Effects of isometric quadriceps strength training at different muscle lengths on dynamic torque production

This study aims to (1) determine whether isometric training at a short vs. long quadriceps muscle length affects concentric torque production; (2) examine the relationship between muscle hypertrophy and concentric torque; and (3) determine whether changes in fascicle length are associated with changes in concentric torque. Sixteen men performed isometric training at a short (SL, n = 8) or a long muscle length (LL, n = 8). Changes in maximal concentric torque were measured at 30, 60, 90, 120, 180, 240 and 300 rad · s−1. The relationships between the changes in concentric torque, cross-sectional area, volume and fascicle length were tested. Concentric torque increased significantly after training only in LL and at angular velocities of 30 and 120 rad · s−1 by 12–13% (P < 0.05). Muscle size increased in LL only, the changes were correlated (r = 0.73–0.93, P < 0.05) with the changes in concentric torque. Vastus lateralis (VL) fascicle length increased in both groups (5.4 ± 4.9%, P = 0.001) but the change was not correlated with changes in concentric torque in either group. Isometric training-induced increases in muscle size and concentric torque were best elicited by training at long muscle lengths. These results highlight a clear muscle length dependence of isometric training on dynamic torque production

Exercise builds the scaffold of life: muscle extracellular matrix biomarker responses to physical activity, inactivity, and aging

Skeletal muscle extracellular matrix (ECM) is critical for muscle force production and the regulation of important physiological processes during growth, regeneration, and remodelling. ECM remodelling is a tightly orchestrated process, sensitive to multi-directional tensile and compressive stresses and damaging stimuli, and its assessment can convey important information on rehabilitation effectiveness, injury, and disease. Despite its profound importance, ECM biomarkers are underused in studies examining the effects of exercise, disuse, or aging on muscle function, growth, and structure. This review examines patterns of short- and long-term changes in the synthesis and concentrations of ECM markers in biofluids and tissues, which may be useful for describing the time course of ECM remodelling following physical activity and disuse. Forces imposed on the ECM during physical activity critically affect cell signalling while disuse causes non-optimal adaptations, including connective tissue proliferation. The goal of this review is to inform researchers, and rehabilitation, medical, and exercise practitioners better about the role of ECM biomarkers in research and clinical environments to accelerate the development of targeted physical activity treatments, improve ECM status assessment, and enhance function in aging, injury, and disease

Intensity of Resistance Exercise Determines Adipokine and Resting Energy Expenditure Responses in Overweight Elderly Individuals

OBJECTIVE - To evaluate the time course of leptin, adiponectin, and testing energy expenditure (REE) responses in overweight elderly mates after acute resistance exercise protocols of various intensity configurations. RESEARCH DESIGN AND METHODS - Forty inactive men (65-82 years) were randomly assigned to one of four groups (n = 10/group): control, low-intensity resistance exercise, moderate-intensity resistance exercise, and high-intensity resistance exercise. Exercise energy cost, REE, leptin, adiponectin, cortisol, insulin, lactate, glucose, nonesterified fatty acids (NEFAs), and glycerol were determined at baseline, immediately after exercise, and during a 72-h recovery period. RESULTS - Exercise energy cost was lower in high-intensity than in low-intensity and moderate-intensity groups (221.6 +/- 8.8 vs. 295.6 +/- 10.7 and 281.6 +/- 9.8 kcal, P < 0.001). Lactate, glucose, NEFAs, and glycerol concentrations increased (P < 0.001) after exercise and returned to baseline thereafter in all groups. REE increased (P < 0.001) in all groups at 12 h in an intensity-dependent manner (P < 0.05). REE reached baseline after 48 h in the low- and mode rate-intensity groups and after 72 h in the high-intensity group. Cortisol peaked in all active groups after exercise (P < 0.001) and remained elevated (P < 0.001) for 12 h. After adjustment for plasma volume shifts, leptin remained unaltered. Adiponectin concentration increased after 12 hand remained elevated for 24 h only in the high-intensity group (P < 0.001). CONCLUSIONS - Resistance exercise does not alter circulating leptin concentration but does increase REE and adiponectin in an intensity-dependent manner for as long as 48 and 24 h, respectively, in overweight elderly individuals. It appears that resistance exercise may represent an effective approach for weight management and metabolic control in overweight elderly individuals