Examining the Cross-Education Phenomenon in Lower Limbs: Insights from the Force-Velocity Profile

This study explored whether the cross-education (CE) phenomenon could be examined through the force-velocity (FV) profile. Nineteen participants completed 5-weeks of unilateral knee extension protocols differing in set configuration. Traditional training group (TT) carried out 4 sets of 8 repetitions and 3 min rest between sets, whereas in-ter-repetition training group (IRT) completed 32 repetitions with 17.4 s rest between repetitions. Intervention was performed with the 10-repetition maximum load on the dominant limb. Individual linear FV profiles (slope: SFV; theoretical maximum force and velocity: F0 and V0; and maximum estimated power: Pmax) were obtained for trained and untrained legs pre-post intervention. The trained limb showed significant increases in post-test for F₀, Pmax, and a steeper SFV (p< 0.05). In the untrained limb, F₀ (p=0.042) and Pmax (p=0.010) also improved, whereas no changes were observed in V₀ nor SFV. Set configuration did not modulate the FV adaptations in either trained or un-trained limb. Our results showed that the CE effect was not manifested in the force–velocity (F–V) profile of the untrained limb (i.e., no shift in SFV.Our results showed that the CE effect was nor manifested in the FV profile of the untrained limb (i.e., no SFV shift). However, these findings indicate that strength and power transfer can be accomplished with low-fatigue training protocols, which may offer a more tolerable and practical option in clinical and performance settings.