Justin Keogh

Possible stimuli for strength and power adaptation: acute hormonal responses

The metabolic response to resistance exercise, in particular lactic acid or lactate, has a marked influence upon the muscular environment, which may enhance the training stimulus (e.g. motor unit activation, hormones or muscle damage) and thereby contribute to strength and power adaptation. Hypertrophy schemes have resulted in greater lactate responses (%) than neuronal and dynamic power schemes, suggesting possible metabolic-mediated changes in muscle growth. Factors such as age, sex, training experience and nutrition may also influence the lactate responses to resistance exercise and thereafter, muscular adaptation. Although the importance of the mechanical and hormonal stimulus to strength and power adaptation is well recognised, the contribution of the metabolic stimulus is largely unknown. Relatively few studies for example, have examined metabolic change across neuronal and dynamic power schemes, and not withstanding the fact that those mechanisms underpinning muscular adaptation, in relation to the metabolic stimulus, remain highly speculative. Inconsistent findings and methodological limitations within research (e.g. programme design, sampling period, number of samples) make interpretation further difficult. We contend that strength and power research needs to investigate those metabolic mechanisms likely to contribute to weight-training adaptation. Further research is also needed to examine the metabolic responses to different loading schemes, as well as interactions across age, sex and training status, so our understanding of how to optimise strength and power development is improved.

The Role of Biomechanics in Maximising Distance and Accuracy of Golf Shots

AbstractGolf biomechanics applies the principles and technique of mechanics to the structure and function of the golfer in an effort to improve golf technique and performance. A common recommendation for technical correction is maintaining a single fixed centre hub of rotation with a two-lever one-hinge moment arm to impart force on the ball. The primary and secondary spinal angles are important for conservation of angular momentum using the kinetic link principle to generate high club-head velocity. When the golfer wants to maximise the distance of their drives, relatively large ground reaction forces (GRF) need to be produced. However, during the backswing, a greater proportion of the GRF will be observed on the back foot, with transfer of the GRF on to the front foot during the downswing/acceleration phase. Rapidly stretching hip, trunk and upper limb muscles during the backswing, maximising the X-factor early in the downswing, and uncocking the wrists when the lead arm is about 30° below the horizontal will take advantage of the summation of force principle. This will help generate large angular velocity of the club head, and ultimately ball displacement. Physical conditioning will help to recruit the muscles in the correct sequence and to optimum effect. To maximise the accuracy of chipping and putting shots, the golfer should produce a lower grip on the club and a slower/shorter backswing. Consistent patterns of shoulder and wrist movements and temporal patterning result in successful chip shots. Qualitative and quantitative methods are used to biomechanically assess golf techniques. Two- and three-dimensional videography, force plate analysis and electromyography techniques have been employed. The common golf biomechanics principles necessary to understand golf technique are stability, Newton’s laws of motion (inertia, acceleration, action reaction), lever arms, conservation of angular momentum, projectiles, the kinetic link principle and the stretch-shorten cycle. Biomechanics has a role in maximising the distance and accuracy of all golf shots (swing and putting) by providing both qualitative and quantitative evidence of body angles, joint forces and muscle activity patterns. The quantitative biomechanical data needs to be interpreted by the biomechanist and translated into coaching points for golf professionals and coaches. An understanding of correct technique will help the sports medicine practitioner provide sound technical advice and should help reduce the risk of golfing injury.

Possible Stimuli for Strength and Power Adaptation

A great deal of literature has investigated the effects of various resistance training programmes on strength and power changes. Surprisingly, however, our understanding of the stimuli that affect adaptation still remains relatively unexplained. It is thought that strength and power adaptation is mediated by mechanical stimuli, that is the kinematics and kinetics associated with resistance exercise (e.g. forces, contraction duration, power and work), and their interaction with other hormonal and metabolic factors. However, the effect of different combinations of kinematic and kinetic variables and their contribution to adaptation is unclear. The mechanical response to single repetitions has been investigated by a number of researchers; however, it seems problematic to extrapolate the findings of this type of research to the responses associated with a typical resistance training session. That is, resistance training is typified by multiple repetitions, sets and exercises, rest periods of varying durations and different movement techniques (e.g. controlled and explosive). Understanding the mechanical stimuli afforded by such loading schemes would intuitively lead to a better appreciation of how various mechanical stimuli affect adaptation. It will be evident throughout this article that very little research has adopted such an approach; hence our understanding in this area remains rudimentary at best. One should therefore remain cognizant of the limitations that exist in the interpretation of research in this field. We contend that strength and power research needs to adopt a set kinematic and kinetic analysis to improve our understanding of how to optimise strength and power.

