Effects of Low-Volume, High-Intensity Whole-Body Calisthenics on Army ROTC Cadets.

Our objective was to determine the effects of high-intensity interval training (HIT) on fitness in Army Reserve Officers' Training Corps cadets. Twenty-six college-aged (20.5 ± 1.7 years) participants completed 4 weeks of exercise training 3 days · wk(-1) consisting of either approximately 60 minutes of typical physical training or HIT whole-body calisthenics involving 4 to 7 sets of 30-second "all out" burpees separated by 4 minutes of active recovery. Several pre- and postintervention fitness variables were compared. We observed no changes across time or differences between groups in aerobic capacity, anaerobic capacity, or Army Physical Fitness Test performance (p > 0.05). However, there was a significant Group × Time interaction (p = 0.015) for skeletal muscle mitochondrial function (Tc: time constant of recovery). For the typical physical training group, we observed improved mitochondrial function (Tc decreased 2.4 ± 4.6 seconds; Cohen's d = -0.51); whereas, mitochondrial function decreased in HIT (Tc increased 2.4 ± 4.6 seconds; d = 0.50). HIT sustained fitness despite the short duration and reduced volume of activity. A program that includes HIT as part of a larger program may be well suited for maintaining fitness in moderately trained armed forces personnel without access to equipment.

Acute and chronic effects of sprint interval exercise on postprandial lipemia in women at-risk for the metabolic syndrome.

Individuals diagnosed with the metabolic syndrome (MetS) exhibit elevated postprandial lipemia (PPL). The aims of this investigation were to determine 1) if an acute bout of sprint interval training (SIT) attenuates PPL; and 2) if the attenuation of PPL following 6 wk of SIT is magnified compared with a single session of SIT prior to training in women at-risk for MetS (n = 45; 30-65 yr). Women were randomized to SIT (n = 22) or a nonexercise control (n = 23; CON) for 6 wk. Postprandial responses to a high-fat meal challenge (HFMC) were assessed in the CON group before (B-HFMC) and after (Post-HFMC) without prior exercise and in the SIT group at baseline (B-HFMC) without prior exercise, after an acute bout of SIT (four 30-s all-out sprints with 4-min recovery) prior to (Pre-HFMC), and after the 6-wk intervention (Post-HFMC). Responses to the HFMC were assessed by collecting venous blood samples in the fasted state and at 0, 30, 60, 120, and 180 min postprandial. Compared with baseline, an acute bout of SIT before (Pre-HFMC) and after the 6-wk intervention (Post-HFMC) significantly attenuated fasted TG (P < 0.05; 16.6% and 12.3%, respectively) and postprandial area under the curve (13.1% and 9.7%, respectively; tAUC) TG responses. There was no difference in fasted or tAUC TG responses between Pre-HFMC and Post-HFMC. SIT is an effective mode of exercise to reduce fasted and postprandial TG concentrations in women at-risk for MetS. Six weeks of SIT does not magnify the attenuation of PPL in response to a single session of SIT.

Critical measurement issues/challenges in assessing aerobic capacity in youth.

We discuss current measurement issues related to tests of aerobic capacity in the FITNESSGRAM. Interpretation of tests of aerobic capacity is difficult because the criterion measure of aerobic capacity, maximal rate of oxygen uptake (VO2(max)) expressed relative to body weight, is inversely related to body fatness and body mass index (BMI). This association cannot be easily be eliminated in a way that maintains the units commonly used to express aerobic capacity (i.e., mL x kg(-1) x min(-1)) and is understandable to typical test users. Requiring the measurement of BMI to predict VO2(max) creates practical problems for users by: (a) uncoupling the relation of predicted VO2(max) to physical performance on the 1-mile run/walk (MRW) and the Progressive Aerobic Cardiovascular Endurance Run (PACER) tests, (b) making explicit the influence of body composition on the ability of children to achieve the aerobic capacity healthy fitness zone, and (c) creating a barrier for users who cannot measure height and weight. The use of test equating improved classification agreement between the MRW and PACER tests but required measurement of BMI to estimate aerobic capacity from the PACER. A new equation to predict aerobic capacity that does not require BMI was recently introduced to address user concerns. This change will improve ease of use of the Fitnessgram with little effect on prediction accuracy but will likely result in poorer classification agreement between the MRW and PACER tests. Although considerable progress has been made in addressing issues related to assessment of aerobic capacity in youth, future work is needed to carefully balance the issues of prediction accuracy, test feasibility, and test agreement.

