Scaling submaximal exercise cardiac output and stroke volume: the HERITAGE Family Study

This study investigated different methods of scaling submaximal cardiac output (Q) and stroke volume (SV) to best normalize for body size (body surface area [BSA], height [Ht], weight [Wt], and fat-free mass [FFM]). Q and SV were measured at both an absolute (50 W) and a relative power output (60 % of VO2max) in 337 men and 422 women, 17 to 65 years of age. Traditional ratio scaling was examined in addition to allometric scaling, where scaling exponents ( B) were determined for each body size variable (x) that best normalized the physiological outcome variables (y) for body size (y = ax(b)). With ratio scaling, regardless of the body size variable (x = BSA, Ht, Wt, FFM), there was no evidence of a linear relationship between x and y (y = Q or SV). A linear relationship is a necessary condition for appropriate normalization. Further, when ratio-scaled variables (e.g., Q/BSA) were correlated to the body size variable (e.g., BSA) by which they were scaled, significant (p 相似文献   

Muscle strength testing: use of normalisation for body size

Assessment of muscle strength tests has been a popular form of testing muscle function in sports and exercises, as well as in other movement-related sciences for several decades. Although the relationship between muscle strength and body size has attracted considerable attention from researchers, this relationship has been often either neglected or incorrectly taken into account when presenting the results from muscle strength tests. Two specific problems have been identified. First, most of the studies have presented strength data either non-normalised for body size, or normalised using inappropriate methods, or even several different normalisations have been applied on the same sets of data. Second, the role of body size in various movement performances has been neglected when functional movement performance was assessed by muscle strength. As a consequence, muscle function, athletic profiles, or functional movement performance assessed by tested muscle strength have been often confounded by the effect of body size. Differences in the normalisation methods applied also do not allow for comparison of the data obtained in different studies. Using the following allometric formula for obtaining index of muscle strength, S, independent of body size (assessed by body mass, m) should be recommended in routine strength testing procedures: The allometric parameter should be either b = 0.67 for muscle force (recorded by a dynamometer), or b = 1 for muscle torque (recorded by an isokinetic apparatus). We also recommend using body-size-independent indices of both muscle strength and movement performance when assessing functional performance from recorded muscle strength or vice versa.     

Allometric scaling of biceps strength before and after resistance training in men

PURPOSE: The purposes of this study were 1) derive allometric scaling models of isometric biceps muscle strength using pretraining body mass (BM) and muscle cross-sectional area (CSA) as scaling variables in adult males, 2) test model appropriateness using regression diagnostics, and 3) cross-validate the models before and after 12 wk of resistance training. METHODS: A subset of FAMuSS (Functional SNP Associated with Muscle Size and Strength) study data (N=136) were randomly split into two groups (A and B). Allometric scaling models using pretraining BM and CSA were derived and tested for group A. The scaling exponents determined from these models were then applied to and tested on group B pretraining data. Finally, these scaling exponents were applied to and tested on group A and B posttraining data. RESULTS: BM and CSA models produced scaling exponents of 0.64 and 0.71, respectively. Regression diagnostics determined both models to be appropriate. Cross-validation of the models to group B showed that the BM model, but not the CSA model, was appropriate. Removal of the largest six subjects (CSA>30 cm) from group B resulted in an appropriate fit for the CSA model. Application of the models to group A posttraining data showed that both models were appropriate, but only the body mass model was successful for group B. CONCLUSION: These data suggest that the application of scaling exponents of 0.64 and 0.71, using BM and CSA, respectively, are appropriate for scaling isometric biceps strength in adult males. However, the scaling exponent using CSA may not be appropriate for individuals with biceps CSA>30 cm. Finally, 12 wk of resistance training does not alter the relationship between BM, CSA, and muscular strength as assessed by allometric scaling.     

