ORCID Profile
0000-0002-4197-2848
Current Organisation
Northumbria University
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Publisher: American Physiological Society
Date: 08-2018
Publisher: Elsevier BV
Date: 11-2013
DOI: 10.1016/J.JSAMS.2012.12.005
Abstract: This study examined distances covered at low (1-2 ms(-2)), moderate (2-3 ms(-2)) and high (>3 ms(-2)) acceleration (L(ACC), M(ACC) and H(ACC) respectively) and deceleration (L(DEC), M(DEC), and H(DEC) respectively) during competitive football games. Temporal and transient patterns of acceleration and deceleration were also examined. Observational, repeated measures. Thirty-six professional male professional footballers were monitored using a 10 Hz non-differential global positioning system (NdGPS). Match data was organised into six 15 min periods (P1: 1-15 min, P2: 16-30 min, P3: 31-45 min, P4: 46-60 min, P5: 61-75 min, and P6: 76-90 min) for analysis of temporal patterns, and into eighteen 5 min periods for analysis of transient patterns. ANOVA with Bonferroni post hoc tests were used to identify significant (p<0.05) differences between periods. Distance covered at L(ACC), M(ACC), H(ACC), L(DEC), M(DEC), and H(DEC) was 424±75 m, 242±25 m, 178±38 m, 365±54 m, 210±23 m and 162±29 m respectively. Between period decrements ranged from 8.0% to 13.2% from P1 to P3, 9.2% to 16.3% from P4 to P6, and from 14.9% to 21.0% from P1 to P6. Following PEAK H(ACC) (148% of mean 5 min H(ACC)), H(ACC) at 5POST was 10.4% lower than mean (p<0.01). Time-dependent reductions in distances covered suggest that acceleration and deceleration capability are acutely compromised during match play. Further, the occurrence of transient fatigue may be supported by the findings that HACC and HDEC performance following PEAK was approximately 10% lower than mean values.
Publisher: Elsevier BV
Date: 04-2008
DOI: 10.1016/J.RESP.2008.02.001
Abstract: We tested the hypothesis that priming exercise would speed V(O2) kinetics during treadmill running. Eight subjects completed a square-wave protocol, involving two bouts of treadmill running at 70% of the difference between the running speeds at lactate threshold (LT) and V(O2) max, separated by 6-min of walking at 4 km h(-1), on two occasions. Oxygen uptake was measured breath-by-breath and subsequently modelled using non-linear regression techniques. Heart rate and blood lactate concentration were significantly elevated prior to the second exercise bout compared to the first. However, V(O2) kinetics was not significantly different between the first and second exercise bouts (mean+/-S.D., phase II time constant, Bout 1: 16+/-3s vs. Bout 2: 16+/-4s V(O2) slow component litude, Bout 1: 0.24+/-0.10 L min(-1)vs. Bout 2: 0.20+/-0.12 L min(-1) mean response time, Bout 1: 34+/-4s vs. Bout 2: 34+/-6s P>0.05 for all comparisons). These results indicate that, contrary to previous findings with other exercise modalities, priming exercise does not alter V(O2) kinetics during high-intensity treadmill running, at least in physically active young subjects. We speculate that the relatively fast V(O2) kinetics and the relatively small V(O2) slow component in the control ('un-primed') condition negated any enhancement of V(O2) kinetics by priming exercise in this exercise modality.
Publisher: Georg Thieme Verlag KG
Date: 21-11-2014
Abstract: This study examined the acceleration demands associated with changing direction and the subsequent physiological consequences of acceleration during running at 3 submaximal speeds. 10 male professional footballers completed four 600 m running bouts at 3 speeds (2.50, 3.25 & 4.00 m·s(-1)). Each bout was in the format of either: i) 3 laps of a 200 m track (CON), ii) ten 60 m shuttles (S60), iii) twenty 30 m shuttles (S30), or iv) thirty 20 m shuttles (S20). Peak heart rate (HRPEAK), blood lactate concentration (BLa) and RPE (Borg CR-10) were recorded for each bout. A single change of direction required 1.2, 1.5 and 2.0 s of acceleration at running speeds of 2.50, 3.25 and 4.00 m s(-1) respectively. An increase in time spent accelerating produced a linear increase in BLa (r=0.43-0.74) and RPE (r=0.81-0.93) at all speeds. Acceleration increases linearly with change of direction frequency during submaximal shuttle running. Increased time spent accelerating elicits proportional increases in perceived exertion, BLa and HRPEAK. The current study further underlines the need to consider acceleration when quantifying training load during activities involving numerous changes of direction.
Publisher: Elsevier BV
Date: 09-2014
DOI: 10.1016/J.JSAMS.2013.08.005
Abstract: To examine the validity and inter-unit reliability of 10 Hz GPS for measuring instantaneous velocity during maximal accelerations. Experimental. Two 10 Hz GPS devices secured to a sliding platform mounted on a custom built monorail were towed whilst sprinting maximally over 10 m. Displacement of GPS devices was measured using a laser s ling at 2000 Hz, from which velocity and mean acceleration were derived. Velocity data was pooled into acceleration thresholds according to mean acceleration. Agreement between laser and GPS measures of instantaneous velocity within each acceleration threshold was examined using least squares linear regression and Bland-Altman limits of agreement (LOA). Inter-unit reliability was expressed as typical error (TE) and a Pearson correlation coefficient. Mean bias ± 95% LOA during accelerations of 0-0.99 ms(-2) was 0.12 ± 0.27 ms(-1), decreasing to -0.40 ± 0.67 ms(-1) during accelerations >4 ms(-2). Standard error of the estimate ± 95% CI (SEE) increased from 0.12 ± 0.02 ms(-1) during accelerations of 0-0.99 ms(-2) to 0.32 ± 0.06 ms(-1) during accelerations >4 ms(-2). TE increased from 0.05 ± 0.01 to 0.12 ± 0.01 ms(-1) during accelerations of 0-0.99 ms(-2) and >4 ms(-2) respectively. The validity and reliability of 10 Hz GPS for the measurement of instantaneous velocity has been shown to be inversely related to acceleration. Those using 10 Hz GPS should be aware that during accelerations of over 4 ms(-2), accuracy is compromised.
Location: United Kingdom of Great Britain and Northern Ireland
No related grants have been discovered for Phil Hayes.