ± 20 bis 6,2 ± 27,0%). Die U16 der KT erreicht Steigerungen im DJ im Mittel von 35,8 ± 28,8 bis 36,9 ± 22,5%. Dies führte zu signifikanten Unterschieden gegenüber der KG, die Steigerungen von 15,1 ± 20,8 bis 22,0 ± 19,0% aufwies. Zwischen den Gruppen der U14 kam es zu signifikanten Unterschieden im Ausgangstest. Die KT der U14 wies höhere Steigerungen (29,2 ± 25,8 bis 41,3 ± 29,3%) auf als die KG (1,5 ± 18,3 bis 15,2 ± 30,8%). Die Abschätzung der Leistungsentwicklung in den Schnellkraftparametern zeigte, dass es mit dem Alter zu leistungspositiven Veränderungen kommt. Unterstellt man, dass die Differenz zwischen den Mittelwerten der Leistungsparameter der einzel-nen Altersklassen der untrainierten Schüler die entwicklungsbedingte Leistungsentwick-lung darstellt, finden sich die höchsten Zunahmen zwischen den Altersklassen der U13 und der U17 und die geringsten Zunahmen bei den ältesten Jugendlichen. Die Gruppen-vergleiche erreichten nicht zwischen allen Altersstufen signifikantes Niveau, sondern zum Teil erst zu mindestens zwei Jahre älteren Probandengruppen. Die Zusammenhangsanalysen zeigen hohe Zusammenhänge zwischen dem SJ und CMJ und den Maximalkraftparametern. Die Zusammenhänge zwischen den Maximalkraftparametern und den Leistungen im DJ klassifizieren sich als gering bis mittel. Die Daten zeigen, dass sowohl dem Faktor körperliche Entwicklung, als auch der Sportart Fußball leistungspositive Einflüsse auf Schnellkraftleistungen zugeordnet wer-den können. Die Datenlage dieser Untersuchung zeigt ferner, dass ein Krafttraining ei-nen positiven Effekt auf Leistungsparameter im Fußball hat. Eine langfristige Trai-ningsintervention von zwei Jahren kann zu einer deutlichen Steigerung des 1RM, des SJ, des CMJ und des DJ führen. Die Maximal- und Schnellkraft ist demnach im Ju-gendalter durch ein langfristig angelegtes Krafttraining sehr gut zu steigern. Demnach ist ein ergänzendes Krafttraining im Nachwuchsleistungssport der Sportart Fußball zu empfehlen.
... Compared to VL, investigation of other muscles is limited. Studies have found changes in the pennation angle of each muscle of the quadriceps femoris 68) , as well as VL, RF 83,84) , BF 55) , MG 85) , LG 59,86) , TB 70,73,87,88) , biceps brachii 89) , brachialis 89) and supraspinous 90) . A positive correlation was shown between the absolute values of muscle thickness and pennation angle for TB 73) and each muscle of the quadriceps femoris 68) before and after the interventions. ...
Article
The present review summarizes current evidence and unresolved issues regarding training-induced changes in the architecture of human skeletal muscles. As architectural parameters, we focused on the fascicle length and pennation angle, which are related to force-generating capability of pennate muscles. Cross-sectional studies in sport athletes suggested changes in both the parameters following chronic sport-specific activities. Longitudinal training intervention experiments indicated direct evidence of the plasticity of the two parameters induced by resistance training, but no consensus has been reached regarding the factors influencing those changes. Considering the importance of fascicle arrangement on muscle function, future studies are required to explain the underpinning mechanisms of the adaptation.
... La arquitectura muscular se relaciona con factores intrínsecos de la persona, como el sexo 9 , la edad 10,11 y la raza 12 , pero a su vez puede sufrir cambios por otros factores, como el entrenamiento de fuerza 13-17 o la inactividad 18 . Con el entrenamiento de fuerza orientado a la hipertrofia, el grosor muscular y los ángulos de pennación aumentan 13,15,19 . Sin embargo, en algunos estudios transversales y longitudinales se han encontrado cambios distintos en los ángulos de pennación 4, 16,19,20 . ...
Article
Muscle architecture describes the geometric design of a muscle. It will have a great influence in the force generating capacity and the shortening velocity of skeletal muscle. The purposes of this study were to analyse and compare, in four groups of young women with different levels of physical activity, the architectural characteristics of lower limb extensor muscles, and the differences between muscles. Twelve elite female volleyball players (ELITE), 12 club level female Volleyball players (MEDIO), 10 physical education students (EST) and 12 sedentary young women (SED) volunteered for the study. Muscle thickness, pennation angles and fascicle length of vastus lateralis (VL), gastrocnemius medialis (GM) and gastrocnemius lateralis (GL) were analysed by means of ultrasonography, and the anthropometric characteristics of each group were determined. The differences among muscles were similar to those reported in the literature, and were related to the functional use of each muscle. The VL muscle architecture was related to the development of great forces at high contraction velocities, because of its muscle thickness and fascicle length. There were significant differences in muscle thicknesses and fascicle lengths between SED and the groups of volleyball players (MED and ELITE). These differences would be related to the ability to develop higher levels of force and velocity, due to the greater number of in-parallel and in-series sarcomeres. The longer fascicle lengths found in the ELITE group would have been caused by their specific training, mainly composed by jumps and explosive movements that led to forced stretching of muscle fascicles. The correlations between fascicle lengths and muscle thickness in ELITE and MED are similar to those found in sports where explosive strength and speed are essential for the performance.
... Further, there is evidence in the literature that even in young healthy adults, strength training using low compared with high loads is equally effective in enhancing muscle strength. For example, isometric strength training at 100 versus 60 % of maximal voluntary contraction (MVC) [56] or dynamic strength training at 55-60 versus 80-90 % 1RM [57] resulted in similar improvements in measures of muscle strength. Thus, there is evidence that application of lower loads during STU provides a sufficient training stimulus to ensure similar strength or power training gains in comparison with STS using higher loads in different age groups. ...