Leg muscle power in 12-year-old black and white Tunisian football players

This study examined leg muscle power of young male Tunisian black and white football players and extended the analysis to determine whether there is a relationship between cycling peak power output (PPO) and some field tests. A total of 113 children (white group (WG) = n = 56; black group (BG) = n = 57) participated in this investigation. Anthropometric data included age, body mass (BM), height, leg length (LL), body mass index (BMI), and leg muscle volume (LMV). Cycling PPO was measured including a force-velocity test. Peak power output (PPO; W and W/kg), Fopt (optimal braking force), and Vopt (optimal velocity) were significantly higher in the WG compared with the BG (p < 0.05). However, jump and sprint performances of the BG were significantly higher than the WG (p < 0.05). Multiple stepwise regression with anthropometric variables and the extrapolated values of the force-velocity test as explanatory factors showed that 33% of the variance of PPO of BG was explained by qualitative factors that may be related to cycling skill, muscle composition, and socioeconomic and training status.     

Power versus strength-power jump squat training: influence on the load-power relationship

PURPOSE: The purpose of this investigation was to compare the impact of power training and strength-power training on the load-power relationship in the jump squat. METHODS: Twenty-six recreationally trained male subjects were randomly assigned to either a power training group (P; N=10), a strength-power training group (SP; N=8), or a control group (C; N=8). The P group trained for 12 wk, performing seven sets of six jump squats with the optimal load for maximal power output (body mass only, no external load), whereas the SP group performed five sets of six jump squats with the optimal load for maximal power output (body mass only, no external load) and three sets of three squats with 90% of their one-repetition maximum (1RM). Work performed by the P and SP subjects was equivalent throughout the 12 wk of training. Peak power relative to body mass (PP), jump height (JH), peak force relative to body mass (PF), and peak velocity (PV) during the jump squat were examined across loads of body mass (BM) and 20, 40, 60, and 80 kg at week 0 (baseline) and after weeks 6 (midtest) and 12 (posttest). RESULTS: After training, the P group significantly increased PP at BM and 20 kg, whereas the SP group significantly increased PP output across all loading conditions. Similarly, jump height was significantly increased by the P group at the lighter loads (BM, 20 kg, and 40 kg) and by the SP group at all loads. Whereas significant improvements in maximal power output and jump height at BM were observed in both P and SP groups, no difference in maximal power output or maximal jump height existed between the training groups. CONCLUSION: Combined lower-body strength-power training is effective as power training for improving maximum jump height and maximum power output in the jump squat, and it is more effective than power training at producing all-around (i.e., from BM to 80 kg) improvements in the load-power relationship of the jump squat.     

Intraindividual allometric development of aerobic power in 8- to 16-year-old boys

PURPOSE: The aims of this study are two-fold: first, to analyze intraindividual allometric development of aerobic power of 73 boys followed at annual intervals from 8 to 16 yr, and second, to relate scaled aerobic power with level of habitual physical activity and biological maturity status. METHODS: Peak VO2 (treadmill), height, and body mass were measured. Biological maturity was based on age at peak height velocity (PHV) and level of physical activity was based on five assessments between 11 and 15 yr and at 17 yr. Interindividual and intraindividual allometric coefficients were calculated. Multilevel modeling was applied to verify if maturity status and activity explain a significant proportion of peak VO2 after controlling for other explanatory characteristics. RESULTS: At most age levels, interindividual allometry coefficients for body mass exceed k = 0.750. Intraindividual coefficients of peak VO2 by body mass vary widely and range from k' = 0.555 to k' = 1.178. Late maturing boys have smaller k' coefficients than early maturing boys. CONCLUSION: Peak VO2 is largely explained by body mass, but activity level and its interaction with maturity status contribute independently to peak VO2 even after adjusting for body mass.     

