Serum creatine kinase (CK) activity reflects muscle membrane disruption. Oestrogen has antioxidant and membrane stabilising properties, yet no study has compared the CK and muscle soreness (DOMS) response to unaccustomed exercise between genders when all menstrual phases are represented in women. Fifteen eumenorrhoeic women (early follicular, EF (n = 5); late follicular, LF (n = 5); mid-luteal, ML (n = 5) phase) and six men performed 20 min of downhill running (−10% gradient) at 9 km/h. Serum CK activity and visual analogue scale rating of perceived muscle soreness were measured before, immediately, 24-h, 48-h and 72-h after exercise. The 24-h peak CK response (relative to pre-exercise) was similar between women and men (mean change (95% confidence interval): 58.5 (25.2 to 91.7) IU/L; 68.8 (31.3 to 106.3) IU/L, respectively). However, serum CK activity was restored to pre-exercise levels quicker in women (regardless of menstrual phase) than men; after 48-h post exercise in women (16.3 (−4.4 to 37.0) IU/L; 56.3 (37.0 to 75.6) IU/L, respectively) but only after 72-h in men (14.9 (−14.8 to 44.6) IU/L). Parallel to the CK response, muscle soreness recovered by 72-h in men. Conversely, the women still reported muscle soreness at 72-h despite CK levels being restored by 48-h; delayed recovery of muscle soreness appeared mainly in EF and LF. The CK and DOMS response to downhill running is gender-specific. The CK response recovers quicker in women than men. The CK and DOMS response occur in concert in men but not in women. The DOMS response in women is prolonged and may be influenced by menstrual phase.

Objectives. The aim of this study was to determine whether the elevated plasma glucose oxidation rate (~ 1.8 g.min-1) in the latter stages of prolonged exercise in subjects in which hyperglycaemia (± 10 mmol.l-1) is maintained via a glucose clamp, improves 100 km cycling time-trial (TT) performance. Design. Seven endurance-trained male cyclists (22±4 yrs) participated in this randomised crossover trial. On two occasions, separated by 7 - 10 days, subjects performed a self-paced TT in the laboratory. During one TT blood glucose was maintained at a euglycaemic concentration of ± 5 mmol.l-1 (ETT) and during the other, at ±10 mmol.l-1 (HTT). Each TT was interspersed with 5 X 1 km high-intensity periods (HIP) and 4 X 4 km HIP, in an attempt to mimic the variable intensity of competitive road races. Subjects were instructed to complete the TT in the ‘fastest time possible', taking the 9 HIP (21 km) into consideration. Results. There were no significant differences between ETT and HTT in overall time (143:09±7:14 v. 142:23±7:16 min:s), mean power (275±39 v. 279±39 W) and heart rate (160±9 v. 158±11 beats.min-1). Conclusion. Time trial performance over 100 km is not improved by maintaining a hyperglycaemic (10 mmol.l-1) blood glucose concentration. South African Journal of Sports Medicine Vol. 19 (3) 2007: pp. 94-98

Swimrun was established in Sweden in 2006. In competition athletes alternate between running and swimming multiple times. It has grown from only being hosted in Sweden to now being a global sport. The swimrun race exposes athletes to environments that require a unique set of skills. For example, participants have to negotiate ocean currents and waves. The environmental conditions change between the runs and the swims. Athletes may be exposed to hot temperatures when running in wetsuits (25 ​°C and hotter) and cold water (colder than 16 ​°C) when swimming. This sudden change in environmental conditions imposes a poorly defined physiological stress on the participants. Research on the demands of swimrun is scarce. More research is needed to improve athlete safety during events. Also, research is needed to provide insight into enhancing training methods and performance.

Objectives. This study investigated the effects of prolonged use of a protein (casein hydrolysate) supplement on perceived muscle soreness and fatigue, in international level Sevens rugby players (n=23) during a pre-season training camp. Methods. A randomised, double-blind, placebo-controlled design was used. Players were assigned to a carbohydrate-only or an isocaloric carbohydrate and protein supplement and ingested the assigned supplement after each training session (17 field training sessions over a 23-day period). Before each training session a questionnaire and 10-point visual analogue scale was completed that assessed muscle soreness and muscle fatigue in the calf, hamstring, and quadriceps. Results. No significant differences were observed in leg fatigue in any of the muscle groups. However, muscle soreness was significantly lower in the experimental group in the quadriceps at Week 3, Day 5 (p=0.04) and calves at Week 4, Day 2 (p=0.02) and Day 3 (p=0.04). Additionally, no significant differences were found during the Heart rate Interval Monitoring System Test (p=0.350) used to determine training load recovery. Conclusion. The results suggest that prolonged use of a protein hydrolysate supplement may be beneficial in reducing muscle soreness, but not muscle fatigue, during periods of continuous high training loads. Keywords. Supplement, protein feeding, recovery

Elliptical trainers and steppers are proposed as useful exercise modalities in the rehabilitation of injured runners due to the reduced stress on muscles and joints when compared to running. This study compared the physiological responses to submaximal running (treadmill) with exercise on the elliptical trainer and stepper devices at three submaximal but identical workloads. Authors had 18 trained runners (male/female: N= 9/9, age: mean +/- SD = 23 +/- 3 years) complete randomized maximal oxygen consumption tests on all three modalities. Submaximal tests of 3 min were performed at 60%, 70%, and 80% of peak workload individually established for each modality. Breath-by-breath oxygen consumption, heart rate, fuel utilization, and energy expenditure were determined. The value of maximal oxygen consumption was not different between treadmill, elliptical, and stepper (49.3 +/- 5.3, 48.0 +/- 6.6, and 46.7 +/- 6.2 ml.min(-1).kg(-1), respectively). Both physiological measures (oxygen consumption and heart rate) as well as carbohydrate and fat oxidation differed significantly between the different exercise intensities (60%, 70%, and 80%) but did not differ between the treadmill, elliptical trainer, and stepper. Therefore, the elliptical trainer and stepper are suitable substitutes for running during periods when a reduced running load is required, such as during rehabilitation from running-induced injury.

An analysis of Comrades marathon records: A 2008 update