Purpose: To evaluate the test–retest reliability, sensitivity, and concurrent validity of a smartphone-based method for assessing eccentric hamstring strength among male professional football players. Methods: A total of 25 healthy male professional football players performed the Chinese University of Hong Kong (CUHK) Nordic break-point test, hamstring fatigue protocol, and isokinetic hamstring strength test. The CUHK Nordic break-point test is based on a Nordic hamstring exercise. The Nordic break-point angle was defined as the maximum point where the participant could no longer support the weight of his body against gravity. The criterion for the sensitivity test was the presprinting and postsprinting difference of the Nordic break-point angle with a hamstring fatigue protocol. The hamstring fatigue protocol consists of 12 repetitions of the 30-m sprint with 30-s recoveries between sprints. Hamstring peak torque of the isokinetic hamstring strength test was used as the criterion for validity. Results: A high test–retest reliability (intraclass correlation coefficient = .94; 95% confidence interval, .82–.98) was found in the Nordic break-point angle measurements. The Nordic break-point angle significantly correlated with isokinetic hamstring peak torques at eccentric action of 30°/s (r = .88, r 2 = .77, P < .001). The minimal detectable difference was 8.03°. The sensitivity of the measure was good enough that a significance difference (effect size = 0.70, P < .001) was found between presprinting and postsprinting values. Conclusion: The CUHK Nordic break-point test is a simple, portable, quick smartphone-based method to provide reliable and accurate eccentric hamstring strength measures among male professional football players.
Justin W.Y. Lee, Ming-Jing Cai, Patrick S.H. Yung and Kai-Ming Chan
Thomas Haugen, Jørgen Danielsen, Leif Olav Alnes, David McGhie, Øyvind Sandbakk and Gertjan Ettema
specific variables related to front- and back-side mechanics are associated with sprint performance. Figure 1 —Definition of angles. The black dot represents CoM. CoM indicates center of mass; θ trunk , trunk angle relative to horizontal; θ thigh , thigh angle relative to horizontal, where an angle of 0
Thomas Cattagni, Vincent Gremeaux and Romuald Lepers
, height = 448 pixels, slice thickness = 5 mm, slice increment = 5 mm, and number of slices = 162. Data were transferred in DICOM format (.DCM file). For both legs, the triceps surae, tibialis anterior, quadriceps, and other thigh muscles (including knee flexor and adductor muscles, and sartorius) were
M. Travis Byrd, Jonathan Robert Switalla, Joel E. Eastman, Brian J. Wallace, Jody L. Clasey and Haley C. Bergstrom
, 13 Thus, CP and AWC represent distinct parameters related to metabolic characteristics of the whole body and active muscle tissue, respectively. There is limited evidence on the contribution of specific body-composition characteristics (thigh cross-sectional area, whole-body fat percentage [%BF
Paul Comfort, Thomas Dos’Santos, Paul A. Jones, John J. McMahon, Timothy J. Suchomel, Caleb Bazyler and Michael H. Stone
(PF) and isometric rate of force development (RFD) during single-joint knee extension 8 , 9 and the isometric mid-thigh pull (IMTP). 10 , 11 In addition, these associations are stronger when RFD is calculated over longer epochs (eg, r = .57 at 30 ms [from onset of force production] compared with
Giovanna Ghiani, Sara Magnani, Azzurra Doneddu, Gianmarco Sainas, Virginia Pinna, Marco Caboi, Girolamo Palazzolo, Filippo Tocco and Antonio Crisafulli
BM and the fat mass. Arm muscular area, arm fat area (AFA), thigh muscle area (TMA), and thigh fat area were also measured using standard formulas ( Frisancho, 1990 ). The athlete filled a semiquantitative food-frequency questionnaire ( Fidanza et al., 1995 ) to assess his usual energy intake, both
Fábio J. Lanferdini, Rodrigo R. Bini, Bruno M. Baroni, Kelli D. Klein, Felipe P. Carpes and Marco A. Vaz
incremental test and a familiarization with the time-to-exhaustion test were performed. In the other sessions (days 2–5), cyclists performed time-to-exhaustion tests after application of different doses of LLLT (135, 270, or 405 J/thigh) or placebo at the knee-extensor muscles, in a randomized order (Figure
Darryn S. Willoughby
This study examined 12 wk of resistance training and cystoseim canariensis supplementation on serum levels of myostatin and follistatin-like related gene (FLRG) and muscle strength and body composition. Twenty-two untrained males were randomly assigned to a placebo (PLC) or myostatin binder (MYO) group in a double-blind fashion. Blood was obtained before and after 6 and 12 wk of training. PLC and MYO trained thrice weekly using 3 sets of 6 to 8 repetitions at 85% to 90% 1 repetition maximum. MYO ingested 1200 mg/d of cystoseim canariensis. Data were analyzed with 2-way ANOVA. After training, total body mass, fat-free mass, muscle strength, thigh volume/mass, and serum myostatin and FLRG increased for both groups (P < 0.05); however, there were no differences between groups (P > 0.05). Twelve wk of heavy resistance training and 1200 mg/d of cystoseim canariensis supplementation appears ineffective at inhibiting serum myostatin and increasing muscle strength and mass or decreasing fat mass.
