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Maximal strength training increases muscle force generating capacity and the anaerobic ATP synthesis flux without altering the cost of contraction in elderly
... However, limited published data exist regarding the effects of HIRT on Wʹ in older adults. In older adults, HIRT induces an increase in anaerobic ATP synthesis flux (via anaerobic glycolysis and creatine kinase reaction), leading to greater knee extensor muscle torque production during sustained maximal contraction [12,13]. The summation of higher torque during sustained maximal contraction may account for a significant portion of Wʹ [14]. ...
... On the other hand, very intense physical training has been shown to improve muscle buffer capacity, reduce the accumulation of H+, and increase the resynthesis of phosphocreatine (PCr) [34]. Berg et al. (2018) demonstrated that HIRT induces an increase in anaerobic ATP synthesis flux, allowing greater muscle torque production during sustained maximal contractions in older adults [12]. Therefore, the increase in Wʹ observed in HIRT, but not LIRT, seems to be associated with muscle adaptations that improve anaerobic ATP synthesis flux, reduce metabolic disturbances and/or accumulation of metabolites, and attenuate the firing frequency of group III/ IV afferents, ultimately increasing exercise tolerance during severe-intensity exercise [2,3] in older adults. ...
... On the other hand, very intense physical training has been shown to improve muscle buffer capacity, reduce the accumulation of H+, and increase the resynthesis of phosphocreatine (PCr) [34]. Berg et al. (2018) demonstrated that HIRT induces an increase in anaerobic ATP synthesis flux, allowing greater muscle torque production during sustained maximal contractions in older adults [12]. Therefore, the increase in Wʹ observed in HIRT, but not LIRT, seems to be associated with muscle adaptations that improve anaerobic ATP synthesis flux, reduce metabolic disturbances and/or accumulation of metabolites, and attenuate the firing frequency of group III/ IV afferents, ultimately increasing exercise tolerance during severe-intensity exercise [2,3] in older adults. ...
Purpose
The torque–duration relationship in muscle group exercise is characterized by two parameters, the critical torque (CT) and the W prime (Wʹ), which define the limit of tolerance. These parameters have significant utility in assessing health and disease. However, there is a lack of information regarding the optimization of CT and/or Wʹ gains through manipulation of resistance training (RT) variables, especially in older adults. Therefore, this study aimed to investigate the impact of different intensities of RT, specifically higher intensity RT (HIRT) versus lower intensity RT (LIRT), on CT and Wʹ in postmenopausal women.
Methods
The study spanned 12 weeks of RT. Postmenopausal women were randomized into three groups: control group (CG, n = 14), LIRT (loads necessary to perform 27–31 repetitions, n = 17), and HIRT (loads necessary to perform 8–12 repetitions, n = 14).
Results
Compared to the CG group, the LIRT group exhibited a significant increase in CT (15%, P < 0.05), while the HIRT group showed a significant increase in Wʹ (36%, P < 0.05).
Conclusions
Different intensities of RT result in distinct adaptations of torque–duration relationship parameters (Wʹ and CT) in postmenopausal women.
... Of note, there is little change in muscle mass with MST and improvements in the rate of force development are much greater than conventional, hypertrophy-inducing, strength training (20). In fact, MST has been documented to provide an effective intervention to mitigate the age-related loss of muscle function and mobility associated with aging (21,22). Furthermore, in terms of the older adults, we have determined that MST increases muscle force generating capacity and the anaerobic ATP synthesis flux without altering the cost of contraction (22). ...
... In fact, MST has been documented to provide an effective intervention to mitigate the age-related loss of muscle function and mobility associated with aging (21,22). Furthermore, in terms of the older adults, we have determined that MST increases muscle force generating capacity and the anaerobic ATP synthesis flux without altering the cost of contraction (22). However, there has yet to be a comprehensive assessment of the impact of MST on mitochondrial respiratory function with advancing age. ...
... Women taking hormone replacement therapy were excluded from the study. Other data from this cohort of subjects have been previously published (22). The study was approved by the Institutional review board of both the University of Utah and the Salt Lake City Veterans Affairs Medical Center. ...
Maximal Strength Training (MST) results in robust improvements in skeletal muscle force production, efficiency, and mass. However, the effects of MST on muscle mitochondria is still unknown. Accordingly, the purpose of this study was to examine, from the molecular level to whole-muscle, mitochondrial adaptations induced by 8 weeks of knee-extension MST in the quadriceps of 10 older adults using immunoblotting, spectrophotometry, high-resolution respirometry in permeabilized muscle fibers, in vivo31P magnetic resonance spectroscopy (31P-MRS) and gas exchange. As anticipated, MST resulted in an increased isometric knee-extensor force from 133±36 to 147±49 Nm (P<0.05) and quadriceps muscle volume from 1410±103 to 1555±455 cm3 (P<0.05). Mitochondrial complex (I-V) protein abundance and citrate synthase activity were not significantly altered by MST. Assessed ex vivo, maximal ADP-stimulated respiration (state 3CI+CII, PRE: 23±6 and POST: 14±5 ρM·mg-1·s-1, P<0.05), was decreased by MST, predominantly, as a result of a decline in complex I linked respiration (P<0.05). Additionally, state 3 free-fatty acid linked respiration was decreased following MST (PRE: 19±5 and POST: 14±3 ρM·mg-1·s-1, P<0.05). Assessed in vivo, MST slowed the PCr recovery time constant (PRE: 49±13 and POST: 57±16 s, P<0.05) and lowered, by ~20% (P=0.055), the quadriceps peak rate of oxidative ATP synthesis, but did not significantly alter the oxidation of lipid. Although these, likely qualitative, mitochondrial adaptations are potentially negative in terms of skeletal muscle energetic capacity, they need to be considered in light of the many improvements in muscle function that MST affords older adults.
... These factors encompass reduced muscle mass, primarily attributed to type II muscle fiber atrophy [29], compromised neural control over skeletal muscle contractile function [21], diminished anaerobic metabolism capacity for energy production during intense contractions [30], decreased perfusion of skeletal muscle [31,32], and inflammation [33]. Moreover, aging's impact on muscle mass and function can be expedited during the menopausal transition [34][35][36]. This diminished capacity for high-intensity exercise, coupled with declining muscle strength, prompts an increased reliance on oxidative sources to sustain ATP production during daily activities among older individuals. ...
... In a recently published perspective, Denadai and Greco proposed that an elevated W might underlie changes in physical capacity following resistance training [28]. Specifically, resistance training involving higher loads could potentially lead to enhancements in muscle buffer capacity (i.e., W ) [35], heightened rates of ATP synthesis from anaerobic glycolysis, and increased expression of fast myosin heavy chain, along with improved PCr resynthesis [36]. These enhancements, resulting from resistance training with higher loads, could ultimately augment exercise tolerance (W ) [38], enabling older adults to sustain superior gait speed performance. ...
Background: The hyperbolic torque-duration curve depicts critical torque (CT) and W prime (W′), with the curve’s asymptote representing CT as the boundary between heavy- and severe-intensity domains. W′, the curvature constant, indicates cumulative work beyond CT. This study investigated age-related reductions in W′, CT, and gait speed, and whether W′ and CT predict gait speed independently of muscle torque. Methods: three groups (adults, middle-aged, older) totaling 131 women were studied. W′ and CT were determined using 60 maximal isometric voluntary contractions of knee extensors. The fast gait speed was calculated in walking tests at 10 m, 400 m, and six minutes (6 MWT). Results: gait speed decreased (p < 0.05) with age, as did W′ and CT. Both W′ and CT correlated positively with gait speed at different distances (10 m, 400 m, 6 MWT). Adjusted for maximum muscle torque, only W′ maintained a positive association (p < 0.05) with all gait speed tests (10 m: β = 0.201, SE = 0.086; 400 m: β = 0.262, SE = 0.085 and; 6 MWT: β = 0.187, SE = 0.086). Conclusion: aging led to declines in W′, CT, and gait speed. W′, not CT, remained a significant predictor of gait speed, indicating its importance for older women’s mobility.
... Thirty four studies (Berg et al., 2018;Cannon et al., 2007;Connelly and Vandervoort, 2000;Fielding et al., 2002;Frontera et al., 1988;Häkkinen et al., 2000Häkkinen et al., , 1998aHakkinen et al., 1998b;Ha¨kkinen et al., 2001;Harridge et al., 1999;Hicks et al., 1991;Hunter et al., 1999;Ivey et al., 2000;Jozsi et al., 1999;Keen et al., 1994;Knight and Kamen, 2001;Kostek et al., 2005;Moritani and Devries, 1980;Newton et al., 2002;Radaelli, B et al., 2014;Radaelli, A et al., 2014;Rodriguez-Lopez et al., 2022;Schlicht et al., 2001;Slivka et al., 2008;Sousa et al., 2011;Tøien et al., 2018;Trappe et al., 2001Trappe et al., , 2000Unhjem et al., 2015;Van Roie et al., 2013Verdijk et al., 2009Verdijk et al., , 2016Wang et al., 2017) measured changes in strength recorded from the trained limb pre-to post-strength-training. Twenty-nine studies trained the lower-body and two studies ( (Keen et al., 1994;Moritani and Devries, 1980) trained the upper-body. ...
... Nine studies (Berg et al., 2018;Connelly and Vandervoort, 2000;Hakkinen et al., 1998b;Häkkinen et al., 1998a;Rodriguez-Lopez et al., 2022;Tøien et al., 2018;Unhjem et al., 2015;Van Roie et al., 2020;Wang et al., 2017) assessed the change in RFD post-strength-training with reports of small to large effect sizes (Cohen's d range − 0.28 to 3.39) (Fig. 10). The included studies provide strong evidence for strength-training to increase RFD in older adults (Table 1, Fig. 10). ...
... Thirty four studies (Berg et al., 2018;Cannon et al., 2007;Connelly and Vandervoort, 2000;Fielding et al., 2002;Frontera et al., 1988;Häkkinen et al., 2000Häkkinen et al., , 1998aHakkinen et al., 1998b;Ha¨kkinen et al., 2001;Harridge et al., 1999;Hicks et al., 1991;Hunter et al., 1999;Ivey et al., 2000;Jozsi et al., 1999;Keen et al., 1994;Knight and Kamen, 2001;Kostek et al., 2005;Moritani and Devries, 1980;Newton et al., 2002;Radaelli, B et al., 2014;Radaelli, A et al., 2014;Rodriguez-Lopez et al., 2022;Schlicht et al., 2001;Slivka et al., 2008;Sousa et al., 2011;Tøien et al., 2018;Trappe et al., 2001Trappe et al., , 2000Unhjem et al., 2015;Van Roie et al., 2013Verdijk et al., 2009Verdijk et al., , 2016Wang et al., 2017) measured changes in strength recorded from the trained limb pre-to post-strength-training. Twenty-nine studies trained the lower-body and two studies ( (Keen et al., 1994;Moritani and Devries, 1980) trained the upper-body. ...
... Nine studies (Berg et al., 2018;Connelly and Vandervoort, 2000;Hakkinen et al., 1998b;Häkkinen et al., 1998a;Rodriguez-Lopez et al., 2022;Tøien et al., 2018;Unhjem et al., 2015;Van Roie et al., 2020;Wang et al., 2017) assessed the change in RFD post-strength-training with reports of small to large effect sizes (Cohen's d range − 0.28 to 3.39) (Fig. 10). The included studies provide strong evidence for strength-training to increase RFD in older adults (Table 1, Fig. 10). ...
There are observable decreases in muscle strength as a result of ageing that occur from the age of 40, which is thought to occur as a result of changes within the neuromuscular system. Strength-training in older adults is a suitable intervention that may counteract the age-related loss in force production. The neuromuscular adaptations (i.e., cortical, spinal and muscular) to strength-training in older adults is largely equivocal and a systematic review with meta-analysis will serve to clarify the present circumstances regarding the benefits of strength-training in older adults. 20 studies entered the meta-analysis and were analysed using a random-effects model. A best evidence synthesis that included 36 studies was performed for variables that had insufficient data for meta-analysis. One study entered both. There was strong evidence that strength-training increases maximal force production and rate of force development and muscle activation in older adults. There was limited evidence for strength-training to improve voluntary-activation, the volitional-wave and spinal excitability, but strong evidence for increased muscle mass. The findings suggest that strength-training performed between 2-12 weeks increases strength, rate of force development and muscle activation, which likely improves motoneurone excitability by increased motor unit recruitment and improved discharge rates.
... The effects of exercise on skeletal muscle energy metabolism are solidly established (Holloszy, 1967), and the notion that apparent effects of ageing on oxidative capacity are secondary to diminished physical activity in older adults is now becoming mainstream . Indeed, prospective exercise intervention studies demonstrate robust improvements inV O 2 peak and skeletal muscle metabolism in older adults Berg et al. 2018), yet cross-sectional studies of highly-trained individuals reveal that even chronically endurance trained older adults exhibit declines inV O 2 peak and modestly altered mitochondrial parameters in skeletal muscle (Proctor & Joyner, 1997;Lanza et al. 2008;Distefano et al. 2018). A recent analysis of data from the Baltimore Longitudinal Study of Aging showed that physical activity was a strong predictor of muscle oxidative capacity measured by 31 P-MRS in 384 men and women across a wide age range (22-92 years) (Adelnia et al. 2019). ...
... Muscle mitochondrial function and whole-body cardiorespiratory fitness are exquisitely responsive to physical activity (Holloszy, 1967;Hickson et al. 1977), and exercise has been shown to forestall many cardiovascular and metabolic abnormalities with ageing (Proctor & Joyner, 1997;Lanza et al. 2008;Robinson et al. 2017;Berg et al. 2018). Inasmuch, it is important to include objective, sensitive measurements of habitual physical activity levels when evaluating the true effects of ageing onV O 2 peak or muscle mitochondrial function (Russ & Lanza, 2011). ...
Key points
Healthy older adults exhibit lower cardiorespiratory fitness (V̇O2peak) than young in the absence of any age‐related difference in skeletal muscle mitochondrial capacity, suggesting central haemodynamics plays a larger role in age‐related declines in V̇O2peak.
Total physical activity did not differ by age, but moderate‐to‐vigorous physical activity was lower in older compared to young adults.
Moderate‐to‐vigorous physical activity is associated with V̇O2peak and muscle oxidative capacity, but physical inactivity cannot entirely explain the age‐related reduction in V̇O2peak.
