(46) THE IMPACT OF BLOOD FLOW RESTRICTION COMBINED WITH VERTICAL COUNTERMOVEMENT JUMPS ON FORCE OUTPUT AND MUSCLE EXCITATION

Blood flow restriction (BFR) commonly combines low-load, high repetition resistance exercise and results in significant fatigue. Decreased blood supply to muscles and increased metabolic stress leads to increased electromyography amplitudes during exercise in order to perform exercises in conjunction with BFR but results in a decrease in force production after exercise. Plyometric exercises, such as vertical countermovement jumps, typically require a high number of repetitions to elicit desired results. It is currently unclear if BFR can be used as a potential method to increase the intensity of maximal vertical countermovement jumps.

Purpose: To examine the effect that BFR had on muscle excitation and force output during maximal vertical countermovement jumps.

Methods: Participants consisted of 12 male resistance trained-subjects between the ages of 18 and 35 years. A cross-over randomized experimental  design was used. Each subject performed two visits, separated by at least two days and were randomly assigned non-BFR (control) or BFR condition on the first visit, and then given the opposite on their second visit. Each visit consisted of 4 sets of 20 repetitions of maximal vertical countermovement jumps and two minutes of rest between sets. Maximal vertical countermovement jump force was measured through peak vertical ground reaction force during a maximum vertical countermovement jump on a Bertec force plate, set at 1000 Hz sampling rate. Surface electromyography (sEMG; biceps femoris (BF), rectus femoris (RF), and medial gastrocnemius (MG)) was measured before and after the 4 sets of 20 repetitions. BFR cuffs were placed at the most proximal position of the thigh using 60% of each individual’s maximal arterial occlusion pressure (AOP) cuff pressure. Three maximal vertical countermovement jumps were performed on a force plate prior to the exercise intervention and were used as the maximal force output baseline. Post-intervention force output was measured without BFR cuffs immediately following the last jump repetition of each visit. Paired sample t-tests and a series of two-way repeated measures ANOVA were used to analyze the data. The propulsion phase of the maximal vertical countermovement jump was analyzed.

Results: Average sEMG amplitudes post exercise captured during the propulsion phase of the vertical countermovement jump were not significantly different between conditions for the RF (Control: 52.0 ± 15.6% vs. BFR: 55.5 ± 13.7%, p=0.590, Cohen’s D = 0.168), BF (Control: 39.7 ± 10.7% vs. BFR: 35.3 ± 13.6%, p=0.454, Cohen’s D = 0.235)  and MG (Control: 33.8 ± 13.3% vs. BFR: 40.9 ± 8.2%, p=0.152, Cohen’s D = 0.468). A significant time main effect for vertical jump height was found from pre to post exercise (43.8 ± 2.1 cm vs. 34.3 ± 2.1 cm, p< 0.001, omega-squared effect size = 0.309). A significant time main effect was also found for the mean propulsive force during the vertical countermovement jump from pre to post exercise (1561.0 ± 85.8 N vs. 1445 ± 85.8 N, p< 0.001, omega-squared effect size = 0.038).

Conclusions: Combining BFR with maximal vertical countermovement jumps results in a similar decrease in sEMG amplitudes and peak vertical ground reaction forces as doing the same jumps without BFR. PRACTICAL APPLICATIONS: BFR combined with maximal vertical countermovement jumps may not be recommended due to both of them resulting in a similarly fatigued state post-exercise. However, chronic studies are needed to verify this. 

Acknowledgements: Acknowledgments to Brigham Young University-Idaho as resources from the exercise physiology lab were used.