David S. Rowlands

Physical and Physiological Factors Associated with Success in the Triathlon

SummaryThe physiological demands of sequential exercise in swimming, cycling and running are unique and require the triathlete to develop physical and physiological characteristics that are a blend of those seen in endurance swimming, cycling and running specialists. Elite triathletes are generally tall, of average to light weight and have low levels of body fat, a physique which provides the advantages of large leverage and an optimal power to surface area or weight ratio.Triathletes have high maximum oxygen uptake (V̇O2max) values, but V̇O2max may be on average marginally lower than values previously observed in endurance specialists. Although V̇O2max is a predictor of performance in triathletes of mixed abilities, it cannot be used to predict performance within homogenous groups of elite performers. Nevertheless, elite triathletes have significantly higher V̇O2max values than sub-elite triathletes and high V̇O2max levels are required for success in triathlons. The ability of the triathlete to exercise at a lower percentage of V̇O2max for a given submaximal workload may be especially important to triathlon success. This is influenced not only by V̇O2max itself, but also by anaerobic threshold and economy of movement.Anaerobic threshold, as indicated by either ventilatory threshold or lactate threshold, improves with triathlon training and when measured in the appropriate exercise mode has been related to swim, cycle and run performance in the triathlon. Economy of movement in swimming, cycling and running is also related to triathlon performance, and swimming economy in particular appears to be an area where triathletes could make large improvements.Future research should utilise experimental methodologies to investigate triathlon physiology, in particular, the influence of sequential exercise in different exercise modes on physiological function and examine the influence of different training interventions on triathlon physiology and performance.

Oxidation of combined ingestion of maltodextrins and fructose during exercise

PURPOSE To determine whether combined ingestion of maltodextrin and fructose during 150 min of cycling exercise would lead to exogenous carbohydrate oxidation rates higher than 1.1 g.min. METHODS Eight trained cyclists VO2max: 64.1 +/- 3.1 mL.kg.min) performed three exercise trials in a random order. Each trial consisted of 150 min cycling at 55% maximum power output (64.2+/-3.5% VO2max) while subjects received a solution providing either 1.8 g.min of maltodextrin (MD), 1.2 g.min of maltodextrin + 0.6 g.min of fructose (MD+F), or plain water. To quantify exogenous carbohydrate oxidation, corn-derived MD and F were used, which have a high natural abundance of C. RESULTS Peak exogenous carbohydrate oxidation (last 30 min of exercise) rates were approximately 40% higher with combined MD+F ingestion compared with MD only ingestion (1.50+/-0.07 and 1.06+/-0.08 g.min, respectively, P<0.05). Furthermore, the average exogenous carbohydrate oxidation rate during the last 90 min of exercise was higher with combined MD+F ingestion compared with MD alone (1.38+/-0.06 and 0.96+/-0.07 g.min, respectively, P<0.05). CONCLUSIONS The present study demonstrates that with ingestion of large amounts of maltodextrin and fructose during cycling exercise, exogenous carbohydrate oxidation can reach peak values of approximately 1.5 g.min, and this is markedly higher than oxidation rates from ingesting maltodextrin alone.

Effect of dietary protein content during recovery from high-intensity cycling on subsequent performance and markers of stress, inflammation, and muscle damage in well-trained men

Nutrition is an important aspect of recuperation for athletes during multi-day competition or hard training. Post-exercise carbohydrate is likely to improve recovery, but the effect of protein is equivocal. The objective of this study was to determine the effect of post-exercise dietary protein content imposed over a high-carbohydrate background on subsequent performance. Using a crossover design, 12 cyclists completed 3 high-intensity rides over 4 days. Day 1 comprised 2.5 h intervals, followed by repeat-sprint performance tests on days 2 (15 h post) and 4 (60 h post), interspersed with a rest day. During 4 h recovery on days 1 and 2, cyclists ingested either 1.4 g.kg(-1).h(-1) carbohydrate, 0.7 g.kg(-1).h(-1) protein and 0.26 g.kg(-1).h(-1) fat (protein-enriched) or 2.1 g.kg(-1).h(-1) carbohydrate, 0.1 g.kg(-1).h(-1) protein, and equal fat (control). At other times, cyclists ingested a standardized high-carbohydrate diet. Anabolism was gauged indirectly by nitrogen balance, stress and inflammation via cortisol and cytokines, skeletal-muscle membrane disruption by creatine kinase, and oxidative stress by malonyl dealdehyde. Sprint mean power was not clearly different on day 2 (0.0%; 95%CL: +/-3.9%), but on day 4 it was 4.1% higher (+/-4.1%) in the protein-enriched condition relative to control. Reduced creatine kinase was possible (26%; +/-30%) but effects on oxidative stress, inflammatory markers, and cortisol were inconclusive or trivial. Overnight nitrogen balance was positive in the protein-enriched condition on day 1 (249+/-70 mg N.kg FFM(-1); mean+/-SD), but negative (-48+/-26 mg N.kg FFM(-1)) in the control condition. A nutritive effect of post-exercise protein content was not discernible short term (15 h), but a delayed performance benefit (60 h) was observed following protein-enriched high-carbohydrate ingestion.

