Effects of Dominant and Nondominant Limb Immobilization on Muscle Activation and Physical Demand during Ambulation with Axillary Crutches.

The purpose of this study was to investigate the effects of how limb dominance and joint immobilization alter markers of physical demand and muscle activation during ambulation with axillary crutches. In a crossover, counterbalanced study design, physically active females completed ambulation trials with three conditions: (1) bipedal walking (BW), (2) axillary crutch ambulation with their dominant limb (DOM), and (3) axillary crutch ambulation with their nondominant limb (NDOM). During the axillary crutch ambulation conditions, the non-weight-bearing knee joint was immobilized at a 30-degree flexion angle with a postoperative knee stabilizer. For each trial/condition, participants ambulated at 0.6, 0.8, and 1.0 mph for five minutes at each speed. Heart rate (HR) and rate of perceived exertion (RPE) were monitored throughout. Surface electromyography (sEMG) was used to record muscle activation of the medial gastrocnemius (MG), soleus (SOL), and tibialis anterior (TA) unilaterally on the weight-bearing limb. Biceps brachii (BB) and triceps brachii (TB) sEMG were measured bilaterally. sEMG signals for each immobilization condition were normalized to corresponding values for BW.HR (p < 0.001) and RPE (p < 0.001) were significantly higher for both the DOM and NDOM conditions compared to BW but no differences existed between the DOM and NDOM conditions (p > 0.05). No differences in lower limb muscle activation were noted for any muscles between the DOM and NDOM conditions (p > 0.05). Regardless of condition, BB activation ipsilateral to the ambulating limb was significantly lower during 0.6 mph (p = 0.005) and 0.8 mph (p = 0.016) compared to the same speeds for BB on the contralateral side. Contralateral TB activation was significantly higher during 0.6 mph compared to 0.8 mph (p = 0.009) and 1.0 mph (p = 0.029) irrespective of condition. In conclusion, limb dominance appears to not alter lower limb muscle activation and walking intensity while using axillary crutches. However, upper limb muscle activation was asymmetrical during axillary crutch use and largely dependent on speed. These results suggest that functional asymmetry may exist in upper limbs but not lower limbs during assistive device supported ambulation.

Acute Beetroot Juice Supplementation Attenuates Morning-Associated Decrements in Supramaximal Exercise Performance in Trained Sprinters.

Diurnal fluctuations in power output have been well established with power loss typically occurring in morning (AM) times. Beetroot juice (BRJ) is a source of dietary nitrate that possess ergogenic properties, but it is unknown if ingestion can mitigate performance decrements in the morning. The purpose of this study was to examine the effects of acute BRJ supplementation on diurnal fluctuations in anaerobic performance in trained sprinters. Male Division 1 National Collegiate Athletic Association (NCAA) sprinters (n = 10) participated. In a double-blinded crossover study design, participants completed three counterbalanced exercise trials under different conditions: Morning-placebo (8:00 HR, AM-PL), Morning-BRJ (8:00 HR, AM-BRJ), and Afternoon-no supplement (15:00 HR, PM). For each trial, participants completed 3 × 15 s Wingate anaerobic tests separated by 2 min of rest. Each trial was separated by a 72 h washout period. Mean power output (p = 0.043), anaerobic capacity (p = 0.023), and total work (p = 0.026) were significantly lower with the AM-PL condition compared to PM. However, BRJ supplementation prevented AM losses of mean power output (p = 0.994), anaerobic capacity (p = 0.941), and total work (p = 0.933) in the AM-BRJ compared to the PM condition. Rate of perceived exertion was not significantly different between any conditions (p = 0.516). Heart rate was significantly lower during the AM-BRJ condition compared to AM-PL (p = 0.030) and PM (p < 0.001). Findings suggest anaerobic capacity suffers during AM versus PM times in trained sprinters, but BRJ ingestion abolishes AM-associated decrements in performance.

Effects of Preferred and Non-Preferred Warm-Up Music on Resistance Exercise Performance.

The purpose of this study was to examine the effects of listening to preferred and non-preferred warm-up music on upper-body resistance exercise performance. Resistance-trained males (ages 18-24) participated in two separate bench press trials each with a different warm-up music condition: preferred warm-up music (PREF) or non-preferred warm-up music (NON-PREF). In each trial, participants listened to PREF or NON-PREF music during a standardized bench press warm-up. Following the warm-up, motivation to exercise was measured using a visual analog scale followed by two sets × repetitions to failure (RTF) at 75% of 1-RM separated by 1 min of rest. A linear position transducer was used to measure mean barbell velocity. Rate of perceived exertion (RPE) was obtained after each set. RTF, velocity, RPE, and motivation were analyzed. RTF were significantly higher during the PREF versus NON-PREF trail (p = 0.001) while mean barbell velocity remained unchanged (p = 0.777). RPE was not significantly different between PREF and NON-PREF trials (p = 0.735). Motivation to exercise was significantly higher during the PREF versus NON-PREF trial (p < 0.001). Findings show that listening to PREF music during a warm-up improves subsequent RTF performance during bench press exercise. However, barbell velocity was largely unaffected. While perceived exertion was similar between trials, motivation to exercise was markedly increased during the PREF warm-up music trial. These findings suggest that competitors listening to warm-up music before giving maximal effort during resistance exercise could optimize performance by ensuring self-selection of their own preferred music.

The Epidemiology of Deltoid Ligament Sprains in 25 National Collegiate Athletic Association Sports, 2009-2010 Through 2014-2015 Academic Years.

CONTEXT: Deltoid ligament sprains among collegiate student-athletes have not been extensively investigated. Research regarding the mechanisms, participation-restriction time, and recurrence of deltoid ligament sprains in collegiate student-athletes is lacking. OBJECTIVE: To describe the epidemiology of deltoid ligament sprains in 25 National Collegiate Athletic Association championship sports. DESIGN: Descriptive epidemiology study. SETTING: National Collegiate Athletic Association Injury Surveillance Program. MAIN OUTCOME MEASURE(S): We analyzed deltoid ligament sprains recorded in the Injury Surveillance Program for the 2009-2010 through 2014-2015 academic years. Deltoid ligament sprain injury rates, rate ratios, and injury proportion ratios with 95% confidence intervals (CIs) were reported. RESULTS: During the study period, 380 deltoid ligament sprains were reported, resulting in a combined injury rate of 0.79/10 000 athlete-exposures (AEs; 95% CI = 0.71, 0.87). Most deltoid ligament sprains occurred in practices (54.2%, n = 206). However, the competition injury rate was higher than the practice injury rate (rate ratio = 3.74; 95% CI = 3.06, 4.57). The highest deltoid ligament sprain rates were in women's gymnastics (2.30/10 000 AEs; 95% CI = 1.05, 3.55), men's soccer (1.73/10 000 AEs; 95% CI = 1.14, 2.32), women's soccer (1.61/10 000 AEs; 95% CI = 1.13, 2.09), and men's football (1.40/10 000 AEs; 95% CI = 1.18, 1.62). Nearly half of all deltoid ligament sprains (49.7%, n = 189) were due to player contact, and 39.5% (n = 150) were non-time-loss injuries (ie, participation restricted for less than 24 hours). Only 8.2% (n = 31) of deltoid ligament sprains were recurrent. CONCLUSIONS: The highest deltoid ligament sprain rates were in women's gymnastics, men's and women's soccer, and men's football. However, the rate for women's gymnastics was imprecise (ie, the CI was wide), highlighting the need for further surveillance of deltoid ligament sprains in the sport. Most deltoid ligament sprains were due to player contact. Future researchers should assess interventions that may prevent deltoid ligament sprains.