Comparison of responses to two high-intensity intermittent exercise protocols.

The purpose of this study was to compare peak cardiorespiratory, metabolic, and perceptual responses to acute bouts of sprint interval cycling (SIC) and a high-intensity intermittent calisthenics (HIC) protocol consisting of modified "burpees." Eleven (8 men and 3 women) moderately trained, college-aged participants (age = 21.9 ± 2.1, body mass index = 24.8 ± 1.9, V[Combining Dot Above]O2peak = 54.1 ± 5.4 ml·kg·min) completed 4 testing sessions across 9 days with each session separated by 48-72 hours. Using a protocol of 4 repeated bouts of 30-second "all-out" efforts interspersed with 4-minute active recovery periods, responses to SIC and HIC were classified relative to peak values. Mean values for %V[Combining Dot Above]O2peak and %HRpeak for SIC (80.4 ± 5.3% and 86.8 ± 3.9%) and HIC (77.6 ± 6.9% and 84.6 ± 5.3%) were not significantly different (p > 0.05). Effect sizes (95% confidence interval) calculated for mean differences were: %V[Combining Dot Above]O2peak Cohen's d = 0.51 (0.48-0.53) and %HRpeak Cohen's d = 0.57 (0.55-0.59). A low-volume, high-intensity bout of repeated whole-body calisthenic exercise induced cardiovascular responses that were not significantly different but were ∼1/2SD lower than "all-out" SIC. These results suggest that in addition to the benefit of reduced time commitment, a high-intensity interval protocol of calisthenics elicits vigorous cardiorespiratory and perceptual responses and may confer physiological adaptations and performance improvements similar to those reported for SIC. The potential efficacy of this alternative interval training method provides support for its application by athletes, coaches, and strength and conditioning professionals.

Effect of prior exercise on postprandial lipemia: an updated quantitative review.

Reducing postprandial triglycerides (TG) can lower the risk for cardiovascular disease. The purpose of this study was to perform a meta-analytic review of the literature to estimate the effect of prior exercise on postprandial lipemia. A total of 121 effects were found from 76 studies for the total TG response and 70 effects from 44 studies for the incremental area under the curve (iAUC) TG response. The weighted mean effect was moderate for the total TG response, Cohen's d = -0.60 (P < 0.0001), and for the iAUC response, Cohen's d = -0.59 (P < 0.0001). Moderator analysis revealed women exhibited a larger reduction (P < .01) in the total TG response following exercise (d = -0.96) than men (d = -0.57); high-intensity interval training induced a larger reduction (P < .05) in the iAUC response (d = -1.49) than aerobic (d = -0.58) or resistance (d = -0.13) exercise, and participants maintaining an energy deficit following exercise exhibited a greater reduction in the iAUC response (d = -0.67) compared with participants in energy balance (d = -0.28). We conclude that prior acute exercise reduces postprandial lipemia, with the magnitude of effect influenced by sex, type of exercise, and energy deficit following exercise.

Sprint interval training effects on aerobic capacity: a systematic review and meta-analysis.

BACKGROUND: Sprint interval training (SIT) involving repeated 30-s "all out" efforts have resulted in significantly improved skeletal muscle oxidative capacity, maximal oxygen uptake, and endurance performance. The positive impact of SIT on cardiorespiratory fitness has far-reaching health implications. OBJECTIVE: The objective of this study was to perform a systematic review of the literature and meta-analysis to determine the effects of SIT on aerobic capacity. METHODS: A search of the literature was conducted using the key words 'sprint interval training', 'high intensity intermittent training/exercise', 'aerobic capacity', and 'maximal oxygen uptake'. Seventeen effects were analyzed from 16 randomized controlled trials of 318 participants. The mean ± standard deviation number of participants was 18.7 ± 5.1. Participant age was 23.5 ± 4.3 years. RESULTS: The effect size calculated for all studies indicates that supramaximal-intensity SIT has a small-to-moderate effect (Cohen's d = 0.32, 95 % CI 0.10-0.55; z = 2.79, P < 0.01) on aerobic capacity with an aggregate improvement of ~3.6 mL·kg⁻¹·min⁻¹ (~8 % increase). The effect is moderate to large in comparison with no-exercise control groups (Cohen's d = 0.69, 95 % CI 0.46-0.93; z = 5.84, P < 0.01) and not different when compared with endurance training control groups (Cohen's d = 0.04, 95 % CI -0.17 to 0.24; z = 0.36, P = 0.72). CONCLUSION: SIT improves aerobic capacity in healthy, young people. Relative to continuous endurance training of moderate intensity, SIT presents an equally effective alternative with a reduced volume of activity. This evaluation of effects and analysis of moderating variables consolidates the findings of small-sample studies and contributes to the practical application of SIT to improve cardiorespiratory fitness and health.

