J Shoulder Elbow Surg. 2023 Mar 16:S1058-2746(23)00243-4. doi: 10.1016/j.jse.2023.02.116. Online ahead of print.
BACKGROUND: Recent evidence indicates that combined upper extremity blood flow restriction (BFR, applied distally to the shoulder) and low-load resistance exercise (LIX) augments clinically meaningful responses in shoulder region tissues proximal to the occlusion site. The purpose of this investigation was to determine the efficacy of BFR-LIX for the shoulder when added to standard offseason training in Division IA collegiate baseball pitchers. We hypothesized that BFR-LIX would augment training-induced increases in shoulder-region lean mass, rotator cuff strength, and endurance. As secondary outcomes, we sought to explore the impact of BFR-LIX rotator cuff training on pitching mechanics.
METHODS: Twenty-eight collegiate baseball pitchers were randomized into 2 groups (BFRN=15, NOBFRN=13) that, in conjunction with offseason training, performed 8wks of shoulder LIX [Throwing arm only; 2/wk, 4 sets (30/15/15/fatigue), 20%isometric max] using 4 exercises [cable external and internal rotation (ER/IR), dumbbell scaption, and side-lying dumbbell ER]. The BFR group also trained with an automated tourniquet on the proximal arm (50%-occlusion). Regional lean mass (dual-energy x-ray absorptiometry), rotator cuff strength (dynamometry: IR0&90, ° ER0&90, ° Scaption, Flexion), and fastball biomechanics were assessed pre- and post-training. Achievable workload (sets × reps × resistance) was also recorded. An ANCOVA (covaried on baseline measures) repeated on training timepoint was used to detect within-group and between-group differences in outcome measures (α=0.05). For significant pairwise comparisons, effect size (ES) was calculated using a Cohen’s d statistic and interpreted as: 0-0.1, negligible(N); 0.1-0.3, small(S); 0.3-0.5, moderate(M); 0.5-0.7, large(L); >0.7, very large(VL).
RESULTS: Following training, the BFR group experienced greater increases in shoulder-region lean mass [BFR: ↑227±60g, NOBFR: ↑75±37g, P=0.018, ES=1.0(VL)] and isometric strength for IR90° (↑2.4±2.3kg, P=0.041, ES=0.9VL). The NOBFR group experienced decreased shoulder flexion (↓1.6±0.8kg, P=0.007, ES=1.4VL) and IR at 0°(↓2.9±1.5kg, P=0.004, ES=1.1VL). The BFR group had a greater increase in achievable workload for the scaption exercise (BFR: ↑190±3.2kg, NOBFR: ↑90±3.3kg, P=0.005, ES=0.8VL). Only the NOBFR group was observed to experience changes in pitching mechanics following training with increased shoulder external rotation at lead foot contact (↑9.0°±7.9, P=0.028, ES=0.8VL) as well as reduced forward (↓3.6°±2.1, P=0.001, ES=1.2VL) and lateral (↓4.6°±3.4, P=0.007, ES=1.0VL) trunk tilt at ball release.
CONCLUSION: BFR-LIX rotator cuff training performed in conjunction with a collegiate offseason program augments increases in shoulder lean mass as well as muscular endurance while maintaining rotator cuff strength and possibly pitching mechanics in a manner that may contribute to favorable outcomes and injury prevention in baseball pitching athletes.