Abstract
Declining fitness (V̇O2peak) is a hallmark of ageing and believed to arise from decreased oxygen delivery and reduced muscle oxidative capacity. Physical activity is a modifiable lifestyle factor that is critical when evaluating the effects of age on parameters of fitness and energy metabolism. The objective was to evaluate the effects of age and sex on V̇O2peak, muscle mitochondrial physiology, and physical activity in young and older adults. An additional objective was to assess the contribution of skeletal muscle oxidative capacity to age‐related reductions in V̇O2peak and determine if age‐related variation in V̇O2peak and muscle oxidative capacity could be explained on the basis of physical activity levels. In 23 young and 52 older men and women measurements were made of V̇O2peak, mitochondrial physiology in permeabilized muscle fibres, and free‐living physical activity by accelerometry. Regression analyses were used to evaluate associations between age and V̇O2peak, mitochondrial function, and physical activity. Significant age‐related reductions were observed for V̇O2peak (P < 0.001), but not muscle mitochondrial capacity. Total daily step counts did not decrease with age, but older adults showed lower moderate‐to‐vigorous physical activity, which was associated with V̇O2peak (R² = 0.323, P < 0.001) and muscle oxidative capacity (R² = 0.086, P = 0.011). After adjusting for sex and physical activity, age was negatively associated with V̇O2peak but not muscle oxidative capacity. Healthy older adults exhibit lower V̇O2peak but preserved mitochondrial capacity compared to young. Physical activity, particularly moderate‐to‐vigorous, is a key factor in observed age‐related changes in fitness and muscle oxidative capacity, but cannot entirely explain the age‐related reduction in V̇O2peak.
... Notably, the 43% increase in bilateral 1RM following early postoperative MST in the current study was, despite the frailty of the elderly hip fracture patients, a similar percentage improvement to what has been previously reported for 8 week MST interventions with 3 sessions per week in both young (50%) 8 and healthy elderly (68% and 53%). 9,13 Moreover, the MST improved unilateral leg press 1RM by 27%, resulting in a maximal strength higher than baseline level. No improvement of unilateral leg press 1RM was observed in the CG. ...
... This is comparable to what has been reported in healthy age matched subjects (92 and 86%) conducting the same volume of MST over 8 weeks. 9,13 Interestingly, it is very similar to the 95% compliance reported to progressive strength training shortly after hip fracture surgery by Overgaard, Kristensen. 7 Of note, the Norwegian health care system cover transportation to and from rehabilitation, and transport was scheduled for the patients when appropriate. ...
Introduction:
Hip fractures predominantly occur in the geriatric population and results in increased physical inactivity and reduced independency, largely influenced by a downward spiral of ambulatory capacity, related to loss of skeletal muscle strength and postural stability. Thus, effective postoperative treatment, targeting improvements in muscle strength, is sought after.
Materials & methods:
Twenty-one hip fracture patients (>65 yr) were randomized to 8 weeks of either conventional physiotherapy control group (CG), or leg press and hip abduction maximal strength training (MST) 3 times per week. MST was performed applying heavy loads (85-90% of 1 repetition maximum; 1RM) and 4-5 repetitions in 4 sets. Maximal strength (bi- and unilateral 1RM), postural stability (unipedal stance test; UPS), and DEXA-scan bone mineral content/ density (BMC/BMD) were measured before and after the 8-week rehabilitation.
Results:
Both MST and conventional physiotherapy improved bilateral leg press 1RM by 41 ± 27 kg and 29 ± 17 kg, respectively (both p < 0.01), while unilateral leg press 1RM only increased after MST (within group and between groups difference: both p < 0.05). MST also resulted in an increase in abduction 1RM in both the fractured (5 kg, 95%CI: 2-7; p < 0.01) and healthy limb (6 kg, 95%CI: 3-9; p < 0.01), while no such improvement was apparent in the CG (between groups difference: p < 0.01). Finally, MST improved UPS of the fractured limb (p < 0.05). No differences were observed in BMC or BMD following the 8 weeks.
Discussion:
Early postoperative MST improved lower extremities maximal muscle strength more than conventional physiotherapy and was accompanied by improvements in postural stability.
Conclusion:
Implementing MST in early rehabilitation after hip fracture surgery should be considered as a relevant treatment to curtail the downward spiral of reduced ambulatory capacity typical for this patient group, possibly reducing the risk of recuring falls and excess mortality.
Trial registration:
https://clinicaltrials.gov/ct2/show/NCT03030092.
... Generally, DFO increases the abundance of proteins for substrate-level phosphorylation (CK), glycolysis (PK, TPI) and mitochondrial Complex I electron transport (NADHD) in Ad rats, while it decreases these proteins in the Ag rats (Figs. 3 and 4). Increased energy metabolism is often reported with interventions that improve muscle function in aged and adult subjects [23,[49][50][51]. In addition, accumulation of glycolytic intermediates (e.g., pyruvate, glycerol 3-phosphate) has been reported in aged vs. adult muscles, suggesting impairments in at least some aspect of glycolytic activity [19,22], though such findings may not translate to humans [52]. ...
... The finding of increased CK abundance in Ag Ctl muscles is consistent with other data [53], though CK activity typically exhibits a decline or no change in aged humans [54], suggesting a possible increase in overall CK to compensate for impaired functionality. Similarly, impaired glycolytic function is often reported with aging [51,54], though declines in enzyme abundance are not necessarily observed, and anerobic ATP provision during contraction is maintained in aged rats and humans [55,56]. It is possible that, in contrast to the Ad group, post-translational modifications in the Ag muscles [17,57,58] might impair function of CK and glycolytic enzymes. ...
Background:
Dietary fish oil (DFO) has been identified as a micronutrient supplement with the potential to improve musculoskeletal health in old age. Few data are available for effects of DFO on muscle contractility, despite the significant negative impact of muscle weakness on age-related health outcomes. Accordingly, the effects of a DFO intervention on the contractile function and proteomic profile of adult and aged in an animal model of aging were investigated.
Methods:
This preliminary study evaluated 14 adult (8 months) and 12 aged (22 months) male, Sprague-Dawley rats consuming a DFO-supplemented diet or a control diet for 8 weeks (7 adult and 6 aged/dietary group). Animal weight, food intake and grip strength were assessed at the start and end of the FO intervention. In situ force and contractile properties were measured in the medial gastrocnemius muscle following the intervention and muscles were processed for 2-D gel electrophoresis and proteomic analysis via liquid chromatography with tandem mass spectrometry, confirmed by immunoblotting. Effects of age, diet and age x diet interaction were evaluated by 2-way ANOVA.
Results:
A significant (P = 0.022) main effect for DFO to increase (~ 15%) muscle contractile force was observed, without changes in muscle mass. Proteomic analysis revealed a small number of proteins that differed across age and dietary groups at least 2-fold, most of which related to metabolism and oxidative stress. In seven of these proteins (creatine kinase, triosephosphate isomerase, pyruvate kinase, parvalbumin, beta-enolase, NADH dehydrogenase and Parkin7/DJ1), immunoblotting corroborated these findings. Parvalbumin showed only an effect of diet (increased with DFO) (P = 0.003). Significant age x diet interactions were observed in the other proteins, generally demonstrating increased expression in adult and decreased expression aged rats consuming DFO (all P > 0.011). However, correlational analyses revealed no significant associations between contractile parameters and protein abundances.
Conclusions:
Results of this preliminary study support the hypothesis that DFO can enhance musculoskeletal health in adult and aged muscles, given the observed improvement in contractile function. The fish oil supplement also alters protein expression in an age-specific manner, but the relationship between proteomic and contractile responses remains unclear. Further investigation to better understand the magnitude and mechanisms muscular effects of DFO in aged populations is warranted.
... While the concentric phase is performed with heavy loading and maximal intended velocity, the potentially more harmful eccentric phase is performed in a slow and controlled fashion to minimize risk of muscle, tendon, and joint damage (Tøien et al., 2018). Previously, MST has been investigated in frail patient populations (e.g., patients with inflammatory rheumatic disease (Haglo et al., 2022), patients undergoing hip surgery , peripheral arterial disease (Wang et al., 2010), and patients with Parkinson's disease (Helgerud et al., 2020)) and older adults (Berg et al., 2018). Similarly, HIIT is documented to be safe and provides excellent results to patient populations at risk for cardiovascular events (Helgerud et al., 2009;Rognmo et al., 2004;Wisløff et al., 2007). ...
Improving peak oxygen uptake (V̇O2peak) and maximal strength are key objectives of rehabilitation for patients with unspecific musculoskeletal disorders (MSDs). Although high‐intensity training yield superior outcomes for these factors, patients with MSDs may not tolerate high‐intensity due to pain and fear. Therefore, we examined the effect and feasibility of incorporating aerobic high‐intensity intervals (HIITs) and maximal strength training (MST) in a standard clinical rehabilitation program for patients with unspecific MSDs. 73 patients (45 ± 10 years) with MSDs partaking in a standard, public, and 4‐week rehabilitation program were randomized to high‐intensity training (HG: 4 × 4 minutes intervals at ∼90% of maximal heart rate; HRmax, and 4 × 4 repetitions leg press at ∼90% of 1 repetition maximum; 1RM, with maximal intended velocity) or keep todays treatment of low‐to moderate‐intensity training (MG: various cycling, walking, and/or running activities at ∼70%–80% of HRmax and 3 × 8 − 10 repetitions leg press at ∼75% of 1RM without maximal intended velocity). HG improved V̇O2peak (12 ± 7%) and leg press 1RM (43 ± 34%) more than moderate‐intensity group (V̇O2peak; 5 ± 6%, 1RM; 19 ± 18%, both p < 0.001). We observed that no adverse events and no between‐group differences in dropout rate or self‐reported quality of life (both p > 0.05). There were positive correlations between improved V̇O2peak and improved physical (p = 0.024) and emotional (0.016) role functioning. We conclude that both high‐intensity interval training and MST are feasible and improve V̇O2peak and maximal strength more than standard low‐to moderate‐intensity treatment of patients with unspecific MSDs. Our findings suggest that high‐intensity training should be implemented as a part of standard clinical care of this patient population.
... About 10-14 days following physical testing in all groups, muscle biopsies were obtained from a depth of $3.5 cm from the middle portion of the vastus lateralis, slightly distal to the ventral midline of the muscle (32,33). Participants were asked to refrain from alcohol and strenuous exercise within 48 h leading up to the biopsy. ...
Aging is typically associated with decreased muscle strength and rate of force development (RFD), partly explained by motor unit remodeling due to denervation, and subsequent loss of fast-twitch type II myofibers. Exercise is commonly advocated to counteract this detrimental loss. However, it is unclear how life-long strength- versus endurance-training may differentially affect markers of denervation and reinnervation of skeletal myofibers and, in turn, affect the proportion and morphology of fast-twitch type II musculature. Thus, we compared fiber type distribution, fiber type grouping, and the prevalence of atrophic myofibers (≤1494µm ² ) in strength-trained (OS) versus endurance-trained (OE) master athletes and compared the results to recreationally active older adults (all >70yr, OC) and young habitually active references (<30yr, YC). Immunofluorescent stainings were performed on biopsy samples from vastus lateralis, along with leg press maximal strength and RFD measurements. OS demonstrated similar type II fiber distribution (OS:52.0±16.4%; YC:51.1±14.4%), fiber type grouping, maximal strength (OS:170.0±18.9kg, YC:151.0±24.4kg), and RFD (OS:3993±894N‧s ⁻¹ , YC:3470±1394N‧s ⁻¹ ) as young, and absence of atrophic myofibers (OS:0.2±0.7%; YC: 0.1±0.4%). In contrast, OE and OC exhibited more atrophic fibers (OE:1.2±1.0%; OC: 1.1±1.4%), more grouped fibers, and smaller proportion of type II fibers (OE:39.3±11.9%; OC: 35.0±12.4%) than OS and YC (all p<0.05). In conclusion, strength-trained master athletes were characterized by similar muscle morphology as young, which was not the case for recreationally active or endurance-trained old. These results indicate that strength training may preserve type II fibers with advancing age in older men, likely as a result of chronic use of high contractile force generation.
... Sampling from a single forearm vein, although a well-established (41,50) and reliable (15) method may not be representative of the total venous outflow. Alternatively, applying a methodology that measures locally in the exercising musculature, such as near-infrared spectroscopy (35) or 31 P magnetic resonance spectroscopy (51), could be utilized to verify the measurements and investigate anaerobic components related to the exercise performance. Thus, our findings should be interpreted cautiously, and further studies are needed to verify the interesting indications of increased metabolic capacity in the forearm musculature of old during handgrip exercise. ...
Maximal oxygen uptake and exercise performance typically decline with age. However, there are indications of preserved vascular function and blood flow regulation during arm exercise. Yet, it is unknown if this potential physiological preservation with age is mirrored in peripheral metabolic capacity and V̇O 2 /watt ratio. Thus, to investigate the effects of aging in the arms, we measured metabolic and vascular responses to 6-minute bouts of dynamic handgrip exercise at 40% and 80% of maximal work rate (WR max ) in eleven young (26±2yr) and twelve old (80±6yr) males, applying Doppler-ultrasound combined with blood samples from a deep forearm vein. At baseline, old had a larger arterial diameter compared to young (p<0.001). During exercise, the two groups reached the same WR max . V̇O 2 , blood flow, and oxygen supply were higher (40%WR max ; 80%WR max , all p<0.01), and arterio-venous oxygen-difference lower (80%WR max , p<0.02), in old compared to young. Old also had a higher oxygen-excess at 80%WR max (p<0.01) than young, while no difference in muscle diffusion or oxygen-extraction was detected. Only young exhibited an increase in intensity-induced arterial dilation (p<0.05), and they had a lower mean arterial pressure than old at 80%WR max (p<0.001). V̇O 2 /watt (40%WR max ; 80%WR max ) was reduced in old compared to young (both p<0.05). In conclusion, in old and young males with a similar handgrip WR max , old had a higher V̇O 2 during 80%WR max intensity, achieved by an increased blood flow. This may be a result of the available cardiac output reserve, compensating for reduced work efficiency and attenuated vascular response observed in old.
... As demonstrated by the association of chair rising, and stair climbing to force generating capacity (Unhjem et al. 2019). Second, MST has previously been documented to improve skeletal muscle work efficiency, consequently reducing the oxygen cost of locomotion (Barrett-O'Keefe et al. 2012;Berg et al. 2018). It is likely that MST also increased lower extremities muscle efficiency in the present study, and that this may have contributed to the patients´ perception of elevated physical function when walking. ...
Purpose
Patients with inflammatory rheumatic disease (IRD) have attenuated muscle strength in the lower extremities, resulting in impaired physical function and quality of life. Although maximal strength training (MST), applying heavy resistance, is documented to be a potent countermeasure for such attenuation, it is uncertain if it is feasible in IRD given the pain, stiffness, and joint swelling that characterize the population.
