Search

We have previously shown that Achilles tendon length is related to walking economy on the flat, presumably because of increased stretch-shortening cycle elastic energy savings. In addition, greater walking economy in African American (AA) women compared to European American (EA) women is explained by longer Achilles tendons in AA women. The purposes of this study were to determine whether economy while walking up a grade and during isometric plantar flexion, two tasks expected to produce proportionately less energy savings from elastic savings are different between AA and EA women. We evaluated walking economy at 4.8 km/h at 0 and 2.5% grade in 48 AA and 48 EA premenopausal women. Plantar flexor muscle metabolic economy (force/ATP) was also evaluated using (31) phosphate magnetic resonance spectroscopy ((31)P-MRS). AA women walked on the flat more economically (net VO(2), AA 8.3 and EA 8.9 ml kg(-1) min(-1), P = 0.04). No significant ethnic differences were observed while walking up a 2.5% grade or in (31)P-MRS determined plantar flexor muscle metabolic economy. These data support our previous study's suggestion that AA women are more economical while walking on the flat. On the other hand, in activities in which stretch-shortening cycle elastic energy savings would be expected to be reduced (grade walking and isometric force production), no differences in economy during grade walking or isometric force production were observed suggesting that biomechanical, i.e. stretch-shortening cycle elastic energy savings differences rather biochemical differences contribute to the better flat walking economy observed in AA women.

An inverse relationship has been shown between running and cycling exercise economy and maximum oxygen uptake (VO2max). The purposes were: 1) determine the relationship between walking economy and VO2max; and 2) determine the relationship between muscle metabolic economy and muscle oxidative capacity and fiber type. Subjects were 77 premenopausal normal weight women. Walking economy (1/VO2max) was measured at 3 mph and VO2max during graded treadmill test. Muscle oxidative phosphorylation rate (OxPhos), and muscle metabolic economy (force/ATP) were measured in calf muscle using 31P MRS during isometric plantar flexion at 70 and 100% of maximum force, (HI) and (MI) respectively. Muscle fiber type and citrate synthase activity were determined in the lateral gastrocnemius. Significant inverse relationships (r from -0.28 to -0.74) were observed between oxidative metabolism measures and exercise economy (walking and muscle). Type IIa fiber distribution was inversely related to all measures of exercise economy (r from -0.51 to -0.64) and citrate synthase activity was inversely related to muscle metabolic economy at MI (r = -0.56). In addition, Type IIa fiber distribution and citrate synthase activity were positively related to VO2max and muscle OxPhos at HI and MI (r from 0.49 to 0.70). Type I fiber distribution was not related to any measure of exercise economy or oxidative capacity. Our results support the concept that exercise economy and oxidative capacity are inversely related. We have demonstrated this inverse relationship in women both by indirect calorimetry during walking and in muscle tissue by 31P MRS.

Using an integrative approach, this review highlights the benefits of resistance training toward improvements in functional status, health and quality of life among older adults. Sarcopenia (i.e. muscle atrophy) and loss of strength are known to occur with age. While its aetiology is poorly understood, the multifactorial sequelae of sarcopenia are well documented and present a major public health concern to our aging population, as both the quality of life and the likelihood of age-associated declines in health status are influenced. These age-related declines in health include decreased energy expenditure at rest and during exercise, and increased body fat and its accompanying increased dyslipidaemia and reduced insulin sensitivity. Quality of life is affected by reduced strength and endurance and increased difficulty in being physically active. Strength and muscle mass are increased following resistance training in older adults through a poorly understood series of events that appears to involve the recruitment of satellite cells to support hypertrophy of mature myofibres. Muscle quality (strength relative to muscle mass) also increases with resistance training in older adults possibly for a number of reasons, including increased ability to neurally activate motor units and increased high-energy phosphate availability. Resistance training in older adults also increases power, reduces the difficulty of performing daily tasks, enhances energy expenditure and body composition, and promotes participation in spontaneous physical activity. Impairment in strength development may result when aerobic training is added to resistance training but can be avoided with training limited to 3 days/week.