Effect of six weeks of sprint interval training on mood and perceived health in women at risk for metabolic syndrome.

The purpose of this investigation was to determine whether 6 weeks of sprint interval training (SIT) is associated with changes in mood and perceived health in women at risk for developing metabolic syndrome (MetS). Physically inactive women (30-65 years) were randomized to 6 weeks of nutrition meetings and SIT (n = 23; 3 bouts/week of 4-8 30-s cycle sprints with 4-min recovery) or a nonexercise control condition (CON; n = 24). Before and after the 6-week intervention, perceived health status and mood were assessed. Clinically relevant increases in role-physical scores (ES = 0.64) and vitality (ES = 0.52) were found after 6 weeks of SIT compared with a nonexercise control group. For middle-aged women at risk for MetS, it is concluded that high-intensity, low-volume SIT (1) increases feelings of vitality and perceptions of having fewer physical limitations and (2) does not induce mood disturbances as occurs with high-volume, high-intensity training.

Physiological responses to an acute bout of sprint interval cycling.

Sprint interval training has been shown to improve skeletal muscle oxidative capacity, V[Combining Dot Above]O2max, and health outcomes. However, the acute physiological responses to 4-7 maximal effort intervals have not been determined. To determine the V[Combining Dot Above]O2, cardiorespiratory responses, and energy expenditure during an acute bout of sprint interval cycling (SIC), health, college-aged subjects, 6 men and 6 women, completed 2 SIC sessions with at least 7 days between trials. Sprint interval cycling was performed on a cycle ergometer and involved a 5-minute warm-up followed by four 30-second all-out sprints with 4-minute active recovery. Peak oxygen uptake (ml·kg·min) during the 4 sprints were 35.3 ± 8.2, 38.8 ± 10.1, 38.8 ± 10.6, and 36.8 ± 9.3, and peak heart rate (b·min) were 164 ± 17, 172 ± 10, 177 ± 12, and 175 ± 22. We conclude that an acute bout of SIC elicits submaximal V[Combining Dot Above]O2 and cardiorespiratory responses during each interval that are above 80% of estimated maximal values. Although the duration of exercise in SIC is very short, the high level of V[Combining Dot Above]O2 and cardiorespiratory responses are sufficient to potentially elicit adaptations to training associated with elevated aerobic energy demand.

Grape consumption's effects on fitness, muscle injury, mood, and perceived health.

Compounds found in the skins of grapes, including catechins, quercetin, and resveratrol, have been added to the diet of rodents and improved run time to exhaustion, fitness, and skeletal-muscle mitochondrial function. It is unknown if such effects occur in humans. The purpose of this experiment was to investigate whether 6 wk of daily grape consumption influenced maximal oxygen uptake (VO(2max)), work capacity, mood, perceived health status, inflammation, pain, and arm-function responses to a mild eccentric-exercise-induced arm-muscle injury. Forty recreationally active young adults were randomly assigned to consume a grape or placebo drink for 45 consecutive days. Before and after 42 d of supplementation, assessments were made of treadmill-running VO(2max), work capacity (treadmill performance time), mood (Profile of Mood States), and perceived health status (SF-36 Health Survey). The day after posttreatment treadmill tests were completed, 18 high-intensity eccentric actions of the nondominant elbow flexors were performed. Arm-muscle inflammation, pain, and function (isometric strength and range of motion) were measured before and on 2 consecutive days after the eccentric exercise. Mixed-model ANOVA showed no significant effect of grape consumption on any of the outcomes. Six weeks of supplemental grape consumption by recreationally active young adults has no effect on VO(2max), work capacity, mood, perceived health status, inflammation, pain, or physical-function responses to a mild injury induced by eccentric exercise.

Cardiovascular drift and Vo2max during cycling and walking in a temperate environment.

