The effect of EMG biofeedback training on muscle activation in an impingement population.

Subacromial impingement syndrome (SAIS) is one of the most diagnosed causes of pain in the upper extremity. The purpose of this study was to investigate muscle activity between asymptomatic and SAIS shoulders on the same subject while understanding the effectiveness of EMG biofeedback training (EBFB) on bilateral overhead movements. Ten participants (7 male), that tested positive for 2/3 SAIS clinical tests, volunteered for the study. Bilateral muscle activity was measured via electrodes on the upper trapezius (UT), lower trapezius (LT), serratus anterior (SA), and lumbar paraspinals (LP). Participants performed bilateral scapular plane overhead movements before and after EBFB. EBFB consisted of 10 bilateral repetitions of I, W, T, and Y exercises focused on reducing UT and increasing LT and SA activity. Prior to EBFB, no significant difference in muscle activity was present between sides. A significant main effect of time indicated that after EBFB both sides exhibited reduced UT activity at 60° (p = 0.003) and 90° (p = 0.036), LT activity was increased at all measured humeral angles (p < 0.0005), and SA muscle activity was increased at 110° (p = 0.001). EBFB in conjunction with scapular based exercise effectively alters muscle activity of asymptomatic and symptomatic scapular musculature.

Creatine electrolyte supplement improves anaerobic power and strength: a randomized double-blind control study.

BACKGROUND: Creatine supplementation aids the Phosphagen system by increasing the amount of free creatine and phosphocreatine available to replenish adenosine triphosphate. The purpose of this study was to investigate the effects of a creatine and electrolyte formulated multi-ingredient performance supplement (MIPS) on strength and power performance compared to a placebo. Maximal strength along with total concentric work, mean rate of force development (mRFD), mean power, peak power, and peak force for both bench press and back squat were determined at pre-test and post-test separated by 6 weeks of supplementation. METHODS: Twenty-two subjects (6 females, 21 ± 2 yrs., 72.46 ± 11.18 kg, 1.72 ± 0.09 m) performed a one-repetition maximum (1RM) for back squat and bench press. Eighty percent of the subject's pre-test 1RM was used for a maximal repetition test to assess performance variables. Testing was separated by 6 weeks of supplementation of a MIPS dose per day in a double-blind fashion for comparison. A two-way mixed analysis of covariance (ANCOVA) was applied with an alpha level of 0.05. RESULTS: For their back squat 1RM, the MIPS group displayed significant increase of 13.4% (95% CI: 2.77, 23.8%) while placebo displayed a decrease of - 0.2% (95% CI: - 1.46, 2.87%) (p = 0.047, ηp2 = 0.201). The MIPS displayed a significant increase of 5.9% (95% CI: 2.5, 10.1%) and placebo displayed a non-significant increase of 0.7% (95% CI: - 3.49, 3.9%) in bench press maximal strength (p = 0.033,0.217). The MIPS group displayed a significant increase as well in total concentric work (26.5, 95% CI: 6.07, 46.87%, p = 0.008, ηp2 = 0.330) and mean power (17.9, 95% CI: 3.42, 32.46%, p = 0.003, ηp2 = 0.402) for the maximal repetition bench press test at 80% of their 1RM. CONCLUSIONS: The MIPS was found to be beneficial to recreationally trained individuals compared to a placebo. The greatest benefits are seen in bench press and back squat maximal strength as well as multiple repetition tests to fatigue during the bench press exercise.

ACUTE EFFECTS OF TWO HIP FLEXOR STRETCHING TECHNIQUES ON KNEE JOINT POSITION SENSE AND BALANCE.

Background: Tightness of hip flexor muscles has been recognized as a risk factor for various musculoskeletal injuries in the lower extremities. Purpose: The purpose of this study was to examine the acute effects of two hip flexor stretching techniques (dynamic and hold-relax proprioceptive neuromuscular facilitation, HR-PNF) on hip extension (ROM), knee joint position sense (JPS) and balance in healthy college age students who exhibit tightness in hip flexor muscles. Study Design: Pretest-posttest randomized experimental groups. Methods: Thirty-six healthy college age students (mean = 22.37 years) with tight hip flexors participated in this study. Hip extension ROM, knee joint position sense and dynamic balance were tested pre- and post-stretching using a digital inclinometer, an iPod touch and the Y-Balance test, respectively. Subjects were randomly divided into dynamic and HR-PNF stretching groups. Three-way mixed analysis of variance was utilized to explore if an interaction existed between the groups in tested variables. Results: There was a significant effect of time on hip extension ROM in both groups (p < 0.001). There was also a significant effect of stretch type on hip extension ROM (p = 0.004) favoring hold-relax over dynamic stretching group. There was a non-significant effect of time on mean knee joint position replication error in both groups. There was a significant main effect of time on the Y-Balance test's mean distance of reach to posteromedial and posterolateral directions (p < 0.001). There was also a significant main effect of directions of reach on distances achieved (p < 0.001) favoring posterolateral over posteromedial, and the latter over anterior direction. Conclusions: The results of this study demonstrated the effectiveness of both HR-PNF and dynamic stretching techniques which resulted in a significant acute improvement in hip extension ROM and dynamic balance measures, with HR-PNF being more effective than dynamic stretch. However, there were no significant improvements in knee joint position replication over time in either stretching group. Level of Evidence: 2b.

Creatine-electrolyte supplementation improves repeated sprint cycling performance: A double blind randomized control study.

BACKGROUND: Creatine supplementation is recommended as an ergogenic aid to improve repeated sprint cycling performance. Furthermore, creatine uptake is increased in the presence of electrolytes. Prior research examining the effect of a creatine-electrolyte (CE) supplement on repeated sprint cycling performance, however, did not show post-supplementation improvement. The purpose of this double blind randomized control study was to investigate the effect of a six-week CE supplementation intervention on overall and repeated peak and mean power output during repeated cycling sprints with recovery periods of 2 min between sprints. METHODS: Peak and mean power generated by 23 male recreational cyclists (CE group: n = 12; 24.0 ± 4.2 years; placebo (P) group: n = 11; 23.3 ± 3.1 years) were measured on a Velotron ergometer as they completed five 15-s cycling sprints, with 2 min of recovery between sprints, pre- and post-supplementation. Mixed-model ANOVAs were used for statistical analyses. RESULTS: A supplement-time interaction showed a 4% increase in overall peak power (pre: 734 ± 75 W; post: 765 ± 71 W; p = 0.040; ηp2 = 0.187) and a 5% increase in overall mean power (pre: 586 ± 72 W; post: 615 ± 74 W; p = 0.019; ηp2 = 0.234) from pre- to post-supplementation for the CE group. For the P group, no differences were observed in overall peak (pre: 768 ± 95 W; post: 772 ± 108 W; p = 0.735) and overall mean power (pre: 638 ± 77 W; post: 643 ± 92 W; p = 0.435) from pre- to post-testing. For repeated sprint analysis, peak (pre: 737 ± 88 W; post: 767 ± 92 W; p = 0.002; ηp2 = 0.380) and mean (pre: 650 ± 92 W; post: 694 ± 87 W; p < 0.001; ηp2 = 0.578) power output were significantly increased only in the first sprint effort in CE group from pre- to post-supplementation testing. For the P group, no differences were observed for repeated sprint performance. CONCLUSION: A CE supplement improves overall and repeated short duration sprint cycling performance when sprints are interspersed with adequate recovery periods.