Early-Phase and Cross-Education Adaptations Following Very Short-Term Unilateral Isokinetic Forearm Extension and Flexion Training in Untrained Women

This study: (1) Determined the time course of early-phase adaptations in average peak torque (APT), the rate of velocity development (RVD), and average power (AP) following very short-term unilateral, reciprocal, concentric isokinetic forearm extension and flexion training in untrained women; and (2) determine whether training the non-dominant arm induced cross-education adaptations in the dominant, non-trained arm. Twelve untrained women (age: 21.7 ± 1.2 yrs) completed four testing and four training visits (pre-test and following 2, 3, and 4 days of training). The testing consisted of three maximal repetitions of the dominant and non-dominant arms at 60°, 180°, and 300°·s^-1, with APT and AP calculated as the average of the 3 repetitions and RVD as the fastest repetition. The training consisted of 6 sets of 10 maximal repetitions at 180°·s^-1 with the non-dominant arm. The differences in mean values across testing visits for APT, AP, and RVD were determined by separate 2 (Arm) × 2 (Muscle Action) × 3 (Velocity) × 4 (Time [across all testing visits]) repeated measures ANOVA (<i>α</i> ≤ 0.05) with Bonferroni-corrected post hoc comparisons. For the trained arm, there were increases in APT (<i>p</i> < 0.001) following four training visits and AP following three (<i>p</i> = 0.006) and four (<i>p</i> = 0.004) training visits. Furthermore, following four training visits, RVD (collapsed across Arms and Muscle Action) decreased at 180°·s^-1 (<i>p</i> = 0.002) and 300°·s^-1 (<i>p</i> = 0.005) following four training visits. There were no changes in APT or AP (<i>p</i> = 0.155-1.000) in the non-trained arm, which indicated no cross-education adaptations. These findings suggested that 3-4 days of moderate-velocity, unilateral, reciprocal, isokinetic training elicited early-phase adaptations for APT, RVD, and AP in untrained women, while cross-education adaptations for APT and AP were not observed within this timeframe.