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Brian Dawson

Repeated-sprint ability (RSA) is now well accepted as an important fitness component in team-sport performance. It is broadly described as the ability to perform repeated short (~3–4 s, 20–30 m) sprints with only brief (~10–30 s) recovery between bouts. Over the past 25 y a plethora of RSA tests have been trialed and reported in the literature. These range from a single set of ~6–10 short sprints, departing every 20–30 s, to team-sport game simulations involving repeating cycles of walk-jog-stride-sprint movements over 45–90 min. Such a wide range of RSA tests has not assisted the synthesis of research findings in this area, and questions remain regarding the optimal methods of training to best improve RSA. In addition, how RSA test scores relate to player “work rate,” match performance, or both requires further investigation to improve the application of RSA testing and training to elite team-sport athletes.

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Laurence Houghton, Brian Dawson and Jonas Rubenson

Effects of prolonged running on Achilles tendon properties were assessed after a 60 min treadmill run and 140 min intermittent shuttle running (simulated cricket batting innings). Before and after exercise, 11 participants performed ramp-up plantar flexions to maximum-voluntary-contraction before gradual relaxation. Muscle-tendon-junction displacement was measured with ultrasonography. Tendon force was estimated using dynamometry and a musculoskeletal model. Gradients of the ramp-up force-displacement curves fitted between 0–40% and 50–90% of the preexercise maximal force determined stiffness in the low- and high-force-range, respectively. Hysteresis was determined using the ramp-up and relaxation force-displacement curves and elastic energy storage from the area under the ramp-up curve. In simulated batting, correlations between tendon properties and shuttle times were also assessed. After both protocols, Achilles tendon force decreased (4% to 5%, P < .050), but there were no changes in stiffness, hysteresis, or elastic energy. In simulated batting, Achilles tendon force and stiffness were both correlated to mean turn and mean sprint times (r = −0.719 to −0.830, P < .050). Neither protocol resulted in fatigue-related changes in tendon properties, but higher tendon stiffness and plantar flexion force were related to faster turn and sprint times, possibly by improving force transmission and control of movement when decelerating and accelerating.

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Daniel Tan, Brian Dawson and Peter Peeling

Purpose:

This study aimed to quantify the hemolytic responses of elite female football (soccer) players during a typical weekly training session.

Methods:

Ten elite female football players (7 field players [FPs] and 3 goalkeepers [GKs]) were recruited from the Australian National Women’s Premier League and asked to provide a venous blood sample 30 min before and at the immediate conclusion of a typical weekly training session. During this training session, the players’ movement patterns were monitored via a 5-Hz global positioning system. The blood samples collected during the training session were analyzed for iron status via serum ferritin (SF) analysis, and the hemolytic response to training, via serum free hemoglobin (Hb) and haptoglobin (Hp) measurement.

Results:

50% of the participants screened were found to have a compromised iron stores (SF <35 μg/L). Furthermore, the posttraining serum free Hb levels were significantly elevated (P = .011), and the serum Hp levels were significantly decreased (P = .005), with no significant differences recorded between the FPs and GKs. However, the overall distance covered and the movement speed were significantly greater in the FPs.

Conclusions:

The increases in free Hb and decreases in Hp levels provide evidence that a typical team-sport training session may result in significant hemolysis. This hemolysis may primarily be a result of running-based movements in FPs and/or the plyometric movements in GKs, such as diving and tackling.

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Claire Rechichi, Brian Dawson and Carmel Goodman

Some reports suggest variation in physiological responses and athletic performance, for female athletes at specific phases of the menstrual cycle. However, inconsistent findings are common due to the inappropriate verification of menstrual cycle phase, small subject numbers, high intra- and interindividual variability in estrogen and progesterone concentration, and the pulsatile secretion of these hormones. Therefore, the oral contraceptive (OC) cycle may provide a more stable environment in which to evaluate the acute effect of reproductive hormones on physiological variables and exercise performance. To date, most of the OC research has compared differences between OC use and nonuse, and few researchers have examined within-cycle effects of the OC. It is also apparent that OC use is becoming far more prevalent in athletes; hence the effect of the different exogenous and endogenous hormonal profiles on athletic performance should be investigated. Research to date identifies potential for variation in aerobic performance, anaerobic capacity, anaerobic power and reactive strength throughout an OC cycle. The purpose of this review is to present and evaluate the current literature on the physiology of exercise and athletic performance during the OC cycle.