Modeling maximum oxygen uptake of elite endurance athletes

PURPOSE: To compare the maximum oxygen uptake V0(2max) of elite endurance athletes and to explain why the body mass exponent, necessary to render V0(2max) independent of body mass, appears to be greater than 0.67. METHODS: Study 1: V0(2max) of 174 international sportsmen and women was assessed. Athletes were recruited from seven sports (middle- and long-distance runners, heavyweight and lightweight rowers, triathletes, and squash and badminton players). Study 2: calf and thigh leg muscle masses were estimated in 106 male and 30 female athletes from 11 sports. Differences in V0(2max) and leg muscle masses between "sports" and "sex" were analyzed independent of body mass by using allometric log-linear ANCOVA. RESULTS: Heavyweight rowers had the greatest V0(2max) when expressed in L.min but long-distance runners had the highest V0(2max)in mL.kg.min. However, the ANCOVA identified no difference in "mass independent" V0(2max) between the five "pure" endurance sports (runners, rowers, and triathletes) (P > 0.05) with the two racket sports being significantly lower. The body mass covariate exponent was inflated, estimated as 0.94. The results from study 2 estimated calf and thigh leg muscle masses to increase in proportion to body mass, and, respectively. CONCLUSIONS: After having controlled for differences in body mass, V0(2max) did not differ between pure endurance sports (P > 0.05). Assuming that athletes' thigh muscle mass increases in proportion to body mass as observed in study 2, a similar disproportional increase in V0(2max) would be anticipated, providing a plausible explanation for the inflated mass exponent associated with V0(2max) identified in this and other studies.     

Scaling cardiac structural data by body dimensions: a review of theory, practice, and problems

Robust estimates of the "true" bivariate relationship between body size (X) and heart size (Y) have seldom been determined empirically. The removal of the covariate influence of body size from cardiac dimension variables facilitates both correct inter- or intra-group comparisons, and the construction of reference standards for normality. In the literature to date this "scaling" or normalisation of cardiac dimensions has been performed typically via a per-ratio standards method, (Y/X), with body surface area chosen as the size denominator. This review demonstrates that the per-ratio standards approach may be theoretically, mathematically, and empirically flawed. The most appropriate scaling procedure appears to be a curvilinear, allometric model of the general form Y = aXb. The cardiac dimension variable (Y) may be regressed upon the body size variable (X) to derive a power function ratio (Y/Xb) that is allegedly size-independent. The current consensus is that an estimate of fat-free mass (FFM) provides the most appropriate body size variable. In the scaling literature allometric modelling procedures have generally yielded FFM exponents (b) consistent with the theory of geometric similarity. We suggest that cardiac dimension data should be scaled by appropriate powers of FFM, derived from allometric modelling. However, despite the potential superiority of FFM as a scaling denominator, reference standards for normality based on FFM have not been developed or proposed. Future research should examine the robustness of the FFM-cardiac dimension relationship in large samples.     

Peak power in obese and nonobese adolescents: effects of gender and braking force

PURPOSE: The aim of this study was to determine the cycling peak power (CPP) of obese compared with nonobese adolescents and to identify possible effects of braking force (BF) and gender on CPP. To adjust for differences in body size, we used ratio standard and allometric model. METHODS: Obese (26 girls, 18 boys) and nonobese (30 girls, 20 boys) adolescents participated. Fat-free mass (FFM) was determined by dual-energy x-ray absorptiometry (DEXA) in obese and by anthropometric method in nonobese groups. A force-velocity test was used to measure peak power (flywheel inertia included) for BF corresponding to applied load: 25, 50, and 75 g x kg(-1) body mass (BM). The highest peak power was defined as CPP. RESULTS: CPP was independent of BF in nonobese adolescents but dependent in obese adolescents. The optimal braking load is approximately 6.5% FFM. Absolute CPP was higher in obese than nonobese adolescents. Related to BM, CPP was significantly lower in obese than nonobese adolescents, using the standard ratio or the allometric model. These differences disappeared when CPP was related to FFM. Multiple stepwise regression showed that FFM was the most important explanatory variable of the variance of CPP (72%) in obese and nonobese adolescents. No significant difference between obese and nonobese adolescents occurred when Fopt was related to FFM (standard or power function ratios used). There was no gender effect on CPP, and the manner of expressing CPP did not affect the results. However, girls showed a higher FFM-related Fopt than boys, using standard and power function ratios. CONCLUSION: There was no significant difference between obese and nonobese girls and boys for anaerobic performance (CPP and Fopt) when FFM was taken into account.     

