Fig. 2.

a Total quadriceps muscle anatomical cross-sectional area (ACSA) pre- and post-endurance training in young and old highly resistance-trained men. b Shows right quadriceps ACSA/femur area pre- and post-endurance exercise in young and old participants. c Shows maximal voluntary isometric contraction of knee extension (MVC) at 50, 70 and 90° (MVC50, MVC70 and MVC90, respectively) of young and old participants pre- and post-endurance exercise. d Shows the specific torque (MVC/quadriceps ACSA) of quadriceps muscles at MVC50, MVC70 and MVC90 for young and old participants pre- and post-endurance exercise. ^yIndicates a significant difference to young participants at p < 0.001; ^aindicates a significant difference to MVC50 at p ≤ 0.007. ^bIndicates a significant difference to MVC70 at p ≤ 0.002. e Shows the quadriceps muscle optical density (OD) in young and old highly resistance-trained men pre- and post-endurance exercise programme. f Shows the relationship between quadriceps anatomical cross-sectional area (ACSA) and maximal oxygen consumption (VO₂max) pre- and post-endurance exercise. ^yIndicates a significant difference in OD compared to young subjects at p ≤ 0.03