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.
Claire Rechichi, Brian Dawson and Carmel Goodman
Andrew Thomas, Brian Dawson and Carmel Goodman
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.
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.
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).
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.
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.
Matthew Finberg, Rebecca Braham, Carmel Goodman, Peter Gregory and Peter Peeling
To assess the efficacy of a 1-off electrostimulation treatment as a recovery modality from acute teamsport exercise, directly comparing the benefits to contrast water therapy.
Ten moderately trained male athletes completed a simulated team-game circuit (STGC). At the conclusion of exercise, participants then completed a 30-min recovery modality of either electrostimulation therapy (EST), contrast water therapy (CWT), or a passive resting control condition (CON). Twenty-four hours later, participants were required to complete a modified STGC as a measure of next-day performance. Venous blood samples were collected preexercise and 3 and 24 h postexercise. Blood samples were analyzed for circulating levels of interleukin-6 (IL-6) and C-reactive protein (CRP).
The EST trial resulted in significantly faster sprint times during the 24-h postrecovery than with CON (P < .05), with no significant differences recorded between EST and CWT or between CWT and CON (P > .05). There were no differences in IL-6 or CRP across all trials. Finally, the perception of recovery was significantly greater in the EST trial than in the CWT and CON (P < .05).
These results suggest that a 1-off treatment with EST may be beneficial to perceptual recovery, which may enhance next-day performance.
David B. Preen, Brian T. Dawson, Carmel Goodman, John Beilby and Simon Ching
This study attempted to determine the relationship between creatine (Cr) accumulation in human skeletal muscle and erythrocytes following Cr supplementation. If a strong relationship exists, a blood test might provide a practical, less invasive alternative than muscle biopsy for evaluating cellular Cr accumulation. Eighteen active, but not well-trained males were supplemented with Cr (4 × 5g/d) for 5 d. Muscle biopsies (vastus lateralis) were obtained pre- and post-loading and analyzed for Cr, phosphocreatine (PCr), and total Cr (TCr) content. Venous blood was also drawn at these times to determine erythrocyte Cr concentrations. Muscle Cr, PCr, and TCr concentrations were elevated (P < 0.05) by 39.8%, 7.5%, and 20.1% respectively following supplementation. Erythrocyte Cr concentrations were also elevated (P < 0.01) following the loading period, although to a greater relative degree than tissue concentrations (129.6%). Pre- and post-loading erythrocyte Cr concentrations were poorly and nonsignificantly correlated with that observed in skeletal muscle. Further, loading-mediated increases in erythrocyte Cr concentrations were poorly correlated with elevations in muscle Cr (r = 0.07), PCr (r = 0.06) or TCr (r = 0.04) concentrations. Erythrocyte Cr concentrations can be augmented by 5 d of Cr supplementation, however, this elevation does not reflect that observed in skeletal muscle obtained by muscle biopsy. Consequently, erythrocyte response to Cr loading is not a reliable measure of skeletal muscle Cr/TCr accumulation.
Daniel Jolley, Brian Dawson, Shane K. Maloney, James White, Carmel Goodman and Peter Peeling
This study investigated the influence of dehydration on urinary levels of pseudoephedrine (PSE) after prolonged repeated effort activity. Fourteen athletes performed a simulated team game circuit (STGC) outdoors over 120 min under three different hydration protocols: hydrated (HYD), dehydrated (DHY) and dehydrated + postexercise fluid bolus (BOL). In all trials, a 60 mg dose of PSE was administered 30 min before trial and at half time of the STGC. Urinary PSE levels were measured before drug administration and at 90 min postexercise. In addition, body mass (BM) changes and urinary specific gravity (USG), osmolality (OSM), creatinine (Cr), and pH values were recorded. No differences in PSE levels were found 90 min postexercise between conditions (HYD: 208.5 ± 116.5; DHY: 238.9 ± 93.5; BOL: 195.6 ± 107.3 μg·ml−1), although large variations were seen within and between participants across conditions (range: 33–475 μg·ml−1: ICC r = .03–0.16, p > .05). There were no differences between conditions in USG, OSM, pH or PSE/Cr ratio. In conclusion, hydration status did not influence urinary PSE levels after prolonged repeated effort activity, with ~70% of samples greater than the WADA limit (>150 μg.ml−1), and ~30% under. Due to the unpredictability of urinary PSE values, athletes should avoid taking any medications containing PSE during competition.
