The Influence Of Unilateral Handgrip Training With Blood Flow Restriction On The Cross-education Of Strength

When one limb is strength trained, strength can increase in the opposite untrained limb. This effect is thought to be greater with higher intensities. However, there is some (albeit scant) evidence for a cross-education effect with low-intensity exercise with blood flow restriction (BFR). It is unclear how this would compare with traditional high intensity exercise. PURPOSE: To examine whether low-intensity training with BFR augments the cross-education of strength compared to exercise without BFR. METHODS: 179 participants (77 males, 102 females; 21.5 ± 3.5 years) completed this 6-week study. A pre-test was performed prior to the start of the first training session and a post visit after the last training session. Participants were randomized into one out of four possible groups. Of the four groups, three included variations of four sets of unilateral isometric handgrip training: 1) low-intensity (30% maximal contraction for two minutes (LI, n = 47), 2) low-intensity plus blood flow restriction (50% arterial occlusion pressure) for two minutes (LI-BFR, n = 41), 3) high-intensity (100% maximal contraction) for five seconds (HI, n = 47), and 4) a time-match, non-exercise control group (CON, n = 44). The training groups visited the laboratory three times a week for six weeks (18 training sessions). A Bayesian ANCOVA was used to determine changes in strength for the trained and untrained limb. The pre-test value was used as the covariate. Data is presented as mean (standard deviation). RESULTS: Strength changed differently between groups in the untrained limb (BF10: 3.35). LI-BFR was the only group that observed a cross-education in strength relative to the CON (BF10: 14.4). The pre to post changes in strength of the untrained limb are as listed: CON: 0.6 (2.9), LI: 0.9 (3.6), LI-BFR: 2.7 (3.3), and HI: 0.8 (3.1) kg. Strength in the trained limb also change differently between groups (BF10: 271147). Changes in the HI [4.8 (2.8) kg] and LI-BFR [2.8 (4.0) kg] groups were greater than that of the CON [0.7 (2.9) kg]. However, the LI group [1.3 (2.8) kg] was not different from CON. CONCLUSION: Contrary to previous work using dynamic contraction, the cross-education effect was not intensity dependent. Cross-education was only observed with LI-BFR, suggesting an intensity independent mechanism with isometric handgrip training.