Scaling behavior of VO2peak in trained wheelchair athletes

PURPOSE: To examine the scaling behavior of peak oxygen uptake (VO2peak) in wheelchair athletes, adjusting for known covariates. METHODS: Body mass, VO2peak, and an estimate of adiposity (sum of four skinfolds) were determined in a sample of 45 highly trained wheelchair basketball and racing athletes. The participants were classified as possessing either "high" or "low" trunk stability and balance using recognized sporting classifications. A wheelchair ergometer was used to obtain the VO2peak measurements. The relationship between VO2peak and body mass was obtained via a nonlinear allometric model with the sum of four skinfolds, trunk stability and balance, and chronological age entered as covariates. RESULTS: The point estimate exponent for body mass was 0.82 (95% CI, 0.54-1.10). After controlling for the influence of body mass, adiposity, and age, the wheelchair athletes with greater trunk stability and balance had on average an 11% greater VO2peak. The regression model explained 54% of the sample variance in VO2peak. CONCLUSIONS: The obtained mass exponent of 0.82 is congruent with that predicted from the multiple-causes allometric cascade model and consideration of the physiological characteristics of spinal cord injured athletes. To compare the body size-independent VO2peak values of athletes within the study sample, the mass exponent of 0.82 may be adopted (i.e., mL x kg(-0.82) x min(-1)). The uncertainty in the point estimate, reflected in the relatively wide 95% CI, highlights the need for further research with larger samples to increase the precision of estimation.     

Relationship of maximum strength to weightlifting performance

PURPOSE: The primary objective was to assess the relationship of maximum strength to weightlifting ability using established scaling methods. The secondary objective was to compare men and women weightlifters on strength and weightlifting ability. METHODS: Two correlational observations were carried out using Pearson's r. In the first observation (N = 65) the relationship of dynamic maximum strength (one-repetition maximum (1RM) squat) was compared with weightlifting ability; in the second observation (N = 16), isometric maximum strength (midthigh pull) was studied. Scaling methods for equating maximum strength and weightlifting results were used (load x (Ht), load x kg, load x lbm(-1), allometric, and Sinclair formula) to assess the association between measures of maximum strength and weightlifting performance. RESULTS: Using scaled values; correlations between maximum strength and weightlifting results were generally strong in both observations (e.g., using allometric scaling for the 1RM squat vs the 1RM snatch: r = 0.84, N = 65). Men were stronger than women (e.g., 1RM squat, N = 65: men = 188.1 +/- 48.6 kg; women = 126.7 +/- 28.3 kg); differences generally held when scaling was applied (e.g., 1RM squat scaled with the Sinclair formula: men = 224.7 +/- 36.5 kg; women = 144.2 +/- 25.4 kg). CONCLUSIONS: When collectively considering scaling methods, maximum strength is strongly related to weightlifting performance independent of body mass and height differences. Furthermore, men are stronger than women even when body mass and height are obviated by scaling methods.     

Physiological consequences of U.S. Army Ranger training

PURPOSE: Soldiers are expected to maintain a high degree of physical readiness as operational demands can severely degrade performance capabilities. This study examined the physiological consequences of U.S. Army Ranger training on strength, power, body composition, and somatotrophic hormones. METHODS: In an intensive 8-wk military training course that included an average daily energy deficit of 1000 kcal.d, lower-body power output, maximal lifting strength, body composition, and serum concentrations of several somatotrophic hormones were measured in 50 male soldiers (24.6 +/- 4.4 y; 176.1 +/- 7.8 cm; 78.4 +/- 8.7 kg; 14.7 +/- 4.2% body fat) before and after the course. RESULTS: Vertical jump height (-16%), explosive power output (-21%), maximal lifting strength. (-20%), body mass (-13%), fat-free mass (-6%), and fat mass (-50%) declined (P < 0.05) after the training course. Circulating total testosterone and insulin-like growth factor-I (IGF-I) experienced significant (P < 0.05) declines, and cortisol was significantly increased. Lower-body power output, but not maximal lifting strength, correlated with changes in fat-free mass. IGF-I and cortisol, but not total testosterone, were correlated with losses of tissue mass. CONCLUSION: Lower-body power output, estimated from vertical jump height and body mass, is a sensitive and field expedient measure that can be used to assess the influence of caloric deficit on physical performance after 8 wk of U.S. Army Ranger training. With severe weight loss (>or=13% of body mass), IGF-I and cortisol correlate more closely with soft-tissue tissue adaptations than does testosterone.     

