Effects of acute alkalosis and acidosis on performance

Ingestion of agents that modify blood buffering action may affect high-intensity performance. Here we present a meta-analysis of the effects of acute ingestion of three such agents - sodium bicarbonate, sodium citrate and ammonium chloride - on performance and related physiological variables (blood bicarbonate, pH and lactate). A literature search yielded 59 useable studies with 188 observations of performance effects. To perform the mixed- model meta-analysis, all performance effects were converted into a percentage change in mean power and were weighted using standard errors derived from exact p-values, confidence limits (CLs) or estimated errors of measurement. The fixed effects in the meta-analytic model included the number of performance-test bouts (linear), test duration (log linear), blinding (yes/no), competitive status (athiete/nonathlete) and sex (male/female). Dose expressed as buffering mmoL/kg/body mass (BM) was included as a strictly proportional linear effect interacted with all effects except blinding. Probabilistic inferences were derived with reference to thresholds for small and moderate effects on performance of 0.5% and 1.5%, respectively. Publication bias was reduced by excluding study estimates with a standard error >2.7%. The remaining 38 studies and 137 estimates for sodium bicarbonate produced a possibly mod- erate performance enhancement of 1.7% (90% CL ± 2.0%) with a typical dose of 3.5mmoL/kg/BM (-0.3g/kgIBM) in a single 1-minute sprint, following blinded consumption by male athletes. In the 16 studies and 45 estimates for sodium citrate, a typical dose of l.SmmoL/kgIBM (-0.5gIkgJBM) had an unclear effect on performance of 0.0% (±1.3%), while the five studies and six estimates for ammonium chloride produced a possibly moderate impairment of 1.6% (±1.9%) with a typical dose of 5.5mmoL/kgIBM (-0.3glkg/BM). Study and subject characteristics had the following modifying small effects on the enhancement of performance with sodium bicarbonate: an increase of 0.5% (±0.6%) with a 1 mmoL/kg/BM increase in dose; an increase of 0.6% (±0.4%) with five extra sprint bouts; a reduction of 0.6% (±0.9%) for each 10-fold increase in test duration (e.g. 1-10 minutes); reductions of 1.1% (± 1 .1%) with nonathletes and 0.7% (±1.4%) with females. Unexplained variation in effects between research settings was typically ± 1.2%. The only noteworthy effects involving physiological variables were a small correlation between performance and pre-exercise increase in blood bicarbonate with sodium bi- carbonate ingestion, and a very large correlation between the increase in blood bicarbonate and time between sodium citrate ingestion and exercise. The approximate equal and opposite effects of sodium bicarbonate and am- monium chloride are consistent with direct performance effects of pH, but sodium citrate appears to have some additional metabolic inhibitory effect. Important future research includes studies of sodium citrate ingestion several hours before exercise and quantification of gastrointestinal symptoms with sodium bicarbonate and citrate. Although individual responses may vary, we recommend ingestion of 0.3-0.5 glkg/BM sodium bicarbonate to improve mean power by 1.7% (±2.0%) in high-intensity races of short duration. ABSTRACT FROM AUTHOR

Effect of caffeine supplementation on repeated sprint running performance

This study examined the effects of 6 mg-kg-1 caffeine ingestion in team-sport players (N.=10) on repeated-sprint running performance (5 sets of 6 x 20 m) and reaction times, 60 min after caffeine or placebo ingestion. Methods. Best single sprint and total set sprint times, blood lactate and simple and choice reaction times (RT) were measured. Total sprint times across sets 1, 3 and 5 (departure every 25 s) were significantly faster after caffeine (85.49±5.55 s) than placebo (86.98±5.78 s) (P<0.05). Similarly, total sprint times across sets 2 and 4 (departure every 60 s), were significantly faster after caffeine (55.99±3.64 s) than placebo (56.77±3.74 s) (P<0.05). Significantly higher blood lactates were recorded in caffeine compared to placebo after set 3 (13.1±1.2 vs 10.3±1.4 mmolL ') (P<0.05) and set 5 (13.1±1.3 vs 103±1.6 mmol-L"1) (P<0.01). There were no significant effects on simple or choice RT, although effect sizes suggested improved post-exercise times after caffeine. Caffeine ingestion 60 min prior to exercise can enhance repeated sprint running performance and is not detrimental to reaction times. [PUBLICATION ABSTRACT]

Effect of different protocols of caffeine intake on metabolism and endurance performance