Methods
23 patients with IRD (49 ± 13 years; 20 females/3 males), diagnosed with spondyloarthritis, rheumatoid arthritis, or systemic lupus erythematosus, were randomized to MST or a control group (CG). The MST group performed four × four repetitions dynamic leg press two times per week for 10 weeks at ~ 90% of one repetition maximum (1RM). Before and after training 1RM, rate of force development (RFD), and health-related quality of life (HRQoL) were measured.
Results
Session attendance in the MST group was 95%, of which 95% conducted according to MST protocol. Furthermore, MST increased 1RM (29 ± 12%, p = 0.001) and early and late phase RFD (33–76%, p < 0.05). All improvements were different from the CG ( p < 0.05). MST also resulted in HRQoL improvements in the dimensions; physical functioning, general health, and vitality ( p < 0.05). Physical functioning was associated with 1RM (rho = 0.55, p < 0.01) and early phase RFD (rho = 0.53–0.71, p < 0.01; different from CG p < 0.05).
Conclusions
Despite being characterized by pain, stiffness, and joint swelling, patients with IRD appear to tolerate MST well. Given the improvements in 1RM, RFD, and HRQoL MST should be considered as a treatment strategy to counteract attenuated muscle strength, physical function, and HRQoL.
Trial registration: ClinicalTrials.gov, NCT04998955, retrospectively registered.
... OCR increased only in the HIIT group. Ιn the COM group, the mean OCR values were not significantly altered post-training, possibly due to a selective optimization of anaerobic mechanisms, i.e. glycolysis and creatine kinase reaction, and an improved mechanical efficiency of muscle work, i.e. reduced oxygen cost for a given workload, induced by addition of strength training.23,24 ...
Aim: The present study investigates the effect of Strength Training addition in a High Intensity Interval Training (HIIT) program, on the inflammatory profile of chronic heart failure (CHF) patients. Materials and Methods: Forty-six CHF patients were randomized into the two different exercise rehabilitation groups. A patient group (control) performed HIIT and another group performed Combined (HIIT and strength training) Exercise Training (COM) for a three- month period. Before and after rehabilitation, all patients performed a maximal cardiopulmonary exercise testing (CPET). Microcirculatory parameters were assessed by Near Infrared Spectroscopy; CRP, IL-2, IL-6, IL-10 and VEGF levels were measured in plasma. Results: Cardiopulmonary parameters and microcirculatory indices improved after rehabilitation. CRP and the IL-6/IL-10 ratio decreased after rehabilitation. By linear regression analysis, a negative correlation was noted between IL-2, IL-6 and IL-10 changes (post-CPET values) and the VE/VCO2 slope change, for the entire patient cohort. The correlation was separately maintained only in the COM group. Conclusions: Overall, the results of the present study reinforce the view of an anti-inflammatory effect of exercise in CHF patients. The significant correlations demonstrated between the cytokine responses and the ventilatory response to exercise, particularly in the COM group, probably ensue from the special effect of strength training on peripheral muscle function.
... That males and females improved relative 1RM to the same extent was as expected, and in line with previous studies. No gender differences in 1RM% were found in Hakkinen et al. (2000), Storen et al. (2008), Sunde et al. (2010), Kanegusuku et al. (2015), Berg et al. (2018), and Winther et al. (2018). ...
Purpose
The present study aimed to investigate the potential impact of age, gender, baseline strength, and selected candidate polymorphisms on maximal strength training (MST) adaptations.
Methods
A total of 49 subjects (22 men and 27 women) aged 20–76 years, divided into five age groups, completed an 8 weeks MST intervention. Each MST session consisted of 4 sets with 4 repetitions at ∼85–90% of one-repetition maximum (1RM) intensity in leg-press, three times per week. 1RM was tested pre and post the intervention and blood samples were drawn to genotype candidate polymorphisms ACE I/D (rs1799752), ACTN3 R577X (rs1815739), and PPARGC1A Gly482Ser (rs8192678).
Results
All age groups increased leg-press 1RM (p < 0.01), with a mean improvement of 24.2 ± 14.0%. There were no differences in improvements between the five age groups or between male and female participants, and there were no non-responders. Baseline strength status did not correlate with 1RM improvements. PPARGC1A rs8192678 T allele carriers had a 15% higher age- and gender corrected baseline 1RM than the CC genotype (p < 0.05). C allele carriers improved 1RM (%) by 34.2% more than homozygotes for the T allele (p < 0.05).
Conclusion
To the best of our knowledge, this is the first study to report improvement in leg-press maximal strength regardless of gender, baseline strength status in all age groups. The present study is also first to demonstrate an association between the PPARGC1A rs8192678 and maximal strength and its trainability in a moderately trained cohort. MST may be beneficial for good health and performance of all healthy individuals.
... In the study of muscle metabolism and physiology, the application of transient stressors, such as an exercise bout or the application of a cuff to reach hypoxic conditions, is a powerful method to unveil physiological changes caused by, for instance, physical training, supplementation, or pathological processes. [1][2][3][4][5] MRI and MRS techniques have been widely used to track hemodynamic and metabolite concentration changes during or following a physiological challenge in the muscle with temporal resolutions ranging from minutes to milliseconds. ...
Purpose
To evaluate the repeatability of multinuclear interleaved ¹H/³¹P NMR dynamic acquisitions in skeletal muscle and the impact of nuclear Overhauser enhancement (nOe) on the ³¹P results at 3T in exercise‐recovery and ischemia‐hyperemia paradigms.
Methods
A ¹H/³¹P interleaved pulse sequence was used to measure every 2.5 s a perfusion‐weighted image, a T2∗ map, a ³¹P spectrum and 32 ¹H spectra sensitive to deoxymyoglobin. 21 subjects performed a plantar flexion exercise and after recovery underwent an 8‐min lower leg ischemia. The procedure was repeated in visit 2 with 12 subjects. An additional exercise bout without ¹H excitation was appended to visit 1. Individual ¹H RF pulse nOe was measured at rest in every visit.
Results
Repeatability scores (coefficient of variation, Bland‐Altman analysis) were similar to those found in the literature using similar mono‐nuclear acquisitions. |Pi]/[PCr], pH drop, creatine rephosphorylation rate (τPCr), maximum perfusion, time to peak perfusion, and blood flow post‐exercise showed high reliability (intraclass correlation coefficient > 0.7), whereas hemodynamic results from reactive hyperemia showed higher repeatability. After accounting for nOe, which increased Pi and PCr signal‐to‐noise ratio by 30%, no differences in ³¹P results were observed between interleaved and ³¹P MRS‐only acquisitions. τPCr was unaffected by nOe.
Conclusion
The method shows good repeatability for both paradigms while simultaneously providing multiple dynamic data sets on a clinical scanner. The nOe effects were accounted for on a per‐subject and per‐visit basis using a short ³¹P reference scan. This multiparametric approach has a multitude of applications for the study of oxygen utilization and ATP turnover in the muscle.
... Regarding this, it has been demonstrated that HIRT induces an increase in anaerobic ATP synthesis flux (anaerobic glycolysis and creatine kinase reaction), allowing for a higher knee extensor muscular torque production during sustained maximal contraction in older adults (Berg et al. 2018). Thus, as the 400-M test is performed in less time and higher velocity than 6MWT, the HIRT may have improved the ability to perform the 400-M test in a domain of heavier load intensity in the current investigation. ...
The primary purpose of this study was to identify the impact of whole-body resistance training (RT) at different load intensities on adipokines, adhesion molecules, and extracellular heat shock proteins in postmenopausal women. As secondary purpose, we analyzed the impact of RT at different load intensities on body fat, muscular strength, and physical performance. Forty participants were randomized into lower-load intensity RT (LIRT, n = 20, 30–35 repetition maximum in the first set of each exercise) or higher-load intensity RT (HIRT, n = 20, 8–12 repetition maximum in the first set of each exercise). Adipokines (adiponectin and leptin), adhesion molecules (MCP-1 and ICAM-1), extracellular heat shock proteins (HO-1 and eHSP60), body fat, muscular strength (1RM), and physical performance [400-meter walking test (400-M) and 6-minute walking test (6MWT)] were analyzed at baseline and after 12-weeks RT. There was a significant time-by-group interaction for eHSP60 (P = 0.049) and 400-M (P = 0.003), indicating superiority of HIRT (d = 0.47 and 0.55). However, both groups similarly improved adiponectin, ICAM-1, HO-1, body fat, 1RM, and 6MWT (P < 0.05). Our study suggests that load intensity does not seem to determine the RT effect on several obesity-related pro-inflammatory and chemotactic compounds, body fat, 1RM, and 6MWT in postmenopausal women, although a greater improvement has been revealed for eHSP60 and 400-M in HIRT.
Novelty:Higher-load intensity resistance training improves eHSP60 and 400-M in postmenopausal women.
Resistance training improves the inflammatory profile, body fat, muscle strength, and 6MWT, regardless of load intensity.
... Resting twitch responses have been associated with muscle fiber type distribution (30) and sarcoplasmic Ca 2+ kinetics (31). Although MST previously has been shown to change muscle fiber type distribution in old by increasing the size and percentage of fast twitch fibers (32), and alter Ca 2+ pump characteristics (33), this has been after a longer duration (8 weeks) of MST. This may explain why muscle fiber contractile characteristics, in response to 3 weeks of MST, were unchanged in the current study. ...
... Resting twitch responses have been associated with muscle fiber type distribution (30) and sarcoplasmic Ca 2+ kinetics (31). Although MST previously has been shown to change muscle fiber type distribution in old by increasing the size and percentage of fast twitch fibers (32), and alter Ca 2+ pump characteristics (33), this has been after a longer duration (8 weeks) of MST. This may explain why muscle fiber contractile characteristics, in response to 3 weeks of MST, were unchanged in the current study. ...
Strength training performed with heavy loads and maximal intended velocity is documented to enhance efferent neural drive to maximally contracting musculature in older adults. However, it remains unclear whether the neural plasticity following training result from motor skill learning or if external resistance is a prerequisite. To investigate this, we assessed electrically evoked potentials (H-reflex and V-waves normalized to maximal M-wave) and voluntary activation (VA) in 36 older adults (73±4 years) randomized to 3 weeks of plantar flexion strength training, with (maximal strength training; MST) or without (unloaded ballistic training; UBT) heavy external loading (90% of one repetition maximum), or a control group. Both training groups aimed to execute the concentric phase of movement as fast and forcefully as possible. The MST group improved maximal voluntary contraction (MVC) and rate of force development (RFD) by 18±13% (p=0.001; Hedges g=0.66) and 35±17% (p<0.001; g=0.94), respectively, and this was different (MVC: p=0.013; RFD: p=0.001) from the UBT group which exhibited a 7±8% (p=0.033; g=0.32) increase in MVC and a tendency to increase RFD (p=0.119; g=0.22). Concomitant improvements in efferent neural drive (Vmax/Msup-ratio: 0.14±0.08 to 0.24±0.20; p=0.010) and a tendency towards increased VA (79±9% to 84±5%; p=0.098), were only apparent after MST. No changes were observed in Hmax/Mmax-ratio for the groups. In conclusion, external loading during exercise training appears to be a prerequisite for efferent neural drive enhancement in older adults. Thus, strength training with heavy loads should be recommended to counteract the typically observed age-related decline in motoneuron firing frequency and recruitment.
... A capacidade funcional é definida como a habilidade de manter as condições físicas e mentais necessárias nas atividades de vida diária de forma independente e autônoma [13]. Estudos descrevem que o declínio da capacidade funcional em idosos pode estar associada a diminuição de força, levando a perda progressiva da independência funcional, aumento do risco de fraturas, aumento do risco de quedas, diminuição da qualidade de vida, bem como, o aumento de doenças e possível mortalidade em idosos [14][15][16][17]. ...
Introdução: As pessoas estão envelhecendo cada vez mais no Brasil e no mundo. Estudos apontam que o processo de envelhecimento populacional é acompanhado com o aumento de ocorrência de morbidade e incapacidade. Diferentes condições podem ser apresentadas pelo envelhecimento, como: diminuição da capacidade funcional, diminuição da força e da massa muscular, entre outros. Objetivo: Investigar a redução da capacidade funcional, secundária a redução de força muscular de membros inferiores em idosos institucionalizados em duas instituições de longa permanência (ILPI) no município de Nova Iguaçu (RJ/Brasil). Métodos: Trata-se de um estudo exploratório de caráter quantitativo em duas IAPI em Nova Iguaçu/RJ no período do mês de julho e agosto de 2017, em que foram selecionados 60 idosos de ambos os sexos (34 homens e 26 mulheres), com faixa etária ≥ 60 anos. Os voluntários foram avaliados quanto a capacidade funcional e a força muscular. Para a capacidade funcional, foi utilizado a escala de Barthel. Para teste de força, o presente estudo usou para forma de avaliação a escala de Medical Research Council (MRC). Resultados: Os resultados do presente estudo mostraram que que 61,7% dos idosos são classificados como independentes pelo índice de Barthel. Na escala de MRC, 95% dos idosos apresentaram fraqueza muscular. Conclusão: Concluímos que a maior proporção de idosos institucionalizados foram considerados independentes, porém, apresentaram quadro de fraqueza muscular.Palavras-chave: envelhecimento, força muscular, autonomia.
... Concerning the increase in muscle mass and strength, our study did not show any association between changes in fatigue and changes in LBM (R 2 = 11%, P = 0.157) and MS (R 2 = 12% and P = 0.118). Concerning the ATP synthesis flux, it was observed that RE induces an increase in anaerobic ATP synthesis flux (anaerobic glycolysis and creatine kinase reaction) but no ATP from oxidative phosphorylation, allowing for greater knee extensor muscle torque production during sustained maximal contraction (more tolerance to exercise) [44]. Concerning the cytokine regulation, the changes in fatigue may be associated with improvements in the inflammatory process [43]. ...
PurposeTo gain more knowledge about the mechanism (i.e., mediators) of resistance exercise (RE)-induced improvements in physical performance (PP), we seek to investigate whether improvements in muscle strength (MS), muscle power (MP), and lean body mass (LBM) and (or) self-reported fatigue (SRF) are mediators of the effect of RE on PP in breast cancer survivor women (BCSW).Methods
The volunteers were randomly divided into two groups: control group (CT; n = 9) and resistance exercise (RE; n = 11). The RE protocol consisted of three sets in each exercise (leg extension, leg curl, 45° leg press, and calf raise), between 8 and 12 repetitions per set, with an estimated load of 80% of one-repetition maximum (1RM), and three times a week on non-consecutive days for 12 weeks. The CT group performed only stretching exercises twice a week. SRF, maximal muscle power (Pmax), MP, LBM, and PP were assessed using the Brief Fatigue Inventory Questionnaire; 1RM test; isoinertial dynamometer; DXA; and walking speed, sit-to-stand (STS), and timed up and go (TUG) test, respectively.ResultsFollowing 12 weeks, the RE group reduced SRF and increased MP, Pmax, LBM, and performance in all tests (walking speed, STS, and TUG) when compared with the CT group. There were significant associations of the changes in LBM, MS, Pmax, and SRF with changes in physical performance tests only in the RE group.Conclusion
Our findings suggest that improvements in LBM, MS, MP, and self-reported fatigue mediate the effect of resistance exercise on physical performance in BCSW.
