Heart rate variability and plasma nephrines in the evaluation of heat acclimatisation status.

PURPOSE: Heat adaptation (HA) is critical to performance and health in a hot environment. Transition from short-term heat acclimatisation (STHA) to long-term heat acclimatisation (LTHA) is characterised by decreased autonomic disturbance and increased protection from thermal injury. A standard heat tolerance test (HTT) is recommended for validating exercise performance status, but any role in distinguishing STHA from LTHA is unreported. The aims of this study were to (1) define performance status by serial HTT during structured natural HA, (2) evaluate surrogate markers of autonomic activation, including heart rate variability (HRV), in relation to HA status. METHODS: Participants (n = 13) were assessed by HTT (60-min block-stepping, 50% VO2peak) during STHA (Day 2, 6 and 9) and LTHA (Day 23). Core temperature (Tc) and heart rate (HR) were measured every 5 min. Sampling for HRV indices (RMSSD, LF:HF) and sympathoadrenal blood measures (cortisol, nephrines) was undertaken before and after (POST) each HTT. RESULTS: Significant (P < 0.05) interactions existed for Tc, logLF:HF, cortisol and nephrines (two-way ANOVA; HTT by Day). Relative to LTHA, POST results differed significantly for Tc (Day 2, 6 and 9), HR (Day 2), logRMSSD (Day 2 and Day 6), logLF:HF (Day 2 and Day 6), cortisol (Day 2) and nephrines (Day 2 and Day 9). POST differences in HRV (Day 6 vs. 23) were + 9.9% (logRMSSD) and - 18.6% (logLF:HF). CONCLUSIONS: Early reductions in HR and cortisol characterised STHA, whereas LTHA showed diminished excitability by Tc, HRV and nephrine measures. Measurement of HRV may have potential to aid real-time assessment of readiness for activity in the heat.

Low serum 25-hydroxyvitamin D is associated with increased risk of stress fracture during Royal Marine recruit training.

UNLABELLED: The aim of this study was to investigate vitamin D status and stress fracture risk during Royal Marine military training. Poor vitamin D status was associated with an increased risk of stress fracture. Vitamin D supplementation may help to reduce stress fracture risk in male military recruits with low vitamin D status. INTRODUCTION: Stress fracture is a common overuse injury in military recruits, including Royal Marine (RM) training in the UK. RM training is recognised as one of the most arduous basic training programmes in the world. Associations have been reported between serum 25-hydroxyvitamin D (25(OH)D) and risk of stress fracture, but the threshold of 25(OH)D for this effect remains unclear. We aimed to determine if serum 25(OH)D concentrations were associated with stress fracture risk during RM training. METHODS: We prospectively followed 1082 RM recruits (males aged 16-32 years) through the 32-week RM training programme. Troops started training between September and July. Height, body weight and aerobic fitness were assessed at week 1. Venous blood samples were drawn at weeks 1, 15 and 32. Serum samples were analysed for 25(OH)D and parathyroid hormone (PTH). RESULTS: Seventy-eight recruits (7.2 %) suffered a total of 92 stress fractures. Recruits with a baseline serum 25(OH)D concentration below 50 nmol L(-1) had a higher incidence of stress fracture than recruits with 25(OH)D concentration above this threshold (χ(2) (1) = 3.564, p = 0.042; odds ratio 1.6 (95 % confidence interval (CI) 1.0-2.6)). Baseline serum 25(OH)D varied from 47.0 ± 23.7 nmol L(-1) in February, to 97.3 ± 24.6 nmol L(-1) in July (overall mean 69.2 ± 29.2 nmol L(-1), n = 1016). There were weak inverse correlations between serum 25(OH)D and PTH concentrations at week 15 (r = -0.209, p < 0.001) and week 32 (r = -0.214, p < 0.001), but not at baseline. CONCLUSION: Baseline serum 25(OH)D concentration below 50 nmol L(-1) was associated with an increased risk of stress fracture. Further studies into the effects of vitamin D supplementation on stress fracture risk are certainly warranted.

