A biomechanical analysis of the heavy sprint-style sled pull and comparison with the back squat

This study compared the biomechanical characteristics of the heavy sprint-style sled pull and squat. Six experienced male strongman athletes performed sled pulls and squats at 70% of their 1RM squat. Significant kinematic and kinetic differences were observed between the sled pull start and squat at the start of the concentric phase and at maximum knee extension. The first stride of the heavy sled pull demonstrated significantly (

Zenith night sky light measurements at College, Alaska

For purposes of studying the character of time fluxuations in arctic night sky brightness, we have erected a photoelectric monitory system at the Ballaine’s Lake Field Station (latitude N64°52', longitude W147°49'). The unit was set in operation September 27, 1949, and dismounted June 6, 1950, when it became evident that further observations would be impossible due to lengthening days. Although no apparatus has been available by which the response curves of phototubes could be calibrated absolutely, a standard by which bright ness recordings of different phototubes can be reduced to approximate absolute values has been evolved. A limited investigation of a possible correlation between fluxuations in the intensity of upper atmospheric emissions and sporadic conditions in the ionosphere has been made.This work was supported in part by the CRPL, National Bureau of Standards. Order No. S-8097

TEST-RETEST RELIABILITY OF SELECTED ERGOMETER GRINDING PERFORMANCE MEASURES

Reliability of grinding performance on a custom-built ergometer was assessed using 18 highly trained America’s Cup sailors. Sixteen grinding conditions varied by load, deck heel (tilt), and grinding direction (forward or backward) were examined. Performance measures were peak power (W) and external work over five seconds (kJ). Statistics were difference in mean (Mdiff), standard error of measurement (SEM) and intra-class correlation coefficients (ICC). External work (SEM = 1.6-6.9%; ICC = 0.91-0.99) was more reliable than peak power (SEM = 1.3-9.6%; ICC = 0.84-0.99). Performance was more consistent when varied by load than by heel condition, and was most reliable in lighter load conditions. Within heel conditions, downhill-uphill tilt was more reliable than right-left tilt. Grinding direction did not appear to affect performance reliability

Maximal sprint speed in boys of increasing maturity

The purpose of this study was to examine the natural development of the mechanical features of sprint performance in relation to maturation within a large cohort of boys. Three hundred and thirty-six boys (11–15 years) were analyzed for sprint performance and maturation. Maximal speed, stride length (SL), stride frequency (SF), flight time (FT) and contact time (CT) were assessed during a 30m sprint. Five maturation groups (G1–5) were established based on age from peak height velocity (PHV) where G1=>2.5years pre-PHV, G2 = 2.49–1.5years pre-PHV, G3 = 1.49–0.5years pre-PHV, G4 = 0.49years pre- to 0.5years post-PHV and G5 = 0.51–1.5years post-PHV. There was no difference in maximal speed between G1, G2 and G3 but those in G4 and G5 were significantly faster (p .05). SF decreased while CT increased (both p .05) were observed for either variable between G3, G4 and G5. While G1–3 increased their SL, concomitant decreases in SF and increases in CT prevented them from improving maximal speed. Maximal sprint speed appears to develop around and post-PHV as SF and CT begin to stabilize, with increases in maximal sprint speed in maturing boys being underpinned by increasing SL

Pre-exercise carbohydrate or protein ingestion influences substrate oxidation but not performance or hunger compared with cycling in the fasted state