Anthropometric, strength, and power predictors of sprinting performance.

BACKGROUND: The purpose of this study was to examine relations between sprinting performance (i.e. average velocity within both the initial acceleration and maximum speed phases of sprint running) and some standard anthropometric, strength, and power tests. METHODS: Twenty-four male students of physical education were timed over the distances of 0.5-15 m and 15-30 m from the sprint start. Several measures of muscle isometric strength (knee extensors, hip extensors and flexors) and power (height of the counter movement jump and the average power of leg extensors during continuous jumping) were also collected, in addition to the lean body mass and the percentage of both muscle and fat tissue. RESULTS: The results obtained demonstrated that, except for the height of the counter movement jump, all correlation coefficients between the selected variables and sprinting performance were low and, therefore, insignificant. As a consequence, multiple correlation coefficients were also low (0.43 and 0.56 for the initial acceleration and maximal speed phase, respectively). CONCLUSIONS: Most of the standard anthropometric, strength and power tests could be poor predictors of sprinting performance. A better assessment of sprinting performance could be based on more specific tests that, unfortunately, require more complex measurements.     

Power output of legs during high intensity cycle ergometry: Influence of hand grip

Traditionally, leg cycle ergometry is used to assess the power output of the lower limbs. However, it is suspected that the upper body makes a significant, albeit as yet unknown, contribution to the measured power output, and as such, the lean mass of the whole body should be considered during ergometric assessment. To test this idea, indices of mechanical power output were obtained from 11 subjects during high intensity leg cycle ergometry tests (20 second duration; 75 grams per kilogram total body mass) using two protocols: one with a standard handle-bar grip (with grip) and one with supinated wrists (without-grip). Peak mechanical power, mean mechanical power, fatigue index and total mechanical work values were calculated for each subject during each test and the sample mean differences associated with the two protocols were compared using paired Student t-tests. The with-grip protocol yielded significantly greater peak mechanical power output than the without-grip protocol (886+/-124 W and 815+/-151 W, respectively), suggesting a significant upper body contribution to the maximum power output measured for the legs. As a first step towards quantifying the upper body involvement during leg cycle ergometry, surface electromyography of the forearm musculature was measured in a twelfth subject whilst performing each of the test protocols. During the with-grip ergometer tests, the intensity of electrical activity in the forearm musculature was similar, if not greater than, the intensity of electrical activity recorded for the forearm musculature during 100% maximum voluntary hand grip-dynamometer contractions, suggesting maximum isometric-type forearm muscle contraction during the with-grip leg ergometry tests. These findings suggest that the performance of traditional-style leg cycle ergometry requires a muscular contribution from the whole body. As such, researchers should be mindful of this, both in terms of the allocation of ergometer loads, and in the analysis of blood-borne metabolites.     