Nutrition research in the military.

Military research performed in an operational environment involves mission-specific considerations. The Institute of Naval Medicine was tasked in 2008 by the Surgeon General to investigate the nutritional status of deployed British military personnel, and how this might affect body composition, physical fitness and operational capability. This paper briefly describes the logistic and technical issues specific to military research that were encountered by the study team, how these issues were overcome and how this research has influenced military practice.

Dietary supplement use among military personnel: international patterns and motivations for use.

Dietary supplements, products that contain one or more dietary ingredients, or their components, typically in a concentrated form, are often consumed for purported health and performance benefits. The frequency, forms and motivations for dietary supplement use may differ between civilian and military populations. The objective of this manuscript is to review patterns and trends in dietary supplement use in military personnel from the USA, France, the UK and Slovenia. Main findings indicate that dietary supplement use may be higher in military personnel as compared with civilian populations. Factors motivating dietary supplement use in military personnel include physical and cognitive performance, recovery, and the maintenance of body weight and composition, whereas civilian populations tend to be motivated by health and wellness. Commonly used dietary supplements in military populations, such as proteins and amino acids, may be associated with performance, body weight management and body composition. The relationship between dietary supplement use and the frequency and severity of adverse events, along with the potential benefits of dietary supplements, has not been carefully assessed in military populations and should be the focus of future studies.

Efficacy of neuromuscular exercises to promote movement quality and reduce musculoskeletal injury during initial military training in Royal Navy recruits.

INTRODUCTION: Musculoskeletal injuries (MSKIs) are a significant problem in the Royal Navy, contributing to 48% of all medical discharges from service between 2019 and 2020. The objective of the study was to assess efficacy of implementing a neuromuscular training intervention to improve movement quality and reduce MSKIs in Royal Navy recruits undertaking initial military training. METHODS: Neuromuscular training (pre-activation exercises, focusing on hip control) was integrated into the warm-up exercise regimen preceding physical training during the 10-week initial naval training (recruits) programme (January-March 2020) at HMS Raleigh (intervention group; n=162). A control group comprised (n=90) of recruits entering training from January 2019, who completed the standard warm-up programme prior to physical training. Movement control of the intervention group (intervention) was assessed before and after the 10-week programme using the Hip and Lower-Limb Movement Screen (HLLMS). Injury incidence proportion for both groups was determined retrospectively by review of medical notes. RESULTS: The control group's MSKI incidence proportion was 31%, which was higher (p<0.05) than the 8% reported in the intervention group. The majority of MSKIs were of the lower limb, and were reported in weeks 1, 2 and 5 of the 10-week training programme. Movement control, as assessed by the HLLMS score, improved (pretraining (week 1) and post-training (week 10) HLLMS score (mean (SD) pre: 11.2 (5.6); post: 8.4 (3.9); t=5.829, p<0.001) following the neuromuscular training in the intervention group but was not assessed in the control group. CONCLUSION: A neuromuscular control intervention was successfully implemented during the initial military training in the Royal Navy. The cohort undertaking the intervention demonstrated lower injury incidence compared with an equivalent cohort of recruits who undertook standard training. Movement control improved following the intervention, indicating better movement quality. Continued use of the programme may reduce military training attrition in the Royal Navy.

Musculoskeletal injuries in UK Service Personnel and the impact of in-theatre rehabilitation during Cold Weather Warfare training: Exercise CETUS 2020.

