Carbohydrate sports drinks produce worthwhile benefits to endurance performance compared with noncaloric controls. However, athletes now consume carbohydrate in a range of formats, including gels and bars, but the comparable performance outcomes are unknown. Therefore, the aim of this study was to establish the relative effects of drink, gel, bar, and mixed carbohydrate formats on intense cycling performance. In a treatmentapparent randomized crossover design, 12 well-trained male cyclists completed 4 trials comprising a 140-min race simulation, followed by a double-blind slow-ramp to exhaustion (0.333 W·s-1). Carbohydrate comprising fructose and maltodextrin was ingested every 20 min via commercial drink, gel, bar, or mix of all 3, providing 80 g carbohydrate·h-1. Fluid ingestion was 705 ml·h-1. Exertion, fatigue, and gastrointestinal discomfort were measured with VAS. Performance peak power (SD) was 370 (41), 376 (37), 362 (51) and 368 W (54) for drink, gels, bars, and mix respectively. The reduction in power (-3.9%; 90%CI ±4.3) following bar ingestion vs. gel was likely substantial (likelihood harm 81.2%; benefit 0.8%), but no clear differences between drinks, gels, and the mix were evident. Bars also produced small-moderate standardized increases in nausea, stomach fullness, abdominal cramps, and perceived exertion, relative to gels (likelihood harm 95–99.5%; benefit <0.01%) and drink (75–95%; <0.01%); mix also increased nausea relative to gels (95%; <0.01%). Relative to a gel, carbohydrate bar ingestion reduced peak power, gut comfort, and ease of exertion; furthermore, no clear difference relative to drink suggests bars alone are the less favorable exogenous-carbohydrate energy source for intense endurance performance.
Mathilde Guillochon and David S. Rowlands
David S. Rowlands and Will G. Hopkins
The effect of pre-exercise meal composition on metabolism and performance in cycling were investigated in a crossover study. Twelve competitive cyclists ingested high-fat, high-carbohydrate, or high-protein meals 90 min before a weekly exercise test. The test consisted of a 1-hour pre-load at 55% peak power, five 10-min incremental loads from 55 to 82% peak power (to measure the peak fat-oxidation rate), and a 50-km time trial that included three 1-km and 4-km sprints. A carbohydrate supplement was ingested throughout the exercise. Relative to the high-protein and high-fat meals, the high-carbohydrate meal halved the peak fat-oxidation rate and reduced the fat oxidation across all workloads by a factor of 0.20 to 0.58 (p = .002–.0001). Reduced fat availability may have accounted for this reduction, as indicated by lower plasma fatty acid, lower glycerol, and higher pre-exercise insulin concentrations relative to the other meals (p = .04–.0001). In contrast, fat oxidation following the high-protein meal was similar to that following the high-fat meal. This similarity was linked to evidence suggesting greater lipolysis and plasma fat availability following high-protein relative to high-carbohydrate meals. Despite these substantial effects on metabolism, meal composition had no clear effect on sprint or 50-km performance.
Jake Pearson, David Rowlands, and Ruth Highet
Achilles tendinopathy is a common and often debilitating condition, and autologous blood injection is a promising treatment option.
To determine whether autologous blood injection added to standard management was effective in alleviating symptoms of Achilles tendinopathy.
A prospective randomized controlled trial.
Private sports medicine clinic.
33 patients (18 women, 15 men) of mean age 50 y (SD 9) with 40 cases of Achilles tendinopathy of mean duration of 11 mo (SD 7).
Participants were randomized to blind peritendinous autologous blood injection added to standard treatment (eccentric-loading exercises) or standard treatment alone for 12 wk.
Main Outcome Measure:
Victorian Institute of Sport Assessment for Achilles (VISA-A) score and ratings of discomfort during and after the injection were measured at baseline and 6 and 12 wk. Analytically derived effect-size thresholds of 5 (small) and 15 (moderate) VISA-A units were used as the reference values for clinical inference.
Improvements in VISA-A of 7.7 units (95%CL: ± 6.7) and 8.7 units (± 8.8) were observed in the treatment and control groups, respectively, at 6 wk relative to baseline, with no clear effect of blood injection. At 12 wk VISA-A score improved to 18.9 units (± 7.4) in the treatment group, revealing a blood-injection effect of 9.6 units (± 11.5), relative to a comparatively unchanged condition in control (9.4 units; ± 9.0). Predictors of response to treatment were unremarkable, and a 21% rate of postinjection flare was the only noteworthy side effect.
