This study investigated how a 6s maximal voluntary isometric conditioning contration (MVIC) affected plantar flexor twitch rate of torque development (RTDTW), as well as peak torque (PTCC) and rate of torque development (RTDCC) of maximal voluntary concentric contractions (MVCC) performed at 60°/s. RTDCC and normalized triceps surae electromyography signals (EMGTS) were measured during different phases of contraction. Additionally, muscle tendon unit passive stiffness index (SI) calculated from the torque-angle relation was measured following each MVCC.
Enhancements were found in the RTDTW immediately (by 59.7%) and up to 480s (by 6.0%) post MVIC (p<0.05). RTDCC during the 100-200ms, 50-200ms, and 0-200ms phases and PTCC were enhanced (by 5.7-9.5%) from 90-300s post conditioning (p<0.05). Neuromuscular efficiency increased (decreased EMGTS/RTDCC) in the 50-200ms and 0-200ms phases by 8.8-12.4%, from 90-480s post MVIC (p<0.05). No significant changes were found in the SI or in RTDCC during the 50-100ms phase, suggesting that the enhancements reported, reflect mainly contractile rather than neural or tensile mechanisms.
PAP effects on PTCC and RTDCC were significant, and more durable at a lower velocity than previously reported. Enhancement in RTDCC and neuromuscular efficiency were found to be more prominent in later phases (>100ms) of the MVCC. This suggests that enhanced contractile properties, attained via MVIC, benefit concentric contraction performance.