Effect of graded fructose coingestion with maltodextrin on exogenous 14C-fructose and 13C-glucose oxidation efficiency and high-intensity cycling performance

The ingestion of solutions containing carbohydrates with different intestinal transport mechanisms (e.g., fructose and glucose) produce greater carbohydrate and water absorption compared with single-carbohydrate solutions. However, the fructose-ingestion rate that results in the most efficient use of exogenous carbohydrate when glucose is ingested below absorption-oxidation saturation rates is unknown. Ten cyclists rode 2 h at 50% of peak power then performed 10 maximal sprints while ingesting solutions containing (13)C-maltodextrin at 0.6 g/min combined with (14)C-fructose at 0.0 (No-Fructose), 0.3 (Low-Fructose), 0.5 (Medium-Fructose), or 0.7 (High-Fructose) g/min, giving fructose:maltodextrin ratios of 0.5, 0. 8, and 1.2. Mean (percent coefficient of variation) exogenous-fructose oxidation rates during the 2-h rides were 0.18 (19), 0.27 (27), 0.36 (27) g/min in Low-Fructose, Medium-Fructose, and High-Fructose, respectively, with oxidation efficiencies (=oxidation/ingestion rate) of 62-52%. Exogenous-glucose oxidation was highest in Medium-Fructose at 0.57 (28) g/min (98% efficiency) compared with 0.54 (28), 0.48 (29), and 0.49 (19) in Low-Fructose, High-Fructose, No-Fructose, respectively; relative to No-Fructose, only the substantial 16% increase (95% confidence limits +/-16%) in Medium-Fructose was clear. Total exogenous-carbohydrate oxidation was highest in Medium-Fructose at 0.84 (26) g/min. Although the effect of fructose quantity on overall sprint power was unclear, the metabolic responses were associated with lower perceptions of muscle tiredness and physical exertion, and attenuated fatigue (power slope) in the Medium-Fructose and High-Fructose conditions. With the present solutions, low-medium fructose-ingestion rates produced the most efficient use of exogenous carbohydrate, but fatigue and the perception of exercise stress and nausea are reduced with moderate-high fructose doses.

Effect of short‐term starvation versus high‐fat diet on intramyocellular triglyceride accumulation and insulin resistance in physically fit men

It is currently believed that intramyocellular triglyceride (IMTG) accumulation and insulin resistance are a consequence of dietary fat ingestion and/or the elevated circulating lipid levels associated with chronic fat surplus. The purpose of this study was to compare the effect of short‐term starvation versus low‐carbohydrate (CHO)/high‐fat diet on IMTG accumulation and the development of insulin resistance in physically fit men. Intramyocellular triglyceride content, measured as intramyocellular lipid (IMCL) by proton magnetic resonance spectroscopy (1H‐MRS), and glucose tolerance/insulin sensitivity, assessed by frequently sampled intravenous glucose tolerance test (IVGTT), were determined after 67 h of: (a) water‐only starvation (S); and (b) very low‐CHO/high‐fat diet (LC). These diets had in common significant restriction of CHO availability but large differences in fat content. All results were compared with those measured after a mixed CHO diet (C). Dietary interventions were administered by cross‐over design. The level of dietary‐induced IMTG accumulation (P= 0.46), insulin resistance (P= 0.27) and glucose intolerance (P= 0.29) was not different between S and LC treatments. Intramyocellular triglyceride content and insulin sensitivity were negatively correlated (r=−0.63, P < 0.01). Therefore, whilst insulin resistance may be due to fat accumulation at a cellular level, in the integrated human organism this outcome is not exclusively a function of dietary fat intake. The comparable level of IMTG accumulation and insulin resistance following S and LC may suggest that these metabolic perturbations are largely a consequence of the increased lipolytic response associated with CHO restriction.

Composite versus single transportable carbohydrate solution enhances race and laboratory cycling performance.

