Showing papers by "Alun G. Williams published in 2007"
TL;DR: The gains in strength with HRST are undoubtedly due to a wide combination of neurological and morphological factors, although there is contrary evidence suggesting no change in cortical or corticospinal excitability.
Abstract: High-resistance strength training (HRST) is one of the most widely practiced forms of physical activity, which is used to enhance athletic performance, augment musculo-skeletal health and alter body aesthetics. Chronic exposure to this type of activity produces marked increases in muscular strength, which are attributed to a range of neurological and morphological adaptations. This review assesses the evidence for these adaptations, their interplay and contribution to enhanced strength and the methodologies employed. The primary morphological adaptations involve an increase in the cross-sectional area of the whole muscle and individual muscle fibres, which is due to an increase in myofibrillar size and number. Satellite cells are activated in the very early stages of training; their proliferation and later fusion with existing fibres appears to be intimately involved in the hypertrophy response. Other possible morphological adaptations include hyperplasia, changes in fibre type, muscle architecture, myofilament density and the structure of connective tissue and tendons. Indirect evidence for neurological adaptations, which encompasses learning and coordination, comes from the specificity of the training adaptation, transfer of unilateral training to the contralateral limb and imagined contractions. The apparent rise in whole-muscle specific tension has been primarily used as evidence for neurological adaptations; however, morphological factors (e.g. preferential hypertrophy of type 2 fibres, increased angle of fibre pennation, increase in radiological density) are also likely to contribute to this phenomenon. Changes in inter-muscular coordination appear critical. Adaptations in agonist muscle activation, as assessed by electromyography, tetanic stimulation and the twitch interpolation technique, suggest small, but significant increases. Enhanced firing frequency and spinal reflexes most likely explain this improvement, although there is contrary evidence suggesting no change in cortical or corticospinal excitability. The gains in strength with HRST are undoubtedly due to a wide combination of neurological and morphological factors. Whilst the neurological factors may make their greatest contribution during the early stages of a training programme, hypertrophic processes also commence at the onset of training.
1,086 citations
TL;DR: It is demonstrated that HR and RPE are only poorly related during the intense drills used in this study, and that HR underestimates the intensity of the 2v2 drill.
Abstract: Recent evidence supports the use of certain soccer drills for combined technical and physical training. Therefore, it is important to be able to accurately monitor training intensity during soccer drills intended for physical development to allow the optimization of training parameters. Twenty-eight professional soccer players were assessed for heart rate (HR) and rating of perceived exertion (RPE) responses to 5 commonly used soccer training drills (2v2 to 8v8 drills). The responses of both HR and RPE differed significantly (p < 0.05) between the drills, generally showing an elevated response to drills involving lower player numbers. However, the 2v2 drill showed a significantly (p < 0.05) lower HR response (mean +/- SD: 88.7 +/- 1.2% HRmax) than 3v3 (91.2 +/- 1.3% HRmax) and 4v4 drills (90.2 +/- 1.6% HRmax). There was no significant correlation between the HR and RPE responses to the various drills (r = 0.60, p = 0.200). This poor relationship is probably because during the 2v2 drill, RPE was higher than during any of the other 6 drills, whereas HR was only fourth highest of the 6 drills. This demonstrates that HR and RPE are only poorly related during the intense drills used in this study, and that HR underestimates the intensity of the 2v2 drill. Heart rate demonstrated lower intersubject variability (1.3-2.2%) than RPE (5.1-9.9%). However, unlike HR, Borg 15-point RPE appears to be a valid marker of exercise intensity over a wide range of soccer training drills by maintaining validity in all drills and demonstrating acceptable intersubject variability. A combination of both HR- and RPE-based training load calculations appears optimal for use in soccer training.
207 citations
TL;DR: A novel finding was that prior potentiation changed the shape of the twitch-voluntary force relationship, and it was recommended that post-contraction potentiated twitches be used, as the superimposed twitch on a high level contraction appears to be potentiated.
93 citations
TL;DR: The present study is the first to examine both variations in sprint distances and rest ratios simultaneously, and the findings may aid the design of repeated sprint training for soccer.