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Background: The effectiveness of strength training on unstable surfaces (STU) versus stable surfaces (STS) or a control condition (CON; i.e. no training or regular training only) for strength, power and balance performance across the lifespan has not yet been investigated in a systematic review and meta-analysis. Objective: The aims of this systematic review and meta-analysis were to determine the general effects of STU versus STS or CON on muscle strength, power and balance in healthy individuals across the lifespan and to investigate whether performance changes following STU are age specific. Data sources: A computerized systematic literature search was performed in the electronic databases PubMed and Web of Science from January 1984 up to February 2015. Study eligibility criteria: Initially, 209 articles were identified for review. Only controlled trials were included if they investigated STU in healthy individuals and tested at least one measure of maximal strength, strength endurance, muscle power, or static/dynamic balance. In total, 22 studies met the inclusion criteria. Study appraisal and synthesis methods: The included studies were coded for the following criteria: age, sex, training status, training modality, exercise and test modality. Effect size measures included within-subject standardized mean differences (SMDw) and weighted between-subject standardized mean differences (SMDb). Heterogeneity between studies was assessed using I (2) and χ (2) statistics. The methodological quality of each study was assessed using the Physiotherapy Evidence Database (PEDro) Scale. Results: Our search failed to identify studies that examined the effects of STU versus STS or CON in children and middle-aged adults. However, four studies were identified that investigated the effects of STU versus CON or STS in adolescents, 15 studies were identified in young adults and three studies were identified in old adults. Compared with CON, STU produced medium effects on maximal strength in young adults and no effects to medium effects in old adults. In addition, large effects were detected on strength endurance in adolescents and in young adults; in old adults, a small effect was found. With regard to muscle power, medium effects were observed in young adults and small effects were observed in old adults. Further, large effects were found for static and dynamic balance in old adults, but only a small effect was found for dynamic balance in young adults. The comparison of STU and STS revealed inconsistent results as indicated by training-induced changes in favour of STU, as well as STS. Small to medium effects were found for maximal strength in adolescents in favour of STS, and small effects were found in young adults in favour of STU. With regard to strength endurance, large effects were found in adolescents in favour of STS and small effects were found in favour of STU. Additionally, we detected small effects in young adults in favour of STU. In terms of muscle power, no effects were observed in adolescents but medium effects were found in favour of STS in young adults. With regard to balance, small effects were detected in adolescents for static and dynamic balance in favour of STU. In young adults, small effects were found for static balance in favour of STS. With regard to dynamic balance, the analysis revealed small effects in young adults in favour of STU. Limitations: The quality of the included studies was rather low, with mean PEDro scores of 5.8, 4.0 and 5.0 for studies including adolescents, young adults and old adults, respectively. Further, trivial to considerable heterogeneity between studies (i.e. 0 % ≤ I (2) ≤ 96 %) was detected. Conclusions: Compared with CON, STU is effective in improving muscle strength, power and balance in adolescents, young adults and old adults. However, inconsistent results were particularly found in adolescents and young adults when the specific effects of STU were compared with those of STS. We conclude that the performance of STU compared with STS has limited extra effects on muscle strength, power and balance performance in healthy adolescents and young adults. Given that our systematic search did not identify studies that examined the effects of STU versus STS in children, middle-aged adults and old adults, further research of high methodological quality is needed to determine whether there are additive effects of STU as compared with STS in those age groups.
... In agreement with previous findings (8,16,17), both training groups showed improved MVF of the elbow flexor and extensor muscles after 6 weeks of MIVCC training performed 3 times per week. These findings showed that short-term training consisting of simultaneous maximal voluntary co-contractions of antagonistic muscle pairs could provide similar results to those obtained with traditional isometric training programs (15,19). Furthermore, the results of combined data performed in 20 participants confirmed that MIVCC training could enhance MVF in the morning and evening independently of the training time, but the highest strength gains were observed at the time-of-day at which training was scheduled for both training groups. ...
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The study investigated the effect of the time-of-day at which maximal isometric voluntary co-contraction (MIVCC) training is conducted on the adaptation and diurnal variation of maximal and explosive force production. Twenty active men underwent 6-week (3 times/week) MIVCC training of the right elbow joint. Participants were randomly assigned to a morning (MTG, 07:00–08:00 h) and evening (ETG, 17:00–18:00 h) training group. Maximal voluntary force (MVF) and maximal rate of force development (MRFD) during isometric elbow flexion (MVFF and MRFDF) and extension (MVFE and MRFDE) were recorded before (T0) and after (T1) training in the morning and in the evening. At T0, MVF and MRFD were higher in the evening compared to the morning for MTG and ETG (p<0.05). At T1, MVFF and MVFE increased at the morning and evening for both groups (p<0.001). MRFDF and MRFDE increased only if training and testing session were scheduled at the same time. The relative increases of MVF was greater at the specific time of training for MTG (12% and 17.6% in MVFF and MVFE, respectively) and ETG (9.8% and 13.4% in MVFF and MVFE, respectively). The diurnal variations in MVF and MRFD during flexion and extension disappeard in MTG and persisted in ETG. MIVCC training enhanced muscle strength whatever the time-of-day at which training was scheduled without alteration of explosive force. In contrast, to optimize the muscle strength our results suggested that morning training may be accompanied by the greatest muscle strength gain and blunted muscle strength variation observed between morning and evening.
... The fact that sarcopenia is caused by disuse supports the idea that sarcopenia can be reversed by physical activity (Manini & Clark, 2012) Resistance training is known to attenuate and/or reverse strength and functional losses associated with the aging process (Aagaard et al., 2001;Blazevich & Giorgi, 2001;Kawakami, Abe, Kuno, & Fukunaga, 1995;Narici et al., 1999). High-intensity resistance training has been deemed as one of the best approaches to cause gains in strength, cross-sectional area, muscle thickness, sarcomere length, and pennation angle of the muscle fibers for older adults (Aagaard et al., 2001;Hazell, Kenno, & Jakobi, 2007;Kanehisa et al., 2002;Kubo et al., 2003;Steib, Schoene, & Pfeifer, 2010). Reeves, Maganaris, Longo, and Narici (2009) reported modification in the muscle architecture after 14 weeks of conventional resistance training (concentric and eccentric actions) and eccentric training performed with loads of 80% of 5RM. ...
Article
Aging is related to a progressive remodeling of the neuromuscular system, which includes muscle mass, strength and power reductions. This study investigated the effect of an eight-week dance program on fascicle pennation angle, fascicle length and thickness of the Vastus Lateralis (VL), Tibialis Anterioris (TA), Bíceps Femoris (BF) and Gastrocnemius Medialis (GM) muscles using ultrasound images. Thirty-four healthy older women were randomly assigned to dancing (DG - n=19, 69.1 ± 6.5 years, 72.5 ± 11.7 kg) and control group (CG - n=15, 71.5 ± 7.4 years, 70.9 ± 9.3 kg). After training, the DG showed greater (p<0.05) thickness for VL (16%), TA (17%), BF (19%) and GM (15%); pennation angle for VL (21%), TA (23%), BF (21%) and GM (17%); fascicle length for VL (11%), TA (12%), BF (10%) and GM (10%). These findings suggest that dance training was effective to change lower limb's muscle architecture in older female adults.
... It must be remembered that such observations only infer plasticity of neural processes considered necessary for lasting behavioral change. It is well known that behavioral changes may manifest in the absence of neural changes, i.e., through changes in muscle composition [5][6][7][8], or refined movement control resulting from repetitive practice [8]. Throughout this review, the distinction between physiological and functional measures of EDP is made. ...