Competitive athletes completed two studies of 2-h steady-state (SS) cycling at 70% peak O2 uptake followed by 7 kJ/kg time trial (TT) with carbohydrate (CHO) intake before (2 g/kg) and during (6% CHO drink) exercise. In Study A, 12 subjects received either 6 mg/kg caffeine 1 h preexercise (Precaf), 6 × 1 mg/kg caffeine every 20 min throughout SS (Durcaf), 2 × 5 ml/kg Coca-Cola between 100 and 120 min SS and during TT (Coke), or placebo. Improvements in TT were as follows: Precaf, 3.4% (0.2-6.5%, 95% confidence interval); Durcaf, 3.1% (-0.1-6.5%); and Coke, 3.1% (-0.2-6.2%). In Study B, eight subjects received 3 × 5 ml/kg of different cola drinks during the last 40 min of SS and TT: decaffeinated, 6% CHO (control); caffeinated, 6% CHO; decaffeinated, 11% CHO; and caffeinated, 11% CHO (Coke). Coke enhanced TT by 3.3% (0.8-5.9%), with all trials showing 2.2% TT enhancement (0.5-3.8%; P < 0.05) due to caffeine. Overall, 1) 6 mg/kg caffeine enhanced TT performance independent of timing of intake and 2) replacing sports drink with Coca-Cola during the latter stages of exercise was equally effective in enhancing endurance performance, primarily due to low intake of caffeine (∼1.5 mg/kg).

Improved 2000-meter rowing performance in competitive oarswomen after caffeine ingestion

Eight competitive oarswomen (age, 22 ± 3 years; mass, 64.4 ± 3.8 kg) performed three simulated 2,000-m time trials on a rowing ergometer. The trials, which were preceded by a 24-hour dietary and training control and 72 hours of caffeine abstinence, were conducted 1 hour after ingesting caffeine (6 or 9 mg · kg-1 body mass) or placebo. Plasma free fatty acid concentrations before exercise were higher with caffeine than placebo (0.67 ± 0.34 vs. 0.72 ± 0.36 vs. 0.30 ± 0.10 mM for 6 and 9 mg · kg-1caffeine and placebo, respectively; p < .05). Performance time improved 0.7% (95% confidence interval [CI] 0 to 1.5%) with 6 mg · kg-1 caffeine and 1.3% (95% CI 0.5 to 2.0%) with 9 mg · kg-1 caffeine. The first 500 m of the 2,000 m was faster with the higher caffeine dose compared with placebo or the lower dose (1.53 ± 0.52 vs. 1.55 ± 0.62 and 1.56 ± 0.43 min; p = .02). We concluded that caffeine produces a worthwhile enhancement of performance in a controlled laboratory setting, primarily by improving the first 500 m of a 2,000-m row.

Effects of ingesting low glycemic index carbohydrate food for the sahur meal on subjective, metabolic and physiological responses, and endurance performance in Ramadan fasted men

To investigate the effect of low glycemic index (LGI) carbohydrate meal on subjective, metabolic and physiological responses, and endurance performance in the Ramadan fasted state.

(1)H-NMR analysis of the human urinary metabolome in response to an 18-month multi-component exercise program and calcium-vitamin-D3 supplementation in older men

The musculoskeletal benefits of calcium and vitamin-D3 supplementation and exercise have been extensively studied, but the effect on metabolism remains contentious. Urine samples were analyzed by (1)H-NMR spectroscopy from participants recruited for an 18-month, randomized controlled trial of a multi-component exercise program and calcium and vitamin-D3 fortified milk consumption. It was shown previously that no increase in musculoskeletal composition was observed for participants assigned to the calcium and vitamin-D3 intervention, but exercise resulted in increased bone mineral density, total lean body mass, and muscle strength. Retrospective metabolomics analysis of urine samples from patients involved in this study revealed no distinct changes in the urinary metabolome in response to the calcium and vitamin-D3 intervention, but significant changes followed the exercise intervention, notably a reduction in creatinine and an increase in choline, guanidinoacetate, and hypoxanthine (p < 0.001, fold change > 1.5). These metabolites are intrinsically involved in anaerobic ATP synthesis, intracellular buffering, and methyl-balance regulation. The exercise intervention had a marked effect on the urine metabolome and markers of muscle turnover but none of these metabolites were obvious markers of bone turnover. Measurement of specific urinary exercise biomarkers may provide a basis for monitoring performance and metabolic response to exercise regimes.

MicroRNA-23a has minimal effect on endurance exercise-induced adaptation of mouse skeletal muscle.