When ingested at high rates (1.8-2.4 g·min(-1)) in concentrated solutions, carbohydrates absorbed by multiple (e.g., fructose and glucose) vs. single intestinal transporters can increase exogenous carbohydrate oxidation and endurance performance, but their effect when ingested at lower, more realistic, rates during intermittent high-intensity endurance competition and trials is unknown. Trained cyclists participated in two independent randomized crossover investigations comprising mountain-bike races (average 141 min; n = 10) and laboratory trials (94-min high-intensity intervals followed by 10 maximal sprints; n = 16). Solutions ingested during exercise contained electrolytes and fructose + maltodextrin or glucose + maltodextrin in 1:2 ratio ingested, on average, at 1.2 g carbohydrate·kg(-1)·h(-1). Exertion, muscle fatigue, and gastrointestinal discomfort were recorded. Data were analysed using mixed models with gastrointestinal discomfort as a mechanism covariate; inferences were made against substantiveness thresholds (1.2% for performance) and standardized difference. The fructose-maltodextrin solution substantially reduced race time (-1.8%; 90% confidence interval = ±1.8%) and abdominal cramps (-8.1 on a 0-100 scale; ±6.6). After accounting for gastrointestinal discomfort, the effect of the fructose-maltodextrin solution on lap time was reduced (-1.1%; ±2.4%), suggesting that gastrointestinal discomfort explained part of the effect of fructose-maltodextrin on performance. In the laboratory, mean sprint power was enhanced (1.4%; ±0.8%) with fructose-maltodextrin, but the effect on peak power was unclear (0.7%; ±1.5%). Adjusting out gastrointestinal discomfort augmented the fructose-maltodextrin effect on mean (2.6%; ±1.9%) and peak (2.5%; ±3.0%) power. Ingestion of multiple transportable vs. single transportable carbohydrates enhanced mountain-bike race and high-intensity laboratory cycling performance, with inconsistent but not irreconcilable effects of gut discomfort as a possible mediating mechanism.

Fructose-maltodextrin ratio in a carbohydrate-electrolyte solution differentially affects exogenous carbohydrate oxidation rate, gut comfort, and performance

Solutions containing multiple carbohydrates utilizing different intestinal transporters (glucose and fructose) show enhanced absorption, oxidation, and performance compared with single-carbohydrate solutions, but the impact of the ratio of these carbohydrates on outcomes is unknown. In a randomized double-blind crossover, 10 cyclists rode 150 min at 50% peak power, then performed an incremental test to exhaustion, while ingesting artificially sweetened water or one of three carbohydrate-salt solutions comprising fructose and maltodextrin in the respective following concentrations: 4.5 and 9% (0.5-Ratio), 6 and 7.5% (0.8-Ratio), and 7.5 and 6% (1.25-Ratio). The carbohydrates were ingested at 1.8 g/min and naturally (13)C-enriched to permit evaluation of oxidation rate by mass spectrometry and indirect calorimetry. Mean exogenous carbohydrate oxidation rates were 1.04, 1.14, and 1.05 g/min (coefficient of variation 20%) in 0.5-, 0.8-, and 1.25-Ratios, respectively, representing likely small increases in 0.8-Ratio of 11% (90% confidence limits; ± 4%) and 10% (± 4%) relative to 0.5- and 1.25-Ratios, respectively. Comparisons of fat and total and endogenous carbohydrate oxidation rates between solutions were unclear. Relative to 0.5-Ratio, there were moderate improvements to peak power with 0.8- (3.6%; 99% confidence limits ± 3.5%) and 1.25-Ratio (3.0%; ± 3.7%) but unclear with water (0.4%; ± 4.4%). Increases in stomach fullness, abdominal cramping, and nausea were lowest with the 0.8- followed by the 1.25-Ratio solution. At high carbohydrate-ingestion rate, greater benefits to endurance performance may result from ingestion of 0.8- to 1.25-Ratio fructose-maltodextrin solutions. Small perceptible improvements in gut comfort favor the 0.8-Ratio and provide a clearer suggestion of mechanism than the relationship with exogenous carbohydrate oxidation.