Kenneth W. Kambis and Sarah K. Pizzedaz
Creatine monohydrate (CrH2O) supplementation has been demonstrated to increase skeletal muscle power output in men. However, its effect upon women is not as clearly defined. This study investigated the effect of oral creatine supplementation upon muscle function, thigh circumference, and body weight in women. Twenty-two consenting college-age women were assigned to 1 of 2 groups matched for dietary and exercise habits, phase of menstrual cycle, and fat-free mass (FFM). After familiarization with testing procedures, pretrial measures of muscle function (5 repetitions 60 deg · s−1 and 50 repetitions 180 deg · s−1) were conducted during maximal voluntary concentric contraction of the preferred quadriceps muscle using an isokinetic dynamometer. Subjects then ingested 0.5 g · kg−1 FFM of either CrH2O or placebo (one fourth dosage 4 times daily) in a double-blind design for 5 days. Resistance exercise was prohibited. After the ingestion phase was completed, all measures were repeated at the same time of day as during pretrials. Statistical analysis revealed time to peak torque in quadriceps extension decreased from pre-test values of 255 ± 11 ms (mean ± SEM) to post-test values of 223 ± 3 ms; average power in extension increased from 103 ± 7 W pre-test to 112 ± 7 W post-test; and, during flexion, average power increased from 59 ± 5 W pre-test to 65 ± 5 W post-test in the creatine group as compared to controls (p ≤ .05). FFM, percent body fat, mid-quadriceps circumference, skinfold thickness of the measured thigh, and total body weight did not change for both groups between trials. We conclude that CrH2O improves muscle performance in women without significant gains in muscle volume or body weight.
Matthew R. Nelson, Robert K. Conlee and Allen C. Parcell
In Delayed Onset Muscle Soreness (DOMS), muscles become sore 24 to 48 hours after eccentric and unaccustomed activity. Fiber stiffness, due to decreased muscle glycogen, may predispose muscle to greater damage during eccentric exercise. This study sought to determine if inadequate carbohydrate intake following a protocol to decrease muscle glycogen would increase DOMS after 15 min of downhill running. Thirty-three male subjects (age, 18–35 years) were randomized into 3 groups for testing over a 7-day period. The depletion (DEP) group (n = 12) underwent a glycogen depletion protocol prior to a 15-min downhill run designed to induce DOMS. The repletion (FED) group (n = 10) underwent a glycogen depletion protocol followed by a carbohydrate repletion protocol (>80% CHO) prior to downhill running. The third (ECC) group (n = 11) performed only the downhill running protocol. Subjective muscle soreness, isometric force production, relaxed knee angle, and thigh circumference were measured pretreatment and on days 1, 2, 3, 4, and 6 post treatment. Subjective muscle soreness for all groups increased from 0 cm pretreatment to 3.05 ± 0.72 cm (on a 10-cm scale) on day 1 post treatment (p < .05). All groups were significantly different from baseline measurements until day 4 post treatment. Each group experienced a decline in isometric force from 281 ± 45 N pre-to 253 ± 13 N on day 1 post treatment (p < .05). The decrease in isometric force persisted in all groups for 4 days post treatment. Increases in thigh circumference and relaxed knee angle elevations in all 3 groups were statistically different (p < .05) from pretreatment until day 4. No differences were noted between groups for any of the parameters examined. In the current study, 15 min of downhill running is sufficient to cause DOMS with the associated functional and morphological changes; however, inadequate carbohydrate intake after a glycogen depleting exercise does not appear to exacerbate DOMS and the associated symptoms.