Article
Experience-dependent plasticity (EDP) is a general term used to describe neural and associated behavioral adaptations resulting from experience. Because the objective of dysphagia rehabilitation is to induce long-term permanent change in swallowing physiology, understanding EDP processes is crucial for documenting the efficacy of treatments. There is little information about natural processes of EDP related to swallowing (i.e., changes associated with aging and impairment). Therefore, the “baseline” on which we apply dysphagia treatments remains unclear. Because EDP is characterized by peripheral and central adaptations of physiologic and functional measures over time, effectively documenting EDP requires multiple outcome measures at multiple time points. This review will discuss mechanisms of endogenously induced EDP, including aging and impairment. A review of current dysphagia rehabilitation literature will be provided to indicate the state of evidence for exogenously induced EDP. Future considerations for the study of EDP related to dysphagia will also be offered.
... A number of studies have shown changes in muscle architecture in response to resistance training (Aagaard et al. 2001;Blazevich et al. 2007;Ema et al. 2013;Kanehisa et al. 2002;Kawakami et al. 1995;Seynnes et al. 2007). The architectural change in a pennate muscle with hypertrophy was modeled by Maxwell et al. (1974). ...
Article
Purpose: This study aimed to ascertain whether training-induced muscle hypertrophy is accompanied by an increase in the aponeurosis width, and to infer its impact on the training-induced increase in the pennation angle. Methods: Eleven young men completed a resistance training program of unilateral knee extensions for 12 weeks. Before and after training, anatomical cross-sectional area (ACSA) of the vastus lateralis and its distal aponeurosis width in the transverse plane were measured with magnetic resonance imaging. The pennation angle and fascicle length were also determined with ultrasonography at the midbelly of the muscle. The effect of change in aponeurosis width on the magnitude of training-induced increase in pennation angle was estimated by using a parallelepipedon model. Results: After the training, there were significant increases in ACSA (10.7 ± 7.6 %), pennation angle (10.8 ± 7.3 %) and aponeurosis width (1.9 ± 3.1 %), whereas no significant change was found in the fascicle length. The model simulation shows that the increase in aponeurosis width by 1.9 % reduces the magnitude of increase in pennation angle by only 0.4°. Conclusions: These results indicate that (1) the aponeurosis width of the vastus lateralis increases after 12 weeks of resistance training and (2) the increase in the aponeurosis width accompanying muscle hypertrophy by the amount of ~10 % does not substantially affect the increase in pennation angle.
... resistance exercise protocols without WBV, there was a significant decrease in quadriceps strength observed. It has also been postulated in previous studies that any gains in strength due to neurological changes would occur after approximately 1 to 4 weeks of chronic resistance training (1,29), and furthermore, any gains in strength due to morphological changes would occur after 6 to 12 weeks of chronic resistance training (2,21,22). In this study, subjects observed a significantly greater decrease in quadriceps strength after the performance of 5 sets static squats compared with the 5 sets of dynamic squats (Figure 2). ...
Article
Numerous studies have shown performance benefits from including whole-body vibration (WBV) whether as a training modality or an acute exercise protocol when utilized as a component of the resistance training program. Some studies have indicated that performing dynamic exercises as compared to static position exercises while exposed to WBV might be beneficial, however, evidence is lacking. Thus, the purpose of this study was to determine if an acute bout of dynamic vs. static squats performed during WBV results in increases in quadriceps force production via dynamic isokinetic knee extension and flexion exercise.
... Muscle architectural adaptations to resistance exercise depend on several factors such as training status, intensity-volume relationship and muscle activation (Folland & Williams, 2007). These resistance-training-induced muscle architectural changes have been commonly quantified through the application of imaging techniques (Kawakami et al., 1995;Kanehisa et al., 2002;Blazevich et al., 2006). In this scenario, ultrasonography constitutes a safe, relatively low-cost and reliable technique (Lima et al., 2012), which has been validated through comparisons to 'gold standard' methods such as magnetic resonance imaging (RMI) and computerized axial tomography (Bemben, 2002;Noorkoiv et al., 2010). ...
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PurposeThis study aimed to determine the architectural changes of rectus femoris muscle at distinctive sites of the thigh length after two different 14-week resistance training programmes.Methods Thirty-five untrained men were randomly allocated into three different groups: conventional resistance training (n = 12), isokinetic training (n = 12) and control (n = 11). Rectus femoris cross-sectional area, thickness and fascicle angle at two specific thigh sites (30% and 50% of the length) were assessed before and after 14 weeks of unilateral knee extension exercise or control. The isometric peak torque of the knee extensors was estimated as a muscle strength index.ResultsConventional (30% = 47·4% versus 50% = 14·4%) and isokinetic (30% = 31·8% versus 50% = 11·4%) training induced significant increases on thickness at both rectus femoris sites. While conventional training resulted in substantial increments on cross-sectional area (30% = 62·1%, 50% = 19·5%), isokinetic training provoked a significant increase only at the distal site (50% = 64·7%). The isometric peak torque increased (22·4 and 29·6%, for conventional and isokinetic groups, respectively) after training independently of the training mode, although no significant changes were observed for any dependent variable in the control group.Conclusions In general, the training modes resulted in similar changes on rectus femoris architecture, whereas their magnitude depended on the thigh site.
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Guidelines encouraging social distancing, limited outings, and remote work due to COVID-19 have increased sedentary periods and reduced levels of physical activity. These habits increase the risk of metabolic diseases, obesity, cardiovascular disease, and diabetes mellitus. The World Health Organization recommends muscle-strengthening exercises as well as regular physical activity to promote overall health. This study investigates the effect of a wearable hip exoskeleton on muscle activity and heart rate during anaerobic exercise in 40 healthy adults (mean age of 40.00 ± 11.51 years; n = 20 females). Bot Fit, a wearable hip-type robotic exoskeleton, was developed by Samsung Electronics Co., Ltd. (Suwon, Republic of Korea) to enhance the effects of both aerobic and anaerobic exercise. All study participants performed a fitness exercise protocol, including knee-ups, good mornings, squats, mountain climbs, kick-backs, reverse lunges, and split jacks, with and without a Bot Fit. To evaluate the effect of anaerobic exercise with the Bot Fit, muscle activity and heart rate were measured during fitness exercises with and without a Bot Fit. Measured muscles were the rectus abdominis (RA), erector spinae (ES), rectus femoris (RF), vastus lateralis (VL), vastus medialis (VM), biceps femoris (BF), tibialis anterior (TA), gastrocnemius medialis (GCM), and gluteus maximus (GM). During anaerobic exercises with the Bot Fit, there was a significant increase in muscle activity compared to exercising without the Bot Fit. Muscle activity increased significantly in the RA, RF, VL, BF and TA muscles during knee-ups; in the ES, BF, and GM during good mornings; in the RF, VL, VM, BF, and GM during squats; in RA, RF, VL, VM, and GM during mountain climbs; in the RA and BF during kick-backs; in the RF, BF, and GCM during reverse lunges; and in the RF and VL during split jacks (p < 0.05). Heart rates showed a statistically significant increase during good mornings, mountain climbs, and reverse lunge exercises while wearing the Bot Fit (p < 0.05). This study demonstrated that anaerobic exercises by healthy adults using a Bot Fit led to enhanced activation of abdominal and lower-limb muscles as well as an improved heart rate, maximizing the effect of anaerobic exercise compared with the same exercise protocol without a Bot Fit. This suggests that use of a Bot Fit can increase the effectiveness of anaerobic exercise in healthy adults.
