Context: Dynamic balance is a measure of core stability. Deficits in the dynamic balance have been related to injuries in the athletic populations. The Star Excursion Balance Test (SEBT) is suggested to measure and improve dynamic balance when used as a rehabilitative tool. Objective: To determine the electromyographic activity of the hip and the trunk muscles during the SEBT. Design: Descriptive. Setting: University campus. Participants: Twenty-two healthy adults (11 males and 11 females; 23.3 [3.8] y, 170.3 [7.6] cm, 67.8 [10.3] kg, and 15.1% [5.0%] body fat). Intervention: Surface electromyographic data were collected on 22 healthy adults of the erector spinae, external oblique, and rectus abdominis bilaterally, and gluteus medius and gluteus maximus muscle of the stance leg. A 2-way repeated measures analysis of variance was used to determine the interaction between the percentage maximal voluntary isometric contraction (%MVIC) and the reach directions. The %MVIC for each muscle was compared across the 8 reach directions using the Sidak post hoc test with α at .05. Main Outcome Measures: %MVIC. Results: Significant differences were observed for all the 8 muscles. Highest electromyographic activity was found for the tested muscles in the following reach directions—ipsilateral external oblique (44.5% [38.4%]): anterolateral; contralateral external oblique (52.3% [40.8%]): medial; ipsilateral rectus abdominis (8% [6.6%]): anterior; contralateral rectus abdominis (8% [5.3%]): anteromedial; ipsilateral erector spinae (46.4% [20.2%]): posterolateral; contralateral erector spinae (33.5% [11.3%]): posteromedial; gluteus maximus (27.4% [11.7%]): posterior; and gluteus medius (54.6% [26.1%]): medial direction. Conclusions: Trunk and hip muscle activation was direction dependent during the SEBT. This information can be used during rehabilitation of the hip and the trunk muscles.
You are looking at 91 - 100 of 24,680 items
Kunal Bhanot, Navpreet Kaur, Lori Thein Brody, Jennifer Bridges, David C. Berry and Joshua J. Ode
Manuel D. Quinones and Peter W.R. Lemon
Hydrothermally modified non-genetically modified organisms corn starch (HMS) ingestion may enhance endurance exercise performance via sparing carbohydrate oxidation. To determine whether similar effects occur with high-intensity intermittent exercise, we investigated the effects of HMS ingestion prior to and at halftime on soccer skill performance and repeated sprint ability during the later stages of a simulated soccer match. In total, 11 male university varsity soccer players (height = 177.7 ± 6.8 cm, body mass = 77.3 ± 7.9 kg, age = 22 ± 3 years, body fat = 12.8 ± 4.9%, and maximal oxygen uptake = 57.1 ± 3.9 ml·kg BM−1·min−1) completed the match with HMS (8% carbohydrate containing a total of 0.7 g·kg BM−1·hr−1; 2.8 kcal·kg BM−1·hr−1) or isoenergetic dextrose. Blood glucose was lower (p < .001) with HMS at 15 min (5.3 vs. 7.7 mmol/L) and 30 min (5.6 vs. 8.3 mmol/L) following ingestion, there were no treatment differences in blood lactate, and the respiratory exchange ratio was lower with HMS at 15 min (0.84 vs. 0.86, p = .003); 30 min (0.83 vs. 0.85, p = .004); and 45 min (0.83 vs. 0.85, p = .007) of the first half. Repeated sprint performance was similar for both treatments (p > .05). Soccer dribbling time was slower with isoenergetic dextrose versus baseline (15.63 vs. 14.43 s, p < .05) but not so with HMS (15.04 vs. 14.43 s, p > .05). Furthermore, during the passing test, penalty time was reduced (4.27 vs. 7.73 s, p = .004) with HMS. During situations where glycogen availability is expected to become limiting, HMS ingestion prematch and at halftime could attenuate the decline in skill performance often seen late in contests.