Vibration therapy reduces plasma IL6 and muscle soreness after downhill running

Objective In this study, the effects of vibration therapy (VT) on delayed-onset muscle soreness (DOMS) and associated inflammatory markers after downhill running were determined. Methods 29 male recreational runners (33 (8) years; Vo2peak 57 (6) ml kg−1 min−1) completed a 40-min downhill run and were randomly allocated to a VT group or Control group. For 5 days post-run, the VT group underwent once-daily sessions of VT on the upper and lower legs. DOMS was assessed pre-run and for 5 days post-run by visual analogue scale. Immune cell subsets and plasma inflammatory markers were assessed pre-run, post-run, 24 and 120 h post-run by full differential cell count, and by ELISA and enzyme immunoassay, respectively. Data were analysed as per cent change from pre-run (ANOVA) and the magnitude of the treatment effect (Cohens effect size statistics). Results VT significantly reduced calf pain 96 h post-run (−50% (40%), 90% confidence limits) and gluteal pain 96 h (−50% (40%)) and 120 h post-run (−30% (30%)); decreased interleukin 6 (IL6) 24 h (−46% (31%)) and 120 h post-run (−65% (30%)); substantially decreased histamine 24 h (−40% (50%)) and 120 h post-run (−37% (48%)); substantially increased neutrophils (8.6% (8.1%)) and significantly decreased lymphocytes (−17% (12%)) 24 h post-run. There were no clear substantial effects of VT on other leukocyte subsets and inflammatory markers. Conclusion VT reduces muscle soreness and IL6. It may stimulate lymphocyte and neutrophil responses and may be a useful modality in treating muscle inflammation.

A Systematic Review of Dietary Protein during Caloric Restriction in Resistance Trained Lean Athletes: A Case for Higher Intakes

UNLABELLED Caloric restriction occurs when athletes attempt to reduce body fat or make weight. There is evidence that protein needs increase when athletes restrict calories or have low body fat. PURPOSE The aims of this review were to evaluate the effects of dietary protein on body composition in energy-restricted resistance-trained athletes and to provide protein recommendations for these athletes. METHODS Database searches were performed from earliest record to July 2013 using the terms protein, and intake, or diet, and weight, or train, or restrict, or energy, or strength, and athlete. Studies (N = 6) needed to use adult (≥ 18 yrs), energy-restricted, resistance-trained (> 6 months) humans of lower body fat (males ≤ 23% and females ≤ 35%) performing resistance training. Protein intake, fat free mass (FFM) and body fat had to be reported. RESULTS Body fat percentage decreased (0.5-6.6%) in all study groups (N = 13) and FFM decreased (0.3-2.7kg) in nine of 13. Six groups gained, did not lose, or lost nonsignificant amounts of FFM. Five out of these six groups were among the highest in body fat, lowest in caloric restriction, or underwent novel resistance training stimuli. However, the one group that was not high in body fat that underwent substantial caloric restriction, without novel training stimuli, consumed the highest protein intake out of all the groups in this review (2.5-2.6g/kg). CONCLUSIONS Protein needs for energy-restricted resistance-trained athletes are likely 2.3-3.1g/kg of FFM scaled upwards with severity of caloric restriction and leanness.

Impact of autologous blood injections in treatment of mid-portion Achilles tendinopathy: double blind randomised controlled trial

Objective To assess the effectiveness of two peritendinous autologous blood injections in addition to a standardised eccentric calf strengthening programme in improving pain and function in patients with mid-portion Achilles tendinopathy. Design Single centre, participant and single assessor blinded, parallel group, randomised, controlled trial. Setting Single sports medicine clinic in New Zealand. Participants 53 adults (mean age 49, 53% men) with symptoms of unilateral mid-portion Achilles tendinopathy for at least three months. Participants were excluded if they had a history of previous Achilles tendon rupture or surgery or had undergone previous adjuvant treatments such as injectable therapies, glyceryl trinitrate patches, or extracorporeal shockwave therapy. Interventions All participants underwent two unguided peritendinous injections one month apart with a standardised protocol. The treatment group had 3 mL of their own whole blood injected while the control group had no substance injected (needling only). Participants in both groups carried out a standardised and monitored 12 week eccentric calf training programme. Follow-up was at one, two, three and six months. Main outcome measures The primary outcome measure was the change in symptoms and function from baseline to six months with the Victorian Institute of Sport Assessment-Achilles (VISA-A) score. Secondary outcomes were the participant’s perceived rehabilitation and their ability to return to sport. Results 26 participants were randomly assigned to the treatment group and 27 to the control group. In total, 50 (94%) completed the six month study, with 25 in each group. Clear and clinically worthwhile improvements in the VISA-A score were evident at six months in both the treatment (change in score 18.7, 95% confidence interval 12.3 to 25.1) and control (19.9, 13.6 to 26.2) groups. The overall effect of treatment was not significant (P=0.689) and the 95% confidence intervals at all points precluded clinically meaningful benefit or harm. There was no significant difference between groups in secondary outcomes or in the levels of compliance with the eccentric calf strengthening programme. No adverse events were reported. Conclusion The administration of two unguided peritendinous autologous blood injections one month apart, in addition to a standardised eccentric training programme, provides no additional benefit in the treatment of mid-portion Achilles tendinopathy. Trial registration Australian New Zealand Clinical Trials Registry ACTRN12610000824066, WHO U1111-1117-2641.