Chapter
Self-rehabilitation has an increasingly important role in rehabilitation. However, there are very few data regarding the methodology for creating a self-rehabilitation program available in the literature.
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This narrative review deals with the topic of strength training in swimming, which has been a controversial issue for decades. It is not only about the importance for the performance at start, turn and swim speed, but also about the question of how to design a strength training program. Different approaches are discussed in the literature, with two aspects in the foreground. On the one hand is the discussion about the optimal intensity in strength training and, on the other hand, is the question of how specific strength training should be designed. In addition to a summary of the current state of research regarding the importance of strength training for swimming, the article shows which physiological adaptations should be achieved in order to be able to increase performance in the long term. Furthermore, an attempt is made to explain why some training contents seem to be rather unsuitable when it comes to increasing strength as a basis for higher performance in the start, turn and clean swimming. Practical training consequences are then derived from this. Regardless of the athlete’s performance development, preventive aspects should also be onsidered in the discussion. The article provides a critical overview of the abovementioned key issues. The most important points when designing a strength training program for swimming are a sufficiently high-load intensity to increase maximum strength, which in turn is the basis for power, year-round trength training, parallel to swim training and working on the transfer of acquired strength skills in swim training, and not through supposedly specific strength training exercises on land or in the water.
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Research in instability has focused on the analysis of muscle activation. The aim of this systematic review was to analyse the effects of unstable devices on speed, strength and muscle power measurements administered in the form of controlled trials to healthy individuals in adulthood. A computerized systematic literature search was performed through electronic databases. According to the criteria for preparing systematic reviews PRISMA, nine studies met the inclusion criteria. The quality of the selected studies was evaluated using STROBE. The average score was 14.3 points, and the highest scores were located in ‘Introduction’ (100%) and ‘Discussion’ (80%). There is great heterogeneity in terms of performance variables. However, instability seems to affect these variables negatively. The strength variable was affected to a greater degree, but with intensities near to the 1RM, no differences are observed. As for power, a greater number of repetitions seems to benefit the production of this variable in instability in the upper limb. Instability, in comparison to a stable condition, decreases the parameters of strength, power, and muscular speed in adults. The differences shown are quite significant in most situations although slight decreases can be seen in certain situations.
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Kubo, K, Ikebukuro, T, and Yata, H. Effects of 4, 8, and 12 repetition maximum resistance training protocols on muscle volume and strength. J Strength Cond Res XX(X): 000-000, 2020-The purpose of this study was to determine skeletal muscle adaptations (strength and hypertrophy) in response to volume-equated resistance training with divergent repetition strategies. Forty-two men were randomly assigned to 4 groups: higher load-lower repetition group performing 4 repetition maximum (RM) for 7 sets (4RM, n = 10), intermediate load-intermediate repetition group performing 8RM for 4 sets (8RM, n = 12), lower load-higher repetition group performing 12RM for 3 sets (12RM, n = 10), and nonexercising control group (CON, n = 10). The volume of the pectoralis major muscle (by magnetic resonance imaging) and 1RM of the bench press were measured before and after 10 weeks of training (2 times per week). No significant difference was observed in the relative increase in the muscle volume among the 4RM, 8RM, and 12RM groups. The relative increase in 1RM was significantly lower in the 12RM group than in the 4RM group (p = 0.029) and the 8RM group (p = 0.021). The relative increase in 1RM was significantly correlated with that in the muscle volume in the 12RM group (r = 0.684, p = 0.042), but not in the 4RM (r = -0.265, p = 0.777) or 8RM (r = -0.045, p = 0.889) groups. These results suggest that the increase in muscle size is similar among the 3 training protocols when the training volume was equated, whereas the increase in muscle strength is lower with the 12RM protocol than the other protocols.
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The purpose of this study was to quantify the effect of the contraction duration of two isometric exercise protocols on the post-activation potentiation of 14 well-trained males (age: 22.6±2.8 yrs., height: 180.3±5.9 cm, body mass: 72.3± 37.9 kg). The protocols consisted of 4x6 maximal plantar flexions, of 3 s (P3) or 6 s (P6) duration, performed in random order, with a 2 minute and 15 s intervals between the sets and repetitions, respectively. The torque during maximal isometric voluntary contraction (MIVC), the peak twitch torque (TT), and the rate of torque development (RTD) after each MIVC were analyzed, for the first and the last trial of each set, the average of all trials of each set, and the trials within each set that had the highest peak TT. The MIVC had an overall greater reduction during P6 compared to P3 (P3: -4.6±2.3% vs. P6: -16.0±1.9%). P6 showed higher potentiation in TT during the initial repetitions of the first 2 sets (p<0.05) in contrast to the P3, which revealed a lower potentiation but for a longer period along the exercise session. However, both protocols had on average the same potential for potentiation (P3: 81.6±6.1% vs. P6: 79.8±6.3%). The twitch RTD presented no systematic difference between the two protocols (p>0.05). These data demonstrate the dependence of the TT potentiation on the conditioning stimulus and verify the cumulative effect of potentiation, suggesting the implementation of longer contractions to achieve maximal but temporal TT potentiation and shorter contractions for less variable but prolonged potentiation.
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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.
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The role of intramuscular metabolite changes in the adaptations following isometric strength training was examined by comparing the effect of short, intermittent contractions (IC) and longer, continuous (CC) contractions. In a parallel study, the changes in phosphate metabolites and pH were examined during the two protocols using whole-body nuclear magnetic resonance spectroscopy (NMRS). Seven subjects trained three time per week for 14 weeks. The right leg was trained using four sets of ten contractions, each lasting 3 s with a 2-s rest period between each contraction and 2 min between each set. The left leg was trained using four 30-s contractions with a 1-min rest period between each. Both protocols involved isometric contractions at 70% of a maximum voluntary isometric contraction (MVC). The MVC, length:tension and force:velocity relationships and cross-sectional area (CSA) of each leg were measured before and after training. The increase in isometric strength was significantly greater (P = 0.041) for the CC leg (median 54.7%; P = 0.022) than for IC (31.5%; P = 0.022). There were no significant differences between the two protocols for changes in the length:tension or force:velocity relationships. There were significant increases in muscle CSA for the CC leg only. NMRS demonstrated that the changes in phosphate metabolites and pH were greater for the CC protocol. These findings suggest that factors related to the greater metabolite changes during CC training results in greater increases in isometric strength and muscle CSA.