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Andrew Thomas, Brian Dawson and Carmel Goodman

Purpose:

The purpose of the study was to determine the reliability of yo-yo intermittent recovery test (yo-yo) scores and their degree of association with a 20-m shuttle run (20MSR) and VO2max values.

Methods:

Subjects were elite (Australian Football League [AFL], n = 23), state-level (hockey, n = 15, and cricket, n = 27), and recreational team-sport players (n = 33). All performed a 20MSR and the yo-yo at either level 1 (recreational and state level) or level 2 (AFL). A recreational subgroup (n = 19) also performed a treadmill VO2max test.

Results:

Test–retest results found the yo-yo (levels 1 and 2) to be reliable (ICC = .86 to .95). The 20MSR and yo-yo level 1 scores correlated (P < .01) in the recreational (r = .81 to .83) and state-level groups (r = .84 to .86), and 20MSR and yo-yo level 2 scores, in the elite (r = .86) and recreational groups (r = .55 to .57). The VO2max and yo-yo level 1 scores in the recreational group correlated (P < .01, r = .87), but no association was found with yo-yo level 2 (r = .40 to .43, non significant).

Conclusions:

We conclude that level 1 (recreational and state level) and level 2 (elite) yo-yo scores were both strongly associated with 20MSR scores and VO2max (level 1: recreational subjects only). The yo-yo appears to measure aerobic fitness similarly to the 20MSR but may also be used as a field test of the ability to repeat high-intensity efforts.

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Kimberley Morrison, Rebecca A. Braham, Brian Dawson and Kym Guelfi

The effects of 8 wk of soft-sand (n = 19) and firm-surface walking (n = 19) on blood lipids, submaximal fitness (8-min walk at 4.5 km/hr), and leg strength in elderly (60+ yr), sedentary women were studied. Significant main time effects (p < .005) were found for blood lipids. The surface interaction effect for high-density lipoprotein approached significance (p = .052), with a tendency for higher levels in the sand group postintervention (p = .06). Neither group reported significant differences across time for submaximal oxygen consumption (p = .223), but a greater percentage reduction in heart-rate response to the 8-min walk was reported in the sand group (p = .016). Knee strength did not change in either group, whereas hip strength significantly improved in both groups (p = .0001), with larger effect sizes reported in the sand group. Overall, both groups showed improvements in blood lipids, fitness, and strength, with strength changes being slightly higher in the sand-walking group.

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Stephen Hill-Haas, Greg Rowsell, Aaron Coutts and Brian Dawson

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Frankie H.Y. Tan, Ted Polglaze and Brian Dawson

Purpose:

To compare the Multistage Shuttle Swim Test (MSST), Water Polo Intermittent Shuttle Test (WIST) and 5 × 200 m Incremental Swimming Test (IST) responses in elite female water polo players.

Methods:

Fourteen Australian Women’s National Water Polo Squad members performed the MSST and WIST, and 13 players from a National Water Polo League club performed the IST, MSST and WIST on separate occasions (no goalkeepers were involved). Peak heart rate, blood lactate and ratings of perceived exertion were obtained for all tests. Expired air was collected following all tests for the National League players.

Results:

The National Squad players scored significantly better (ie, distance covered) in the MSST and WIST than the National League players (effect sizes = 1.60 to 1.79, P < .001). The MSST and WIST scores were significantly correlated (r = .80 to 0.88, P < .001). The MSST scores were significantly correlated with peak oxygen uptake (VO2peak; mL·kg−1·min−1) obtained for all tests (r = .58 to 0.59, P < .05). In contrast, there were no significant correlations between the WIST scores and VO2peak obtained for any of the tests (r = .43 to 0.52, P > .05). Differences in VO2peak for the IST, MSST and WIST were nonsignificant (P > .05).