Purpose: The study purpose was to determine the relationship: 1) of muscle metabolism to exercise performance and 2) of exercise performance to rate of weight gain., Methods: Eighty-three black and white premenopausal women were evaluated for maximum oxygen uptake (VO2max ), isometric quadriceps and triceps surae strength, and 31P magnetic resonance spectroscopy of calf muscle metabolic capacity. Rate of weight gain was determined 1 yr later. Multiple regression was used to model dependent variables., Results: Muscle aerobic capacity and strength of the quadriceps muscle independently contributed to endurance time on the treadmill (ET) in one model (overall R = 0.47, P < 0.01), and VO2max and strength of the quadriceps muscle independently contributed to ET in another model (R = 0.85, P < 0.001). In models of muscle strength, maximum creatine kinase activity and maximum anaerobic glycolytic rate independently contributed to triceps surae strength, after adjusting for triceps surae cross-section area (R = 0.63, P < 0.001). In another model, maximum creatine kinase activity was related to quadriceps strength independent of leg lean tissue (R = 0.31, P < 0.05). Rate of weight gain was related to muscle metabolic economy (r = -0.25, = 0.04), quadriceps strength (r = -0.34, P < 0.01), VO2max (r = -0.22, = 0.04), and ET (r = -0.21, = 0.04). Rate of weight gain was modeled by muscle metabolic economy, VO2max, and quadriceps strength (R = 0.48, P < 0.01)., Conclusions: Implications of findings are 1) greater strength and aerobic fitness-at the muscle and whole-body levels-improve endurance; 2) greater muscle anaerobic metabolism is associated with greater muscle strength, independent of muscle size; and 3) greater exercise endurance reduces weight gain.

Purpose: The purpose of this study was to examine muscle morphological and neural activation adaptations resulting from the interaction between concurrent strength and endurance training., Methods: Thirty sedentary healthy male subjects were randomly assigned to one of three training groups that performed 10 wk of 3-d x wk(-1) high-intensity strength training (S), cycle endurance training (E), or concurrent strength and endurance training (CC). Strength, quadriceps-muscle biopsies, computed tomography scans at mid-thigh, and surface electromyogram (EMG) assessments were made before and after training., Results: S and CC groups demonstrated similar increases (P < 0.0001) in both thigh extensor (12 and 14%) and flexor/adductor (7 and 6%) muscle areas. Type II myofiber areas similarly increased (P < 0.002) in both S (24%) and CC (28%) groups, whereas the increase (P < 0.004) in Type I area with S training (19%) was also similar to the nonsignificant (P = 0.041) increase with CC training (13%). Significant increases (P < 0.005) in maximal isometric knee-extension torque were accompanied by nonsignificant (P 0.38) in the EMG/torque relation across 20 to 100% maximal voluntary contractions occurred in any group. A small 3% increase (P < 0.01) in thigh extensor area was the only change in any of the above variables with E training., Conclusions: Findings indicate 3-d x wk(-1) concurrent performance of both strength and endurance training does not impair adaptations in strength, muscle hypertrophy, and neural activation induced by strength training alone. Results provide a physiological basis to support several performance studies that consistently indicate 3-d x wk(-1) concurrent training does not impair strength development over the short term.

This article describes how one strength and conditioning youth development program implements the teaching personal and social responsibility (TPSR) framework with a portfolio-based system. Some scholars have noted that using portfolios helps connect assessment to instruction by promoting individualized learning for students. The purpose of this article is to share how one program is implementing TPSR by using graphic organizers that make up the portfolio system. First, the important components of TPSR, and how they guide the creation of portfolios, are described. Second, each section of a daily program format, and how a graphic organizer called the workout card guides student work in each section, is described. The workout card helps coaches capture physical activity planning, self-reflection, self-assessment, and written coach feedback. Third, a graphic organizer referred to as the zoom out is explained. This tool collects and organizes student work and coach feedback completed over an extended period of time. Finally, some lessons learned from years of developing the program and portfolio-based system are shared.

Purpose: Secondary analyses were performed to test whether combined aerobic and resistance training altered walking economy (i.e., net oxygen uptake) and/or stretch-shortening cycle potentiation (SSCP). A further objective was to determine if walking economy and SSCP were related before or after training. Methods: Ninety-two postmenopausal women were enrolled wherein 76 completed 16 weeks of supervised aerobic and resistance training. Participants were randomized to one of three training groups based on frequencies: (a) 1 d⋅wk–1 (n = 23); (b) 2 d⋅wk–1 (n = 30) or; (c) 3 d⋅wk–1 (n = 23). Following assessments were performed at baseline and post-training. Indirect calorimetry was used to measure maximal oxygen uptake () and walking economy (submaximal – resting = net) during a graded exercise test and steady-state treadmill task, respectively. SSCP was determined by measuring the difference between a concentric (CO) and counter-movement (CM) leg press throw. Results: , walking economy, CO and CM velocity were significantly improved (p < 0.05) for all training groups, however; no time by group interactions were observed. Paired t -tests revealed participants exercise training 2 d⋅wk–1 exhibited a significant time effect for SSCP (+0.04 ± 0.09 ms–1; p = 0.03). At baseline, multiple linear regression showed a negative relationship between walking net and SSCP (r = −0.22; p < 0.04) adjusted for relative proportion of. No such relationship was found post-training. Conclusion: Among older postmenopausal women, our results indicate that irrespective of frequency of training, 16 weeks of combined aerobic and resistance exercise training increased ease of walking and economy. Additionally, only participants exercising 2 d⋅wk–1 exhibited significant improvement in SSCP. [ABSTRACT FROM AUTHOR]