Nutritional intake can influence exercise metabolism and performance, but there is a lack of research comparing protein-rich pre-exercise meals with endurance exercise performed both in the fasted state and following a carbohydrate-rich breakfast. The purpose of this study was to determine the effects of three pre-exercise nutrition strategies on metabolism and exercise capacity during cycling. On three occasions, seventeen trained male cyclists (VO2peak 62.2 ± 5.8 mL·kg−1·min−1, 31.2 ± 12.4 years, 74.8 ± 9.6 kg) performed twenty minutes of submaximal cycling (4 × 5 min stages at 60%, 80%, and 100% of ventilatory threshold (VT), and 20% of the difference between power at the VT and peak power), followed by 3 × 3 min intervals at 80% peak aerobic power and 3 × 3 min intervals at maximal effort, 30 min after consuming a carbohydrate-rich meal (CARB; 1 g/kg CHO), a protein-rich meal (PROTEIN; 0.45 g/kg protein + 0.24 g/kg fat), or water (FASTED), in a randomized and counter-balanced order. Fat oxidation was lower for CARB compared with FASTED at and below the VT, and compared with PROTEIN at 60% VT. There were no differences between trials for average power during high-intensity intervals (367 ± 51 W, p = 0.516). Oxidative stress (F2-Isoprostanes), perceived exertion, and hunger were not different between trials. Overall, exercising in the overnight-fasted state increased fat oxidation during submaximal exercise compared with exercise following a CHO-rich breakfast, and pre-exercise protein ingestion allowed similarly high levels of fat oxidation. There were no differences in perceived exertion, hunger, or performance, and we provide novel data showing no influence of pre-exercise nutrition ingestion on exercise-induced oxidative stress

Comparison of Multiple Hop Test Kinematics Between Force-Platforms and Video Footage – A Cross Sectional Study

Background: Multiple hop performances have been assessed using force-platforms and motion-capture cameras. However, the accessibility of these technologies might be a hindering factor for many performance coaches. Currently, tablet devices are being used as alternatives to measure jumping and hopping performances. Objective: This study aimed to compare multiple hop kinematics using the Kinovea application with force-platforms, the gold standard. Methods: Using an observational cross-sectional study design, male athletes (n=44; age 20.1 ± 1.4 years) completed triple hops (3-Hop) and quintuple hops (5-Hop) on force-platforms while being filmed using an iPad. Ground contact time, flight time and total time were analysed using Kinovea and compared with the force platform data. Results: Statistical analysis showed a high level of agreement across all variables of interest but significant differences (flight time; -2.14 to -5.96 %, ground contact time; 4.89 to 5.83 %, total time; -0.37 to -0.58%) were observed across all variables of interest. A systematic bias for flight and ground contact times were seen for 3-Hop and 5-Hop. Conclusion: The use of iPad and Kinovea application can be used as a valid alternative to measure multiple hop kinematics when performance coaches do not have access to expensive force-platforms or motion-capture cameras

The influence of biological maturity on dynamic force–time variables and vaulting performance in young female gymnasts

Purpose: This cross-sectional study investigated dynamic force–time variables and vaulting performance in young female gymnasts of different maturity status. Methods: 120 gymnasts aged 5–14 years were sub-divided into maturity groupings using percent of predicted adult height (%PAH) attained. Participants performed three jumping protocols, the squat jump (SJ), countermovement jump (CMJ) and drop jump (DJ), before completing straight jump vaults that were recorded using two-dimensional video. Results: Jumping performance improved with biological maturity evidenced by the most mature gymnasts’ producing significantly more absolute force (P \u3c 0.05; all d \u3e 0.78), impulse (P \u3c 0.05; all d \u3e 0.75) and power (P \u3c 0.05; all d \u3e 0.91) than the least mature group, resulting in the greater jump heights (P \u3c 0.05; all d \u3e 0.70). While, no significant differences were observed in relative peak force across multiple tests, measures of relative peak power did significantly increase with maturity. Based upon regression analyses, maturation was found to influence vertical take-off velocity during vaulting, explaining 41% of the variance in each jumping protocol. Across all tests, the DJ was found to have the highest predictive ability of vaulting vertical take-off velocity, explaining 55% of the total variance. Conclusion: Biological maturation impacts jump height and underpinning mechanical variables in young female gymnasts. Vaulting vertical take-off velocity appears to be influenced by maturation and various dynamic force–time variables, particularly those during DJ, which had the highest explained total variance