Conclusions:

The MSST and WIST can discriminate players of different competition standards. The MSST can be used to estimate a player’s aerobic fitness and peak heart rate. The WIST appears to better mimic the intermittent activity pattern of the game, but its application to female players, to assess maximal intermittent endurance swimming performance, requires further evaluation.

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David Preen, Brian Dawson, Carmel Goodman, John Beilby and Simon Ching

The purposes of this investigation were first to determine the impact of 3 different creatine (Cr) loading procedures on skeletal muscle total Cr (TCr) accumulation and, second, to evaluate the effectiveness of 2 maintenance regimes on retaining intramuscular TCr stores, in the 6 weeks following a 5-day Cr loading program (20 g · day−1). Eighteen physically active male subjects were divided into 3 equal groups and administered either: (a) Cr (4 X 5 g · day−1 X 5 days), (b) Glucose+Cr (1 g · kg−1 of body mass twice per day), or (c) Cr in conjunction with 60 min of daily muscular (repeated-sprint) exercise. Following the 5-day loading period, subjects were reassigned to 3 maintenance groups and ingested either 0 g · day−1, 2 g · day−1 or 5 g · day−1 of Cr for a period of 6 weeks. Muscle biopsy samples (vastus lateralis) were taken pre- and post-loading as well as post-maintenance and analyzed for skeletal muscle ATP, phosphocreatine (PCr), Cr, and TCr concentrations. Twenty-four hour urine samples were collected for each of the loading days and last 2 maintenance days, and used to determine whole body Cr retention. Post-loading TCr stores were significantly (p < .05) increased in all treatment conditions. The Glucose+Cr condition produced a greater elevation (p < .05) in TCr concentrations (25%) than the Cr Only (16%) or Exercise+Cr (18%) groups. Following the maintenance period, muscle TCr stores were still similar to post-loading values for both the 2 g · day−1 and 5 g · day−1 conditions. Intramuscular TCr values for the 0 g · day−1 condition were significantly lower than the other conditions after the 6-week period. Although not significantly different from pre-loading concentrations, muscle TCr for the 0 g · day−1 group had not fully returned to baseline levels at 6 weeks post-loading. The data suggests that Glucose+Cr (but with a much smaller glucose intake than currently accepted) is potentially the most effective means of elevating TCr accumulation in human skeletal muscle. Furthermore, after 5 days of Cr loading, elevated muscle TCr concentrations can be maintained by the ingestion of small daily Cr doses (2-5 g) for a period of 6 weeks and that TCr concentrations may take longer than currently accepted to return to baseline values after such a Cr loading regime.

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Ted Polglaze, Brian Dawson, Daniel J. Hiscock and Peter Peeling

Purpose:

To determine the relationship between distance covered and player load (PL: sum of accelerations in all 3 planes of movement) in hockey training and competition.

Methods:

Elite male hockey players (N = 24) wore player-tracking devices in 7 international matches and 7 training sessions. Players were arranged in 4 positional groups (strikers, attacking midfielders, defensive midfielders, defenders) in competition but had generic roles in training. Relationships between distance and PL were assessed in both absolute (m, AU) and relative (m/min, AU/min) terms and were compared between matches and training and between positions within matches, using the Fisher Z test.

Results:

In competition, the absolute distance–PL relationship was very large overall (r = .868), with no differences between positions. The relative distance–PL relationship was moderate overall (r = .486) and weaker in strikers than in defensive midfielders (Z = 1.785, P = .037) and defenders (Z = 1.690, P = .045). In training, the absolute distance–PL relationship was very large (r = .742), and large (r = .633) in relative terms. The relationship was stronger in competition than training for absolute values (Z = 2.824, P = .005) but not different for relative values.

Conclusions:

The strong relationship between these variables suggests that PL in hockey is mostly accumulated through running and other locomotor actions, such that PL is not effective in quantifying other activities (evasion, low stance) that contribute to physiological demands, particularly in training.