Skeletal muscles contain several subtypes of myofibers that differ in contractile and metabolic properties. Transcriptional control of fiber-type specification and adaptation has been intensively investigated over the past several decades. Recently, microRNA (miRNA)-mediated posttranscriptional gene regulation has attracted increasing attention. MiR-23a targets key molecules regulating contractile and metabolic properties of skeletal muscle, such as myosin heavy-chains and peroxisome proliferator-activated receptor gamma, coactivator 1 alpha (PGC-1α). In the present study, we analyzed the skeletal muscle phenotype of miR-23a transgenic (miR-23a Tg) mice to explore whether forced expression of miR-23a affects markers of mitochondrial content, muscle fiber composition, and muscle adaptations induced by 4 weeks of voluntary wheel running. When compared with wild-type mice, protein markers of mitochondrial content, including PGC-1α, and cytochrome c oxidase complex IV (COX IV), were significantly decreased in the slow soleus muscle, but not the fast plantaris muscle of miR-23a Tg mice. There was a decrease in type IId/x fibers only in the soleus muscle of the Tg mice. Following 4 weeks of voluntary wheel running, there was no difference in the endurance exercise capacity as well as in several muscle adaptive responses including an increase in muscle mass, capillary density, or the protein content of myosin heavy-chain IIa, PGC-1α, COX IV, and cytochrome c. These results show that miR-23a targets PGC-1α and regulates basal metabolic properties of slow but not fast twitch muscles. Elevated levels of miR-23a did not impact on whole body endurance capacity or exercise-induced muscle adaptations in the fast plantaris muscle.

A randomised controlled trial investigating the effects of Mediterranean diet and aerobic exercise on cognition in cognitively healthy older people living independently within aged care facilities: The Lifestyle Intervention in Independent Living Aged Car

Background: The rapid ageing of the population is becoming an area of great concern, both globally and in Australia. On a societal level, the cost of supporting an ageing demographic, particularly with their associated medical requirements, is becoming an ever increasing burden that is only predicted to rise in the foreseeable future. The progressive decline in individuals' cognitive ability as they age, particularly with respect to the ever increasing incidence of Alzheimer's Disease (AD) and other cognitive complications, is in many respects one of the foundation stones of these concerns. There have been numerous observational studies reporting on the positive effects that aerobic exercise and the Mediterranean diet appear to have on improving cognitive ability. However, the ability of such interventions to improve cognitive ability, or even reduce the rate of cognitive ageing, has not been fully examined by substantial interventional studies within an ageing population. Methods: The LIILAC trial will investigate the potential for cognitive change in a cohort of cognitively healthy individuals, between the ages of 60 and 90 years, living in independent accommodation within Australian aged care facilities. This four-arm trial will investigate the cognitive changes which may occur as a result of the introduction of aerobic exercise and/or Mediterranean diet into individuals' lifestyles, as well as the mechanisms by which these changes may be occurring. Participants will be tested at baseline and 6 months on a battery of computer based cognitive assessments, together with cardiovascular and blood biomarker assessments. The cardiovascular measures will assess changes in arterial stiffness and central pulse pressures, while the blood measures will examine changes in metabolic profiles, including brain derived neurotrophic factor (BDNF), inflammatory factors and insulin sensitivity. Conclusion: It is hypothesised that exercise and Mediterranean diet interventions, both individually and in combination, will result in improvements in cognitive performance compared with controls. Positive findings in this research will have potential implications for the management of aged care, particularly in respect to reducing the rate of cognitive decline and the associated impacts both on the individual and the broader community.

Modulating exercise-induced hormesis: does less equal more?

Hormesis encompasses the notion that low levels of stress stimulate or upregulate existing cellular and molecular pathways that improve the capacity of cells and organisms to withstand greater stress. This notion underlies much of what we know about how exercise conditions the body and induces long-term adaptations. During exercise, the body is exposed to various forms of stress, including thermal, metabolic, hypoxic, oxidative, and mechanical stress. These stressors activate biochemical messengers, which in turn activate various signaling pathways that regulate gene expression and adaptive responses. Historically, antioxidant supplements, nonsteroidal anti-inflammatory drugs, and cryotherapy have been favored to attenuate or counteract exercise-induced oxidative stress and inflammation. However, reactive oxygen species and inflammatory mediators are key signaling molecules in muscle, and such strategies may mitigate adaptations to exercise. Conversely, withholding dietary carbohydrate and restricting muscle blood flow during exercise may augment adaptations to exercise. In this review article, we combine, integrate, and apply knowledge about the fundamental mechanisms of exercise adaptation. We also critically evaluate the rationale for using interventions that target these mechanisms under the overarching concept of hormesis. There is currently insufficient evidence to establish whether these treatments exert dose-dependent effects on muscle adaptation. However, there appears to be some dissociation between the biochemical/molecular effects and functional/performance outcomes of some of these treatments. Although several of these treatments influence common kinases, transcription factors, and proteins, it remains to be determined if these interventions complement or negate each other, and whether such effects are strong enough to influence adaptations to exercise.

Measuring and evaluating coaching performance using a 360° feedback process: a development and pilot study

 The research examined the development, design and use of 360° feedback in sports coaching. The results suggest that using outcomes in competition as a means of evaluating coaching performance overlooks many aspects of their work. 360° feedback is capable of providing a useful and insightful means of evaluating coaching performance.

