Blood Flow Restriction Training Effects on Pennation Angles

Pennation angle (PA) represents the angle between muscle fibers and the force-generating axis of the muscle. Blood flow resistance (BFR) training involves the occlusion of venous blood flow in working muscles to promote muscular growth signaling with reduced training intensity. PURPOSE: The purpose is to examine if hypertrophy through BFR may result in PA alterations to accommodate muscle fiber volume alterations. METHODS: Males (N=11, 20.35±1.59 yrs, 177.97±9.22 cm, 83.66±20.69 kg), and females (N=12, 23.20±9.53 yrs, 164.60±6.42 cm, 63.2±10.65 kg) participated in resistance training with BFR for 3 times/week, for 8 weeks at 60% occlusion pressure, at 30% of one-repetition maximum in four compound exercises performed for 4 sets of 30, 15, 15, and 15 reps. A Tearson ultrasound was used to quantify PA for Biceps Brachii (BB), Rectus Femoris (RF), and Biceps Femoris (BF). RESULTS: Comparing percent change (PC) in PA, for males, there was similar PC in B2RT and control for BB (8.56±12.27 vs. 9.03±14.19%, p>0.05), RF (8.64±16.53 vs. -0.310±19.11%, p>0.05), but significantly higher PC for B2RT then control for BF (55.85±15.43 vs. 4.10±17.82%, p=0.029). In females, there was similar PC in B2RT and control for BB (11.61±13.98 vs. 16.49±11.77%, p>0.05), BF (55.24±17.59 vs. 46.74±14.80%, p>0.05), but PC trended higher in PA in B2RT than the control for RF (37.86±18.84 vs. 11.50±15.85%, p=0.272). CONCLUSION: This short-term protocol demonstrated altered muscle architecture in select lower-extremity muscles for males and potential trends in females which justifies additional studies to discern muscle specific adaptations.