INTRODUCTION: The Royal Marines provide the lead Service for UK Defence Mountain and Cold Weather Warfare capability. This is the first prospective study addressing musculoskeletal injury rates sustained during Cold Weather Warfare training, with the aim of informing injury mitigation interventions and assist military medical planning with respect to delivering primary care rehabilitation in theatre. METHODS: All musculoskeletal injuries were surveyed by the Forward Rehabilitation Team (Nov 2019-Mar 2020) during a Cold Weather Deployment to Norway (Ex CETUS 2019/20). The frequency, nature of injury (new or recurrent), onset (sudden or gradual), cause, location and exercise/treatment outcome were recorded. RESULTS: Eleven per cent (n=136 cases) of the deployed population (n=1179) reported a musculoskeletal injury, which were mainly 'new' (62%), and with a 'sudden' onset (64%). Injury rate was 17.8 injuries per 10 000 personnel days. The majority of injuries occurred due to military training (88%), specifically during ski-related (61%) and load carriage (10%) activities.The average Service Person treated by the Forward Rehabilitation Team improved from 'injured with restricted duties' to 'fully fit', and with an improvement in their self-reported Musculoskeletal Health Questionnaire from 33 to 45 over an average of two rehabilitation sessions. One hundred and seventeen Service Personnel were able to continue on Ex CETUS with rehabilitation in theatre, thus negating the requirement for aeromedical evacuation for continuation of rehabilitation in the UK. Nineteen patients were unable to continue their Cold Weather Deployment due to the nature of their musculoskeletal injury and returned to the UK for continued care in firm base rehabilitation centres. CONCLUSION: This study identifies the nature, causation and injury location. It demonstrates the effectiveness of in-theatre rehabilitation and the ability to treat patients when deployed. Recommendations are presented to support strategies to mitigate musculoskeletal injury risk during future Cold Weather Warfare deployments to Norway.

Assessing injury risk in male and female Royal Navy recruits: does the Functional Movement Screen provide understanding to inform effective injury mitigation?

INTRODUCTION: Musculoskeletal injuries (MSKIs) are common during military and other occupational physical training programmes, and employers have a duty of care to mitigate this injury risk. MSKIs account for a high number of working days lost during initial military training, contribute to training attrition and impact training costs. Poorer movement quality may be associated with increased MSKI risk. METHODS: The present study evaluated the relationship between the Functional Movement Screen (FMS) Score, as a measure of movement quality, and injury risk in Royal Navy (RN) recruits. A cohort of 957 recruits was assessed using the FMS prior to the 10-week phase I training programme. Injury occurrence, time, type and severity were recorded prospectively during the training period. RESULTS: Total FMS Score was associated with injury risk (p≤0.001), where recruits scoring ≥13 were 2.6 times more likely to sustain an injury during training. However, FMS Score accounted for only 10% of the variance in injury risk (R2=0.1). Sex was the only additional variable to significantly affect the regression model. Mean FMS Scores for men (14.6±2.3) and women (14.4±2.4) were similar, but injury occurrence in women was 1.7 times greater than in men. Examining the influence of individual FMS movement tests on injury prediction did not improve the model, where those movements that significantly contributed to injury prediction only accounted for a small amount of the variance (R2=0.01). CONCLUSION: There was a weak relationship between FMS and injury risk in RN recruits. Evidence is provided that FMS score alone would not be appropriate to use as an injury prediction tool in military recruits.

Staphylococcus aureus colonization and acquisition of skin and soft tissue infection among Royal Marines recruits: a prospective cohort study.