Resistive simulated weightbearing exercise with whole body vibration reduces lumbar spine deconditioning in bed-rest

STUDY DESIGN: Randomized controlled trial. OBJECTIVE: Determine the effectiveness a resistive exercise countermeasure with whole-body vibration in relation to lumbo-pelvic muscle and spinal morphology changes during simulated spaceflight (bed-rest). SUMMARY OF BACKGROUND DATA: Spinal lengthening, flattening of the spinal curves, increases in disc size, and muscle atrophy are commonly seen in spaceflight simulation. This may represent a risk for low back injury. Consideration of exercise countermeasures against these changes is critical for success of long-term spaceflight missions. METHODS: Twenty healthy male subjects underwent 8-weeks of bed-rest with 6-months follow-up and were randomly allocated to an inactive control or countermeasure exercise group. Magnetic resonance imaging of the lumbo-pelvic region was conducted at regular time-points during and after bed-rest. Using uniplanar images at L4, cross-sectional areas of the multifidus, lumbar erector spinae, quadratus lumborum, psoas, anterolateral abdominal, and rectus abdominis muscles were measured. Sagittal scans were used to assess lumbar spine morphology (length, sagittal disc area and height, and intervertebral angles). RESULTS: The countermeasure group exhibited less multifidus muscle atrophy (P = 0.024) and its atrophy did not persist long-term as in the control group (up to 3-months; P < 0.006). Spinal lengthening (P = 0.03) and increases in disc area (P = 0.041) were also reduced. Significant partial correlations (P < 0.001) existed between spinal morphology and muscle cross-sectional area changes. CONCLUSION: The resistive vibration exercise countermeasure reduced, but did not entirely prevent, multifidus muscle atrophy and passive spinal tissue deconditioning during bed-rest. Atrophy of the multifidus muscles was persistent long-term in the inactive subjects. Future work could consider closer attention to spinal posture during exercise and optimizing exercise dose.

Short-duration resistive exercise sustains neuromuscular function after bed rest

PURPOSE: The study's purpose was to assess the effectiveness of a short-duration three-times-weekly high-load resistive exercise program on preventing deterioration in neuromuscular function after prolonged bed rest. METHODS: Twenty-four male subjects performed high-load resistive exercise (n = 8), high-load resistive exercise with whole-body vibration (n = 9), or no exercise (control, n = 9) during 60-d head-down tilt bed rest as part of the 2nd Berlin Bed Rest Study. Peak countermovement jump power and height, sit-to-stand performance, sprint time over 15 and 30 m, and leg press one-repetition maximum were measured before and after bed rest. RESULTS: The exercise interventions were capable of ameliorating losses of peak countermovement jump power (P < 0.001) and height (P < 0.001), deterioration of sit-to-stand time from 45-cm (P = 0.034) and 30-cm (P < 0.001) sitting positions, increases of 15-m (P = 0.037) and 30-m (P = 0.005) sprint time, and losses of leg press one-repetition maximum (P < 0.001). CONCLUSIONS: The short-duration (6-min time under tension per training session) exercise countermeasure program performed three times a week was capable of reducing the effect of prolonged bed rest on many neuromuscular function measures.

Vibration or balance training on neuromuscular performance in osteopenic women

Maintaining neuromuscular function in older age is an important topic for aging societies, especially for older women with low bone density who may be at risk of falls and bone fracture. This randomized controlled trial investigated the effect of resistive exercise with either whole-body vibration training (VIB) or coordination/balance training (BAL) on neuromuscular function (countermovement jump, multiple 1-leg hopping, sit-to-stand test). 68 postmenopausal women with osteopenia or osteoporosis were recruited for the study. 57 subjects completed the 9-month, twice weekly, intervention period. All subjects conducted 30 min of resistance exercise each training day. The VIB-group performed additional training on the Galileo vibration exercise device. The BAL-group performed balance training. An "intent-to-treat" analysis showed greater improvement in the VIB-group for peak countermovement power (p=0.004). The mean [95% confidence interval] effect size for this parameter was a  + 0.9[0.3 to 1.5] W/kg greater change in VIB than BAL after 9 months. In multiple 1-leg hopping, a significantly better performance in the VIB-group after the intervention period was seen on a "per-protocol" analysis only. Both groups improved in the sit-to-stand test. The current study provides evidence that short-duration whole-body vibration exercise can have a greater impact on some aspects of neuromuscular function in post-menopausal women with low bone density than proprioceptive training.

Fighting fires and fatigue: sleep, physical activity, and physical task performance

 During bushfires, firefighters often work long shifts with little sleep. Grace’s research showed that although firefighters’ sleep is restricted, it does not adversely affect their ability to perform physical tasks. This contrasts the cognitive impairments associated with sleep loss and could prompt revision of fatigue management guidelines in physically-demanding occupations.