There is some evidence for small short-term symptomatic improvements with the addition of autologous blood injection to standard treatment for Achilles tendinopathy, although double-blinded studies with longer follow-up and larger sample size are required.
Hani Kopetschny, David Rowlands, David Popovich, and Jasmine Thomson
This study explored the information sources long-distance triathletes used to inform their training and nutrition plans, and evaluated these plans over a training macrocycle. Seventy-four long-distance triathletes completed the online survey. Coaches were the most popular training information source (69%), whereas nonprofessional sources (internet 65%, other athletes 53%) were more popular than nutritionists (29%) for nutrition information. Attributes valued most in an information source were: source prior personal experience, individualized advice, breadth of knowledge, and credibility. Sixty-five percent of participants reported previously manipulating dietary intake to improve performance. Forty-three percent reported carbohydrate loading previously, but only 29% planned to carbohydrate load for their upcoming event. Thirty-six percent of participants planned to reduce carbohydrate intake at some point in training, predominantly early (28%) and toward the end (22%) of their macrocycles. Twenty percent of participants planned to maintain energy intake early, and increase (14%) or maintain energy intake (15%) mid-cycle. Triathletes’ training plans showed intentions for concurrent increases in volume and intensity, rather than a classical periodized training progression. Limitations of this study include the lack of diet intake and training data, quantitative comparison with dietary guidelines and high/low carbohydrate classification, and an overrepresentation of women in the study cohort. This research showed the popularity of the internet and other athletes to inform triathletes’ nutrition plans, and revealed intentions to reduce carbohydrate intakes alongside training load increases, contrary to professional guidelines. Understanding athletes’ intentions and sources of nutrition information is crucial to developing effective nutrition education strategies.
Thomas W. Rowland, Richard C. McFaul, and David A. Burton
Syncope during sports participation may serve as the first manifestation of cardiovascular disease that poses a risk for athletic training and competition. Other causes of syncope (vasovagal, dehydration) during physical activity may be more benign. The athlete who faints during sports deserves a comprehensive diagnostic evaluation that addresses the wide-ranging differential diagnosis involved. The case of a 14-year-old male with two syncopal spells during athletic training is presented to review the components of such a workup and subsequent management implications.
David S. Rowlands, Darrell L. Bonetti, and Will G. Hopkins
Isotonic sports drinks are often consumed to offset the effects of dehydration and improve endurance performance, but hypotonic drinks may be more advantageous. The purpose of the study was to compare absorption and effects on performance of a commercially available hypotonic sports drink (Mizone Rapid: 3.9% carbohydrate [CHO], 218 mOsmol/kg) with those of an isotonic drink (PowerAde: 7.6% CHO, 281 mOsmol/kg), a hypertonic drink (Gatorade: 6% CHO, 327 mOsmol/kg), and a noncaloric placebo (8 mOsmol/kg). In a crossover, 11 cyclists consumed each drink on separate days at 250 ml/15 min during a 2-hr preload ride at 55% peak power followed by an incremental test to exhaustion. Small to moderate increases in deuterium oxide enrichment in the preload were observed with Mizone Rapid relative to PowerAde, Gatorade, and placebo (differences of 88, 45, and 42 parts per million, respectively; 90% confidence limits ±28). Serum osmolality was moderately lower with Mizone Rapid than with PowerAde and Gatorade (–1.9, –2.4; mOsmol/L; ±1.2 mOsmol/L) but not clearly different vs. placebo. Plasma volume reduction was small to moderate with Mizone Rapid, PowerAde, and Gatorade relative to placebo (–1.9%, –2.5%, –2.9%; ± 2.5%). Gut comfort was highest with Mizone Rapid but clearly different (8.4% ± 4.8%) only vs PowerAde. Peak power was highest with Mizone Rapid (380 W) vs. placebo and other drinks (1.2–3.0%; 99% confidence limits ±4.7%), but differences were inconclusive with reference to the smallest important effect (~1.2%). The outcomes are consistent with fastest fluid absorption with the hypotonic sports drink. Further research should determine whether the effect has a meaningful impact on performance.