OBJECTIVES: Skin and soft tissue infections (SSTIs) are a serious health issue for military personnel. Of particular importance are those caused by methicillin-resistant Staphylococcus aureus and Panton-Valentine leucocidin (PVL)-positive S. aureus (PVL-SA), as they have been associated with outbreaks of SSTIs. A prospective observational study was conducted in Royal Marine (RM) recruits to investigate the prevalence of PVL-SA carriage and any association with SSTIs. METHODS: A total of 1012 RM recruits were followed through a 32-week training programme, with nose and throat swabs obtained at weeks 1, 6, 15 and 32. S. aureus isolates were characterized by antibiotic susceptibility testing, spa typing, presence of mecA/C and PVL genes. Retrospective review of the clinical notes for SSTI acquisition was conducted. RESULTS: S. aureus colonization decreased from Week 1 to Week 32 (41% to 26%, p < 0.0001). Of 1168 S. aureus isolates, three out of 1168 (0.3%) were MRSA and ten out of 1168 (0.9%) PVL-positive (all MSSA) and 169 out of 1168 (14.5%) were resistant to clindamycin. Isolates showed genetic diversity with 238 different spa types associated with 25 multi-locus sequence type (MLST) clonal complexes. SSTIs were seen in 35% (351/989) of recruits with 3 training days lost per recruit. SSTI acquisition rate was reduced amongst persistent carriers (p < 0.0283). CONCLUSIONS: Nose and throat carriage of MRSA and PVL-SA was low among recruits, despite a high incidence of SSTIs being reported, particularly cellulitis. Carriage strains were predominantly MSSA with a marked diversity of genotypes. Persistent nose and/or throat carriage was not associated with SSTI acquisition. Putative person-to-person transmission within troops was identified based on spa typing requiring further research to confirm and explore potential transmission routes.

Asymptomatic group A Streptococcal throat carriage in Royal Marines recruits and Young Officers.

AIMS: A prospective observational study was conducted in Royal Marines (RM) recruits to investigate throat carriage of group A Streptococcus (GAS) and incidence of soft tissue infections. METHODS: 1012 RM recruits were followed through a 32-week training programme, with throat swabs being obtained in weeks 1, 6, 15, and 32. Alongside a separate cohort of 46 RM Young Officers (YO) undergoing training were sampled in parallel. RESULTS: Carriage of group A Streptococcus was detected in only 5/1012 (0.49%) recruits at the beginning of training and remained low throughout training. There was no association between GAS carriage and development of soft tissue infection. There was no carriage of GAS in the smaller YO cohort at the start of training, (0/46). At week 6, a surge in GAS carriage was detected in 8/46 (17%) YO, that could be ascribed to a cluster of GAS genotype emm83. CONCLUSIONS: Asymptomatic GAS carriage is very infrequent among young adults in England and this should be borne in mind when considering the relevance of a positive throat swab result in symptomatic patients or outbreaks. Despite low prevalence, there is however potential for GAS to rapidly and transiently disseminate among adults during outbreaks.

The gonadotrophic response of Royal Marines during an operational deployment in Afghanistan.

Military training has been associated with changes in the hypothalamic-pituitary-gonadal axis consistent with central hypogonadism. Often such changes have been associated with body mass loss, though sleep deprivation and other psychological stress may also contribute. The effects of deployment in a combat zone on the hypothalamic-pituitary-gonadal axis in military personnel are not known. The objective was to investigate the hypothalamic-pituitary-gonadal axis in male military personnel deployed in Afghanistan. Eighty-nine Royal Marines were investigated pre-deployment, following 3 months in Afghanistan and following 2 weeks mid-tour leave. Testosterone, sex hormone-binding globulin (SHBG), follicle-stimulating hormone (FSH), luteinising hormone (LH), 17-hydroxyprogesterone, androstenedione (AD) and insulin were assayed and body mass recorded. The results showed that body mass (kg) dropped from 83.2 ± 9.2 to 79.2 ± 8.2 kg during the first 3 months of deployment (p < 0.001). Total testosterone did not change, but SHBG increased (30.7 ± 9.7 vs. 42.3 ± 14.1 nmol/L, p < 0.001), resulting in a significant (p < 0.001) fall in calculated free testosterone (435.2 ± 138 vs. 375.1 ± 98 pmol/L). Luteinising hormone and FSH increased by 14.3% (p < 0.001) and 4.9% (p = 0.003) respectively. Free testosterone, SHBG, LH and FSH returned to baseline following 2 weeks of mid-tour leave. Androstenedione (AD) decreased by 14.5% (p = 0.024), and insulin decreased by 26% (p = 0.039), over the course of deployment. In this study of lean Royal Marines, free testosterone decreased during operational deployment to Afghanistan. There was no evidence to suggest major stress-induced central hypogonadism. We postulate that reduced body mass, accompanied by a decrease in insulin and AD synthesis, may have contributed to an elevated SHBG, leading to a decrease in free testosterone.

