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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.

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.

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.

This investigation examined the effect of intramuscular iron injections on aerobic-exercise performance in iron-deficient women. Sixteen athletes performed a 10-min steady-state sub maximal economy test, a VO_2max test, and a timed test to exhaustion at VO_2max workload. Subjects were randomly assigned to an iron-supplemented group (IG) receiving intramuscular iron injections or to a placebo group (PG). Twenty days after the first injection, exercise and blood testing were repeated. A final blood test occurred on Day 28. Post supplementation, no differences were found between the groups’ sub maximal or maximal VO₂, heart rate, or blood lactate (P > 0.05). Time to exhaustion was increased in the IG (P < 0.05) but was not greater than that of the PG (P > 0.05). The IG’s serum ferritin (SF) was significantly increased on Days 20 and 28 (mean ± standard error: 19 ± 3 to 65 ± 11 to 57 ± 12 µg/L; P < 0.01), with a percentage change from baseline significantly greater than in the PG (P < 0.01). It was concluded that intramuscular iron injections can effectively increase SF without enhancing sub maximal or maximal aerobic-exercise performance in iron-depleted female athletes.

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.

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.

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 (Hb_mass) 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 Hb_mass. 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 Hb_mass treatment (p = .146) or interaction (p = .249) effects existed; however, a significant effect for sex indicated that Hb_mass was 140.85 g higher (p = .004) in males compared with females. Training load (p = .001) and dietary iron intake (p = .015) also affected Hb_mass. 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.