THE EFFECTS OF A HIGH INTENSITY FREE-WEIGHT BACK SQUAT ON POSTURAL STABILITY IN RESISTANCE-TRAINED MALES

Ryan M. Thiele1, Eric C. Conchola1, Ty B. Palmer1, Brennan J. Thompson2 & Doug B. Smith1 1Oklahoma State University, Stillwater, OK; 2Texas Tech University, Lubbock, TX Previous studies have revealed that high intensity aerobic and anaerobic exercise may have adverse effects on postural stability, which could lead to lower performances and an increased risk of injury. PURPOSE: The purpose of this study was to investigate the effects of a high-intensity free-weight back squat on static balance in resistance-trained males. METHODS: Eighteen young (mean ± SD: age = 22.9 ± 2.9 years; height = 175.8± 6.4 cm; mass = 86.3 ± 9.3 kg), resistance-trained males performed balance testing before and after completing 5 sets of 8 repetitions of the back squat exercise at 80% 1-repetition maximum. A commercially designed balance test unit was used to assess sway index (SI) at pre (Pre) and at 0 (Post 0), 5 (Post 5), 10 (Post 10), 15 (Post 15), and 20 (Post 20) minutes post-intervention following the back squat. Each balance assessment consisted of 4, 20-second static stance conditions: eyes-open firm surface (EOFS), eyes-closed firm surface (ECFS), eyes-open soft surface (EOSS) and eyes-closed soft surface (ECSS). RESULTS: SI was greater (P= 0.001-0.020) at Post 0 than at Pre- , Post 5 , Post 10 , Post 15 , and Post 20. No differences (P\u3e0.05) were observed for SI between any other time phases. SI was greater (P\u3c 0.001) for ECSS than for EOFS, ECFS, and EOSS; and was greater (P\u3c 0.001) for ECFS and EOSS than for EOFS. CONCLUSIONS: These findings revealed that SI for all four conditions significantly increased following completion of the back squat; however, SI returned to baseline within 5 minutes of the exercise. The presence of higher SI values immediately after the back squat exercise demonstrated the adverse effects on postural sway and balance performance that may be induced as a consequence of neuromuscular fatigue. If reductions in balance decrease performance and increase the risk of injury, then the present findings suggest that for athletes who are performing a multiple-exercise workout, a recovery period ranging from 0 – 5 minutes of rest after completing a high intensity back squat may be necessary prior to beginning additional exercises