Search Results

Recent research has reported performance improvements after chronic NaHCO₃ ingestion in conjunction with high-intensity interval training (HIT) in moderately trained athletes. The purpose of the current study was to determine the effects of altering plasma H⁺ concentration during HIT through NaHCO₃ ingestion over 4 wk (2 HIT sessions/wk) in 12 Australian representative rowers (M ± SD; age 22 ± 3 yr, mass 76.4 ± 4.2 kg, VO_2peak 65.50 ± 2.74 ml · kg⁻¹ · min⁻¹). Baseline testing included a 2,000-m time trial and an incremental exercise test. After baseline testing, rowers were allocated to either a chronic NaHCO₃ (ALK) or placebo (PLA) group. Starting 90 min before each HIT session, subjects ingested a 0.3-g/kg body mass dose of NaHCO₃ or a placebo substance. Fingertip blood samples were taken throughout the study to analyze bicarbonate and pH levels. The ALK group did not produce any additional improvements in 2,000-m rowing performance time compared with PLA (p > .05). Magnitude-based inferential analysis indicated an unclear or trivial effect on 2,000-m power, 2,000-m time, peak power output, and power at 4 mmol/L lactate threshold in the ALK group compared with the PLA group. Although there was no difference between groups, during the study there was a significant mean (± SD) 2,000-m power improvement in both the ALK and PLA groups of 17.8 ± 14.5 and 15.2 ± 18.3 W, respectively. In conclusion, despite overall improvements in rowing performance after 4 wk of HIT, the addition of chronic NaHCO₃ supplementation during the training period did not significantly enhance performance further.

Beta-alanine may benefit short-duration, high-intensity exercise performance. The aim of this randomized double-blind placebo-controlled study was to examine the effects of beta-alanine supplementation on aspects of muscular performance in highly trained cyclists. Sixteen highly trained cyclists (mean ± SD; age = 24 ± 7 yr; mass = 70 ± 7kg; VO_2max = 67 ± 4ml·kg⁻¹·min–¹) supplemented with either beta-alanine (n = 8, 65 mg·kg⁻¹BM) or a placebo (n = 8; dextrose monohydrate) over 4 weeks. Pre- and postsupplementation cyclists performed a 4-minute maximal cycling test to measure average power and 30 reciprocal maximal isokinetic knee contractions at a fixed angular velocity of 180°·sec⁻¹ to measure average power/repetition, total work done (TWD), and fatigue index (%). Blood pH, lactate (La⁻) and bicarbonate (HCO₃ ^-) concentrations were measured preand postisokinetic testing at baseline and following the supplementation period. Beta-alanine supplementation was 44% likely to increase average power output during the 4-minute cycling time trial when compared with the placebo, although this was not statistically significant (p = .25). Isokinetic average power/repetition was significantly increased post beta-alanine supplementation compared with placebo (beta-alanine: 6.8 ± 9.9W, placebo: –4.3 ± 9.5 W, p = .04, 85% likely benefit), while fatigue index was significantly reduced (p = .03, 95% likely benefit). TWD was 89% likely to be improved following beta-alanine supplementation; however, this was not statistically significant (p = .09). There were no significant differences in blood pH, lactate, and HCO₃ ⁻ between groups (p > .05). Four weeks of beta-alanine supplementation resulted in worthwhile changes in time-trial performance and short-duration muscular force production in highly trained cyclists.

Purpose: To assess the reliability of power-output measurements of a Wahoo KICKR Power Trainer (KICKR) on 2 separate occasions separated by 14 mo of regular use (∼1 h/wk). Methods: Using the KICKR to set power outputs, powers of 100–600 W in increments of 50 W were assessed at cadences of 80, 90, and 100 rpm that were controlled and validated by a dynamic calibration rig. Results: A small ratio bias of 1.002 (95% limits of agreement [LoA] 0.992–1.011) was observed over 100–600 W at 80–100 rpm between trials 1 and 2. Similar ratio biases with acceptable limits of agreement were observed at 80 rpm (1.003 [95% LoA 0.987–1.018]), 90 rpm (1.000 [0.996–1.005]), and 100 rpm (1.002 [0.997–1.007]). The intraclass correlation coefficient with 95% confidence interval (CI) for mean power between trials was 1.00 (95% CI 1.00–1.00) with a typical error (TE) of 3.1 W and 1.6% observed between trials 1 and 2. Conclusion: When assessed at 2 separate time points 14 mo apart, the KICKR has acceptable reliability for combined power outputs of 100–600 W at 80–100 rpm, reporting overall small ratio biases with acceptable LoA and low TE. Coaches and sport scientists should feel confident in the power output measured by the KICKR over an extended period of time when performing laboratory training and performance assessments.