Elevated serum antioxidant capacity and plasma malondialdehyde concentration in response to a simulated half-marathon run.

PURPOSE AND METHODS: Indices of antioxidant status, membrane permeability, and lipid peroxidation were investigated in venous blood immediately before and after a simulated half-marathon run. In serum, these included the ability to scavenge free radicals (total antioxidant capacity, TAC), the concentration of uric acid (UA), and the activities of creatine kinase (CK) and beta-glucuronidase (beta G). The plasma concentration of malondialdehyde (MDA) was used as a marker of lipid peroxidation. Data were analyzed with paired t-tests. After a standardized warm-up, 17 trained male runners (mean +/- SD, age 31 +/- 4 yr, peak VO2 63.2 +/- 4.8 mL.kg-1.min-1) each completed a self-paced half-marathon run, on a motorized treadmill. Average exercise intensity was 77.1 +/- 1.0% peak VO2, with a performance time of 87.1 +/- 7.0 min. RESULTS: After exercise, elevations were observed in MDA from 1.48 +/- 0.39 mmol.L-1 to 1.65 +/- 0.32 mmol.L-1 (P < 0.05), TAC from 475 +/- 84 to 564 +/- 113 mmol Trolox Eq.L-1 (P < 0.0001), UA from 268 +/- 45 to 312 +/- 51 mmol.L-1 (P < 0.001), serum cortisol concentration from 339 +/- 95 to 557 +/- 157 nmol.L-1 (P < 0.01), CK from 98 +/- 67 to 133 +/- 89 IU.L-1 (P < 0.0001), and beta G from 15.39 +/- 5.34 to 17.05 +/- 5.7 Sigma Units.mL-1 (P < 0.001). CONCLUSIONS: The rise in TAC did not prevent exercise-induced lipid peroxidation and muscle damage as both MDA and CK were elevated after exercise. This may indicate inadequacies in the antioxidant defense system during the half-marathon run.

Resting serum antioxidant status is positively correlated with peak oxygen uptake in endurance trained runners.

BACKGROUND: This study tested the hypothesis that the ability to scavenge free radicals in serum was compromised in trained runners. EXPERIMENTAL DESIGN: peak VO2, the ability to scavenge free radicals in serum and the plasma concentration of malondialdehyde (MDA) were assessed in 18 male runners. PARTICIPANTS: subject characteristics (mean +/- SEM) were height 1.77 +/- 0.01 m, mass 71.4 +/- 1.2 kg, age 31 +/- 1 years and weekly training distance 45 +/- 5 km.week-1. MEASURES: venous blood samples were collected at rest. Serum total antioxidant capacity (TAC) was determined using a chemiluminescent technique. This involved the oxidation of luminol, in a reaction catalysed by horseradish peroxidase. Serum antioxidant protection was quantified relative to a soluble vitamin E analogue (Trolox) and expressed as Trolox equivalents (Trolox Eq.). MDA was determined using a highly specific assay, using HPLC with fluorimetric detection. Peak VO2 was determined from expired gas measurements collected during an incremental running test on a motorised treadmill. Data were analysed using Pearson correlations. RESULTS: Serum TAC was 500 +/- 26 mumol Trolox Eq.l-1, with a plasma MDA concentration of 1.5 +/- 0.1 mmol.l-1 and serum urate concentration of 274 +/- 12 mmol.l-1. Peak VO2 was 63 +/- 1 ml.kg-1.min-1. Significant correlations were observed between peak VO2 and serum TAC (r = 0.365, p < 0.05); peak VO2 and serum urate (r = 0.463, p < 0.05) and serum urate and serum TAC (r = 0.807, p < 0.001). Plasma MDA and serum TAC were not significantly correlated (r = 0.026, p > 0.05). CONCLUSIONS: These data demonstrate that the ability to quench free radicals in serum in increased in relation to the maximum ability to consume oxygen, however this response does not appear to provide any additional protection against peroxidative damage at rest.

