Phil Hayes

Foot strike patterns and ground contact times during high-calibre middle-distance races

Abstract The aims of this study were to examine ground contact characteristics, their relationship with race performance, and the time course of any changes in ground contact time during competitive 800 m and 1500 m races. Twenty-two seeded, single-sex middle-distance races totalling 181 runners were filmed at a competitive athletics meeting. Races were filmed at 100 Hz. Ground contact time was recorded one step for each athlete, on each lap of their race. Forefoot and midfoot strikers had significantly shorter ground contact times than heel strikers. Forefoot and midfoot strikers had significantly faster average race speed than heel strikers. There were strong large correlations between ground contact time and average race speed for the womens events and men’s 1500 m (r = −0.521 to −0.623; P < 0.05), whereas the mens 800 m displayed only a moderate relationship (r = −0.361; P = 0.002). For each event, ground contact time for the first lap was significantly shorter than for the last lap, which might reflect runners becoming fatigued.

The Physiological Consequences of Acceleration During Shuttle Running

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.

Effect of pre-exercise stretching on repeat sprint performance

The purpose of this study was to investigate the effect of pre-exercise stretching on repeated sprint performance over 20 m. Eight participants completed three conditions, active static stretching (AS), dynamic stretching (DS) and control (CON), in a counterbalanced order. Each pre-exercise condition was preceded by a 3-min walk. After stretching, participants completed the first 15 min of the Loughborough intermittent shuttle test (LIST). All statistical comparisons are made using qualitative magnitude based inferences comparing the stretching condition with CON. The results show that AS has probably had no beneficial or disadvantageous effect on performance on the first 20-m sprint (positive 57%, trivial 27%, negative 16%). There appear to be no beneficial or negative effects with the use of AS on 20-m sprint performance halfway through the LIST (positive 31%, trivial 32%, negative 37%). After 15 min of the LIST, AS appeared to exert a negative effect on sprint performance with 20-m sprint slowing (positive 35%, trivial 0%, negative 65%). DS improved performance on the first sprint (positive 89%, trivial 9%, negative 16%). By the midpoint, the beneficial effects of DS on sprint performance appear equivocal (positive 53%, trivial 28%, negative 18%). In the last sprint DS appeared to have a positive effect on performance (positive 80%, trivial 0%, negative 20%). Sprint performance during a 15-min segment of the LIST appears to be enhanced with DS. By contrast, 20-m sprint performance declined over the 15 min after AS.

Test–retest reliability of isokinetic concentric knee extension and flexion

Isokinetic dynamometry, which is a useful tool for the assessment of muscular function, must have sufficient reliability to be certain that changes are due to experimental intervention. Isokinetic concentric knee extension and flexion measured with a range of dynamometers has high reliability, but differences in measured variables exist between different dynamometers. Therefore, the aim of this study was to determine the reliability of isokinetic concentric knee extension and flexion on a Cybex Norm. Following familiarisation, 14 participants (23±3 years; 171±9 cm; 65.9±9.6 kg) attended the laboratory on 3 separate occasions, separated by 1 week. On each visit, participants completed 6 maximal concentric knee extension/flexions at 1.05 rad/s on a Cybex Norm Isokinetic Dynamometer. Reliability was assessed using intraclass correlation coefficients (ICC) and group coefficients of variation (CV). CVs for peak torque were 4.0%, 5.1%, 4.9% and 4.5% for dominant quadriceps, nondominant quadriceps, dominant hamstrings and nondominant hamstrings, respectively. ICCs for peak torque of each measurement ranged from 0.82 to 0.97. The results demonstrate that the protocol and dynamometer used are reliable measures of concentric peak torque of the knee extensors and flexors, and are in line with other data examining isokinetic dynamometry.