Abstract: The purpose of this study was to examine the physiological effects of different sprint repetition protocols on professional footballers. Of particular interest were the abilities of repeated sprint protocols to induce fatigue to an extent observed during competitive soccer. Six professional soccer players were assessed for fatigue rate and physiological responses of heart rate (HR), blood lactate (BLa), and rating of perceived exertion (RPE) during the performance of 4 repeated sprint drills, each totaling a sprint distance of 600 m. The 4 drills used 15- or 40-m sprints with 1:4 or 1:6 exercise: rest ratios. The 15-m sprint drill with 1:4 exercise:rest ratio induced the greatest fatigue (final sprint time 15% greater than initial sprint time) and greatest physiological responses. The 40-m sprint drill using a 1:4 exercise:rest ratio produced similar BLa and HR responses to the 15-m drill (13-14 mmol.L(-1) and 89% HRmax, respectively) but significantly lower RPE (mean +/- SD: 17.1 +/- 0.4 vs. 18.8 +/- 0.4, p < 0.05) and fatigue rates (11.1 vs. 15.0%, p < 0.01). Both sprint distance and exercise:rest ratio independently influenced fatigue rate, with the 15-m sprint distance and the 1:4 exercise:rest ratio inducing significantly (p < 0.01) greater fatigue than the 40-m sprint distance and the 1:6 exercise:rest ratio. The magnitude of fatigue during the 40- x 15-m sprint drill using a 1:6 exercise:rest ratio was 7.5%, which is close to the fatigue rate previously reported during actual soccer play. The present study is the first to examine both variations in sprint distances and rest ratios simultaneously, and the findings may aid the design of repeated sprint training for soccer.
59 citations
TL;DR: The physical training performed by the Regular soldiers and the Reserve soldiers seems to be of sufficient volume and intensity to maintain performance levels comparable with each other and equivalent new army recruits.
Abstract: The main objective of this research was to compare the materials handling ability, aerobic power, and body composition of fully trained Reserve and Regular male British Army soldiers (∼6–7 years of military experience). Twenty-one Reserve soldiers and 15 Regular soldiers completed fitness tests, including a maximal box lift to 1.45 m and a repetitive 22-kg box lift-and-carry test. There were no statistically significant differences (p > 0.05) between the two groups in any parameter measured. The performance levels observed in these fully trained soldiers (maximal box lift ∼63 kg, repetitive lift and carry ∼34 repetitions) were broadly comparable to those reported previously for new recruits. The physical training performed by the Regular soldiers (both within and beyond their military service) and the Reserve soldiers (predominantly outside their military duties) seems to be of sufficient volume and intensity to maintain performance levels comparable with each other and equivalent new army recruits.
12 citations
TL;DR: Upright row 1RM strength appears to be a useful tool in the prediction of box-lifting ability to approximately chest height for most adults, probably due to a close match between the muscle groups and contraction modes required during both tasks.
Abstract: Box-lifting ability is an important characteristic of military personnel. The purpose of this paper was to determine the usefulness of the upright row free weight exercise and simple anthropometric tests to predict maximal box-lifting performance that simulates the loading of military supply vehicles. Two groups of adults performed maximal box lifts to 1.4 m (study 1) and 1.7 m (study 2), respectively. All subjects were also tested for upright row 1 repetition maximum (1RM) strength, body mass, height, and body composition. In study 1, a remarkably good prediction of maximal box-lift performance to 1.4 m (42 +/- 12 kg) was obtained from a regression equation including the variables body mass, body composition, and upright row 1RM. Approximately 95% of the variation in 1.4-m box-lifting performance could be accounted for. In contrast, in study 2, only 80% of the variation in 1.7-m box-lifting performance (51 +/- 15 kg) could be accounted for by the best predictor equation. Upright row 1RM strength appears to be a useful tool in the prediction of box-lifting ability to approximately chest height for most adults, probably due to a close match between the muscle groups and contraction modes required during both tasks. Military or other organizations could use the data reported here to substitute simple anthropometry and a 1RM test of strength and for the direct assessment of 1.4-m box-lifting performance.
8 citations
2 citations