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

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

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.

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 < 0.001, η²_p = 0.458) and T_ecc (p = 0.002, η²_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.

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.