INTRODUCTION: Different muscle recruitment patterns during cycling and walking may influence the magnitude of cardiovascular drift (CV drift) during these respective modes of exercise, but whether this also influences the magnitude of reduced maximal oxygen uptake (Vo2max) associated with CV drift is unknown.This study tested the hypothesis that cycling results in greater CV drift and a greater decrement in Vo2max than walking in a temperate environment. METHODS: CV drift was measured in nine recreationally active women (ages = 23 +/- 2 yr, Vo2max = 43.0 +/- 5.5 ml x kg(-1) x min(-1)) between 15 and 45 min of cycling or walking at 60% Vo2max on Separate occasions in 22 degrees C, 44% relative humidity. A graded exercise test to measure Vo2max was performed immediately after the submaximal exercise bout with no cessation of exercise. During separate trials involving each exercise mode, Vo2max was measured after 15 min of submaximal exercise so that changes in Vo2max between 15 and 45 min of exercise could be assessed between the same points in time in which CV drift occurred. RESULTS: Across both conditions, heart rate (HR) increased 5.4% and stroke volume (SV) decreased 11% from 15 to 45 min, but Vo2max was not significantly affected (7% reduction; 2.70 +/- 0.5 L min(-1) vs. 2.52 +/- 0.6 L min(-1)). CONCLUSION: In a temperate environment, a small CV drift corresponds to a small, non-significant decrease in Vo2max, regardless of whether the exercise performed is cycling or walking.

Cardiovascular drift during heat stress: implications for exercise prescription.

Cardiovascular drift, the progressive increase in heart rate and decrease in stroke volume that begins after approximately 10 min of prolonged moderate-intensity exercise, is associated with decreased maximal oxygen uptake, particularly during heat stress. Consequently, the increased heart rate reflects an increased relative metabolic intensity during prolonged exercise in the heat when cardiovascular drift occurs, which has implications for exercise prescription.

Development of youth aerobic-capacity standards using receiver operating characteristic curves.

BACKGROUND: Cardiovascular fitness has important implications for current and future health in children. PURPOSE: In this paper, criterion-referenced standards are developed for aerobic capacity (an indicator of cardiovascular fitness) based on receiver operating characteristic (ROC) curves. METHODS: The sample was drawn from participants aged 12-18 years in the National Health and Nutrition Examination Survey (1999-2002, N=1966). Subjects completed a treadmill exercise test from which maximal oxygen uptake (VO(2)max) was estimated from heart rate response. Metabolic syndrome was classified using previously published standards based on the National Cholesterol Education Program/Adult Treatment Panel III adult values at age 20 years. Using aerobic fitness z-scores as the test and metabolic syndrome as the criterion, ROC curve analysis was used to identify aerobic-capacity thresholds. RESULTS: The area under the curve (AUC) value for boys (83.1%) was high, indicating good utility for detecting risk of metabolic syndrome with aerobic fitness values. The AUC for girls (77.2%) was slightly below the recommended value of 80%. Although the ROC plots identified a defensible point for classifying levels of fitness, the approach in the present study was to establish two independent thresholds, one aimed at high specificity and one aimed at high sensitivity. The resulting z values for the low- and higher-risk threshold lines were then converted back to VO(2)max estimates using published LMS (L=skewness, M=median, and S=coefficient of variation) parameters. Values at the low-risk threshold ranged from 40 to 44 mL/kg/min for boys and from 38 to 40 mL/kg/min for girls. CONCLUSIONS: In summary, aerobic fitness can be used with moderate accuracy to differentiate between adolescents with and without metabolic syndrome. Age- and gender-specific aerobic-capacity thresholds for creating separate risk groups were identified using nationally representative growth percentiles.

Effects of acute sprint interval cycling and energy replacement on postprandial lipemia.

High postprandial blood triglyceride (TG) levels increase cardiovascular disease risk. Exercise interventions may be effective in reducing postprandial blood TG. The purpose of this study was to determine the effects of sprint interval cycling (SIC), with and without replacement of the energy deficit, on postprandial lipemia. In a repeated-measures crossover design, six men and six women participated in three trials, each taking place over 2 days. On the evening of the first day of each trial, the participants either did SIC without replacing the energy deficit (Ex-Def), did SIC and replaced the energy deficit (Ex-Bal), or did not exercise (control). SIC was performed on a cycle ergometer and involved four 30-s all-out sprints with 4-min active recovery. In the morning of day 2, responses to a high-fat meal were measured. Venous blood samples were collected in the fasted state and at 0, 30, 60, 120, and 180 min postprandial. There was a trend toward a reduction with treatment in fasting TG (P = 0.068), but no significant treatment effect for fasting insulin, glucose, nonesterified fatty acids, or betahydroxybutryrate (P > 0.05). The postprandial area under the curve (mmol·l(-1)·3 h(-1)) TG response was significantly lower in Ex-Def (21%, P = 0.006) and Ex-Bal (10%, P = 0.044) than in control, and significantly lower in Ex-Def (12%, P = 0.032) than in Ex-Bal. There was no treatment effect (P > 0.05) observed for area under the curve responses of insulin, glucose, nonesterified fatty acids, or betahydroxybutryrate. SIC reduces postprandial lipemia, but the energy deficit alone does not fully explain the decrease observed.

