belt around the waist. Each monitor was previously initialized at 50-Hz frequency, and raw acceleration files were downloaded in Actilife 6 ® full software (ActiGraph LLC). The acceleration of gravity (9.81 m/s 2 = 1g) was subtracted, expressed as Euclidean Norm Minus One, and initial values of the
Erreka Gil-Rey, Kevin C. Deere, Sara Maldonado-Martín, Natalia Palacios-Samper, Agueda Azpeitia, Esteban M. Gorostiaga and Jon H. Tobias
Tom Kempton, Anita Claire Sirotic, Ermanno Rampinini and Aaron James Coutts
To describe the metabolic demands of rugby league match play for positional groups and compare match distances obtained from high-speed-running classifications with those derived from high metabolic power.
Global positioning system (GPS) data were collected from 25 players from a team competing in the National Rugby League competition over 39 matches. Players were classified into positional groups (adjustables, outside backs, hit-up forwards, and wide-running forwards). The GPS devices provided instantaneous raw velocity data at 5 Hz, which were exported to a customized spreadsheet. The spreadsheet provided calculations for speed-based distances (eg, total distance; high-speed running, >14.4 km/h; and very-highspeed running, >18.1 km/h) and metabolic-power variables (eg, energy expenditure; average metabolic power; and high-power distance, >20 W/kg).
The data show that speed-based distances and metabolic power varied between positional groups, although this was largely related to differences in time spent on field. The distance covered at high running speed was lower than that obtained from high-power thresholds for all positional groups; however, the difference between the 2 methods was greatest for hit-up forwards and adjustables.
Positional differences existed for all metabolic parameters, although these are at least partially related to time spent on the field. Higher-speed running may underestimate the demands of match play when compared with high-power distance—although the degree of difference between the measures varied by position. The analysis of metabolic power may complement traditional speed-based classifications and improve our understanding of the demands of rugby league match play.
Veerle Segers, Peter Aerts, Matthieu Lenoir and Dirk De Clercq
The purpose of this study was to examine the kinetics of the walk-to-run transition (WRT) and run-to-walk transition (RWT), when accelerating or decelerating across transition speed (a = 0.17 m·s−2). Nine women performed gait transitions on a 50-m-long walkway. Vertical ground reaction forces (GRFs) and the center of pressure (COP) were examined in the range from 3 steps before to 3 steps after transition in order to identify the possible occurrence of a transition process, in order to facilitate the actual realization of transition. The actual transition is realized in one step, during WRT and RWT. This transition step was characterized by an outlying vertical GRF and COP trajectory (deviating from walking and running). Despite this clear discontinuity, a transitional adaptation period (process) appeared in both transitions. In the WRT, transition was prepared and kinetic adaptations were found in the last step before transition. The RWT was pre- and “post”-pared and only completed during the first walking step after transition. Thus, the WRT and RWT are two distinct phenomena, with different kinetics.
William Abbott, Adam Brett, Emma Cockburn and Tom Clifford
Purpose: To examine whether consuming casein protein (CP) before sleep would enhance recovery after a nighttime soccer match in professional players. Methods: In a randomized, crossover design, 10 professional soccer players from the reserve squad of a team in the highest tier of English soccer consumed 40 g of CP or 40 g of carbohydrates (CON) 30 min presleep after a soccer match (kick off: 7 PM). To assess recovery, countermovement-jump height, reactive strength index, muscle soreness, and the adapted Brief Assessment of Mood (BAM+) Questionnaire were measured before and 12, 36, and 60 h after each match. Dietary intake across the testing period was also recorded. Results: There were unclear differences in external load in the matches and dietary intake between CON and CP. Casein protein had a most likely and likely beneficial effect on countermovement-jump recovery at 12 and 36 h postmatch (CP −1.6; ±1.2% vs CON −6.6; ±1.7%; −4.1; ±2.3% vs −0.4; ±1.1%, respectively). Reactive strength index recovery was most likely enhanced with CP at 12 and 36 h postmatch, and muscle soreness, as measured with a visual analog scale (in millimeters), was most likely greater in CON versus CP at 12 h postmatch (72; ±17 vs 42; ±20 mm). BAM+ was possibly lower in CON at 36 h postmatch but unaffected at other time points. Conclusions: Presleep CP accelerates functional recovery in professional soccer players and, therefore, provides a practical means of attenuating performance deficits in the days after a match.
Richard A. Schmidt
Daniel P. Muise, Sasho J. MacKenzie and Tara M. Sutherland
The increased awareness of concussion in sport has led to an examination of head impacts and the associated biomechanics that occur during these sporting events. The high rate of concussions in football makes it particularly relevant.1 The purpose of this study was to examine how frequently, and to what magnitude, Canadian University football players get hit in training camp and how this compares to practices and games in regular season. An ANOVA with repeated measures indicated that, on average, players were hit significantly more in games (45.2 hits) than training camp sessions (17.7 hits) and practices (8.0 hits), while training camp was associated with significantly more hits than practices (p < .001, η2 = .392). Multiple positional differences were found. In particular, significantly more hits were experienced by offensive linemen (36.7 hits) and defensive linemen (31.6 hits) compared with all other positions (p < .001, η2 = .247). Study outcomes determined players/positions most at risk for concussion due to head impacts, which is beneficial in forming concussion prevention and assessment strategies.
Hatice Mujde Ayık and Michael J. Griffin
.m.s.) average acceleration as one of the measures of the magnitude of a vibration. However, the discomfort of seated people exposed to whole-body vibration depends on the motion waveform, with greater sensitivity to random vibration than to sinusoidal vibration of the same frequency and the same r
Anamaria Laudet Silva Mangubat, Janet Hanwen Zhang, Zoe Yau-Shan Chan, Aislinn Joan MacPhail, Ivan Pui-Hung Au and Roy Tsz-Hei Cheung
postural stability. However, each step cycle subjects our eyes, and consequently our heads, to a changing vertical acceleration, which may lead to blurring of the visual field if head accelerations are not stabilized. 2 Each foot strike during gait sends a shock wave from our lower bodies and is
Yoshifumi Kijima, Ryoji Kiyama, Masaki Sekine, Toshiyo Tamura, Toshiro Fujimoto, Tetsuo Maeda and Tadasu Ohshige
methods ( Kobsar, Olson, Paranjape, Hadjistavropoulos, & Barden, 2014 ). A previous study analyzed the effect of age on acceleration of the trunk during walking and found that older adults had a lower gait regularity than did young adults ( Menz, 2003 ). Matsumoto et al. ( 2015 ) reported that regularity
Garrett M. Hester, Zachary K. Pope, Mitchel A. Magrini, Ryan J. Colquhoun, Alejandra Barrera-Curiel, Carlos A. Estrada, Alex A. Olmos and Jason M. DeFreitas
peak velocity (PV) and acceleration (sometimes termed rate of velocity development) of the knee extensors are negatively affected by age ( Thompson, Conchola, Palmer, & Stock, 2014 ; Wallace, Power, Rice, & Dalton, 2016 ). Similar to the effect of age on other rapid, time-sensitive measures (e