Thomas Reeve, Ralph Gordon, Paul B. Laursen, Jason K.W. Lee and Christopher J. Tyler
Purpose: To investigate the effects of short-term, high-intensity interval-training (HIIT) heat acclimation (HA). Methods: Male cyclists/triathletes were assigned into either an HA (n = 13) or a comparison (COMP, n = 10) group. HA completed 3 cycling heat stress tests (HSTs) to exhaustion (60% W max; HST1, pre-HA; HST2, post-HA; HST3, 7 d post-HA). HA consisted of 30-min bouts of HIIT cycling (6 min at 50% W max, then 12 × 1-min 100%-W max bouts with 1-min rests between bouts) on 5 consecutive days. COMP completed HST1 and HST2 only. HST and HA trials were conducted in 35°C/50% relative humidity. Cycling capacity and physiological and perceptual data were recorded. Results: Cycling capacity was impaired after HIIT HA (77.2 [34.2] min vs 56.2 [24.4] min, P = .03) and did not return to baseline after 7 d of no HA (59.2 [37.4] min). Capacity in HST1 and HST2 was similar in COMP (43.5 [8.3] min vs 46.8 [15.7] min, P = .54). HIIT HA lowered resting rectal (37.0°C [0.3°C] vs 36.8°C [0.2°C], P = .05) and body temperature (36.0°C [0.3°C] vs 35.8°C [0.3°C], P = .03) in HST2 compared with HST1 and lowered mean skin temperature (35.4°C [0.5°C] vs 35.1°C [0.3°C], P = .02) and perceived strain on day 5 compared with day 1 of HA. All other data were unaffected. Conclusions: Cycling capacity was impaired in the heat after 5 d of consecutive HIIT HA despite some heat adaptation. Based on data, this approach is not recommended for athletes preparing to compete in the heat; however, it is possible that it may be beneficial if a state of overreaching is avoided.
Gareth N. Sandford, Simon A. Rogers, Avish P. Sharma, Andrew E. Kilding, Angus Ross and Paul B. Laursen
Purpose: Anaerobic speed reserve (ASR), defined as the speed range from velocity associated with maximal oxygen uptake (vVO2max) to maximal sprint speed, has recently been shown to be an important tool for middle-distance coaches to meet event surge demands and inform on the complexity of athlete profiles. To enable field application of ASR, the relationship between gun-to-tape 1500-m average speed (1500v) and the vVO2max for the determination of lower landmark of the ASR was assessed in elite middle-distance runners. Methods: A total of 8 national and 4 international middle-distance runners completed a laboratory-measured vVO2max assessment within 6 wk of a nonchampionship 1500-m gun-to-tape race. ASR was calculated using both laboratory-derived vVO2max (ASR-LAB) and 1500v (ASR-1500v), with maximal sprint speed measured using radar technology. Results: 1500v was on average +2.06 ± 1.03 km/h faster than vVO2max (moderate effect, very likely). ASR-LAB and ASR-1500v mean differences were −2.1 ± 1.5 km/h (large effect, very likely). 1500v showed an extremely large relationship with vVO2max, r = .90 ± .12 (most likely). Using this relationship, a linear-regression vVO2max-estimation equation was derived as vVO2max (km/h) = (1500v [km/h] − 14.921)/0.4266. Conclusions: A moderate difference was evident between 1500v and vVO2max in elite middle-distance runners. The present regression equation should be applied for an accurate field prediction of vVO2max from 1500-m gun-to-tape races. These findings have strong practical implications for coaches lacking access to a sports physiology laboratory who seek to monitor and profile middle-distance runners.
John M. Rosene, Christian Merritt, Nick R. Wirth and Daniel Nguyen
Subconcussive head impacts in sport may have a greater impact on neurological degradation versus concussive hits given the repetitive nature of these head impacts. The purpose of this investigation was to quantify the frequency, magnitude, and location of head impacts in an NCAA Division III men’s lacrosse team. There was no significant difference (p ≤ .05) in peak linear acceleration, peak rotational acceleration, and peak rotational velocity between games and practices. There was no significant difference (p ≤ .05) for PLA among player position and location of head impact. The quantity and intensity of subconcussive head impacts between practices and games were similar. These multiple subconcussive head impacts have the potential to lead to future neurological impairments.
Amanda L. Zaleski, Linda S. Pescatello, Kevin D. Ballard, Gregory A. Panza, William Adams, Yuri Hosokawa, Paul D. Thompson and Beth A. Taylor
Context: Compression socks have become increasingly popular with athletes due to perceived enhancement of exercise performance and recovery. However, research examining the efficacy of compression socks to reduce exercise-associated muscle damage has been equivocal, with few direct measurements of markers of muscle damage. Objective: To examine the influence of compression socks worn during a marathon on creatine kinase (CK) levels. Design: A randomized controlled trial. Setting: 2013 Hartford Marathon, Hartford, CT. Participants: Adults (n = 20) randomized to control (CONTROL; n = 10) or compression sock (SOCK; n = 10) groups. Main Outcome Measures: Blood samples were collected 24 hours before, immediately after, and 24 hours following the marathon for the analysis of CK, a marker of muscle damage. Results: Baseline CK levels did not differ between CONTROL (89.3 [41.2] U/L) and SOCK (100.0 [56.2] U/L) (P = .63). Immediately following the marathon (≤1 h), CK increased 273% from baseline (P < .001 for time), with no difference in exercise-induced changes in CK from baseline between CONTROL (+293.9 [278.2] U/L) and SOCK (+233.1 [225.3] U/L; P = .60 for time × group). The day following the marathon (≤24 h), CK further increased 1094% from baseline (P < .001 for time), with no difference in changes in CK from baseline between CONTROL (+ 1191.9 [1194.8] U/L) and SOCK (+889.1 [760.2] U/L; P = .53 for time × group). These similar trends persisted despite controlling for potential covariates such as age, body mass index, and race finishing time (Ps > .29). Conclusions: Compression socks worn during a marathon do not appear to mitigate objectively measured markers of muscle damage immediately following and 24 hours after a marathon.