The use of physical fitness scores and anthropometric data to predict selection in an elite under 18 Australian rules football team

This study was conducted to determine if anthropometric and fitness testing scores can be used to discriminate between players that were selected or not selected in an elite Under 18 Australian Rules Football side. A training squad of 40 Australian Rules Football players was assessed on a battery of standard anthropometric and fitness tests just prior to the selection of the 30 man player roster for the upcoming season. Results showed that the selected players were significantly (P<0.05) taller and had greater upper body strength than non-selected players. A discriminant analysis was performed which predicted with an accuracy of 80% whether each player was successful or unsuccessful in gaining selection. This suggested that physical conditioning and anthropometric measurements do play an important part in determining selection in elite junior Australian Rules Football teams. However the discriminant function predicted non-selected players (90.9%) better than it predicted selected players (75.9%). Selected Under 18 players were found to be similar to the values reported for elite to sub-elite senior players on height, sit and reach, CMJ and perhaps aerobic fitness, but considerably less than the senior players on 3RM bench press and body mass.

The salivary testosterone and cortisol response to three loading schemes.

This aim of this study was to examine the free hormone (in saliva) responses to squat workouts performed by recreationally weight-trained males, using either a power (8 sets of 6 reps, 45% 1 repetition maximum [1RM], 3-minute rest periods, ballistic movements), hypertrophy (10 sets of 10 reps, 75% 1RM, 2-minute rest periods, controlled movements), or maximal strength scheme (6 sets of 4 reps, 88% 1RM, 4-minute rest periods, explosive intent). To determine the relative importance of the different training variables, these schemes were equated by workout duration with the power and strength schemes also equated by load volume. Salivary testosterone (T) and cortisol (C) both increased following the hypertrophy scheme (P < 0.05), with little to no hormonal change across the power and maximal strength schemes (P > 0.05). In general, the postexercise T and C responses to the hypertrophy scheme exceeded the other two schemes (P < 0.05). The greater volume of load lifted in the hypertrophy protocol over the same workout duration may explain the endocrine differences observed. The similar T and C responses to the power and maximal strength schemes (of equal volume) support such a view and suggest that differences in load intensity, rest periods, and technique are secondary to volume. Because the acute hormonal responses to resistance exercise contribute to protein metabolism, then load volume may be the most important workout variable activating the endocrine system and stimulating muscle growth.

Neuromuscular performance of elite rugby union players and relationships with salivary hormones

Crewther, BT, Lowe, T, Weatherby, RP, Gill, N, and Keogh, J. Neuromuscular performance of elite rugby union players and relationships with salivary hormones. J Strength Cond Res 23(7): 2046-2053, 2009-This study compared the neuromuscular performance (speed, power, strength) of elite rugby union players, by position, and examined the relationship between player performance and salivary hormones, by squad and position. Thirty-four professional male rugby players were assessed for running speed (10-m, 20-m or 30-m sprints), concentric mean (MP) and peak power (PP) during a 70-kg squat jump (SJ) and 50-kg bench press throw (BT), and estimated 1 repetition maximum (1RM) strength for a box squat (BS) and bench press (BP). Tests were performed on separate days with absolute and normalized (power and strength only) values computed. Saliva was collected before each test and assayed for testosterone (Sal-T) and cortisol (Sal-C). In absolute terms, the backs demonstrated greater speed and BT MP, whereas the forwards produced greater SJ PP and MP and BS 1RM (p < 0.01). However, BT, SJ and BS performances were no different when normalized for body mass in kg0.67 (p > 0.05). A comparison (absolute and normalized) of BT PP showed no positional differences (p > 0.05), whereas BP 1RM was greater for the forwards (p < 0.05). These results may be attributed to genetic and/or training factors relating to the positional demands of rugby. The Sal-T and/or Sal-C concentrations of players correlated to speed, power, and strength, especially for the backs (p < 0.05), thereby confirming relationships between neuromuscular performance and hormone secretion patterns. Based on these findings, it was suggested that training to increase whole-body and muscle mass might facilitate general performance improvements. Training prescription might also benefit from acute and chronic hormone monitoring to identify those individuals likely to respond more to hormonal change.

Changes in strength, power, and steroid hormones during a professional rugby union competition

Argus, CK, Gill, ND, Keogh, JWL, Hopkins, WG, and Beaven, CM. Changes in strength, power, and steroid hormones during a professional rugby union competition. J Strength Cond Res 23(5): 1583-1592, 2009-The purpose of this investigation was to assess changes in strength, power, and levels of testosterone and cortisol over a 13-week elite competitive rugby union season. Thirty-two professional rugby union athletes from a Super 14 rugby team (age, 24.4 ± 2.7 years; height, 184.7 ± 6.2 cm; mass, 104.0 ± 11.2 kg; mean ± SD) were assessed for upper-body and lower-body strength (bench press and box squat, respectively) and power (bench throw and jump squat, respectively) up to 5 times throughout the competitive season. Salivary testosterone and cortisol samples, along with ratings of perceived soreness and tiredness, were also obtained before each power assessment. An effect size of 0.2 was interpreted as the smallest worthwhile change. A small increase in lower-body strength was observed over the study period (8.5%; 90% confidence limits ±7.2%), whereas upper-body strength was maintained (−1.2%; ±2.7%). Decreases in lower-body power (−3.3%; ±5.5%) and upper-body power (−3.4; ±4.9%) were small and trivial. There were moderate increases in testosterone (54%; ±27%) and cortisol (97%; ±51%) over the competitive season, and the testosterone to cortisol ratio showed a small decline (22%; ±25%), whereas changes in perceived soreness and tiredness were trivial. Individual differences over the competitive season for all measures were mostly trivial or inestimable. Some small to moderate relationships were observed between strength and power; however, relationships between hormonal concentrations and performance were mainly trivial but unclear. Positive adaptation in strength and power may be primarily affected by cumulative training volume and stimulus over a competitive season. Greater than 2 resistance sessions per week may be needed to improve strength and power in elite rugby union athletes during a competitive season.