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Five men underwent unilateral resistance training of elbow extensor (triceps brachii) muscles for 16 weeks. Before and after training, muscle layer thickness and fascicle angles of the long head of the triceps muscle were measured in vivo using B-mode ultrasound, and fascicle lengths were estimated. Series anatomical cross-sectional areas (ACSA) of the triceps brachii muscle were measured by magnetic resonance imaging, from which muscle volume (Vm) was determined and physiological cross-sectional area (PCSA) was calculated. Elbow extension strength (isometric; concentric and eccentric at 30, 90 and 180°·s−1) was measured using an isokinetic dynamometer to determine specific tension. Muscle volumes, ACSA, PCSA, muscle layer thickness and fascicle angles increased after training and their relative changes were similar, while muscle and fascicle length did not change. Muscle strength increased at all velocities; however, specific tension decreased after training. Increase in fascicle angles, which would be the result of increasedV m and PCSA, would seem to imply the occurrence of changes in muscle architecture. This might have given a negative effect on the force-generating properties of the muscles.
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The effects of maximal effort strength training with different loads on maximal strength, muscle cross-sectional area, the load-power and load-velocity relationship were investigated in the elbow flexors. Physical education students were matched into three groups; G90 (n = 9) trained with a load of 90%. G35 (n = 11) with 35%, and G15 (n = 10) with 15% of IRM (1 repetition maximum). Training consisted of three to five sets, performed three times a week for 9 weeks. Each set consisted of two, seven and ten repetitions in G90. G35 and G15, respectively. Training was performed with the nondominant arm, and the dominant arm served as control. The IRM increased 15.2 (SD 4.5)% (P < 0.001) in G90, 10.1 (SD 5.9)% (P < 0.001) in G35 and 6.6 (SD 7.9)% (P < 0.05) in G15. The increase in G90 was significantly larger than for G15 (P < 0.05). In the untrained arm, IRM also increased for G90 and G15. In contrast to G90. G15 showed a similar increase in IRM in both arms. Cross-sectional area of the elbow, flexors did not change for G90 and G15. while G35 increased 2.8% (P < 0.05). Maximal power and velocity were tested at 2.5 kg and at 15%, 25%, 35%, 50%, 70% and 90% of pretraining IRM. Power increased for all tested loads in G90 and G35, and G15 showed an increase in power at 15%, 25% and 50% of IRM. No significant differences in increase in power could be found among the three groups at loads equal to or less than 50%, but at 70% and 90% of IRM the increase was larger for G90 and G35 than for G15 (P < 0.05). The G35 showed a similar increase in power at all loads tested whereas G90 showed load specificity in the effect of the training. There was a correlation between IRM and maximal power (r = 0.93, P < 0.0001), and between IRM and power at load 2.5 kg (r = 0.73, P < 0.0001). In conclusion, training with loads of 15% and 35% of IRM resulted in an increase in IRM. Although the increase in maximal power after training at 90% of IRM showed some load specificity. It also increased maximal power at 15% of IRM. Training at loads near maximal power output would seem to increase power efficiently over a wide load range. The high correlation between IRM and maximal power at load 2.5 kg also would indicate that maximal strength is important for performance at light loads.
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In clinical measurement comparison of a new measurement technique with an established one is often needed to see whether they agree sufficiently for the new to replace the old. Such investigations are often analysed inappropriately, notably by using correlation coefficients. The use of correlation is misleading. An alternative approach, based on graphical techniques and simple calculations, is described, together with the relation between this analysis and the assessment of repeatability.
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Isometric and dynamic strength and endurance of knee extensors were tested in 18 young males. The relative composition of slow (ST) and fast twitch (FT) fibers in the vastus lateralis muscle was registered from needle biopsies. Thigh muscle volume was evaluated from ultrasonic measurements. Six subjects served as controls, six trained with 50%, and six with 80% dynamic strength three times per week for 7 weeks with 20 and 12 repetitions per session, respectively. The training load was adjusted to the increases in strength observed during training. Dynamic strength increased by 42.3% in the 80% group (p< 0.01). In the control group and 50% group no significant increases were observed. Dynamic endurance: Controls showed no change. There was an over-all increase in the 50% group, while the 80% group only increased dynamic endurance for heavier loads. Isometric strength and endurance and fiber composition did not change in any group. In the 50% group the area of FT-realtive to ST-fibers increased 12.4% (p>0.05). Dynamic strength relative to muscle cross section increased by 30% in the 80% group (p<0.01) positively correlated to relative content of FT fibers. The present results confirm the specificity of training and indicate that a high content of FT fibers is a prerequisite for a successful strength training.
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Magnetic resonance imaging techniques were used to determine the physiological cross-sectional areas (PCSAs) of the major muscles or muscle groups of the lower leg. For 12 healthy subjects, the boundaries of each muscle or muscle group were digitized from images taken at 1-cm intervals along the length of the leg. Muscle volumes were calculated from the summation of each anatomical CSA (ACSA) and the distance between each section. Muscle length was determined as the distance between the most proximal and distal images in which the muscle was visible. The PCSA of each muscle was calculated as muscle volume times the cosine of the angle of fiber pinnation divided by fiber length, where published fiber length:muscle length ratios were used to estimate fiber lengths. The mean volumes of the major plantarflexors were 489, 245, and 140 cm3 for the soleus and medial (MG) and lateral (LG) heads of the gastrocnemius. The mean PCSA of the soleus was 230 cm2, about three and eight times larger than the MG (68 cm2) and LG (28 cm2), respectively. These PCSA values were eight (soleus), four (MG), and three (LG) times larger than their respective maximum ACSA. The major dorsiflexor, the tibialis anterior (TA), had a muscle volume of 143 cm2, a PCSA of 19 cm2, and an ACSA of 9 cm2. With the exception of the soleus, the mean fiber length of all subjects was closely related to muscle volume across muscles. The soleus fibers were unusually short relative to the muscle volume, thus potentiating its force potential.(ABSTRACT TRUNCATED AT 250 WORDS)
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Real-time ultrasound scanning was used to measure the angles of fibre pennation of vastus lateralis (VL) and vastus intermedius (VI) of the human quadriceps (n = 12) in vivo. The maximum isometric force and cross-sectional area of the quadriceps were also measured. With the knee at right-angles the mean fibre angles for VL and VI respectively were 0.133 (0.021) rad [7.6 degrees (1.2 degrees)] and 0.143 (0.028) rad [8.2 degrees (1.6 degrees)] [mean (SD)], which is within the range of angles measured on cadavers. The mean angle decreased in going from the contracted [VL, 0.244 rad (14 degrees); VI, 0.279 rad (16 degrees)] to the stretched [VL, 0.105 rad (6 degrees); VI, 0.122 rad (7 degrees)] position. There was a significant positive correlation between fibre angle and muscle cross-sectional area but no relationship between fibre angle and force per cross-sectional area. No increase in fibre angle was detected after 3 months strength training. We conclude that ultrasound can be used to measure pennation angles of superficial muscle groups but we could not demonstrate a relationship between pennation and force-generating capacity.