Jan Wilke, Philipp Niemeyer, Daniel Niederer, Robert Schleip and Winfried Banzer
Context: Foam rolling (FR) increases joint range of motion (RoM), but the optimal training parameters are unknown. Objective: To investigate the effect of FR velocity on RoM and tissue stiffness. Design: Randomized, controlled crossover trial. Setting: University. Participants: A total of 17 healthy, physically active adults (10 females; 25  y). Interventions: (1) Four 45-second high-velocity FR of the anterior thigh (FAST-FR), (2) four 45-second slow-velocity FR of the anterior thigh (SLOW-FR), and (3) inactive control. Outcome Measures: Maximal knee-flexion RoM (ultrasonic movement analysis) and anterior thigh tissue stiffness (semielectronic tissue compliance meter) assessed pre, immediately post (T0), as well as 5 (T5) and 10 (T10) minutes postintervention. Statistical analysis included Friedman tests with adjusted post hoc comparisons (Wilcoxon tests). Results: According to omnibus testing, RoM remained unchanged in all 3 conditions and at all time points (P > .05), while differences were found for tissue stiffness (P < .05). Post hoc tests revealed significant decreases following FAST-FR (T5: −17%, T10: −24%; P < .05) and SLOW-FR (T10: −15%; P < .05). The observed stiffness changes were significant in comparison with control (P < .01), but no difference was found between the 2 FR conditions (P > .05). Conclusions: FR of the anterior thigh decreases myofascial stiffness regardless of velocity. The lack of effects on RoM contrasts findings of recent literature and warrants further investigation.
Rich D. Johnston
Purpose: To explore the relationship between technical errors during rugby league games, match success, and physical characteristics. Methods: A total of 27 semiprofessional rugby league players participated in this study (24.8 [2.5] y, 183.5 [5.3] cm, 97.1 [11.6] kg). Aerobic fitness, strength, and power were assessed prior to the start of the competitive season before technical performance was tracked during 22 competitive fixtures. Attacking errors were determined as any error that occurred in possession of the ball that resulted in a handover to the opposition. Defensive errors included line breaks, penalties, and missed or ineffective tackles. Match outcome, the zone on the field in which each error occurred, and the number of errors in an error chain (≤60 s between errors) were assessed. Results: During a loss, there were more defensive errors in the 0- to 40-m zone than when a match was won (effect size = 0.99 [0.04–1.94]). Error chains were a predictor of conceding a try (P = .0001, r 2 = .22), with the odds ratio increasing to 2.33 when there were 7 errors per chain. High lower-body strength was associated with fewer defensive errors for backs (Bayes factor = 3.67) and forwards (Bayes factor = 19.31); relative bench press was also important for backs (Bayes factor = 3.21). Conclusions: Fewer defensive errors occur in the 0- to 40-m zone during winning matches; lower-body strength is strongly associated with fewer defensive errors in rugby league players.
Sada Reed and Guy Harrison
Past research has examined the use of anonymous sources in news content and its impact on perceived credibility. Studies applying these theories in the context of sport media consumption, however, are scant and outdated. This matters because sport media is consumed for different reasons from news and has a historically symbiotic relationship with the people and events it covers. The current case study explores sources in National Basketball Association (NBA) trade stories in both national news and sport-specific publications. The study found that about 82% of trade speculation was not credited to a source. Unnamed and named sources’ trade predictions were cross-referenced with the NBA transaction log to determine if the trades actually manifested before the trade deadline. Neither sources predicted trades well: Of the 95 unsourced, speculated trades, 14 actually took place. Of the 20 sourced speculations, four took place. There was no statistically significant difference between how well named and unnamed sources predicted trades.
Daniel G. Hursh, Marissa N. Baranauskas, Chad C. Wiggins, Shane Bielko, Timothy D. Mickleborough and Robert F. Chapman
Endurance exercise performance in hypoxia may be influenced by an ability to maintain high minute ventilation (