Effects of 6 weeks of quercetin supplementation on energy, fatigue, and sleep in ROTC cadets.

PURPOSE: To investigate the effects of 6 weeks of quercetin supplementation on energy, fatigue, and sleep quality in young persons conducting military physical training. METHODS: Using a randomized, double-blind, repeated-measures, placebo-controlled design, 58 healthy, moderately trained men and women were assigned to quercetin group and placebo group. Energy, fatigue, and sleep quality were evaluated before, in the middle, at the end, and 2 weeks following 42 to 54 days of supplementation with 1 g/day of quercetin in a soft chew or a placebo. RESULTS: Changes in energy and fatigue, assessed by the Profile of Mood States-Brief and the Mental and Physical State Energy and Fatigue Scales, and changes in sleep quality, measured by the Pittsburgh Sleep Quality Index were not significantly different (p > 0.05) in quercetin and placebo groups. CONCLUSION: Six weeks of quercetin supplementation in young persons conducting military physical training does not influence energy, fatigue, or sleep quality.

Effect of sprint interval training on circulatory function during exercise in sedentary, overweight/obese women.

Very high-intensity, low-volume, sprint interval training (SIT) increases muscle oxidative capacity and may increase maximal oxygen uptake ([Formula: see text]), but whether circulatory function is improved, and whether SIT is feasible in overweight/obese women is unknown. To examine the effects of SIT on [Formula: see text] and circulatory function in sedentary, overweight/obese women. Twenty-eight women with BMI > 25 were randomly assigned to SIT or control (CON) groups. One week before pre-testing, subjects were familarized to [Formula: see text] testing and the workload that elicited 50% [Formula: see text] was calculated. Pre- and post-intervention, circulatory function was measured at 50% of the pre-intervention [Formula: see text], and a GXT was performed to determine [Formula: see text]. During the intervention, SIT training was given for 3 days/week for 4 weeks. Training consisted of 4-7, 30-s sprints on a stationary cycle (5% body mass as resistance) with 4 min active recovery between sprints. CON maintained baseline physical activity. Post-intervention, heart rate (HR) was significantly lower and stroke volume (SV) significantly higher in SIT (-8.1 and 11.4%, respectively; P < 0.05) during cycling at 50% [Formula: see text]; changes in CON were not significant (3 and -4%, respectively). Changes in cardiac output ([Formula: see text]) and arteriovenous oxygen content difference [(a - v)O(2) diff] were not significantly different for SIT or CON. The increase in [Formula: see text] by SIT was significantly greater than by CON (12 vs. -1%). Changes by SIT and CON in HR(max) (-1 vs. -1%) were not significantly different. Four weeks of SIT improve circulatory function during submaximal exercise and increases [Formula: see text] in sedentary, overweight/obese women.

Effects of six weeks of quercetin supplementation on physical performance in ROTC cadets.

OBJECTIVE: To investigate the effects of 6 weeks of quercetin supplementation on physical performance during military physical training. METHODS: Using a randomized, double-blind, repeated-measures, placebo-controlled design, 58 healthy, moderately trained men and women were randomly assigned to quercetin (Q) or placebo (P) groups. Peak oxygen uptake (VO(2peak)) during maximal effort uphill treadmill running and four physical performance measures (Army Physical Fitness Test, [APFT], Baumgartner Modified Pull-Up Test [BMPU], Wingate Anaerobic Test [WanT], and a 36.6-m sprint) were evaluated before and after 42-54 days of supplementation with 1 g/d of quercetin with vitamins and other substances in a soft chew or placebo chew. RESULTS: Pretreatment-to-posttreatment changes in VO(2peak) and physical performance were not significantly different (p > 0.05) in Q and P. CONCLUSIONS: Six weeks of dietary quercetin supplementation in moderately trained individuals conducting military physical training did not improve VO(2peak) or performance on the APFT, BMPU, WAnT, and 36.6-m sprint.

Dietary quercetin supplementation is not ergogenic in untrained men.