The age-related attenuation in neuromuscular function can be mitigated with strength training. Current recommendations for untrained and elderly recommend performing the strength training with a controlled movement velocity (CON). However, applying maximal intended velocity (MIV) in the concentric phase of movement may augment neuromuscular stimulation and potentially enhance training adaptations. Thus, applying rate of electromyography (EMG) rise (RER) recordings, we examined the acute early phase neuromuscular response to these two contraction types in quadriceps femoris during leg extension, along with actual movement velocity, in 12 older (76 ± 6 years) and 12 young men (23 ± 2 years). Results revealed that older adults had a lower one repetition maximum (1RM) than young (33 ± 9 kg vs. 50 ± 9 kg; p = 0.001) and lower actual velocity across relative intensities of ~ 10%, 30%, 50%, 70% and 90% of 1RM for CON and MIV (all p < 0.05). Older adults also had consistently reduced RER compared to young during both conditions (old: 1043–1810 μV; young: 1844–3015 μV; all p < 0.05). However, RER was higher in contractions with MIV compared to CON for both age groups, and across all intensities (98–674%, all p < 0.05). In conclusion, despite decreased maximal strength and attenuated neuromuscular response with advancing age, our results document an augmented neuromuscular activation when repetitions are performed with MIV in the concentric phase of movement.
Parkinson's disease (PD) is characterized by progressive neurological deterioration, typically accompanied by reductions in skeletal muscle force-generating capacity (FGC) and functional performance. Physical activity has the potential to counteract this debilitating outcome, however, it is elusive if high intensity strength training included in conventional treatment may improve results. Therefore, we randomly assigned 22 PD patients (74±9 years) to conventional rehabilitation with or without maximal strength training (MST) performed as leg press and chest press at ~90% of one repetition maximum (1RM), five times per week for four weeks. FGC, physical performance, and efferent neural drive assessed as evoked potentials (V-wave normalized to M-wave in m.soleus) were measured following training. Results revealed that only MST improved 1RM leg press (101±23 to 118±18kg) and chest press (36±15 to 41±15kg), plantar flexion maximal voluntary contraction (235±125 to 293±158N·m ⁻¹ ) and rate of force development (373±345 to 495±446N⋅m ⁻¹ ⋅s ⁻¹ ; all p<0.05; different from controls p<0.05). FGC-improvements were accompanied by an increased efferent neural drive to maximally contracting musculature (V/M-ratio: 0.17±0.12 to 0.24±0.15; p<0.05; different from controls p<0.05), improved physical performance (stair climbing: 21.0±9.2 to 14.4±5.2seconds; timed up and go: 7.8±3.3 to 6.2±2.5seconds; both p<0.05), and self-perceived improvement in health (3.1±0.5 to 2.6±0.9) and social activities functioning (2.2±1.0 to 1.5±1.1; both p<0.05). No changes were observed in the control group. In conclusion, this study shows that MST improves FGC, neuromuscular function, and functional performance, and advocate that high intensity strength training should be implemented as an adjunct therapy in the treatment of PD patients.
Menopause transition may impair muscle function, decreasing exercise tolerance. The torque-duration relationship (hyperbolic curve) forms a practical framework within which exercise tolerance may be explored. In this regard, resistance training (RT) increases the curvature constant of this relationship (W'). Muscle hypertrophy and strength gains have been suggested as possible mediators of RT-induced improvement in W', however, it is unclear what the main mediator is. Higher-volume RT (HV-RT), beyond that recommended by RT-guidelines (i.e. three sets per exercise), may promote greater hypertrophy, but not higher strength gains. Hence, this study aimed to investigate whether greater hypertrophy in HV-RT maximises W' gain when compared to LVRT in postmenopausal women (PW). Fifty-eight PW were randomised to the control group (CTRL), HV-RT (six sets per exercise) or LV-RT (three sets per exercise). They underwent a 12-week RT program and were assessed for W', thigh lean body mass (TLBM) and maximal isometric voluntary contraction (MIVC). The TLBM gain was higher (P < 0.001) in the HV-RT (9.4%) than LV-RT (3.7%). However, both HV-RT and LV-RT similarly increased MIVC (9.7% vs. 16.5%, P = 0.063) and W' (26.4% vs. 34.6% P = 0.163). Additionally, the changes in W' were associated with the changes in TLBM (31%, P = 0.003) and MIVC (52%, P= <0.001). However, when the changes in TLBM and MIVC were inserted into the predictive model, only the MIVC (33%, P = 0.002) was a predictor of W'. Thus, although HV-RT promoted greater hypertrophy than LV-RT, HV-RT does not seem to maximise W' in PW.
Muscle weakness in the elderly has been linked to recurrent falls and morbidity, therefore, elucidating the mechanisms contributing to the loss of muscle function and mobility with advancing age is critical. To this aim, we comprehensively examined skeletal muscle metabolic function and hemodynamics in 11 young (23±2 yrs), 11 old (68±2 yrs), and 10 oldest-old (84±2 yrs) physical activity-matched subjects. Specifically, oxidative stress markers, mitochondrial function and the ATP cost of contraction as well as peripheral hemodynamics were assessed during dynamic plantar flexion exercise at 40% of maximal work rate (WRmax). Both the PCr recovery time constant and the peak rate of mitochondrial ATP synthesis were not significantly different between groups. In contrast, the ATP cost of dynamic contractions (young: 1.5±1.0, old: 3.4±2.1, oldest-old: 6.1±3.6 mM.min⁻¹.W⁻¹) and systemic markers of oxidative stress were signficantly increased with age, with the ATP cost of contraction being negatively correlated with WRmax (r=0.59, P<0.05). End-of-exercise blood flow per Watt rose significantly with increasing age (young: 37±20, old: 82±68, oldest-old: 154±93 ml.min⁻¹.W⁻¹). These findings suggest that the progressive deterioration of muscle contractile efficiency with advancing age may play an important role in the decline in skeletal muscle functional capacity in the elderly.
Skeletal muscle mitochondrial oxidative capacity declines with age and negatively affects walking performance, but the mechanism for this association is not fully clear. We tested the hypothesis that impaired oxidative capacity affects muscle performance and, through this mechanism, has a negative effect on walking speed. Muscle mitochondrial oxidative capacity was measured by in vivo phosphorus magnetic resonance spectroscopy as the postexercise phosphocreatine resynthesis rate, kPCr, in 326 participants (154 men), aged 24–97 years (mean 71), in the Baltimore Longitudinal Study of Aging. Muscle strength and quality were determined by knee extension isokinetic strength, and the ratio of knee extension strength to thigh muscle cross-sectional area derived from computed topography, respectively. Four walking tasks were evaluated: a usual pace over 6 m and for 150 s, and a rapid pace over 6 m and 400 m. In multivariate linear regression analyses, kPCr was associated with muscle strength (β = 0.140, P = 0.007) and muscle quality (β = 0.127, P = 0.022), independent of age, sex, height, and weight; muscle strength was also a significant independent correlate of walking speed (P < 0.02 for all tasks) and in a formal mediation analysis significantly attenuated the association between kPCr and three of four walking tasks (18–29% reduction in β for kPCr). This is the first demonstration in human adults that mitochondrial function affects muscle strength and that inefficiency in muscle bioenergetics partially accounts for differences in mobility through this mechanism.
The challenge of global population aging has been brought into sharper focus by the financial crisis of 2008. In particular,
growing national debt has drawn government attention to two apparently conflicting priorities: the need to sustain public
spending on pensions and health care versus the need to reduce budget deficits. A number of countries are consequently reconsidering
their pension and health care provisions, which account for up to 40% of all government spending in advanced economies. Yet
population aging is a global phenomenon that will continue to affect all regions of the world. By 2050 there will be the same
number of old as young in the world, with 2 billion people aged 60 or over and another 2 billion under age 15, each group
accounting for 21% of the world’s population.
Key points
Release and uptake of Ca ²⁺ ions by the sarcoplasmic reticulum (SR) regulates contraction in skeletal muscle. SR Ca ²⁺ uptake and leak properties in human muscle are presently not well defined.
The surface membrane of individual human muscle fibres was removed by microdissection, and the rate of SR Ca ²⁺ uptake at different applied [Ca ²⁺ ] assessed from the amount of Ca ²⁺ accumulated.
Ca ²⁺ uptake occurred at lower [Ca ²⁺ ] in type I fibres than in type II fibres, consistent with the contractile apparatus properties in the respective fibre types. Maximal uptake rate was slightly greater in type II fibres, and approximately two Ca ²⁺ were taken up per ATP hydrolysed.
Ca ²⁺ leaking out of the SR ultimately has to be pumped back in again at the cost of ATP usage. SR Ca ²⁺ leakage in human muscle fibres was smaller and regulated differently to that in rat muscle fibres, probably reflecting different contributions to thermogenesis.
Abstract
The Ca ²⁺ uptake properties of the sarcoplasmic reticulum (SR) were compared between type I and type II fibres of vastus lateralis muscle of young healthy adults. Individual mechanically skinned muscle fibres were exposed to solutions with the free [Ca ²⁺ ] heavily buffered in the pCa range (–log 10 [Ca ²⁺ ]) 7.3–6.0 for set times and the amount of net SR Ca ²⁺ accumulation determined from the force response elicited upon emptying the SR of all Ca ²⁺ . Western blotting was used to determine fibre type and the sarco(endo)plasmic reticulum Ca ²⁺ ‐ATPase (SERCA) isoform present in every fibre examined. Type I fibres contained only SERCA2 and displayed half‐maximal Ca ²⁺ uptake rate at ∼pCa 6.8, whereas type II fibres contained only SERCA1 and displayed half‐maximal Ca ²⁺ uptake rate at ∼pCa 6.6. Maximal Ca ²⁺ uptake rate was ∼0.18 and ∼0.21 mmol Ca ²⁺ (l fibre) –1 s –1 in type I and type II fibres, respectively, in good accord with previously measured SR ATPase activity. Increasing free [Mg ²⁺ ] from 1 to 3 m m had no significant effect on the net Ca ²⁺ uptake rate at pCa 6.0, indicating that there was little or no calcium‐induced calcium release occurring through the Ca ²⁺ release channels during uptake in either fibre type. Ca ²⁺ leakage from the SR at pCa 8.5, which is thought to occur at least in part through the SERCA, was ∼2‐fold lower in type II fibres than in type I fibres, and was little affected by the presence of ADP, in marked contrast to the larger SR Ca ²⁺ leak observed in rat muscle fibres under the same conditions. The higher affinity of Ca ²⁺ uptake in the type I human fibres can account for the higher relative level of SR Ca ²⁺ loading observed in type I compared to type II fibres, and the SR Ca ²⁺ leakage characteristics of the human fibres suggest that the SERCAs are regulated differently from those in rat and contribute comparatively less to resting metabolic rate.
The assessment of muscle volume, and changes over time, have significant clinical and research-related implications. Methods to assess muscle volume vary from simple and inexpensive to complex and expensive. Therefore, this study sought to examine the validity of muscle volume estimated simply by anthropometry in comparison to the more complex proton magnetic resonance imaging ((1)H-MRI) across a wide spectrum of individuals including those with a spinal cord injury (SCI), a group recognized to exhibit significant muscle atrophy. Accordingly, muscle volume of the thigh and lower leg of 8 subjects with a SCI and 8 able-bodied subjects (Controls) was determined by anthropometry and 1H-MRI. With either method, muscle volumes were significantly lower in the SCI compared to the Controls (P<0.05) and using pooled data from both groups, anthropometric measurements of muscle volume were strongly correlated to the values assessed by (1)H-MRI in both the thigh (r(2) = 0.89; P<0.05) and lower leg (r(2) = 0.98; P<0.05). However, the anthropometric approach systematically overestimated muscle volume compared to (1)H-MRI in both the thigh (mean bias = 2407cm(3)) and the lower (mean bias = 170 cm(3)) leg. Thus, with an appropriate correction for this systemic overestimation, muscle volume estimated from anthropometric measurements is a valid approach and provides acceptable accuracy across a spectrum of adults with normal muscle mass to a SCI and severe muscle atrophy. In practical terms, this study provides the formulas that add validity to the already simple and inexpensive anthropometric approach to assess muscle volume in clinical and research settings.
This study compared maximal strength training (MST) with equal training volume (kg × sets × repetitions) of conventional strength training (CON) primarily with regard to work economy, and second one repetition maximum (1RM) and rate of force development (RFD) of single leg knee extension. In an intra-individual design, one leg was randomized to knee-extension MST (4 or 5RM) and the other leg to CON (3 × 10RM) three times per week for 8 weeks. MST was performed with maximal concentric mobilization of force while CON was performed with moderate velocity. Eight untrained or moderately trained men (26 ± 1 years) completed the study. The improvement in gross work economy was -0.10 ± 0.08 L min(-1) larger after MST (P = 0.011, between groups). From pre- to post-test the MST and CON improved net work economy with 31 % (P < 0.001) and 18 % (P = 0.01), respectively. Compared with CON, the improvement in 1RM and dynamic RFD was 13.7 ± 8.4 kg (P = 0.002) and 587 ± 679 N s(-1) (P = 0.044) larger after MST, whereas isometric RFD was of borderline significance 3,028 ± 3,674 N s(-1) (P = 0.053). From pre- to post-test, MST improved 1RM and isometric RFD with 50 % (P < 0.001) and 155 % (P < 0.001), respectively whereas CON improved 1RM and isometric RFD with 35 % (P < 0.001) and 83 % (P = 0.028), respectively. Anthropometric measures of quadriceps femoris muscle mass and peak oxygen uptake did not change. In conclusion, 8 weeks of MST was more effective than CON for improving work economy, 1RM and RFD in untrained and moderately trained men. The advantageous effect of MST to improve work economy could be due to larger improvements in 1RM and RFD.