Brian Dawson, Carmel Goodman, Tanya Blee, Gary Claydon, Peter Peeling, John Beilby and Alex Prins
Non-anemic, iron depleted women were randomly assigned to an injection group (IG) or oral group (OG) to assess which method is more efficient for increasing iron stores over a short time period. IG received a course of 5 × 2 mL intramuscular injections over 10 d, and OG received one tablet daily for 30 d. Fourteen, 21 and 28 d after commencing supplementation, ferritin concentration in OG significantly increased from baseline (means ± standard error: 27 ± 3 to 40 ± 5 to 41 ± 5 to 41 ± 5 µg/L; P < 0.01). Similarly, on days 15, 20, and 28 post the first injection, ferritin concentration in IG significantly increased from baseline (means ± standard error: 20 ± 2 to 71 ± 17 to 63 ± 11 to 63 ± 7 µg/L; P < 0.01), and was also significantly greater than OG at day 15 and 28 (P < 0.05). Iron injections are significantly more effective (both in time and degree of increase) in improving ferritin levels over 30 d than oral tablets.
Peter Peeling, Brian Dawson, Carmel Goodman, Grant Landers, Erwin T. Wiegerinck, Dorine W. Swinkels and Debbie Trinder
Urinary hepcidin, inflammation, and iron metabolism were examined during the 24 hr after exercise. Eight moderately trained athletes (6 men, 2 women) completed a 60-min running trial (15-min warm-up at 75–80% HRpeak + 45 min at 85–90% HRpeak) and a 60-min trial of seated rest in a randomized, crossover design. Venous blood and urine samples were collected pretrial, immediately posttrial, and at 3, 6, and 24 hr posttrial. Samples were analyzed for interleukin-6 (IL-6), C-reactive protein (CRP), serum iron, serum ferritin, and urinary hepcidin. The immediate postrun levels of IL-6 and 24-hr postrun levels of CRP were significantly increased from baseline (6.9 and 2.6 times greater, respectively) and when compared with the rest trial (p ≤ .05). Hepcidin levels in the run trial after 3, 6, and 24 hr of recovery were significantly greater (1.7–3.1 times) than the pre- and immediate postrun levels (p ≤ .05). This outcome was consistent in all participants, despite marked variation in the magnitude of rise. In addition, the 3-hr postrun levels of hepcidin were significantly greater than at 3 hr in the rest trial (3.0 times greater, p ≤ .05). Hepcidin levels continued to increase at 6 hr postrun but failed to significantly differ from the rest trial (p = .071), possibly because of diurnal influence. Finally, serum iron levels were significantly increased immediately postrun (1.3 times, p ≤ .05). The authors concluded that high-intensity exercise was responsible for a significant increase in hepcidin levels subsequent to a significant increase in IL-6 and serum iron.
Rachel McCormick, Brian Dawson, Marc Sim, Leanne Lester, Carmel Goodman and Peter Peeling
The authors compared the effectiveness of two modes of daily iron supplementation in athletes with suboptimal iron stores: oral iron (PILL) versus transdermal iron (PATCH). Endurance-trained runners (nine males and 20 females), with serum ferritin concentrations <50 μg/L, supplemented with oral iron or iron patches for 8 weeks, in a parallel group study design. Serum ferritin was measured at baseline and fortnightly intervals. Hemoglobin mass and maximal oxygen consumption (
Rachel McCormick, Alex Dreyer, Brian Dawson, Marc Sim, Leanne Lester, Carmel Goodman and Peter Peeling
The authors compared the effectiveness of daily (DAY) versus alternate day (ALT) oral iron supplementation in athletes with suboptimal iron. Endurance-trained runners (nine males and 22 females), with serum ferritin (sFer) concentrations <50 μg/L, supplemented with oral iron either DAY or ALT for 8 weeks. Serum ferritin was measured at baseline and at fortnightly intervals. Hemoglobin mass (Hbmass) was measured pre- and postintervention in a participant subset (n = 10). Linear mixed-effects models were used to assess the effectiveness of the two strategies on sFer and Hbmass. There were no sFer treatment (p = .928) or interaction (p = .877) effects; however, sFer did increase (19.7 μg/L; p < .001) over the 8-week intervention in both groups. In addition, sFer was 21.2 μg/L higher (p < .001) in males than females. No Hbmass treatment (p = .146) or interaction (p = .249) effects existed; however, a significant effect for sex indicated that Hbmass was 140.85 g higher (p = .004) in males compared with females. Training load (p = .001) and dietary iron intake (p = .015) also affected Hbmass. Finally, there were six complaints of severe gastrointestinal side effects in DAY, but only one in ALT. In summary, both supplement strategies increased sFer in athletes with suboptimal iron status; however, the ALT approach was associated with lower incidence of gastrointestinal upset.