Intra- and interday reliability of voluntary and electrically stimulated isometric contractions of the quadriceps femoris.

The reliability of voluntary and electrically stimulated isometric contractions of m. quadriceps femoris of male participants (n=10; age 30±8years; height 1.79±0.05m; body mass 79.4±8.3kg) was investigated using ratio limits of agreement (LoA) on a time scale common to examine recovery from muscle damaging exercise. No systematic changes in reliability occurred over time (baseline versus 2, 24, 48, and 72h). Maximal voluntary contraction (MVC) and interpolated twitch technique (ITT) showed no mean bias (P>0.05) with 95% LoA of ±12.7 and ±5.4, respectively. Resting twitch and potentiated doublet peak force showed no mean bias (P>0.05). However, 95% LoA were smaller for the doublet (±13.9) than the twitch (±32.0). Twitch and doublet rates showed similar trends. Ratio of low (20Hz) to high (50Hz) frequency forces showed no mean bias (P>0.05) and 95% LoA of (±9.2). However, there was significant mean bias (P<0.05) and wider 95% LoA for peak force, contraction and relaxation parameters of the low and high frequency forces. In conclusion, MVC, ITT, potentiated doublet and the ratio of low to high frequency forces are recommended to most reliably examine functional muscle recovery between 2 and 72h after damaging exercise.

The absorption of orally supplied beta-alanine and its effect on muscle carnosine synthesis in human vastus lateralis.

Beta-alanine in blood-plasma when administered as A) histidine dipeptides (equivalent to 40 mg . kg(-1) bwt of beta-alanine) in chicken broth, or B) 10, C) 20 and D) 40 mg . kg(-1) bwt beta-alanine (CarnoSyn, NAI, USA), peaked at 428 +/- SE 66, 47 +/- 13, 374 +/- 68 and 833 +/- 43 microM. Concentrations regained baseline at 2 h. Carnosine was not detected in plasma with A) although traces of this and anserine were found in urine. Loss of beta-alanine in urine with B) to D) was <5%. Plasma taurine was increased by beta-alanine ingestion but this did not result in any increased loss via urine. Pharmacodynamics were further investigated with 3 x B) per day given for 15 d. Dietary supplementation with I) 3.2 and II) 6.4 g . d(-1) beta-alanine (as multiple doses of 400 or 800 mg) or III) L-carnosine (isomolar to II) for 4 w resulted in significant increases in muscle carnosine estimated at 42.1, 64.2 and 65.8%.

Carbohydrate intake and recovery from prolonged exercise.

The influence of increased carbohydrate intake on endurance capacity was investigated following a bout of prolonged exercise and 22.5 hrs of recovery. Sixteen male subjects were divided into two matched groups, which were then randomly assigned to either a control (C) or a carbohydrate (CHO) condition. Both groups ran at 70% VO2max on a level treadmill for 90 min or until volitional fatigue, whichever came first (T1), and 22.5 hours later they ran at the same % VO2max for as long as possible to assess endurance capacity (T2). During the recovery, the carbohydrate intake of the CHO group was increased from 5.8 (+/- 0.5) to 8.8 (+/- 0.1) g kg-1 BW. This was achieved by supplementing their normal diet with a 16.5% glucose polymer solution. An isocaloric diet was prescribed for the C group, in which additional energy was provided in the form of fat and protein. Run times over T1 did not differ between the groups. However, over T2 the run time of the C group was reduced by 15.57 min (p < 0.05), whereas those in the CHO group were able to match their T1 performance. Blood glucose remained stable throughout T1 and T2 in both groups. In contrast, blood lactate, plasma FFA, glycerol, ammonia, and urea increased. Thus, a high carbohydrate diet restored endurance capacity within 22.5 hrs whereas an isocaloric diet without additional carbohydrate did not.