Context: Time of day has been shown to impact athletic performance, with improved performance observed in the late afternoon–early evening. Diurnal variations in physiological factors may contribute to variations in pacing selection; however, research investigating time-of-day influence on pacing is limited. Purpose: To investigate the influence of time-of-day on pacing selection in a 4-km cycling time trial (TT). Methods: Nineteen trained male cyclists (mean [SD] age 39.0 [10.7] y, height 1.8 [0.1] m, body mass 78.0 [9.4] kg, VO₂max 62.1 [8.7] mL·kg⁻¹·min⁻¹) completed a 4-km TT on 5 separate occasions at 08:30, 11:30, 14:30, 17:30, and 20:30. All TTs were completed in a randomized order, separated by a minimum of 2 d and maximum of 7 d. Results: No time-of-day effects were observed in pacing as demonstrated by similar power outputs over 0.5-km intervals (P = .78) or overall mean power output (333.0 [38.9], 339.8 [37.2], 335.5 [31.2], 336.7 [35.2], and 334.9 [35.7] W; P = .45) when TTs were performed at 08:30, 11:30, 14:30, 17:30, and 20:30. Preexercise tympanic temperature demonstrated a time-of-day effect (P < .001), with tympanic temperature higher at 14:30 and 17:30 than at 08:30 and 11:30. Conclusion: While a biological rhythm was present in tympanic temperature, pacing selection and performance when completing a 4-km cycling TT were not influenced by time of day. The findings suggest that well-trained cyclists can maintain a robust pacing strategy for a 4-km TT regardless of time of the day.

Adherence to a gluten-free diet (GFD) for nonceliac athletes (NCA) has become increasingly popular despite a paucity of supportive medical or ergogenic evidence. This study aimed to quantify the demographics of NCA and determine associated experiences, perceptions, and sources of information related to GFD. Athletes (n = 910, female = 528, no gender selected = 5) completed a 17-question online survey. Forty-one percent of NCA respondents, including 18-world and/or Olympic medalists, follow a GFD 50–100% of the time (GFD > 50): only 13% for treatment of reported medical conditions with 57% self-diagnosing their gluten sensitivity. The GFD > 50 group characteristics included predominantly endurance sport athletes (70.0%) at the recreationally competitive level (32.3%), between 31 and 40 years of age (29.1%). Those who follow a GFD > 50 reported experiencing, abdominal/gastrointestinal (GI) symptoms alone (16.7%) or in conjunction with two (30.7%) or three (35.7%) additional symptoms (e.g., fatigue) believed to be triggered by gluten. Eighty-four percent of GFD > 50 indicated symptom improvement with gluten-removal. Symptom-based and non-symptom-based self-diagnosed gluten-sensitivity (56.7%) was the primary reason for adopting a GFD. Leading sources of GFD information were online (28.7%), trainer/coach (26.2%) and other athletes (17.4%). Although 5–10% of the general population is estimated to benefit clinically from a GFD a higher prevalence of GFD adherence was found in NCA (41.2%). Prescription of a GFD among many athletes does not result from evidence-based practice suggesting that adoption of a GFD in the majority of cases was not based on medical rationale and may be driven by perception that gluten removal provides health benefits and an ergogenic edge in NCA.