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The purposes of this study were to 1) determine the effect of concentric isokinetic training on strength and cross-sectional area (CSA) of selected extensor and flexor muscles of the forearm and leg, 2) examine the potential for preferential hypertrophy of individual muscles within a muscle group, 3) identify the location (proximal, middle, or distal level) of hypertrophy within an individual muscle, and 4) determine the effect of unilateral concentric isokinetic training on strength and hypertrophy of the contralateral limbs. Thirteen untrained male college students [mean age 25.1 +/- 6.1 (SD) yr] volunteered to perform six sets of 10 repetitions of extension and flexion of the nondominant limbs three times per week for 8 wk, using a Cybex II isokinetic dynamometer. Pretraining and posttraining peak torque and muscle CSA measurements for both the dominant and nondominant limbs were determined utilizing a Cybex II isokinetic dynamometer and magnetic resonance imaging scanner, respectively. The results indicated significant (P less than 0.0008) hypertrophy in all trained muscle groups as well as preferential hypertrophy of individual muscles and at specific levels. None of the muscles of the contralateral limbs increased significantly in CSA. In addition, significant (P less than 0.0008) increases in peak torque occurred for trained forearm extension and flexion as well as trained leg flexion. There were no significant increases in peak torque, however, for trained leg extension or for any movement in the contralateral limbs. These data suggest that concentric isokinetic training results in significant strength and hypertrophic responses in the trained limbs.
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Eight men (20-23 years) weight trained 3 days.week-1 for 19 weeks. Training sessions consisted of six sets of a leg press exercise (simultaneous hip and knee extension and ankle plantar flexion) on a weight machine, the last three sets with the heaviest weight that could be used for 7-20 repetitions. In comparison to a control group (n = 6) only the trained group increased (P less than 0.01) weight lifting performance (heaviest weight lifted for one repetition, 29%), and left and right knee extensor cross-sectional area (CAT scanning and computerized planimetry, 11%, P less than 0.05). In contrast, training caused no increase in maximal voluntary isometric knee extension strength, electrically evoked knee extensor peak twitch torque, and knee extensor motor unit activation (interpolated twitch method). These data indicate that a moderate but significant amount of hypertrophy induced by weight training does not necessarily increase performance in an isometric strength task different from the training task but involving the same muscle group. The failure of evoked twitch torque to increase despite hypertrophy may further indicate that moderate hypertrophy in the early stage of strength training may not necessarily cause an increase in intrinsic muscle force generating capacity.
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Eight elite male bodybuilders (MB), five elite female bodybuilders (FB), eight male control (MC), and eight female control recreational weight-trainers (FC) performed maximal elbow flexions on an isokinetic dynamometer at velocities between 1.02 and 5.24 rad.s-1, from which peak torque (PT) was measured. Elbow flexor cross-sectional area (CSA) was measured by computed tomographic scanning. Flexor CSA.lean body mass-1 ratios were greater in MB than in other subject groups. Correlations of PT were positively related to CSA but negatively to CSA.lean body mass-1 and to PT.CSA-1. PT.CSA-1 at low-velocity contractions were greater in MC and FC than in MB and FB groups, suggesting a training effect. The velocity-associated declines in torque between velocities of 1.02 and 5.24 rad.s-1 averaged 28.4 +/- 0.9% and were statistically identical in men and women among the subject groups, suggesting that neither gender nor training had affected this variable.
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The picture of training that emerges is of a process that can be divided into a number of phases. In the first phase there is a rapid improvement in the ability to perform the training exercise such as lifting weights which is the result of a learning process in which the correct sequence of muscle contractions is laid down as a motor pattern in the central nervous system. This phase is associated with little or no increase in the size or strength of individual muscles. The learning process appears to be very specific in that lifting weights makes better weight lifters but not better sprinters. The second phase is an increase in the strength of individual muscles which occurs without a matching increase in the anatomical cross-section. The mechanism for this is not clear but could be a result of increased neural activation or some change in the fibre arrangement or connective tissue content. The third phase starts at a point where scientific studies usually end, at about 12 weeks when non-athletic subjects are beginning to tire of the repeated training and testing. After this point, if training continues, there is probably a slow but steady increase in both size and strength of the exercised muscles. The stimulus for these changes remains enigmatic but almost certainly involves high forces in the muscle, probably to induce some form of damage that promotes division of satellite cells and their incorporation into existing muscle fibres. Our information on the effect of long-term training comes primarily from observations on elite athletes whose physique may well be the result of genetic endowment or the use or abuse of drugs. For the athlete or patient hoping to increase muscle size by weight training the best combination of intensity, frequency and type of exercise still remains a matter of individual choice rather than a scientific certainty.
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Strength performance depends not only on the quantity and quality of the involved muscles, but also upon the ability of the nervous system to appropriately activate the muscles. Strength training may cause adaptive changes within the nervous system that allow a trainee to more fully activate prime movers in specific movements and to better coordinate the activation of all relevant muscles, thereby effecting a greater net force in the intended direction of movement. The evidence indicating neural adaptation is reviewed. Electromyographic studies have provided the most direct evidence. They have shown that increases in peak force and rate of force development are associated with increased activation of prime mover muscles. Possible reflex adaptations related to high stretch loads in jumping and rapid reciprocal movements have also been revealed. Other studies, including those that demonstrate the "cross-training" effect and specificity of training, provide further evidence of neural adaptation. The possible mechanisms of neural adaptation are discussed in relation to motor unit recruitment and firing patterns. The relative roles of neural and muscular adaptation in short- and long-term strength training are evaluated.