The article discusses a study which was aimed to determine the optimal frequency of combined aerobic and resistance training for improving muscular strength (MS), cardiovascular fitness (CF), and functional tasks (FTs) in women older than 60 years. The study included 63 women who were randomly assigned to 1 of 3 exercise training groups. The study found no significant differences for MS, CF, or FT outcomes between groups.

The article discusses research investigating where the potentiation of force, power, velocity, and acceleration occurs across the concentric phase of stretch-shortening cycle (SSC) ballistic leg presses Participants performed SSC and concentric-only (CO) ballistic leg press throws. Researchers analyzed the concentric range of motion (ROM) across six equal time intervals and found that force and acceleration only occurs early during the concentric phase of SSC ballistic leg presses.

The article presents the study which examines the hypothesis that members of the muscle-specific MicroRNA (miRNA) family, myomiR, network has a central role in the regulation of skeletal muscle plasticity. It maintains that myomiR's central role in the regulation of skeletal muscle plasticity is by coordinating changes in fiber type and muscle mass in response to altered contractile activity. It also notes that miRNA regulates gene expression through posttranscriptional mechanism.

The purposes of this study were to (a) determine whether structural differences in triceps surae muscle-tendon complex and walking economy exist between 14 African American and 19 Caucasian sedentary women and (b) determine whether muscle-tendon parameters are associated with walking economy. African American and Caucasian subjects were matched on body weight, height, and body composition. Muscle-tendon parameters were determined by magnetic resonance imaging and walking economy was evaluated at 4.8 km ·h-1. Medial gastrocnemius and total triceps surae muscle shape were different across ethnicity despite no ethnic differences in plantar flexion strength or in maximal cross-sectional area for any triceps surae muscles. African American women had shorter gastrocnemius muscles and longer tendons and performed walking more economically. Tendon length was the only variable related to walking economy. No ethnic differences were observed in walking economy after adjusting for tendon length. Data show gastrocnemius tendon length is related to level walking and longer gastrocnemius tendons may partly explain more economical walking in African American women. These preliminary findings indicate the structure of the muscle-tendon complex could be a factor partially accounting for reported ethnic differences in certain types of athletic-related performance. [ABSTRACT FROM AUTHOR]

Purpose: To examine the effects of three different frequencies of combined resistance and aerobic training on total energy expenditure (TEE) and activity-related energy expenditure (AEE) in a group of older adults. Methods: Seventy-two women, 60-74 yr old, were randomly assigned to one of three groups: 1 d•wk-1 of aerobic training and 1 d•wk-1 of resistance training (1 + 1), 2 d•wk-1 of aerobic training and 2 d•wk-1 resistance training (2 + 2), or 3 d•wk-1 of aerobic training and 3 d•wk-1 of resistance training (3 + 3). Body composition (dual-energy x-ray absorptiometry), feeling of fatigue, depression, and vigor (questionnaire), strength (one-repetition maximum), serum cytokines (enzyme- linked immunosorbent assay), maximal oxygen uptake (progressive treadmill test), resting energy expenditure, and TEE were measured before and after 16 wk of training. Aerobic training consisted of 40 min of aerobic exercise at 80% maximum heart rate, and resistance training consisted of two sets of 10 repetitions for 10 different exercises at 80% of one repetition maximum. Results: All groups increased fat-free mass, strength, and aerobic fitness and decreased fat mass. No changes were observed in cytokines or perceptions of fatigue/depression. No time-group interaction was found for any fitness/body composition variable. TEE and AEE increased with the 2 + 2 group but not with the other two groups. Nonexercise training AEE (nonexercise training activity-related thermogenesis) increased significantly in the 2 + 2 group (+200 kcal•d-1), group 1 + 1 showed atrend for an increase (+68 kcal•d-1), and group 3 + 3 decreased significantly (-150 kcal•d-1). Conclusion: Results indicate that 3 + 3 training may inhibit nonexercise training activity- related thermogenesis by being too time consuming and does not induce superior training adaptations to 1 + 1 and 2 + 2 training. [ABSTRACT FROM AUTHOR]