Muscle contractions strongly activate p38 MAP kinases, but the precise contraction-associated sarcoplasmic event(s) (e.g. force production, energetic demands and/or calcium cycling) that activate these kinases are still unclear. We tested the hypothesis that during contraction the phosphorylation of p38 isoforms is sensitive to the increase in ATP demand relative to ATP supply. Energetic demands were inhibited using N-benzyl-p-toluene sulphonamide (BTS, type II actomyosin) and cyclopiazonic acid (CPA, SERCA). Extensor digitorum longus muscles from Swiss Webster mice were incubated in Ringer's solution (37°C) with or without inhibitors and then stimulated at 10 Hz for 15 min. Muscles were immediately freeze-clamped for metabolite and western blot analysis. BTS and BTS+CPA treatment decreased force production by 85%, as measured by the tension time integral, while CPA alone potentiated force by 310%. In control muscles, contractions resulted in a 73% loss of ATP content and a concomitant 7-fold increase in IMP content, a measure of sustained energetic imbalance. BTS or CPA treatment lessened the loss of ATP, but BTS+CPA treatment completely eliminated the energetic imbalance since ATP and IMP levels were nearly equal to those of non-stimulated muscles. The independent inhibition of cytosolic ATPase activities had no effect on contraction-induced p38 MAPK phosphorylation, but combined treatment prevented the increase in phosphorylation of the γ isoform while the α/β isoforms unaffected. These observations suggest that an energetic signal may trigger phosphorylation of the p38γ isoform while other factors are involved in activating the α/β isoforms, and also may explain how contractions differentially activate signaling pathways. J. Cell. Biochem. © 2013 Wiley Periodicals, Inc.
Changing demographics make it ever more important to understand the modifiable risk factors for disability and loss of independence with advancing age. For more than two decades there has been increasing interest in the role of sarcopenia, the age-related loss of muscle or lean mass, in curtailing active and healthy aging. There is now evidence to suggest that lack of strength, or dynapenia, is a more constant factor in compromised wellbeing in old age and it is apparent that the decline in muscle mass and the decline in strength can take quite different trajectories. This demands recognition of the concept of muscle quality; that is the force generating per capacity per unit cross-sectional area (CSA). An understanding of the impact of aging on skeletal muscle will require attention to both the changes in muscle size and the changes in muscle quality. The aim of this review is to present current knowledge of the decline in human muscle mass and strength with advancing age and the associated risk to health and survival and to review the underlying changes in muscle characteristics and the etiology of sarcopenia. Cross-sectional studies comparing young (18–45 years) and old (>65 years) samples show dramatic variation based on the technique used and population studied. The median of values of rate of loss reported across studies is 0.47% per year in men and 0.37% per year in women. Longitudinal studies show that in people aged 75 years, muscle mass is lost at a rate of 0.64–0.70% per year in women and 0.80–00.98% per year in men. Strength is lost more rapidly. Longitudinal studies show that at age 75 years, strength is lost at a rate of 3–4% per year in men and 2.5–3% per year in women. Studies that assessed changes in mass and strength in the same sample report a loss of strength 2–5 times faster than loss of mass. Loss of strength is a more consistent risk for disability and death than is loss of muscle mass.
Physical activity guidelines from around the world are typically expressed in terms of frequency, duration, and intensity parameters. Objective monitoring using pedometers and accelerometers offers a new opportunity to measure and communicate physical activity in terms of steps/day. Various step-based versions or translations of physical activity guidelines are emerging, reflecting public interest in such guidance. However, there appears to be a wide discrepancy in the exact values that are being communicated. It makes sense that step-based recommendations should be harmonious with existing evidence-based public health guidelines that recognize that "some physical activity is better than none" while maintaining a focus on time spent in moderate-to-vigorous physical activity (MVPA). Thus, the purpose of this review was to update our existing knowledge of "How many steps/day are enough?", and to inform step-based recommendations consistent with current physical activity guidelines. Normative data indicate that healthy adults typically take between 4,000 and 18,000 steps/day, and that 10,000 steps/day is reasonable for this population, although there are notable "low active populations." Interventions demonstrate incremental increases on the order of 2,000-2,500 steps/day. The results of seven different controlled studies demonstrate that there is a strong relationship between cadence and intensity. Further, despite some inter-individual variation, 100 steps/minute represents a reasonable floor value indicative of moderate intensity walking. Multiplying this cadence by 30 minutes (i.e., typical of a daily recommendation) produces a minimum of 3,000 steps that is best used as a heuristic (i.e., guiding) value, but these steps must be taken over and above habitual activity levels to be a true expression of free-living steps/day that also includes recommendations for minimal amounts of time in MVPA. Computed steps/day translations of time in MVPA that also include estimates of habitual activity levels equate to 7,100 to 11,000 steps/day. A direct estimate of minimal amounts of MVPA accumulated in the course of objectively monitored free-living behaviour is 7,000-8,000 steps/day. A scale that spans a wide range of incremental increases in steps/day and is congruent with public health recognition that "some physical activity is better than none," yet still incorporates step-based translations of recommended amounts of time in MVPA may be useful in research and practice. The full range of users (researchers to practitioners to the general public) of objective monitoring instruments that provide step-based outputs require good reference data and evidence-based recommendations to be able to design effective health messages congruent with public health physical activity guidelines, guide behaviour change, and ultimately measure, track, and interpret steps/day.
The purpose of this study was to investigate whether maximal strength leg press training improves walking mechanical efficiency in coronary artery disease patients. Ten coronary artery disease patients trained 24 sessions of horizontal leg press. Each training session consisted of 4 sets with 4 repetitions of maximal mobilization of concentric force to exhaustion. Seven healthy age matched subjects served as time controls. Maximal strength training improved walking mechanical efficiency (i.e. the oxygen cost to generate a given work load) by 35% (p=0.007) in coronary artery disease patients (from 18+/-4% at pre test to 25+/-6% at post test), and restored walking efficiency to the level of the healthy age matched controls ( approximately 25%). Strength training further improved one repetition maximum from 138+/-24 to 198+/-24 kg (44%) (p=0.000) and rate of force development by 85% (p=0.001), with no change in the control group. Maximal strength leg press training restores walking mechanical efficiency and significantly improves one repetition maximum and rate of force development in coronary artery disease patients after 24 training sessions each lasting only 20 min.
We tested the proposition that muscle cell types have different contents of phosphocreatine (PCr), ATP, and Pi by 31P NMR spectroscopy and HPLC analyses of adult rat and mouse muscles containing various volume fractions of different fiber types. There was a 2-fold difference in the PCr content between muscles with a high volume fraction of fiber types 1 and 2x versus those with fast-twitch (types 2a and 2b) fiber types. Pi content was low, and PCr and ATP contents were high in muscles with large contents of type 2b and 2a fibers; the reverse was true in muscles with a large volume fraction of type 1 and 2x fibers. There is a large range in the Pi/PCr ratios in normal resting muscles, from less than 0.05 in type 2 to 0.51 in type 1 fibers, depending upon the distribution of their component fiber types. In all muscles, the peak area resulting from the beta phosphate of ATP constituted approximately 13% of the sum of all peak areas observable in the 31P spectrum. Fiber types 2a and 2b were not distinguishable, and the content of type 2x fibers was similar to type 1 fibers. From the profile of these metabolites, we could distinguish only two classes of fibers. For type 2a and 2b fibers, the intracellular concentrations were 8 mM ATP, 39 mM total creatine, 32 mM PCr, 0.8 mM Pi, and 8 microM ADP. For type 1 and 2x fibers, these quantities were 5 mM ATP, 23 mM total creatine, 16 mM PCr, 6 mM Pi, and 11 microM ADP. Thus our results establish an additional criterion upon which to distinguish skeletal muscle cells, one based on the resting content of bioenergetically important metabolites. These results also provide the basis for estimating skeletal muscle fiber-type composition from noninvasive NMR spectroscopic data.
The energetic cost of activation was measured during an isometric tetanus of white muscle fibres from the dogfish Scyliorhinus canicula. The total heat production by the fibres was taken as a measure of the total energetic cost. This energy consists of two parts. One is due to crossbridge interaction which produces isometric force, and this part varies linearly with the degree of filament overlap in the fibres. The other part of the energy is that associated with activation of the crossbridges by Ca2+, mainly with uptake of Ca2+ into the sarcoplasmic reticulum by the ATP-driven Ca2+ pump. Total heat production was measured at various degrees of filament overlap beyond the optimum for force development. Extrapolation of heat versus force production data to evaluate the heat remaining at zero force gave a value of 34±5 % (mean ± s.e.m., N=24) for activation heat as a percentage of total heat production in a 2.0 s isometric tetanus. Values for 0.4 and 1.0 s of stimulation were similar. Comparison with values in the literature shows that the energetic cost of activation in dogfish muscle is very similar to that of frog skeletal muscle and it cannot explain the lower maximum efficiency of dogfish muscle compared with frog muscle. The proportion of energy for activation (Ca2+ turnover) is similar to that expected from a simple model in which Ca2+ turnover was varied to minimize the total energy cost for a contraction plus relaxation cycle.
Effects of a 24-week strength training performed twice weekly (24 ST) (combined with explosive exercises) followed by either a 3-week detraining (3 DT) and a 21-week re-strength-training (21 RST) (experiment A) or by a 24-week detraining (24 DT) (experiment B) on neural activation of the agonist and antagonist leg extensors, muscle cross-sectional area (CSA) of the quadriceps femoris, maximal isometric and one repetition maximum (1-RM) strength and jumping (J) and walking (W) performances were examined. A group of middle-aged (M, 37-44 years, n = 12) and elderly (E, 62-77, n = 10) and another group of M (35-45, n = 7) and E (63-78, n = 7) served as subjects. In experiment A, the 1-RM increased substantially during 24 ST in M (27%, P<0.001) and E (29%, P<0.001) and in experiment B in M (29%, P<0.001) and E (23%, P<0.01). During 21 RST the 1-RM was increased by 5% at week 48 (P<0.01) in M and 3% at week 41 in E (n.s., but P<0.05 at week 34). In experiment A the integrated electromyogram (IEMG) of the vastus muscles in the 1-RM increased during 24 ST in both M (P<0.05) and E (P<0.001) and during 21 RST in M for the right (P<0.05) and in E for both legs (P<0.05). The biceps femoris co-activation during the 1-RM leg extension decreased during the first 8-week training in M (from 29+/-5% to 25+/-3%, n.s.) and especially in E (from 41+/-11% to 32+/-9%, P<0.05). The CSA increased by 7% in M (P<0.05) and by 7% in E (P<0.001), and by 7% (n.s.) in M and by 3% in E (n.s.) during 24 ST periods. Increases of 18% (P<0.001) and 12% (P<0.05) in M and 22% (P<0.001) and 26% (P<0.05) in E occurred in J. W speed increased (P<0.05) in both age groups. The only decrease during 3 DT was in maximal isometric force in M by 6% (P<0.05) and by 4% (n.s.) in E. During 24 DT the CSA decreased in both age groups (P<0.01), the 1-RM decreased by 6% (P<0.05) in M and by 4% (P<0.05) in E and isometric force by 12% (P<0.001) in M and by 9% (P<0.05) in E, respectively, while J and W remained unaltered. The strength gains were accompanied by increased maximal voluntary neural activation of the agonists in both age groups with reduced antagonist co-activation in the elderly during the initial training phases. Neural adaptation seemed to play a greater role than muscle hypertrophy. Short-term detraining led to only minor changes, while prolonged detraining resulted in muscle atrophy and decreased voluntary strength, but explosive jumping and walking actions in both age groups appeared to remain elevated for quite a long time by compensatory types of physical activities when performed on a regular basis.
Maximal strength-training with an emphasis on maximal mobilization during cross-country skiing increases exercise economy when double-poling. The aim of this experiment was to investigate whether the mechanism of this increase is a change in the force-velocity relationship and the mechanical power output. A group of 19 cross-country skiers having an average peak oxygen uptake of 255 ml x kg(-0.67) body mass x min(-1) or 61 ml x kg(-1) x min(-1) were randomly assigned to either a high resistance-training group (n=10) or a control group (n=9). Upper body endurance was tested on a ski ergometer. The high-resistance-training group trained for 15 min on three occasions a week for 9 weeks. Training consisted of three series of five repetitions using 85% of one repetition maximum (1RM), with emphasis on high velocity in the concentric part of the movement. Upper body exercise economy, 1RM and time to exhaustion increased significantly in the high resistance-training group, but was unchanged in the control group. Peak power and the velocities for a given load increased significantly, except for the two lowest loads. We conclude that the increased exercise economy after a period of upper body high resistance-training can be partly explained by a specific change in the force-velocity relationship and the mechanical power output.
Maximal strength training (MST) improves work efficiency. However, since blood flow is greatly dictated by muscle contractions in arms during exercise, and vascular conductance is lower, it has been indicated that arms rely more upon adapting oxygen extraction than legs in response to the enhanced work efficiency. Thus, to investigate if metabolic and vascular responses are arm-specific, we utilized Doppler-ultrasound and a catheter placed in the subclavian vein to measure blood flow and a-vO2diff during steady state work in seven young males (24{plus minus}3(SD) years) following six-weeks of handgrip MST. As expected, MST improved maximal strength (49{plus minus}9 to 62{plus minus}10kg) and rate of force development (923{plus minus}224 to 1086{plus minus}238N·s-1), resulting in a reduced submaximal V̇O2 (30{plus minus}9 to 24{plus minus}10ml·min-1) and concomitantly increased work efficiency (9.3{plus minus}2.5 to 12.4{plus minus}3.9%) (all p<0.05). In turn, the work efficiency improvement was associated with a reduced blood flow (486{plus minus}102 to 395{plus minus}114ml·min-1), mediated by a lower blood velocity (43{plus minus}8 to 32{plus minus}6cm·s-1) (all p<0.05). Conduit artery diameter and a-vO2diff remained unaltered. The maximal work test revealed increased time to exhaustion (949{plus minus}239 to 1102{plus minus}292seconds) and maximal work rate (both p<0.05), but no change in peak oxygen uptake. In conclusion, despite prior indications of metabolic and vascular limb-specific differences, these results reveal that improved work efficiency following small muscle mass strength training in the upper extremities is accompanied by a blood flow reduction, and coheres with what has been documented for lower extremities.
