Cross Education Training Effects are Evident with Twice Daily, Self-Administered Band Stretch Training.

Currently there are recommendations for stretching type, repetitions and duration within a training session to improve flexibility. It is, however, unclear whether multiple daily stretch training sessions provide greater flexibility than single daily sessions. The objective was to investigate the effectiveness of single (1×day) versus twice daily (2×day) unilateral stretch training sessions on hip flexion range of motion (ROM), agonist and antagonist force and jump performance of the stretched and contralateral, non-stretched legs. Groups included a control, 1×day and 2×day stretch training groups. Static stretching (SS) involved self-administered (stretch band), unilateral, hamstrings and quadriceps stretching for 2-weeks. Pre- and post-testing involved hip flexion ROM, knee extension and flexion maximal voluntary isometric contraction (MVIC) forces and unilateral drop jumps (DJ). The 2×day group showed a 12.8% (p = 0.08) greater active ROM versus Control. The 1×day group showed a 7.5% (p=0.1) ballistic ROM increase with no significant changes with the 2×day and Control groups. The stretched leg experienced a 5.01% (p = 0.1) hip flexion ballistic ROM increase contrasting with a 2.3% increase for the contralateral leg. Twice daily training provided 7.1% (p = 0.07) and 6.6% (p = 0.01) quadriceps MVC force increases of the stretched trained and contralateral legs respectively. Contralateral DJ height improved 22.6% (p = 0.002) with 2×day training. In conclusion, 1xday and 2×day stretch training tended to improved ballistic and active ROM respectively, whereas 2×day training improved MVIC force and DJ height. The findings may apply to fitness enthusiasts and rehabilitation as unilateral stretching may retain performance and active ROM of the stretched and contralateral limbs.

Unilateral hamstrings static stretching can impair the affected and contralateral knee extension force but improve unilateral drop jump height.

PURPOSE: Prolonged static stretching (SS) in isolation (no dynamic warm-up) can impair muscle performance. There are conflicting reports whether impairments are present in antagonist and contralateral muscles. The objective of this study was to assess the effect of unilateral hamstrings SS on ipsilateral stretched and contralateral limbs' strength and jump power. METHODS: The SS (four repetitions of 30-s) and control sessions involved unilateral testing of the stretched leg and contralateral leg for knee extension (KE) maximum voluntary isometric contraction (MVIC) force and electromyography (EMG), drop jump (DJ) height and contact time at 1-min post-stretching. RESULTS: There were significant KE MVIC force impairments for both the SS (p = 0.006, d = 0.3, - 8.1%) and contralateral (p = 0.02, d = 0.20, - 4.2%) leg. With normalized data, there was a near-significant (p = 0.1), small magnitude (d = 0.29), greater force impairment with the ipsilateral (93.0 ± 12.8% of pre-test) versus the contralateral (96.2 ± 9.1% of pre-test) KE MVIC force. DJ height significantly improved for the stretched leg (p = 0.03, d = 0.18, + 9.2%) with near-significant, improvements for the contralateral leg (p = 0.06, d = 0.22, + 12.1%). For the stretched leg, DJ contact time was significantly (p = 0.04, d = 0.18, + 3.4%) prolonged, but there was no significant change with the contralateral leg. CONCLUSIONS: Unilateral hamstrings SS induced strength deficits in the ipsilateral and contralateral knee extension MVIC and a prolongation of the stretched leg DJ contact period. In anticipation of maximal force outputs, prolonged SS in isolation (no dynamic warm-up included) can have negative consequences on antagonist and contralateral muscle performance.