David S. Rowlands, Rhys M. Thorp, Karin Rossler, David F. Graham, and Mike J. Rockell
Carbohydrate ingestion after prolonged strenuous exercise enhances recovery, but protein might also be important. In a crossover with 2-wk washout, 10 cyclists completed 2.5 h of intervals followed by 4-h recovery feeding, provided 218 g protein, 435 g carbohydrate, and 79 g fat (protein enriched) or 34 g protein, 640 g carbohydrate, and 79 g fat (isocaloric control). The next morning, cyclists performed 10 maximal constant-work sprints on a Velotron cycle ergometer, each lasting ~2.5 min, at ~5-min intervals. Test validity was established and test reliability and the individual response to the protein-enriched condition estimated by 6 cyclists’ repeating the intervals, recovery feeding, and performance test 2 wk later in the protein-enriched condition. During the 4-h recovery, the protein-enriched feeding had unclear effects on mean concentrations of plasma insulin, cortisol, and growth hormone, but testosterone was 25% higher (90% confidence limits, ± 14%). Protein enrichment also reduced plasma creatine kinase by 33% (±38%) the next morning and reduced tiredness and leg-soreness sensations during the sprints, but effects on mean sprint power were unclear (–1.4%, ±4.3%). The between-subjects trial-to-trial coefficient of variation in overall mean sprint power was 3.1% (±3.4%), whereas the variation in the protein-enriched condition was 5.9% (±6.9%), suggesting that individual responses to the protein-enriched treatment contributed to the unclear performance outcome. To conclude, protein-enriched recovery feeding had no clear effect on next-day performance.
Eric R. Helms, Caryn Zinn, David S. Rowlands, and Scott R. Brown
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.
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.
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.
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).
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.
Eric R. Helms, Caryn Zinn, David S. Rowlands, Ruth Naidoo, and John Cronin
Athletes risk performance and muscle loss when dieting. Strategies to prevent losses are unclear. This study examined the effects of two diets on anthropometrics, strength, and stress in athletes.
This double-blind crossover pilot study began with 14 resistance-trained males (20-43 yr) and incurred one dropout. Participants followed carbohydrate-matched, high-protein low-fat (HPLF) or moderate-protein moderate-fat (MPMF) diets of 60% habitual calories for 2 weeks. Protein intakes were 2.8g/kg and 1.6g/kg and mean fat intakes were 15.4% and 36.5% of calories, respectively. Isometric midthigh pull (IMTP) and anthropometrics were measured at baseline and completion. The Daily Analysis of Life Demands of Athletes (DALdA) and Profile of Mood States (POMS) were completed daily. Outcomes were presented statistically as probability of clinical benefit, triviality, or harm with effect sizes (ES) and qualitative assessments.
Differences of effect between diets on IMTP and anthropometrics were likely or almost certainly trivial, respectively. Worse than normal scores on DALDA part A, part B and the part A “diet” item were likely more harmful (ES 0.32, 0.4 and 0.65, respectively) during MPMF than HPLF. The POMS fatigue score was likely more harmful (ES 0.37) and the POMS total mood disturbance score (TMDS) was possibly more harmful (ES 0.29) during MPMF than HPLF.
For the 2 weeks observed, strength and anthropometric differences were minimal while stress, fatigue, and diet-dissatisfaction were higher during MPMF. A HPLF diet during short-term weight loss may be more effective at mitigating mood disturbance, fatigue, diet dissatisfaction, and stress than a MPMF diet.
Ann V. Rowlands, Sarah M. Powell, Roger G. Eston, and David K. Ingledew
This study aimed to determine the relationship between bone mineral content, habitual physical activity, and calcium intake in children. Fifty-seven children, aged 8–11 years, wore pedometers for seven days to assess activity. Calcium intake was estimated by a 4-day food diary. Bone mineral content (BMC) and areal density (BMD) were measured at the total proximal femur and femoral neck using dual energy X-ray absorptiometry. Regression analysis was used to assess contributions of physical activity and calcium intake to BMC, residualized for bone area and body mass. Physical activity explained 11.6% of the variance in residualized BMC at the proximal femur and 14.3% at the femoral neck (p < 0.05). Calcium intake added to the variance explained at the proximal femur only (9.8%, p < 0.05). This study provides evidence for an association between BMC and habitual physical activity.