Muscle mechanical and architectural adaptations in response to different endurance training modalities in older adults.

Introduction: This study examined the effects of various cycling endurance training modalities, matched for total workload, on muscle mechanical and architectural characteristics in older adults.

Methods: Fifty healthy participants (25 females, 59-79 yrs) were randomly assigned to five age and sex matched groups: one control and four workload-matched training groups (moderate-intensity continuous, heavy-intensity continuous, high-intensity interval, and heavy-intensity continuous in eccentric cycling). Training consisted of three weekly sessions over 8 weeks, with evaluations conducted at the beginning and end of the intervention with maximal voluntary isometric contractions at five different knee angles (90, 75, 60, 45, 30°) and maximal concentric and eccentric isokinetic contractions at five different knee angular velocities (45, 90, 150, 210, 250°/s). Maximum voluntary isometric torque (T max ) and optimal knee angle (KA opt ) were obtained from the isometric contractions; eccentric torque (T ecc ) and maximum concentric knee angular velocity (V max ) were obtained from the isokinetic contractions. The muscle architecture of vastus lateralis (VL) at rest (muscle thickness, pennation angle, and fascicle length) was investigated as well.

Results: No statistical differences were detected between groups or time points in VL architecture, in KA opt and in V max . A main effect of time was observed for T max (p 2 p = 0.458) and T ecc (p = 0.002, η 2 p = 0.191) in all the investigated training groups. The within-group comparisons indicate significant increases in T max in the training groups, but not in the control group.

Conclusions: Commonly applied endurance exercises improve muscle mechanical capacity (T max and T ecc ) in older adults, with no structural (architectural) muscle remodelling, when matched for workload.