Effects of an entire season on physical fitness in elite female handball players

PURPOSE: Sixteen elite female handball players were studied to examine the effects of an entire season on anthropometric characteristics, physical fitness, and throwing velocity. METHODS: One-repetition-maximum bench press (1RMBP), jumping explosive strength, power-load relationship of the leg and arm extensor muscles, 5- and 15-m sprint running time, endurance running, and handball throwing velocity were assessed in four periods. Individual volumes and intensities of training and competition were quantified for 11 activities. RESULTS: During the season, significant increases (P < 0.05-0.01) occurred in fat-free mass (1.8 +/- 1.2%), 1RMBP (11 +/- 7.4%), bench press (12-21%) and half-squat (7-13%) muscle power output, vertical jumping height (12 +/- 7.2%), throwing velocity (8 +/- 5.9%), and a significant decrease in percent body fat (9 +/- 8.7%). No changes were observed in sprint and endurance running. Significant correlations (P < 0.05-0.01) were observed between time devoted to games and changes in velocity at submaximal loads during bench press actions, as well as between changes in muscle velocity output of the upper and lower extremities and changes in throwing velocity. Changes in percent body fat or body mass correlated (P < 0.01) positively with changes in maximal strength and muscle power. CONCLUSION: The handball season resulted in significant increases in anthropometric characteristics, physical fitness, and throwing velocity. The correlations observed suggest the importance of including explosive strength exercises of the knee and elbow extensions. Special attention may be needed to be paid to the mode of body fat loss, to increase endurance capacity without interfering in strength gains. Official and training games may be an adequate stimulus for enhancing certain physical fitness characteristics in female elite handball players.     

Physical fitness, injuries, and team performance in soccer

PURPOSE: To investigate the relationship between physical fitness and team success in soccer, and to test for differences in physical fitness between different player positions. METHODS: Participants were 306 male soccer players from 17 teams in the two highest divisions in Iceland. Just before the start of the 1999 soccer season, the following variables were tested: height and weight, body composition, flexibility, leg extension power, jump height, and peak O2 uptake. Injuries and player participation in matches and training were recorded through the 4-month competitive season. Team average physical fitness was compared with team success (final league standing) using a linear regression model. Physical fitness was also compared between players in different playing positions. RESULTS: A significant relationship was found between team average jump height (countermovement jump and standing jump) and team success (P = 0.009 and P = 0.012, respectively). The same trend was also found for leg extension power (P = 0.097), body composition (% body fat, P = 0.07), and the total number of injury days per team (P = 0.09). Goalkeepers demonstrated different fitness characteristics from outfield players. They were taller and heavier, more flexible in hip extension and knee flexion, and had higher leg extension power and a lower peak O2 uptake. However, only minor differences were observed between defenders, midfield players, and attackers. CONCLUSION: Coaches and medical support teams should pay more attention to jump and power training, as well as preventive measures and adequate rehabilitation of previous injuries to increase team success.     

Mitochondrial macrohaplogroup associated with muscle power in healthy adults

The present study was undertaken to examine the effect of mitochondrial haplogroups on aerobic and anaerobic performance phenotypes such as maximum oxygen consumption, muscle power, and muscle mass. We recruited 474 healthy Japanese individuals and measured their physical performance phenotypes such as peak oxygen uptake, muscle power, and muscle mass. The genotypes for 186 polymorphisms in the mitochondrial DNA were determined, and the haplotypes were classified into 2 macrohaplogroups (i. e., N and M) and 12 haplogroups (i. e., F, B, A, N9a, N9b, M7a, M7b, G1, G2, D4a, D4b, and D5). When we compared the 2 major Japanese macrohaplogroups, leg extension power (P=0.0395), leg extension power based on body weight (P=0.0343), and vertical jump performance (P=0.0485) were significantly higher in subjects with mitochondrial macrohaplogroup N than in those with macrohaplogroup M. However, peak oxygen uptake was similar between the 2 groups. When we analyzed the 12 haplogroups, all of the measured parameters were similar among them. In conclusion, mitochondrial macrohaplogroup N may be one of the determinant factors of anaerobic physical performance phenotype such as muscle power.     