Efferent neural drive during strong muscle contractions is attenuated with age, even after lifelong strength training. However, it is unknown if this deterioration may impede contralateral neural plasticity, and limit the clinical value of unilateral strength training. We assessed muscle force-generating capacity, evoked potentials recordings (V-wave and H-reflex normalized to M-wave; V/M-ratio and H/M-ratio) and voluntary activation (VA) in the plantar flexors of the contralateral limb following unilateral maximal strength training (MST) with the dominant limb for three weeks (9 sessions). Twenty-three 73±4(SD) year old males were randomized to a MST group (N=11), exercising with an intensity of ~90% of maximal strength, or a control group (CG, N=12). MST improved contralateral maximal strength (107.6±27.0 to 119.1±34.8Nm;10%) and rate of force development (197.3±54.1 to 232.8±77.7Nms ⁻¹;18%) (both p<0.05). These strength gains were associated with (r=0.465 to 0.608) an enhanced soleus V/M-ratio (0.12±0.09 to 0.21±0.17) and VA (79.5±5.1 to 83.3±5.2%) (all p<0.05). H/M-ratio (10% maximal strength) remained unaltered after MST, and no changes were apparent in the CG. In conclusion, cross-limb effects in older adults are regulated by efferent neural drive enhancement, and advocate the clinical relevance of MST to improve neuromuscular function in individuals with conditions that results in unilateral strength reductions.
The molecular transducers of benefits from different exercise modalities remain incompletely defined. Here we report that 12 weeks of high-intensity aerobic interval (HIIT), resistance (RT), and combined exercise training enhanced insulin sensitivity and lean mass, but only HIIT and combined training improved aerobic capacity and skeletal muscle mitochondrial respiration. HIIT revealed a more robust increase in gene transcripts than other exercise modalities, particularly in older adults, although little overlap with corresponding individual protein abundance was noted. HIIT reversed many age-related differences in the proteome, particularly of mitochondrial proteins in concert with increased mitochondrial protein synthesis. Both RT and HIIT enhanced proteins involved in translational machinery irrespective of age. Only small changes of methylation of DNA promoter regions were observed. We provide evidence for predominant exercise regulation at the translational level, enhancing translational capacity and proteome abundance to explain phenotypic gains in muscle mitochondrial function and hypertrophy in all ages.
Although aging is typically associated with a decreased efficiency of locomotion, somewhat surprisingly, there is also a reduction in the proportion of less efficient fast-twitch Type II skeletal muscle fibers and subsequently a greater propensity for falls. Maximal strength training (MST), with an emphasis on velocity in the concentric phase, improves maximal strength, the rate of force development (RFD), and work efficiency, but the impact on muscle morphology in the elderly is unknown. Therefore we evaluated force production, walking work efficiency, and muscle morphology in 11 old (72 ± 3 years) subjects before and after MST of the legs. Additionally, for reference, the MST-induced morphometric changes were compared with 7 old (74 ± 6 years) subjects who performed conventional strength training (CST), with focus on hypertrophy, as well as 13 young (24 ± 2 years) controls. As expected, MST in the old improved maximal strength (68%), RFD (48%), and work efficiency (12%), restoring each to a level similar to the young. However, of importance, these MST-induced functional changes were accompanied by a significant increase in the size (66%) and shift toward a larger percentage (56%) of Type II skeletal muscle fibers, mirroring the adaptations in the hypertrophy trained old subjects, with muscle composition now being similar to the young. In conclusion, MST can increase both work efficiency and Type II skeletal muscle fiber size and percentage in the elderly, supporting the potential role of MST as a countermeasure to maintain both physical function and fall prevention in this population.
This study investigated the relationship between motor unit (MU) properties and the isometric strength and power of two lower limb muscles in healthy young and older adults. Twelve older adults (6 men, mean age, 77±5yrs) and twelve young adults (6 men, mean age, 24±3yrs) were studied. MU properties of the tibialis anterior (TA) and vastus medialis (VM) muscles were determined electrophysiologically using decomposition-enhanced spike-triggered averaging (DE-STA). Motor unit number estimates (MUNE) of the TA were significantly reduced (p<0.05) in older adults (102±76) compared to young adults (234±109), primarily as a result of significantly larger surface-detected motor unit potentials (S-MUP) in older adults (63±29μV) compared to young adults (27±14μV). Although VM S-MUP values were larger in older adults (60±31μV) compared to young (48±42μV), the difference was not significant. Maximal isometric strength was significantly larger in both the TA and knee extensors of young adults (TA: 0.56Nm/kg, KE: 2.2Nm/kg) compared to old (TA: 0.4Nm/kg, KE: 1.3Nm.kg). Similar reductions in peak muscle power were observed between young (TA: 33W, KE: 357W) and old adults (TA: 26W, KE: 224W). The greatest deficit between young and old subjects in peak power output occurred at 20% MVC for the TA and 40% MVC for the knee extensors. Results from this study indicate that there are changes in MU properties with age, and that this effect may be greater in the more distal TA muscle. Further, this study demonstrates that muscle power may be a sensitive marker of changes in neuromuscular function with aging.
Copyright © 2015. Published by Elsevier Inc.
Although skeletal muscle work efficiency likely plays a key role in limiting mobility of the elderly, the physiological mechanisms responsible for this diminished function remain incompletely understood. Thus, in the quadriceps of young (n=9) and old (n=10) subjects, we measured the cost of muscle contraction (ATP cost) with 31P-magnetic resonance spectroscopy (31P-MRS) during 1) maximal intermittent contractions to elicit a metabolic demand from both cross-bridge cycling and ion pumping and 2) a continuous maximal contraction to predominantly tax cross-bridge cycling. The ATP cost of the intermittent contractions was significantly greater in the old (0.30 ± 0.22 mM.min-1.N m-1) compared to the young (0.13 ± 0.03 mM.min-1.N m-1, P<0.05). In contrast, at the end of the continuous contraction protocol, the ATP cost in the old (0.10 ± 0.07 mM.min-1.N m-1) was not different from the young (0.06 ± 0.02 mM.min-1.N m-1, P=0.2). In addition, the ATP cost of the intermittent contractions correlated significantly with the single leg peak power of the knee-extensors assessed during incremental dynamic exercise (r = -0.55; P<0.05,). Overall, this study reveals an age-related increase in the ATP cost of contraction, likely mediated by an excessive energy demand from ion pumping, which probably contributes to both the decline in muscle efficiency and functional capacity associated with aging.
The aim of this study was to determine whether the net efficiency of mammalian muscles depends on muscle fibre type. Experiments were performed in vitro (35°C) using bundles of muscle fibres from the slow-twitch soleus and fast-twitch extensor digitorum longus (EDL) muscles of the mouse. The contraction protocol consisted of 10 brief contractions, with a cyclic length change in each contraction cycle. Work output and heat production were measured and enthalpy output (work + heat) was used as the index of energy expenditure. Initial efficiency was defined as the ratio of work output to enthalpy output during the first 1 s of activity. Net efficiency was defined as the ratio of the total work produced in all the contractions to the total, suprabasal enthalpy produced in response to the contraction series, i.e. net efficiency incorporates both initial and recovery metabolism. Initial efficiency was greater in soleus (30 ± 1%; n= 6) than EDL (23 ± 1%; n= 6) but there was no difference in net efficiency between the two muscles (12.6 ± 0.7% for soleus and 11.7 ± 0.5% for EDL). Therefore, more recovery heat was produced per unit of initial energy expenditure in soleus than EDL. The calculated efficiency of oxidative phosphorylation was lower in soleus than EDL. The difference in recovery metabolism between soleus and EDL is unlikely to be due to effects of changes in intracellular pH on the enthalpy change associated with PCr hydrolysis. It is suggested that the functionally important specialization of slow-twitch muscle is its low rate of energy use rather than high efficiency.
Muscle adaptations can be induced by high-resistance exercise. Despite being potentially more suitable for older adults, low-resistance exercise protocols have been less investigated. We compared the effects of high- and low-resistance training on muscle volume, muscle strength, and force-velocity characteristics. Fifty-six older adults were randomly assigned to 12 weeks of leg press and leg extension training at either HIGH (2 x 10-15 repetitions at 80% of one repetition maximum (1RM)), LOW (1 x 80-100 repetitions at 20% of 1RM), or LOW+ (1 x 60 repetitions at 20% of 1RM, followed by 1 x 10-20 repetitions at 40% 1RM). All protocols ended with muscle failure. Leg press and leg extension 1RM were measured at baseline and post intervention, and before the first training session in week 5 and 9. At baseline and post intervention, muscle volume (MV) was measured by CT-scan. A Biodex dynamometer evaluated knee extensor static peak torque in different knee angles (PTstat90°, PTstat120°, PTstat150°), dynamic peak torque at different speeds (PTdyn60°s(-1), PTdyn180°s(-1), PTdyn240°s(-1)), and speed of movement at 20% (S20), 40% (S40), and 60% (S60) of PTstat90°. HIGH and LOW+ resulted in greater improvements in 1RM strength than LOW (p < 0.05). These differences were already apparent after week 5. Similar gains were found between groups in MV, PTstat, PTdyn60°s(-1), and PTdyn180°s(-1). No changes were reported in speed of movement. HIGH tended to improve PTdyn240°s(-1) more than LOW or LOW+ (p = 0.064). In conclusion, high- and low- resistance exercise ending with muscle failure may be similarly effective for hypertrophy. High-resistance training led to a higher increase in 1RM strength than low-resistance training (20% of 1RM), but this difference disappeared when using a mixed low-resistance protocol in which the resistance was intensified within a single exercise set (40% of 1RM). Our findings support the need for more research on low-resistance programs in older age, in particular long-term training studies and studies focusing on residual effects after training cessation.
The purpose of this study was to determine whether improvements in endurance exercise performance elicited by strength training were accurately reflected by changes in parameters of the power-duration hyperbola for high-intensity exercise. Before and after 8 weeks of strength training (N=14) or no-exercise control (N=5), 19 males (age 20.6±2.0 years; weight: 78.2±15.9 kg) performed a maximal incremental exercise test on a cycle ergometer and also cycled to exhaustion during 4 constant-power exercise bouts. Critical Power (CP) and anaerobic work capacity (W') were estimated using nonlinear and linear models. Subjects in the strength training group improved significantly more than controls (p<0.05) for strength (∼30%), power at VO2peak (7.9%), and time to exhaustion (TTE) for all 4 constant-power tests (∼39%). Contrary to our hypothesis, CP did not change significantly after strength training (p>0.05 for all models). Strength training improved W' (mean range of improvement = +5.8 to +10.0 kJ; p<0.05) for both linear models. Increases in W' were consistently positively correlated with improvements in TTE, whereas changes in CP were not. Our findings indicate that strength training alters the power-duration hyperbola such that W' is enhanced without any improvement in CP. Consequently, CP may not be robust enough to track changes in endurance capacity elicited by strength training and we do not recommend it to be used for this purpose. Conversely, W' may be the better indicator of improvement in endurance performance elicited by strength training.
Maximal strength training (MST) reduces pulmonary oxygen uptake (VO(2)) at a given submaximal exercise work rate (i.e. efficiency). However, whether the increase in efficiency originates in the trained skeletal muscle, and therefore the impact of this adaptation on muscle blood flow and arterial-venous oxygen difference (a-vO(2diff)), is unknown. Thus, five trained subjects partook in an 8 wk MST intervention consisting of half-squats with an emphasis on the rate of force development during the concentric phase of the movement. Pre- and post-training measurements of pulmonary VO(2) (indirect calorimetry), single leg blood flow (thermodilution), single leg a-vO(2diff) (blood gases) were performed, to allow the assessment of skeletal muscle VO(2) during submaximal cycling (237 ± 23 Watts; ~60% of their peak pulmonary VO(2) (VO(2peak))). Pulmonary VO(2peak) (~4.05 L/min) and peak work rate (~355 Watts), assessed during a graded exercise test, were unaffected by MST. As expected, following MST there was a significant reduction in pulmonary VO(2) during steady state submaximal cycling (~237 Watts: 3.2 ± 0.1 to 2.9 ± 0.1 L/min). This was accompanied by a significant reduction in single leg VO(2) (1,101 ± 105 to 935 ± 93 ml/min) and single leg blood flow (6,670 ± 700 to 5,649 ± 641ml/min), but no change in single leg a-vO(2diff) (16.7 ± 0.8 to 16.8 ± 0.4 ml/dl). These data confirm an MST-induced reduction in pulmonary VO(2) during submaximal exercise and identifies that this change in efficiency originates solely in skeletal muscle, reducing muscle blood flow, but not altering muscle a-vO(2diff).
31P magnetic resonance spectroscopy (31P MRS) can yield much information about bioenergetics in skeletal muscle. During mixed aerobic/glycolytic exercise, changes in phos-phocreatine (PCr) concentration and pH may be abnormal because of reduced muscle mass or reduced efficiency (which the authors combine here as “effective muscle mass”) or because of reduced oxidative capacity. The authors show how these can be distinguished by calculating the nonoxidative and oxidative costs of mechanical work, and also of work per unit of effective muscle mass (measured using the initial rate of ATP turnover). These quantities are substantially time-independent during incremental exercise, and so can be used to compare exercise studies of differing duration. The authors illustrate this analysis by showing that in dialyzed patients with chronic renal failure, the substantial exercise abnormalities seen by 31P MRS are due mainly to a decrease in effective muscle mass, which outweighs the oxidative defect implied by the abnormal PCr recovery kinetics.
Evidence suggests that consumption of over-the-counter cyclooxygenase (COX) inhibitors may interfere with the positive effects that resistance exercise training has on reversing sarcopenia in older adults. This study examined the influence of acetaminophen or ibuprofen consumption on muscle mass and strength during 12 wk of knee extensor progressive resistance exercise training in older adults. Thirty-six individuals were randomly assigned to one of three groups and consumed the COX-inhibiting drugs in double-blind placebo-controlled fashion: placebo (67 ± 2 yr; n = 12), acetaminophen (64 ± 1 yr; n = 11; 4 g/day), and ibuprofen (64 ± 1 yr; n = 13; 1.2 g/day). Compliance with the resistance training program (100%) and drug consumption (via digital video observation, 94%), and resistance training intensity were similar (P > 0.05) for all three groups. Drug consumption unexpectedly increased muscle volume (acetaminophen: 109 ± 14 cm(3), 12.5%; ibuprofen: 84 ± 10 cm(3), 10.9%) and muscle strength (acetaminophen: 19 ± 2 kg; ibuprofen: 19 ± 2 kg) to a greater extent (P < 0.05) than placebo (muscle volume: 69 ± 12 cm(3), 8.6%; muscle strength: 15 ± 2 kg), when controlling for initial muscle size and strength. Follow-up analysis of muscle biopsies taken from the vastus lateralis before and after training showed muscle protein content, muscle water content, and myosin heavy chain distribution were not influenced (P > 0.05) by drug consumption. Similarly, muscle content of the two known enzymes potentially targeted by the drugs, COX-1 and -2, was not influenced (P > 0.05) by drug consumption, although resistance training did result in a drug-independent increase in COX-1 (32 ± 8%; P < 0.05). Drug consumption did not influence the size of the nonresistance-trained hamstring muscles (P > 0.05). Over-the-counter doses of acetaminophen or ibuprofen, when consumed in combination with resistance training, do not inhibit and appear to enhance muscle hypertrophy and strength gains in older adults. The present findings coupled with previous short-term exercise studies provide convincing evidence that the COX pathway(s) are involved in the regulation of muscle protein turnover and muscle mass in humans.