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Eight untrained women (F), 13 untrained men (M), and 11 male bodybuilders (BB) did maximal elbow flexions on an isokinetic dynamometer at velocities of 30, 120, 180, 240, and 300 degrees/s, from which impact torque (IT), peak torque (PT), and work (W) were measured. Biceps and total flexor cross-sectional area (CSA) were measured by computerized tomographic scanning. Muscle fiber area, fiber composition, and collagen volume density were determined from single needle biopsies of biceps brachii. Biceps fiber number was estimated as the ratio of biceps CSA (corrected for connective tissue) to mean fiber area. PT and W decreased at higher velocities in M and BB but not in F; consequently, the correlation between CSA and PT and W was lower at 300 degrees/s (r = 0.58, 0.60) than 30 degrees/s (r = 0.80, 0.79). The ratio of PT to flexor CSA was similar in all groups at 30 degrees/s, whereas F had greater ratios than M and BB at the remaining velocities. F had greater W/CSA ratios than M and BB at all velocities. IT increased at higher velocities in all groups; the increase was greater in F and M than in BB. In contrast to PT and W, the correlation between IT and CSA was greater at 300 degrees/s (r = 0.67) than 30 degrees/s (r = 0.58), and there were no differences among groups in the IT/CSA ratios. Flexor CSA correlated negatively with the ratio of IT, PT, and W to CSA. Muscle fiber composition failed to correlate with any measure of strength. M and BB had greater biceps area, fiber number, and fiber area than F.(ABSTRACT TRUNCATED AT 250 WORDS)
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The architectural features of the major knee extensors and flexors and ankle plantar flexors and dorsiflexors were determined in three human cadavers. There was marked uniformity of fiber length throughout a given muscle and a trend toward similar fiber lengths within muscles of a synergistic group. Muscle length/fiber length ratios were remarkably similar for all three limbs. Angles of fiber pinnation were relatively small (0 degree-15 degrees) and generally consistent throughout the muscle. From these architectural data, the performance of a muscle was studied with respect to its tension production and velocity of shortening potentials. The tension is a function of the number of sarcomeres in parallel, and the velocity of shortening is a function of the number of sarcomeres in series. Muscles were grouped according to whether they showed a predilection for tension or velocity of shortening.
Article
In five healthy males sustained isometric torques during elbow flexion, knee extension, and plantar flexion correlated positively with intramuscular tissue pressure (MTP) in the range 0-80% of the maximal voluntary contraction (MVC). During passive compression of the muscle at rest 133-Xenon muscle clearance stopped when MTP reached diastolic arterial pressure (DAP) indicating that the muscle vascular bed was occluded. However, during sustained contraction this relation between DAP, flow and MTP was not seen. In two cases 133-Xenon clearance from M. soleus did not stop in spite of an 80% maximal contraction and MTP stayed below DAP. In other cases MTP would reach as high as 240 mm Hg before clearance was zero. In the deeper parts of the muscles MTP during contraction was increased in relation to the more superficial parts. The means values for the % MVC that would stop MBF varied between 50 and 64% MVC for the investigated muscles. Mean rectified EMG (MEMG) showed a high correlation to MTP during sustained exhaustive contractions: When MEMG was kept constant MTP also remained constant while the exerted force decreased; when force was kept constant both MEMG and MTP increased in parallel. This demonstrated that muscle tissue compliance is decreasing during fatigue. Muscle ischemia occurring during sustained isometric contractions is partly due to the developed MTP, where especially the MTP around the veins in the deeper parts of the muscle can be considered of importance. However, ischemia is also affected by muscle fiber texture and anatomical distorsion of tissues.
Article
The maximum voluntary force (strength) which could be produced by the knee-extensor muscles, with the knee held at a right angle, was measured in a group of healthy young subjects comprising twenty-five males and twenty-five females. Both legs were tested: data from the stronger leg only for each subject were used in the present study. Computed tomography was used to obtain a cross-sectional image of the subjects' legs at mid-thigh level, measured as the mid-point between the greater trochanter and upper border of the patella. The cross-sectional area of the knee-extensor muscles was determined from the image obtained by computer-based planimetry. The subjects' height and weight were measured. An estimate of body fat content was obtained from measurements of skinfold thicknesses and used to calculate lean body mass. Male subjects were taller (P less than 0.001), heavier (P less than 0.001), leaner (P less than 0.001) and stronger (P less than 0.001) than the female subjects. No significant correlation was found to exist between strength of the knee-extensor muscles and body weight in the male or in the female subjects. In the male subjects, but not in the female group, there was a positive correlation (r = 0.50; P less than 0.01) between strength and lean body mass. Muscle cross-sectional area of the male subjects was greater than that of the female subjects (P less than 0.001). The ratio of strength to cross-sectional area for the male was 9.49 +/- 1.34 (mean +/- S.D.). This is greater but not significantly so, than that for females (8.92 +/- 1.11). In both male and female groups, there was a significant (P less than 0.01) positive correlation between muscle strength and cross-sectional area. A wide variation in the ratio of strength to muscle cross-sectional area was observed. This variability may be a result of anatomical differences between subjects or may result from differences in the proportions of different fibre types in the muscles. The variation between subjects is such that strength is not a useful predictive index of muscle cross-sectional area.
Article
Thirty young male adults matched in two experimental groups (n = 12) and a control group (n = 6) were investigated before and after an 8-week strength training period. Group A trained with few repetitions and maximal loads, whereas group B had more repetitions with smaller loads. Both groups lifted the same total load during each training period, four times a week. Maximal voluntary strength (MVS) of a shot-put arm movement, muscular excitability and contractile properties (time to peak of contraction with threshold stimuli, half relaxation time) were measured in M. deltoideus and M. triceps brachii, C. longum, for two durations of stimulation. Increases of 14.8% (group A) and 12.2% (group B) in MVS were observed. Muscle excitability significantly increased in all types of training and both muscles. Significant shortening of the contraction time, dependent on the type of training, was observed in both studied muscles. It appears that the strength training in group A involved the fast fibers of both muscles, whereas in group B the training influence was less marked, and affected both fast and slow fiber types.
Article
The structural and functional characteristics of the elbow flexors in five elderly males were studied before and after 12 wk of heavy-resistance training. Muscle volume and cross-sectional area of two of the elbow flexor (biceps brachii and brachialis) muscles were determined by magnetic resonance imaging. Mean muscle fiber area, percent fiber distribution, and collagen and noncontractile tissue densities were determined on histological sections from needle biopsies. Isokinetic strength of the elbow flexors was measured at velocities between 60 and 300 degrees/s. Muscle volume and cross-sectional area of the biceps brachii and brachialis significantly increased by 13.9 and 22.6%, respectively, after the training program. A preferential hypertrophy of type II fibers (37.2%) was observed. Significant increases in peak torque were observed at all the tested velocities. The amount of work a subject could perform during a 25-repetition test at 240 degrees/s increased by 41% after training. These results demonstrate that the skeletal muscles of elderly individuals can adapt to heavy-resistance exercise and do so by increases in both muscle size and strength.
