Important Methodological Concern Regarding the Article "Effect of Leg Half-Squat Training With Blood Flow Restriction Under Different External Loads on Strength and Vertical Jumping Performance in Well-Trained Volleyball Players": A Letter to the Editor.

We would like to commend Wang et al 1 on their investigation into the 8-week chronic training effects of blood fl ow restriction (BFR) on trained volleyball players. Novel to the fi eld was the comparison between low-load BFR (30% 1-repetition maximum, RM) and heavy loads (70% 1-RM) (HL) with and without BFR applied at an estimated 50% arterial occlusion pressure (AOP). BFR was prescribed in a commonly rec-ommended fi xed scheme (30 repetitions followed by 3 sets of 15) 2 while HL strength training was performed for 4 sets of 8 repetitions. Results indicate that HL strength training with BFR performed better in thigh muscle strength and jumping performance than low-load BFR exercise and in some measures exhibited non-signi fi cant improvements over HL strength training. The results are surprising given previous research has indicated no additional bene fi t with the addition of BFR to HL on muscle strength measures 3 although one study did show improvements of performance in rugby athletes. 4 Nonetheless, the results of this study provide prelim-inary support for the use of BFR during HL strength training to elicit signi fi cant gains in strength and jumping performance — factors thought to be important in improving volleyball performance. However, we want to highlight a signi fi cant methodological limitation that impacts the interpretation of the study. We agree that utilizing a limb circumference equation is an appropriate surrogate for determining AOP when using single-chambered bladder systems capable of achieving full arterial