D3-肌酸稀释法在小鼠骨骼肌质量检测中的应用

目的 探讨能否利用D3-肌酸稀释法检测小鼠骨骼肌质量,为小鼠骨骼肌质量检测提供新的方法 .方法 选择4周龄、10周龄和13月龄的清洁级雄性C57BL/6小鼠各10只,经EchoMRITM小动物体成分分析仪检测体成分后单次给予D3-肌酸(2mg/kg)灌胃,于24、48h和72h收集小鼠尿液,采用液相色谱串联质谱法(LC-MS/MS)检测尿液中D3-肌酸和D3-肌酐的含量,计算肌酸池大小,并对其EchoMRITM检测的瘦体重进行相关性分析.结果 EchoMRITM测量的瘦体重及D3-肌酸稀释法得出的肌酸池均为老年鼠>成年鼠>幼年鼠.相关性分析显示,D3-肌酸稀释法计算得出的总体肌酸池与EchoMRITM测量的瘦体重呈显著正相关(r=0.687,P=0.000).结论 D3-肌酐稀释法可用于检测小鼠骨骼肌质量.     

对标准体型病人行低管电压CT肺动脉成像的可行性研究

目的通过对比低管电压CT肺动脉成像(CTPA)与常规CTPA的影像质量与辐射剂量,从而评价低管电压CTPA应用于标准体型病人的临床价值。方法前瞻性选取我院2013年2月—2014年8月标准体型(体质量指数≤25 kg/m2,体质量≤80 kg)病人60例,并随机分为2组。A、B两组管电压分别设置为80 k V和120 k V。管电流设置基于循环时间测试峰值。评价并对比A、B两组影像质量与辐射剂量,选取肺动脉干影像质量参数与辐射剂量进行Pearson相关性分析。结果 A组总体肺动脉CT值与噪声值高于B组,差异具有统计学意义(P=0.000)。A组总体肺动脉SNR和CNR与B组相比差异无统计学意义(分别P=0.187,P=0.309)。A组有效剂量显著低于B组[(1.69±0.43)m Sv∶(5.63±1.84)m Sv,P=0.000]。有效剂量与CT值和噪声值呈负相关。结论低管电压CTPA应用于标准体型病人可以有效减低辐射剂量,同时保证影像质量,具有临床应用价值。     

Chronic exercise preserves lean muscle mass in masters athletes

Aging is commonly associated with a loss of muscle mass and strength, resulting in falls, functional decline, and the subjective feeling of weakness. Exercise modulates the morbidities of muscle aging. Most studies, however, have examined muscle-loss changes in sedentary aging adults. This leaves the question of whether the changes that are commonly associated with muscle aging reflect the true physiology of muscle aging or whether they reflect disuse atrophy. This study evaluated whether high levels of chronic exercise prevents the loss of lean muscle mass and strength experienced in sedentary aging adults. A cross-section of 40 high-level recreational athletes ("masters athletes") who were aged 40 to 81 years and trained 4 to 5 times per week underwent tests of health/activity, body composition, quadriceps peak torque (PT), and magnetic resonance imaging of bilateral quadriceps. Mid-thigh muscle area, quadriceps area (QA), subcutaneous adipose tissue, and intramuscular adipose tissue were quantified in magnetic resonance imaging using medical image processing, analysis, and visualization software. One-way analysis of variance was used to examine age group differences. Relationships were evaluated using Spearman correlations. Mid-thigh muscle area (P = 0.31) and lean mass (P = 0.15) did not increase with age and were significantly related to retention of mid-thigh muscle area (P < 0.0001). This occurred despite an increase in total body fat percentage (P = 0.003) with age. Mid-thigh muscle area (P = 0.12), QA (P = 0.17), and quadriceps PT did not decline with age. Specific strength (strength per QA) did not decline significantly with age (P = 0.06). As muscle area increased, PT increased significantly (P = 0.008). There was not a significant relationship between intramuscular adipose tissue (P = 0.71) or lean mass (P = 0.4) and PT. This study contradicts the common observation that muscle mass and strength decline as a function of aging alone. Instead, these declines may signal the effect of chronic disuse rather than muscle aging. Evaluation of masters athletes removes disuse as a confounding variable in the study of lower-extremity function and loss of lean muscle mass. This maintenance of muscle mass and strength may decrease or eliminate the falls, functional decline, and loss of independence that are commonly seen in aging adults.