The influence of a high carbohydrate intake during recovery from prolonged, constant-pace running.

The present study examined the influence of ingesting 3.0 g CHO . kg-1 body mass . 2 hr-1 after prolonged exercise on recovery and running capacity 4 hr later. Nine men and 8 women completed two trials in a counterbalanced design. Each trial consisted of a 90-min run on a level treadmill at 70% VO2 max (R1) followed by 4 hr recovery (REC) and a further exhaustive run at 70% VO2 max (R2). During REC, subjects ingested either two feedings of a 6.9% glucosepolymer (GP) solution (D trial) or two feedings of a 19.3% GP solution (C trial). There were no differences in mean (+/- SE) R2 run times between the C and D trials or between the male and female subjects. More stable blood glucose concentrations were maintained during REC in the C trial, such that blood glucose was elevated in the C trial in comparison with the D trial after 210 min of REC. It was concluded that increasing postexercise carbohydrate intake from 1.0 to 3.0 g CHO . kg-1 body mass . 2 hr-1 does not improve endurance capacity 1 hr later.

The influence of ingesting a carbohydrate-electrolyte beverage during 4 hours of recovery on subsequent endurance capacity.

Recovery from prolonged exercise involves both rehydration and replenishment of endogenous carbohydrate stores. The present study examined the influence of ingesting a carbohydrate-electrolyte (CE) solution following prolonged running, on exercise capacity 4 hr later. Twelve men and 4 women were divided into two matched groups, which were randomly assigned to either a control (P) or a carbohydrate (CHO) condition. Both groups ran at 70% of maximal oxygen uptake (VO2max) on a level treadmill for 90 min or until volitional fatigue (R1), and they ran at the same % VO2max to exhaustion 4 hr later to assess endurance capacity (R2). The CHO group ingested a 6.9% CE solution providing 1.0 g CHO.kg body weight-1 immediately post-R1 and again 2 hr later. The P group ingested equal volumes of a placebo solution. Run times (mean +/- SEM) for R1 did not differ between the groups (P 86.3 +/- 3.8 min; CHO 87.5 +/- 2.5 min). The CHO group ran 22.2 (+/- 3.5) min longer than the P group during R2 (P 39.8 +/- 6.1 min; CHO 62.0 +/- 6.2 min) (p < .05). Thus, ingesting a 6.9% carbohydrate-electrolyte beverage following prolonged, constant-pace running improves endurance capacity 4 hr later.

Effects of a training taper on tissue damage indices, serum antioxidant capacity and half-marathon running performance.

This study investigated the effects of a training taper on muscle damage indices and performance. Two matched groups of seven male runners each performed two self paced half-marathons on a motorised treadmill. After the first half-marathon one group maintained their normal weekly training volume, while the taper group progressively reduced weekly training volume by 85 %. Venous blood was drawn immediately before and after the first half-marathon. Subsequent samples were taken 7 days later, immediately before and after the second half-marathon. Serum samples were analysed for antioxidant capacity, urate concentration and creatine kinase activity (CK). The plasma concentration of malondialdehyde (MDA) was used as a marker of lipid peroxidation. There were no differences in running performance either between the first and second half-marathon within each group, or between groups (86.75 +/- 2.65 min and 87.67 +/- 2.87 min for the "normal training" group vs 85.62 +/- 2.81 min and 85.39 +/- 3.52 min for the "training taper" group). Serum antioxidant capacity and CK were increased over time (P < 0.05, ANOVA), with significant elevations after each half-marathon (P<0.025, t-test). Elevations in MDA attained significance for the first half-marathon (P < 0.05, t-test) when data for both subject groups were pooled. There were no differences in serum antioxidant capacity, or urate concentration between groups. Postexercise CK was lower following the training taper (149 +/- 22% baseline, for the training taper vs 269 +/- 55 % baseline for the normal training group, P<0.05, t-test). Despite evidence that the training taper reduced muscle damage, relative to the normal training group, half-marathon performance was not enhanced.