Article
Quadriceps muscle and fibre cross-sectional areas (CSA), torque and neural activation were studied in seven healthy males during 6 months of weight training on alternate days with six series of eight unilateral leg extensions at 80% of one repetition maximum. After training, the quadriceps cross-sectional area increased by 18.8 +/- 7.2% (P < 0.001) and 19.3 +/- 6.7% (P < 0.001) in the distal and proximal regions respectively, and by 13.0 +/- 7.2% (P < 0.001) in the central region of the muscle. Hypertrophy was significantly different between and within the four constituents of the quadriceps. Biopsies of the vastus lateralis at mid-thigh did not show any increase in mean fibre cross-sectional area. Maximum isometric voluntary torque increased by 29.6 +/- 7.9%-21.1 +/- 8.6% (P < 0.01-0.05) between 100 degrees and 160 degrees of knee extension, but no change in the optimum angle (110 degrees-120 degrees) for torque generation was found. A 12.0 +/- 10.8% (P < 0.02) increase in torque per unit area together with a right shift in the IEMG-torque relation and no change in maximum IEMG were observed. Time to peak isometric torque decreased by 45.8% (P < 0.03) but no change in time to maximum IEMG was observed. In conclusion, strength training of the quadriceps results in a variable hypertrophy of its components without affecting its angle-torque relation. The increase in torque per unit area, in the absence of changes in IEMG, may indicate changes in muscle architecture. An increase in muscle-tendon stiffness may account for the decrease in time to peak torque.
Article
The purpose of this study was to investigate the difference in the morphological and functional aspects of the triceps brachii muscle between highly trained male and female athletes who were members of the 1996 Japanese Olympic teams in each of three different events: soccer, gymnastics and judo. The thickness (TBmt) and fibre pennation angle (TBpen) of the triceps brachii muscle and force output during elbow extensions were determined using a B-mode ultrasound apparatus and an isokinetic dynamometer, respectively. The TBmt and its value relative to upper arm length (TBmt/l ua) were significantly larger in the men than in the women in all the events except judo. In all the subjects, a significant correlation was found between TBmt/l ua) and TBpen (r= 0.721, P < 0.05). The existence of the sex difference in TBpen within the same event was in agreement with that observed in TBmt/l ua except for the soccer players. The TBpen of the soccer players were similar in both sexes although a significant sex differences was found in TBmt/l ua. The isokinetic forces measured using the two velocities 60°· s−1 (F 60) and 180°· s−1 (F 180) were significantly correlated to the cross-sectional area (CSA) of the triceps brachii muscle estimated from TBmt (r= 0.702, P < 0.05 for F 60, and r= 0.776, P < 0.05 for F 180). No significant sex differences were found in either F 60/CSA or F 180/CSA in any of the events. From these results, it could be assumed, at least in the Olympic athletes tested in this study, that the fibre angulation of the triceps brachii muscle was almost the same in the two sexes if allowance was made for the difference in the muscle size, and the sex difference in force generation capability of the triceps brachii muscle could in the main be attributed to the difference in CSA rather than in the architectural characteristics.
Article
Recent experimental advances in structural biology, biophysics, and molecular biology have dramatically increased our understanding of the molecular mechanism of muscle contraction, as well as the assembly of myosin filaments. Future studies are required to detail, for example, the molecular cause of the conformational change during the power stroke and ATP hydrolysis, as well as the nature of the communication between nucleotide and actin binding sites. Based on the structural and functional homology between myosin and other molecular motors, these findings have implications not only for understanding muscle contraction, but for understanding numerous aspects of motility in all cellular systems as well.
Article
Muscle force (MF) is linearly related to physiological cross-sectional area (CSA), which is obtained from muscle volume (MV) divided by fibre length. Taking into account the fact that joint torque (TQ) is determined by MF multiplied by the moment arm, the maximal TQ would be a function of MV. This proposition was tested in the present study by investigating the relationship between MV and TQ for elbow flexor (EF) and extensor (EE) muscles of 26 males. The MVs of EF and EE were determined from a series of muscle CSA by magnetic resonance imaging (MRI), and pennation angle (theta) and FL by ultrasonography (US). Maximal isometric TQ was measured at right angle of elbow joint for EF and EE. There was a highly significant correlation between MV and TQ both for EF and EE (r=0.95 and 0.96 respectively) compared with that between muscle CSA and TQ, suggesting the dependence of TQ on MV. Furthermore, prediction equations for MV (MVULT) from muscle thickness (MT) measured by US was developed with reference to MVMRI by the MRI on 26 subjects, and the equations were applied to estimate MV of healthy university students (CON; 160 males) and sports athletes (ATH; 99 males). There were significant linear relationships between MVULT and TQ both for EF (r=0.783) and EE (r=0.695) for all subjects (n=259). The MVULT was significantly higher in ATH (by 32% for EF and 33% for EE, respectively) than in CON. Similarly, significantly greater TQ was observed in ATH (by 35% for EF, 37% for EE, respectively). The theta for EE showed no difference between both groups (17.8 degrees for CON and 17.5 degrees for ATH). On the other hand, the TQ to MV ratio were identical for CON and ATH. The results reveal that the muscle volume of the upper arm is a major determinant of joint torque (TQ), regardless of athletic training.
Article
Although it has long been supposed that resistance training causes adaptive changes in the CNS, the sites and nature of these adaptations have not previously been identified. In order to determine whether the neural adaptations to resistance training occur to a greater extent at cortical or subcortical sites in the CNS, we compared the effects of resistance training on the electromyographic (EMG) responses to transcranial magnetic (TMS) and electrical (TES) stimulation. Motor evoked potentials (MEPs) were recorded from the first dorsal interosseous muscle of 16 individuals before and after 4 weeks of resistance training for the index finger abductors (n = 8), or training involving finger abduction-adduction without external resistance (n = 8). TMS was delivered at rest at intensities from 5 % below the passive threshold to the maximal output of the stimulator. TMS and TES were also delivered at the active threshold intensity while the participants exerted torques ranging from 5 to 60 % of their maximum voluntary contraction (MVC) torque. The average latency of MEPs elicited by TES was significantly shorter than that of TMS MEPs (TES latency = 21.5 +/- 1.4 ms; TMS latency = 23.4 +/- 1.4 ms; P < 0.05), which indicates that the site of activation differed between the two forms of stimulation. Training resulted in a significant increase in MVC torque for the resistance-training group, but not the control group. There were no statistically significant changes in the corticospinal properties measured at rest for either group. For the active trials involving both TMS and TES, however, the slope of the relationship between MEP size and the torque exerted was significantly lower after training for the resistance-training group (P < 0.05). Thus, for a specific level of muscle activity, the magnitude of the EMG responses to both forms of transcranial stimulation were smaller following resistance training. These results suggest that resistance training changes the functional properties of spinal cord circuitry in humans, but does not substantially affect the organisation of the motor cortex.
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