To assess physical outcome of early maximal strength training after total hip arthroplasty.
Six- and 12-mo follow-up of 24 (22) total hip arthroplasty patients randomly assigned to 4 wks of maximal strength training and conventional rehabilitation and to conventional rehabilitation only was conducted. After the intervention period, all patients attended conventional rehabilitation. Outcome measures were hip abduction and leg press strength, gait patterns, work efficiency, maximal oxygen consumption, and health-related quality of life.
Work efficiency was significantly higher in the strength training and conventional rehabilitation group compared with the conventional rehabilitation-only group after 6 and 12 mos by 29% and 30%, respectively. Leg press for the healthy leg and rate of force development for the operated leg were significantly higher in the strength training and conventional rehabilitation group compared with the conventional rehabilitation-only group 12 mos postoperatively by 36% and 74%, respectively.
This study demonstrates higher work efficiency after 6 and 12 mos and improved rate of force development after 12 mos in total hip arthroplasty patients who performed early maximal strength training combined with conventional rehabilitation after total hip arthroplasty surgery compared with total hip arthroplasty patients receiving conventional rehabilitation only. However, the study indicates that a prolonged maximal strength training program and aerobic endurance training are required to fully recover total hip arthroplasty patients.
Today's available chemical shift imaging (CSI) analysis tools are based on Fourier transform of the entire data set prior to interactive display. This strategy is associated with limitations particularly when arbitrary voxel positions within a 3D spatial volume are needed by the user. In this work, we propose and demonstrate a processing-resource-efficient alternative strategy for both interactive and automated CSI data processing up to three spatial dimensions.
This approach uses real-time voxel-shift by first-order phase manipulation as a basis and therefore allows grid-free voxel positioning within the 3D volume. The corresponding spectrum is extracted from the 4D data (3D spatial/1D spectral) at each time a voxel position is selected. The spatial response function and hence the exact voxel size and shape are calculated in parallel including the same processing parameters. Using this mechanism sequentially along with AMARES time-domain modeling, we also implemented automated quantitative and B (0)-insensitive metabolite mapping.
Metabolite maps of N-acetyl aspartate, choline and creatine were generated using (1)H-CSI data from the brain of healthy volunteers and patients with tumor and epilepsy. (31)P-3D-CSI of the heart of a healthy volunteer is also shown.
The calculated metabolite maps demonstrate good stability and accuracy of the algorithm in all situations tested. The suggested algorithm constitutes therefore an attractive alternative to existing CSI processing strategies.
Aim: Force generation and transmembrane ion pumping account for the majority of energy expended by contracting skeletal muscles. Energy turnover for ion pumping, activation energy turnover (EA), can be determined by measuring the energy turnover when force generation has been inhibited. Most measurements show that activation accounts for 25–40% of isometric energy turnover. It was recently reported that when force generation in mouse fast-twitch muscle was inhibited using N-benzyl-p-toluenesulphonamide (BTS), activation accounted for as much as 80% of total energy turnover during submaximal contractions. The purpose of this study was to compare EA measured by inhibiting force generation by: (1) the conventional method of reducing contractile filament overlap; and (2) pharmacological inhibition using BTS.
Methods: Experiments were performed in vitro using bundles of fibres from mouse fast-twitch extensor digitorum longus (EDL) muscle. Energy turnover was quantified by measuring the heat produced during 1-s maximal and submaximal tetanic contractions at 20 and 30 °C.
Results: EA measured using reduced filament overlap was 0.36 ± 0.04 (n = 8) at 20 °C and 0.31 ± 0.05 (n = 6) at 30 °C. The corresponding values measured using BTS in maximal contractions were 0.46 ± 0.06 and 0.38 ± 0.06 (n = 6 in both cases). There were no significant differences among these values. EA was also no different when measured using BTS in submaximal contractions.
Conclusion: Activation energy turnover is the same whether measured using BTS or reduced filament overlap and accounts for slightly more than one-third of isometric energy turnover in mouse EDL muscle.
Peripheral arterial disease (PAD) patients have reduced muscle strength and impaired walking ability. The aim of this study was to examine the effects of maximal strength training (MST) on walking economy and walking performance in PAD patients. Ten patients with mild to moderate-severe claudication, classified as Fontaine stage II PAD and with functional limitations from intermittent claudication were recruited and went through an 8-week control period followed by an 8-week, three times a week, MST period. The patients performed four sets of five repetitions dynamic leg press with emphasis on maximal mobilization of force in the concentric action and with a progressive adjusted intensity corresponding to 85-90% of one repetition maximum (1 RM). After the MST period, leg press 1 RM significantly increased by 35.0 ± 10.8 kg (31.3%). Dynamic rate of force development, measured on a force plate installed on the leg press, increased by 1424 ± 1217 N/s (102.7%). The strength improvements led to a significant increase in walking economy of 9.7% when walking horizontally, and to a significant increase in walking performance of 13.6% measured on an incremental treadmill test to exhaustion. No changes were apparent after the control period. No changes in body mass or peak oxygen uptake were observed. MST increases strength in Fontaine stage II PAD patients and leads to improved walking economy. These results suggest that application of MST could accompany aerobic endurance training as a part of the treatment of PAD patients with mild to moderate-severe claudication.
In many small animals there are distinct differences in fiber-type composition among limb muscles, and these differences typically correspond to marked disparities in the oxidative capacities. However, whether there are similar differences in the oxidative capacity among leg muscles in humans is less clear. The purpose of this study was to compare the rate of phosphocreatine (PCr) recovery, a functional in vivo marker of oxidative capacity, in the lateral and medial gastrocnemius, soleus, and the anterior compartment of the leg (primarily the tibialis anterior) of humans. Subjects performed plantar flexion and dorsiflexion gated exercise protocols consisting of 70 sets of three rapid dynamic contractions (<2.86 s) at 20 s intervals (total: 23.3 min). Starting after the sixth set of contractions, (31)P 2-D CSI (8 x 8 matrix, 14-16 cm FOV, 3 cm slice, TR 2.86 s) were acquired via a linear transmit/receive surface coil using a GE 3T Excite System. The CSI data were zero-filled (32 x 32) and a single FID was produced for each time point in the lateral and medial gastrocnemius, soleus, and anterior compartment. The time constant for PCr recovery was calculated from tau = -Deltat/ln[D/(D + Q)], where Q is the percentage change in PCr due to contraction during the steady-state portion of the protocol, D the additional drop in PCr from rest, and Deltat is the interval between contractions. The tau of PCr recovery was longer (p < 0.05) in the anterior compartment (32 +/- 3 s) than in the lateral (23 +/- 2 s) and medial gastrocnemius muscles (24 +/- 3 s) and the soleus (22 +/- 3 s) muscles. These findings suggest that the oxidative capacity is lower in the anterior compartment than in the triceps surae muscles and is consistent with the notion that fiber-type phenotypes vary among the leg muscles of humans.
To evaluate the effects of 26 wk of aerobic and resistance training on the incidence of injury and program adherence in 70- to 79-yr-old men and women, 57 healthy volunteers (25 males, 32 females) were randomly assigned to a walk/jog (W/J, N = 21), strength (STREN, N = 23), or control (CONT, N = 13) group. Walk/jog training was for 30-45 min, 3 d.wk-1 with intensity equal to 40-70% heart rate max reserve (HRmax reserve) during the first 13 wk, and 75-85% HRmax reserve for weeks 14-26. STREN training consisted of one set (10-12 repetitions) each of 10 variable resistance exercises performed to volitional fatigue. Forty-nine of the original participants completed the training program. Walk/jog training increased VO2max from 22.5 to 27.1 ml.kg-1.min-1 (P less than or equal to 0.05) while STREN and CONT showed no change. STREN improved significantly in chest press and leg extension strength (P less than or equal to 0.05) while W/J and CONT showed no change. Adherence to training was 20/23 (87%) and 17/21 (81%) in STREN and W/J, respectively. One repetition maximum (1-RM) strength testing resulted in 11 injuries in the 57 subjects (19.3%) while STREN training resulted in only two injuries in 23 subjects (8.7%). Walk training during weeks 1-13 resulted in one injury in 21 subjects (4.8%). Eight of 14 subjects (57%) who began jogging intervals at week 14 incurred an injury: two of eight (25%) of the men and all of the women (6 of 6). All W/J training injuries were to the lower extremity.(ABSTRACT TRUNCATED AT 250 WORDS)
1. A method has been developed to discriminate between the rate of ATP hydrolysis associated with calcium uptake into the sarcoplasmic reticulum (SR) and force development of the contractile apparatus in mechanically or saponin-skinned skeletal muscle fibres. The rate of ATP hydrolysis was determined in fibres of different types from the iliofibularis muscle of Xenopus laevis by enzymatic coupling of ATP re-synthesis to the oxidation of NADH. 2. The ATPase activity was determined before and after exposure of the preparations for 30 min to a solution containing 0.5% Triton X-100, which effectively abolishes the SR ATPase activity. The fibres were activated in a solution containing 5 mM caffeine to ensure that calcium uptake into the SR was maximal. 3. At saturating Ca2+ concentrations the actomyosin (AM) and SR ATPase activities in fast-twitch fibres, at 4.3 degrees C, amounted to 1.52 +/- 0.07 and 0.58 +/- 0.10 mumol s-1 (g dry wt)-1, respectively (means +/- S.E.M.; n = 25). The SR ATPase activity was 25% of the total ATPase activity. At submaximal calcium concentrations the AM ATPase activity varied in proportion to the isometric force. 4. The calcium sensitivity of the SR ATPase was larger than that of the AM ATPase and its dependence on [Ca2+] was less steep. The AM ATPase activity was half-maximal at a pCa of 6.11 (pCa = -log [Ca2+]) whereas the SR ATPase activity was half-maximal at a pCa of 6.62. 5. In Triton X-100-treated fibres, at different 2,3-butanedione monoxime (BDM) concentrations, the AM ATPase activity and isometric force varied proportionally. The SR ATPase activity determined by extrapolation of the total ATPase activity in mechanically skinned or saponin-treated fibres to zero force, was independent of the BDM concentration in the range studied (0-20 mM). The values obtained for the SR ATPase activity in this way were similar to those obtained with Triton X-100 treatment. 6. The AM ATPase activity in slow-twitch fibres amounted to 0.74 +/- 0.13 mumol s-1 (g dry wt)-1, i.e. about a factor of two smaller than in fast-twitch fibres. The SR ATPase activity amounted to 0.47 +/- 0.07 mumol s-1 (g dry wt)-1, i.e. rather similar to the value in fast-twitch fibres. The proportion of the total ATPase activity that was due to SR ATPase (40%) was larger than in fast-twitch fibres. 7. The temperature dependence of the AM and SR ATPase activities in fast-twitch fibres differed. In the temperature range 5-10 degrees C, the relative changes in AM and SR ATPase activities for a 10 degrees C temperature change (Q10) were 3.9 +/- 0.3 and 7.2 +/- 1.5, respectively.(ABSTRACT TRUNCATED AT 400 WORDS)
The effects of a depolarizing (decamethonium, DECA) and a nondepolarizing neuromuscular blocking agent (vecuronium, VECU) on the phosphorus-31 nuclear magnetic resonance (31P-NMR)-detected metabolic response to muscle contractions were studied separately in six healthy untrained males. Subjects who showed splitting of the P(i) peak during graded rhythmic forearm exercise without the drugs were selected. It was found that both drugs abolished the P(i) peak splitting during exercise. Despite a similar reduction in phosphocreatine (PCr) during exercise with each drug, a smaller increase in P(i) was observed with DECA than with VECU (P < 0.05). End-exercise muscle pH was higher with DECA (6.93 +/- 0.07) than with VECU (6.79 +/- 0.11) (P < 0.05). The PCr and P(i) recovery was two- and threefold faster with DECA than with VECU, respectively (P < 0.05). On the basis of the concept that depolarizing and nondepolarizing agents have a preferential effect on fast- and slow-twitch muscle fibers, respectively, the present results support the hypothesis that the NMR-observed splitting of the P(i) peak reflects the metabolic differences between the two major fiber types of human skeletal muscle.
This study examined the effect of resistance training on exercise-induced contrast shift in magnetic resonance (MR) images. It was hypothesized that a given load could be lifted after training with less muscle showing contrast shift, thereby suggesting less muscle was used to perform the exercise. Nine males trained the left quadriceps femoris (QF) muscle 2 days/wk for 9 wk using 3-6 sets of 12 knee extensions each day. The right QF served as a "control." Exercise-induced contrast shifts in MR images evoked by each of three bouts of exercise (5 sets of 10 knee extensions with a load equal to 50, 75, and 100% of the maximum pretraining load that could be lifted for 5 sets of 10 repetitions) were quantified pre- and posttraining. MR image contrast shift was quantified by determining QF cross-sectional area (CSA) showing increased spin-spin relaxation time. One repetition maximum increased 14% in the left trained QF and 7% in the right untrained QF. Left QF CSA increased 5%, with no change in right QF CSA. Left QF CSA showing contrast shift was less after each bout of the exercise test posttraining. This was also true, to a lesser extent, for the right QF at the higher two loads. The results suggest that short-term resistance training reduces MR image contrast shift evoked by a given effort, thereby reflecting the use of less muscle to lift the load. Because this response was evident in both trained and contralateral untrained muscle, neural factors are suggested to be responsible.(ABSTRACT TRUNCATED AT 250 WORDS)
In the study of skeletal muscle bioenergetics, 31P magnetic resonance spectroscopy (MRS) allows frequent measurement of the cytosolic pH and the concentrations of phosphocreatine, inorganic phosphate, and adenosine diphosphate (ADP) during exercise and recovery, which can be supplemented by 1H MRS (or biopsy) measurements of muscle lactate content and 13C MRS (or biopsy) measurements of muscle glycogen. We review the many methods now described by which 31P MRS measurements can be made to yield quantitative estimates of adenosine triphosphate (ATP) turnover, oxidative capacity, and proton handling in skeletal muscle. In particular, we describe how to estimate the rates of glycogenolytic and aerobic ATP synthesis during exercise and oxidative ATP synthesis and proton efflux during recovery from exercise and how to assess oxidative capacity using data from steady-state exercise, work jumps, or recovery. We discuss the metabolic relationships that make these methods possible and the assumptions (e.g., about cytosolic buffer capacity and mitochondrial control mechanisms) on which they depend. We show how these methods, although sometimes based on apparently conflicting metabolic models, can be analysed in a common framework. Finally, we discuss some examples of the current and potential applications of these methods in clinical and experimental studies of skeletal muscle.
