Predicting middle-distance track and cross-country performances of national and international level adolescent runners.

AbstractThis study evaluated the contribution of physiological data collected during laboratory testing in predicting race performances of trained junior middle-distance track (TK) and cross-country (XC) athletes. Participants performed a submaximal incremental ramp test, followed by an incremental test to exhaustion in a laboratory, with the results used to predict either 800 m TK, 1500 m TK or 4000-6000 m XC race performance. Twenty-eight participants (male (M), 15; female (F), 13) were analysed (age = 17 ± 2 years, height = 1.72 ± 0.08 m, body mass = 58.9 ± 8.9 kg). Performance times (min:s) for 800 m were: M, 1:56.55 ± 0:05.55 and F, 2:14.21 ± 0:03.89; 1500 m: M, 3:51.98 ± 0:07.35 and F 4:36.71 ± 0:16.58; XC: M (4900 ± 741 m), 16:00 ± 01:53; F (4628 ± 670 m), 17:41 ± 02:09. Stepwise regression analysis indicated significant contributions of speed at ⩒O2max (s⩒O2max), and heart rate maximum (HRmax) to the prediction of 800 m TK (F(2,15) = 22.51, p < 0.001, adjusted R2 = 0.72), s⩒O2max for 1500 m TK (F(1,13) = 36.65, p < 0.001, adjusted R2 = 0.72) and ⩒O2max, allometrically scaled to body mass and speed at lactate threshold (sLT) for XC (F(2,17) = 25.1, p < 0.001, adjusted R2 = 0.72). Laboratory-based physiological measures can explain 72% of the variance in junior TK and XC events, although factors that explain performance alter depending on the race distance and tactics. The factors determining performance in TK and XC events are not interchangeable.

Variability and physical demands of international seam bowlers in one-day and Twenty20 international matches across five years.

OBJECTIVES: To quantify and compare the match demands and variability of international One-Day (ODI) with Twenty20 (T20) cricket matches and to compare ODI match demands when competing home and away. DESIGN: Single cohort, longitudinal observation. METHODS: Thirteen international male seam bowlers across 204matches (ODI=160; T20=44) were investigated over five-years (2015-2019). Using global positioning sensors and accelerometers, physical demands were quantified using distance covered at different velocities and the number of entries into high and low intensity acceleration and deceleration bands. Variability was quantified using coefficient of variation (CV) and smallest worthwhile change. RESULTS: Significantly greater (p<0.05) match demands were found for all physical variables relative to minutes played for T20 against ODI matches, except for distance covered 20-25kmh-1 which was greater for ODI. Distance covered between 0-7km∙h-1 showed no significance difference (p=0.60). The number of moderate decelerations (2-4m∙s2) were greater (p=0.04) away compared to home in ODI. All other variables showed no significance. Relative to minutes played, decelerations ≤4m∙s2 (within-player ODI CV=75.5%. T20=72.0%) accelerations >4m∙s2 (within-player ODI CV=79.2%. T20 CV=77.2%. Between-player ODI CV=84.7%. T20=38.8%) and distance covered >25kmh-1 (within-player ODI CV=65.5%. T20=64.1%) showed the greatest variability. CONCLUSIONS: Players are exposed to different physical demands in ODI Vs T20 matches, but not for home Vs away ODI matches. Practitioners should be aware of the large variability in high-speed/intensity accelerations and decelerations across matches.

A comparison of two global positioning system devices for team-sport running protocols.

The comparability and reliability of global positioning system (GPS) devices during running protocols associated with team-sports was investigated. Fourteen moderately-trained males completed 690 m of straight-line movements, a 570 m change of direction (COD) course and a 642.5 m team-sport simulated circuit (TSSC); on two occasions. Participants wore a FieldWiz GPS device and a Catapult MinimaxX S4 10-Hz GPS device. Typical error of measurement (TE) and coefficient of variation (CV%) were calculated between GPS devices, for the variables of total distance and peak speed. Reliability comparisons were made within FieldWiz GPS devices, between sessions. Small TE were observed between FieldWiz and Catapult GPS devices for total distance and peak speed during straight-line (16.9 m [2%], 1.2 km·h-1 [4%]), COD (31.8 m [6%], 0.4 km·h-1 [2%]) and TSSC protocols (12.9 m [2%], 0.5 km·h-1 [2%]), respectively, with no significant mean bias (p > 0.05). Small TE were also observed for the FieldWiz GPS device between sessions (p > 0.05) for straight-line (9.6 m [1%], 0.2 km·h-1 [1%]), COD (12.8 m [2%], 0.2 km·h-1 [1%]) and TSSC protocols (6.9 m [1%], 0.6 km·h-1 [2%]), respectively. Data from the FieldWiz GPS device appears comparable to established devices and reliable across a range of movement patterns associated with team-sports.

CAERvest® - a novel endothermic hypothermic device for core temperature cooling: safety and efficacy testing.

INTRODUCTION: Cooling of the body is used to treat hyperthermic individuals with heatstroke or to depress core temperature below normal for neuroprotection. A novel, chemically activated, unpowered cooling device, CAERvest®, was investigated for safety and efficacy. METHODS: Eight healthy male participants (body mass 79.9 ± 1.9 kg and body fat percentage 16.1 ± 3.8%) visited the laboratory (20 °C, 40% relative humidity) on four occasions. Following 30-min rest, physiological and perceptual measures were recorded. Participants were then fitted with the CAERvest® proof of concept (PoC) or prototype 1 (P1), 2 (P2) or 3 (P3) for 60 min. Temperature, cardiovascular and perceptual measures were recorded every 5 min. After cooling, the CAERvest® was removed and the torso checked for cold-related injuries. RESULTS: Temperature measures significantly (p < 0.05) reduced pre to post in all trials. Larger reductions in core and skin temperatures were observed for PoC (-0.36 ± 0.18 and -1.55 ± 0.97 °C) and P3 (-0.36 ± 0.22 and -2.47 ± 0.82 °C), compared with P1 and P2. No signs of cold-related injury were observed at any stage. CONCLUSION: This study demonstrates that the CAERvest® is an effective device for reducing body temperature in healthy normothermic individuals without presence of cold injury. Further research in healthy and clinical populations is warranted.