The purpose of this study was to investigate if acute caffeine exposure via mouth-rinse improved endurance cycling time-trial performance in well-trained cyclists. It was hypothesized that caffeine exposure at the mouth would enhance endurance cycling time-trial performance. Ten well-trained male cyclists (mean± SD: 32.9 ± 7.5 years, 74.7 ± 5.3kg, 176.8 ± 5.1cm, VO_2peak = 59.8 ± 3.5ml·kg–1·min–1) completed two experimental timetrials following 24 hr of dietary and exercise standardization. A randomized, double-blind, placebo-controlled, cross-over design was employed whereby cyclists completed a time-trial in the fastest time possible, which was equivalent work to cycling at 75% of peak aerobic power output for 60 min. Cyclists were administered 25ml mouth-rinses for 10 s containing either placebo or 35mg of anhydrous caffeine eight times throughout the time-trial. Perceptual and physiological variables were recorded throughout. No significant improvement in time-trial performance was observed with caffeine (3918 ± 243s) compared with placebo mouth-rinse (3940 ± 227s). No elevation in plasma caffeine was detected due to the mouth-rinse conditions. Caffeine mouth-rinse had no significant effect on rating of perceived exertion, heart rate, rate of oxygen consumption or blood lactate concentration. Eight exposures of a 35 mg dose of caffeine at the buccal cavity for 10s does not significantly enhance endurance cycling time-trial performance, nor does it elevate plasma caffeine concentration.

Context: The reliable measurement of shoulder strength is important when assessing athletes involved in overhead activities. Swimmers' shoulders are subject to repetitive humeral elevation and consequently have a high risk of developing movement-control issues and pain. Shoulder-strength tests performed in positions of elevation assist with the detection of strength deficits that may affect injury and performance. The reliability of isometric strength tests performed in positions of humeral elevation without manual stabilization, which is a typical clinical scenario, has not been established. Objective: To establish the relative and absolute intrarater reliability of shoulder-strength tests functional to swimming in 3 body positions commonly used in the clinical setting. Design: Repeated-measures reliability study. Setting: Research laboratory. Subjects: 15 university students and staff (mean ± SD age 24 ± 8.2 y). Intervention: Isometric shoulder-strength tests were performed in positions of humeral elevation (flexion and extension in 140° abduction in the scapular plane, internal and external rotation in 90° abduction) on subjects without shoulder pain in supine, prone, and sitting. Subjects were tested by 1 examiner with a handheld dynamometer and retested after 48 h. Main Outcome Measures: Relative reliability (ICC_3,1) values with 95% CI. Absolute reliability was reported by minimal detectable change (MDC). Results: Good to excellent intrarater reliability was found for all shoulder-strength tests (ICC .87-.99). Intrarater reliability was not affected by body position. MDC% was <16% for every test and ≤11% for tests performed in supine. Conclusions: Shoulder flexion, extension, and internal- and external-rotation strength tests performed in humeral elevation demonstrated excellent to good intrarater reliability regardless of body position. A strength change of more than 15% in any position can be considered meaningful.

Postexercise fat oxidation may be important for exercise prescription aimed at optimizing fat loss. The authors examined the effects of exercise intensity, duration, and modality on postexercise oxygen consumption (VO₂) and substrate selection/respiratory-exchange ratio (RER) in healthy individuals. Three experiments (n = 7 for each) compared (a) short- (SD) vs. long-duration (LD) ergometer cycling exercise (30 min vs. 90 min) matched for intensity, (b) low- (LI) vs. high-intensity (HI) cycling (50% vs. 85% of VO_2max) matched for energy expenditure, and (c) continuous (CON) vs. interval (INT) cycling matched for energy expenditure and mean intensity. All experiments were administered by crossover design. Altering exercise duration did not affect postexercise VO₂ or RER kinetics (p > .05). However, RER was lower and fat oxidation was higher during the postexercise period in LD vs. SD (p < .05). HI vs. LI resulted in a significant increase in total postexercise energy expenditure and fat oxidation (p < .01). Altering exercise modality (CON vs. INT) did not affect postexercise VO₂, RER, or fat oxidation (p > .05). These results demonstrate that postexercise energy expenditure and fat oxidation can be augmented by increasing exercise intensity, but these benefits cannot be exploited by undertaking interval exercise (1:2-min work:recovery ratio) when total energy expenditure, duration, and mean intensity remain unchanged. In spite of the apparent benefit of these strategies, the amount of fat oxidized after exercise may be inconsequential compared with that oxidized during the exercise bout.