Effects of a short-term pre-season training programme on the body composition and anaerobic performance of professional rugby union players

Abstract Pre-season rugby training develops the physical requisites for competition and consists of a high volume of resistance training and anaerobic and aerobic conditioning. However, the effects of a rugby union pre-season in professional athletes are currently unknown. Therefore, the purpose of this investigation was to determine the effects of a 4-week pre-season on 33 professional rugby union players. Bench press and box squat increased moderately (13.6 kg, 90% confidence limits ±2.9 kg and 17.6 ± 8.0 kg, respectively) over the training phase. Small decreases in bench throw (70.6 ± 53.5 W), jump squat (280.1 ± 232.4 W), and fat mass (1.4 ± 0.4 kg) were observed. In addition, small increases were seen in fat-free mass (2.0 ± 0.6 kg) and flexed upper-arm girth (0.6 ± 0.2 cm), while moderate increases were observed in mid-thigh girth (1.9 ± 0.5 cm) and perception of fatigue (0.6 ± 0.4 units). Increases in strength and body composition were observed in elite rugby union players after 4 weeks of intensive pre-season training, but this may have been the result of a return to fitness levels prior to the off-season. Decreases in power may reflect high training volumes and increases in perceived of fatigue.

Biological movement variability during the sprint start: Performance enhancement or hindrance?

In the current study, we quantified biological movement variability on the start and early acceleration phase of sprinting. Ten male athletes aged 17–23 years (100-m personal best: 10.87 ± 0.36 s) performed four 10-m sprints. Two 250-Hz cameras recorded the sagittal plane action to obtain the two-dimensional kinematics of the block start and initial strides from subsequent manually digitized APAS motion analysis. Infra-red timing lights (80 Hz) were used to measure the 10-m sprinting times. The coefficient of variation (CV%) calculation was adjusted to separate biological movement variability (BCV%) from estimates of variability induced by technological error (SEM%) for each individual sprinter and measure. Pearsons product–moment correlation and linear regression analysis were used to establish relationships between measures of BCV% and 10-m sprint start performance (best 10-m time) or 10-m sprint start performance consistency (10-m time BCV%) using SPSS version 12.0. Measurement error markedly inflated traditional measures of movement variability (CV%) by up to 72%. Variability in task outcome measures was considerably lower than that observed in joint rotation velocities. Consistent generation of high horizontal velocity out of the blocks led to more stable and faster starting strides.

Retrospective Injury Epidemiology of One Hundred One Competitive Oceania Power Lifters: The Effects of Age, Body Mass, Competitive Standard, and Gender

The injury epidemiology of competitive power lifters was investigated to provide a basis for injury prevention initiatives in power lifting. Self-reported retrospective injury data for 1 year and selected biographical and training information were obtained via a 4-page injury survey from 82 men and 19 women of varying ages (Open and Masters), body masses (lightweight and heavyweight), and competitive standards (national and international). Injury was defined as any physical damage to the body that caused the lifter to miss or modify one or more training sessions or miss a competition. A total of 118 injuries, which equated to 1.2 ± 1.1 injuries per lifter per year and 4.4 ± 4.8 injuries per 1,000 hours of training, were reported. The most commonly injured body regions were the shoulder (36%), lower back (24%), elbow (11%), and knee (9%). More injuries appeared to be of a sudden (acute) (59%) rather than gradual (chronic) nature (41%). National competitors had a significantly greater rate of injury (5.8 ± 4.9 per 1,000 hours) than international competitors (3.6 ± 3.6 per 1,000 hours). The relative proportion of injuries at some body regions varied significantly as a function of competitive standard and gender. No significant differences in injury profile were seen between Open and Masters or between lightweight and heavyweight lifters. Power lifting appears to have a moderately low risk of injury, regardless of the lifters age, body mass, competitive standard, or gender, compared with other sports. Future research should utilize a prospective cohort or case-controlled design to examine the effect of a range of other intrinsic and extrinsic factors on injury epidemiology and to assess the effects of various intervention strategies.