ATP consumption and force development were determined in single skinned muscle fibres of the rat at 12 °C. Myofibrillar ATPase consumption was measured photometrically from NADH oxidation which was coupled to ATP hydrolysis. Myosin heavy chain (MHC) and light chain (MLC) isoforms were identified by gel electrophoresis.
Slow fibres ( n = 14 ) containing MHCI and fast fibres ( n = 18 ) containing MHCIIB were compared. Maximum shortening velocity was 1.02 ± 0.63 and 3.05 ± 0.23 lengths s ⁻¹ , maximum power was 1.47 ± 0.22 and 9.59 ± 0.84 W l ⁻¹ , and isometric ATPase activity was 0.034 ± 0.003 and 0.25 ± 0.01 m M s ⁻¹ in slow and in fast fibres, respectively.
In fast as well as in slow fibres ATP consumption during shortening increased above isometric ATP consumption. The increase was much greater in fast fibres than in slow fibres, but became similar when expressed relative to the isometric ATPase rate.
Efficiency was calculated from mechanical power and free energy change associated with ATP hydrolysis. Maximum efficiency was larger in slow than in fast fibres (0.38 ± 0.04 versus 0.28 ± 0.03) and was reached at a lower shortening velocity.
Within the group of fast fibres efficiency was lower in fibres which contained more MLC 3f . We conclude that both MHC and essential MLC isoforms contribute to determine efficiency of chemo‐mechanical transduction.
We introduce AMARES (advanced method for accurate, robust, and efficient spectral fitting), an improved method for accurately and efficiently estimating the parameters of noisy magnetic resonance spectroscopy (MRS) signals in the time domain. As a reference time domain method we take VARPRO. VARPRO uses a simple Levenberg-Marquardt algorithm to minimize the variable projection functional. This variable projection functional is derived from a general functional, which minimizes the sum of squared differences between the data and the model function. AMARES minimizes the general functional which improves the robustness of MRS data quantification. The newly developed method uses a version of NL2SOL, a sophisticated nonlinear least-squares algorithm, to minimize the general functional. In addition, AMARES uses a singlet approach for imposition of prior knowledge instead of the multiplet approach of VARPRO because this greatly extends the possibilities of the kind of prior knowledge that can be invoked. Other new features of AMARES are the possibility of fitting echo signals, choosing a Lorentzian as well as a Gaussian lineshape for each peak, and imposing lower and upper bounds on the parameters. Simulations, as well as in vivo experiments, confirm the better performance of AMARES compared to VARPRO in terms of accuracy, robustness, and flexibility. Copyright 1997 Academic Press. Copyright 1997Academic Press
To determine the effects of strength training (ST) on muscle quality (MQ, strength/muscle volume of the trained muscle group), 12 healthy older men (69 +/- 3 yr, range 65-75 yr) and 11 healthy older women (68 +/- 3 yr, range 65-73 yr) were studied before and after a unilateral leg ST program. After a warm-up set, four sets of heavy-resistance knee extensor ST exercise were performed 3 days/wk for 9 wk on the Keiser K-300 leg extension machine. The men exhibited greater absolute increases in the knee extension one-repetition maximum (1-RM) strength test (75 +/- 2 and 94 +/- 3 kg before and after training, respectively) and in quadriceps muscle volume measured by magnetic resonance imaging (1,753 +/- 44 and 1, 955 +/- 43 cm3) than the women (42 +/- 2 and 55 +/- 3 kg for the 1-RM test and 1,125 +/- 53 vs. 1,261 +/- 65 cm3 for quadriceps muscle volume before and after training, respectively, in women; both P < 0.05). However, percent increases were similar for men and women in the 1-RM test (27 and 29% for men and women, respectively), muscle volume (12% for both), and MQ (14 and 16% for men and women, respectively). Significant increases in MQ were observed in both groups in the trained leg (both P < 0.05) and in the 1-RM test for the untrained leg (both P < 0.05), but no significant differences were observed between groups, suggesting neuromuscular adaptations in both gender groups. Thus, although older men appear to have a greater capacity for absolute strength and muscle mass gains than older women in response to ST, the relative contribution of neuromuscular and hypertrophic factors to the increase in strength appears to be similar between genders.
The time to fatigue (t) in response to high-intensity constant-load exercise decreases hyperbolically with increasing power (W), at least in active and younger individuals [i.e. (W - thetaF)t = W', where thetaF is the critical power asymptote and W' is the curvature constant]. Little is known, however, about the combined effects of age and sedentarity on these parameters. We therefore evaluated 17 non-trained males (9 aged 60-75 years and 8 aged below 30 years) who underwent ramp-incremental cycle ergometry and, on different days, 4 high-intensity constant-load tests to t. Compared to their younger counterparts, the older subjects presented significantly lower maximum oxygen uptake (i.e. the maximum value of oxygen uptake attained at the end of a progressive exercise with the subject exerting a presumably maximal effort, muVO2), estimated lactate threshold (VO2thetaL), VO2thetaF, and W' (P < 0.05). Interestingly, however, both VO2thetaL and VO2thetaF, when expressed as a percentage of muVO2, were higher in older than in younger men [61.8 (6.2)% versus 45.4 (4.6)% and 87.8 (7.3)% versus 79.0 (8.2)%, P < 0.05, respectively]. Therefore, age was associated with an increase in the relative magnitude of the "moderate", sub-thetaL exercise-intensity domain (+30.4%), mainly at the expense of the "very-heavy", supra-thetaF domain (-56%). Our results demonstrate that age and sedentarity are associated with: (1) marked reductions in both the aerobic (thetaF) and anaerobic (W') determinants of the W/t relationship, and (2) changes in either the absolute or relative magnitudes of the exercise-intensity domains. These findings are consistent with the notion that endurance-related parameters are less diminished with ageing than the maximal capacity, thereby mitigating the deleterious effects of senescence in the functional capacity.
Muscle metabolism and force production were studied in sprint trained runners, endurance trained runners and in untrained subjects, using ³¹P-MRS. ³¹P-spectra were obtained at a time resolution of 5 s during four maximal isometric contractions of 30-sec duration, interspersed by 60-sec recovery intervals. Resting CrP/ATP ratio averaged 3.3 ± 0.3, with no difference among the three groups. The sprint trained subjects showed about 20 % larger contraction forces in contraction bouts 1 and 2 (p < 0.05). The groups differed with respect to CrP breakdown (p < 0.05), with sprinters demonstrating about 75 % breakdown in each contraction compared to about 60 % and 40 % for untrained and endurance trained subjects, respectively (p < 0.05). The endurance trained runners showed almost twice as fast CrP recovery (t1/2 = 12.5 ± 1.5) compared to sprint trained (t1/2 = 22.5 ± 2.53) and untrained subjects (t1/2 = 26.4 ± 2.8). From the initial rate of CrP resynthesis the rate of maximal aerobic ATP synthesis was estimated to 0.74 ± 0.07, 0.73 ± 0.10 and 0.33 ± 0.07 mmol ATP × kg⁻¹ wet muscle × sec⁻¹ for sprint trained, endurance trained and untrained subjects, respectively.
Only the sprint trained and the untrained subjects displayed a significant drop in pH and only during the first of the four contractions, about 0.2 and 0.1 pH units, respectively, indicating that only under those contractions was the glycolytic proton production larger than the proton consumption by the CK reaction. Also, in the first contraction the energy cost of contraction was higher for the sprinters compared to the two other groups.
The simple ³¹P-MRS protocol used in the present study demonstrates marked differences in force production, aerobic as well as anaerobic muscle metabolism, clearly allowing differentiation between endurance trained, sprint trained and untrained subjects.
Energy turnover was measured during isometric contractions of intact and Triton-permeabilized white fibres from dogfish (Scyliorhinus canicula) at 12 degrees C. Heat + work from actomyosin in intact fibres was determined from the dependence of heat + work output on filament overlap. Inorganic phosphate (Pi) release by permeabilized fibres was recorded using the fluorescent protein MDCC-PBP, N-(2-[1-maleimidyl]ethyl)-7-diethylamino-coumarin-3 carboxamide phosphate binding protein. The steady-state ADP release rate was measured using a linked enzyme assay. The rates decreased five-fold during contraction in both intact and permeabilized fibres. In intact fibres the rate of heat + work output by actomyosin decreased from 134 +/-s.e.m. 28 microW mg(-1) (n = 17) at 0.055 s to 42% of this value at 0.25 s, and to 20% at 3.5 s. The force remained constant between 0.25 and 3.5 s. Similarly in permeabilized fibres the Pi release rate decreased from 5.00 +/- 0.39 mmol l(-1) s(-1) at 0.055 s to 39% of this value at 0.25 s and to 19% at 0.5 s. The steady-state ADP release rate at 15 s was 21% of the Pi rate at 0.055 s. Using a single set of rate constants, the time courses of force, heat + work and Pi release were described by an actomyosin model that took account of the transition from the initial state (rest or rigor) to the contracting state, shortening and the consequent work against series elasticity, and reaction heats. The model suggests that increasing Pi concentration slows the cycle in intact fibres, and that changes in ATP and ADP slow the cycle in permeabilized fibres.
The aim of this study was to determine whether changes in oxygen efficiency occur with aging or exercise training in healthy young and older subjects.
Exercise capacity declines with age and improves with exercise training. Whether changes in oxygen efficiency, defined as the oxygen cost per unit work, contributes to the effects of aging or training has not yet been defined.
Sixty-one healthy subjects were recruited into four groups of younger women (ages 20 to 33 years, n = 15), younger men (ages 20 to 30 years, n = 12), older women (ages 65 to 79 years, n = 16), and older men (ages 65 to 77 years, n = 18). All subjects underwent cardiopulmonary exercise testing to analyze aerobic parameters before and after three to six months of supervised aerobic exercise training.
Before training, younger subjects had a much higher exercise capacity, as shown by a 42% higher peak oxygen consumption (VO2) (ml/kg/min, p < 0.0001). This was associated with an 11% lower work VO2/W (p = 0.02) and an 8% higher efficiency than older subjects (p = 0.03). With training, older subjects displayed a larger increase in peak W/kg (+29% vs. +12%, p = 0.001), a larger decrease in work VO2/W (-24% vs. -2%, p < 0.0001), and a greater improvement in exercise efficiency (+30% vs. 2%, p < 0.0001) compared to the young.
Older age is associated with a decreased exercise efficiency and an increase in the oxygen cost of exercise, which contribute to a decreased exercise capacity. These age-related changes are reversed with exercise training, which improves efficiency to a greater degree in the elderly than in the young.
A diminished mechanical efficiency (work/O2 consumed) accompanies chronic obstructive pulmonary disease (COPD), and increased mechanical efficiency has been attained by maximal strength training (MST) with an emphasis on the maximal rate of force mobilization in the concentric phase in healthy subjects. This study combined these observations and evaluated the impact of short-term MST on patients with COPD.
Twelve patients with COPD (FEV1 = 1.1 +/- 0.1) were pretested and then randomly assigned to either an MST group (N = 6) or a normal activity control group (N = 6). Within each MST training session (three times per week for 8 wk), patients performed four sets of seated leg presses with a focus on the rate of force development at an intensity that only allowed the performance of five repetitions.
Patients who performed MST significantly improved their rate of force development (105 +/- 22.8%), mechanical efficiency (32 +/- 7%), and FEV1 (21.5 +/- 6.8%), whereas these variables were unchanged in the controls. Neither group changed either peak oxygen consumption (VO2peak) or body mass.
In combination with the observed improvement in FEV1, these data certainly support the therapeutic role for MST in the treatment of COPD.
Although it is well accepted that an increase in muscle size is linked to an increase in muscle force, the relationship between muscle size and maximal strength during maturation is still discussed. In the present study we aimed at determining whether maturation affects the relationship between muscle size and maximal strength, and we investigated the reasons accounting for the discrepancies among previous studies.
Maximal isometric handgrip force (Fmax) and forearm muscle size were measured in 14 prepubertal boys (11.3 +/- 0.8 yr old), 16 adolescents (13.3 +/- 1.4 yr old), and 16 men (35.4 +/- 6.4 yr old). Anatomic maximal cross-sectional area (MCSA) and muscle volume (VM) were measured using MRI, and these results were compared with muscle volume (VL) obtained from anthropometric measurements.
Fmax was linearly correlated with VM (r2 = 0.90), VL (r2 = 0.85), and MCSA (r2 = 0.87), while VM was strongly correlated with VL (r2 = 0.90). The Fmax/VM ratio did not differ among groups, whereas Fmax/VL and Fmax/MCSA ratios were significantly higher in adults than in children and adolescents. These results demonstrated that, when compared with MRI, anthropometric measurements led to a systematic overestimation of muscle volume. In addition, this overestimation was significantly larger in children (43.1%) and adolescents (38.5%) as compared with adults (20.5%) (P < 0.05).
Our results showed that the maximal isometric strength exerted by the forearm muscles in humans is proportional to their size whatever the age, and that VM is the best index of muscle size during growth. The previously reported increased ability to produce maximal strength from childhood to adulthood could be explained by systematic bias introduced by the method used to characterize muscle size instead of physiological or neural changes.
Strength training at high versus low external resistance in older adults: effects on muscle volume, muscle strength, and force-velocity characteristics
- C Tudor-Locke
- C L Craig
- W J Brown
- S A Clemes
- K De Cocker
- B Giles-Corti
- Y Hatano
- S Inoue
- S M Matsudo
- N Mutrie
- J M Oppert
- D A Rowe
- M D Schmidt
- G M Schofield
- J C Spence
- P J Teixeira
- M A Tully
- S N Blair
- E Van Roie
- C Delecluse
- W Coudyzer
- S Boonen
- I Bautmans
Tudor-Locke, C., Craig, C.L., Brown, W.J., Clemes, S.A., De Cocker, K., Giles-Corti, B.,
Hatano, Y., Inoue, S., Matsudo, S.M., Mutrie, N., Oppert, J.M., Rowe, D.A., Schmidt,
M.D., Schofield, G.M., Spence, J.C., Teixeira, P.J., Tully, M.A., Blair, S.N., 2011. How
many steps/day are enough? For adults. Int. J. Behav. Nutr. Phys. Act. 8, 79.
Van Roie, E., Delecluse, C., Coudyzer, W., Boonen, S., Bautmans, I., 2013. Strength
training at high versus low external resistance in older adults: effects on muscle
volume, muscle strength, and force-velocity characteristics. Exp. Gerontol. 48,
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- O K Berg
O.K. Berg et al.
Experimental Gerontology 111 (2018) 154-161