Quercetin supplementation increases muscle oxidative capacity and endurance in mice, but its ergogenic effect in humans has not been established. Our study investigates the effects of short-duration chronic quercetin supplementation on muscle oxidative capacity; metabolic, perceptual, and neuromuscular determinants of performance in prolonged exercise; and cycling performance in untrained men. Using a double-blind, pretest-posttest control group design, 30 recreationally active, but not endurance-trained, young men were randomly assigned to quercetin and placebo groups. A noninvasive measure of muscle oxidative capacity (phosphocreatine recovery rate using magnetic resonance spectroscopy), peak oxygen uptake (Vo(2peak)), metabolic and perceptual responses to submaximal exercise, work performed on a 10-min maximal-effort cycling test following the submaximal cycling, and voluntary and electrically evoked strength loss following cycling were measured before and after 7-16 days of supplementation with 1 g/day of quercetin in a sports hydration beverage or a placebo beverage. Pretreatment-to-posttreatment changes in phosphocreatine recovery time constant, Vo(2peak,) substrate utilization, and perception of effort during submaximal exercise, total work done during the 10-min maximal effort cycling trial, and voluntary and electrically evoked strength loss were not significantly different (P > 0.05) in the quercetin and placebo groups. Short duration, chronic dietary quercetin supplementation in untrained men does not improve muscle oxidative capacity; metabolic, neuromuscular and perceptual determinants of performance in prolonged exercise; or cycling performance. The null findings indicate that metabolic and physical performance consequences of quercetin supplementation observed in mice should not be generalized to humans.

Effect of intensity of resistance exercise on postprandial lipemia.

The purpose of this study is to determine whether moderate-intensity resistance exercise (MOD) lowers postprandial lipemia (PPL) as much as high-intensity resistance exercise (HI) of equal work. Ten healthy men performed three trials, each conducted over 2 days. On day 1 of each treatment, they either did not exercise (CON), performed 3 sets of 16 repetitions of 10 exercises at 50% of 8 repetitions maximum (MOD), or performed 3 sets of 8 repetitions of 10 exercises at 100% of 8 repetitions maximum (HI). On the morning of day 2 at 15.5 h postexercise, participants ate a high-fat meal. Venous blood samples were collected, and metabolic rate was measured at rest and 3 h postprandial. HI reduced fasting triglyceride (TG) and TG area under the curve (AUC) (36%, P = 0.011 and 35%, P = 0.014) compared with CON. MOD tended to reduce fasting TG and TG AUC (21%, P = 0.054 and 26%, P = 0.052) compared with CON, but MOD and HI did not differ in fasting TG or TG AUC. Incremental TG AUC did not differ among treatments. MOD and HI did not change resting metabolic rate. HI increased fat oxidation at rest (21%, P = 0.021) and at 3 h postprandial (39%, P = 0.009) relative to CON. MOD tended to increase fat oxidation at rest (18%, P = 0.060) relative to CON. Fat oxidation and metabolic rate did not differ in MOD and HI. MOD and HI increased the fasting quantitative insulin-sensitivity check index (4%, P = 0.001 and P = 0.004) relative to CON. As MOD and HI resulted in similar reductions in PPL and increases in fat oxidation, resistance exercise intensity does not influence PPL.

Ergogenic effects of low doses of caffeine on cycling performance.

The purpose of this experiment was to learn whether low doses of caffeine have ergogenic, perceptual, and metabolic effects during cycling. To determine the effects of 1, 2, and 3 mg/kg caffeine on cycling performance, differentiated ratings of perceived exertion (D-RPE), quadriceps pain intensity, and metabolic responses to cycling exercise, 13 cyclists exercised on a stationary ergometer for 15 min at 80% VO, then, after 4 min of active recovery, completed a 15-min VO2peak performance ride 60 min after ingesting caffeine or placebo. Work done (kJ/kg) during the performance ride was used as a measure of performance. D-RPE, pain ratings, and expired-gas data were obtained every 3 min, and blood lactate concentrations were obtained at 15 and 30 min. Compared with placebo, caffeine doses of 2 and 3 mg/kg increased performance by 4% (95% CI: 1.0-6.8%, p = .02) and 3% (95% CI: -0.4% to 6.8%, p = .077), respectively. These effects were ergogenic, on average, but varied considerably in magnitude among individual cyclists. There were no effects of caffeine on D-RPE or pain throughout the cycling task. Selected metabolic variables were affected by caffeine, consistent with its known actions. The authors conclude that caffeine preparations of 2 and 3 mg/kg enhanced performance, but future work should aim to explain the considerable interindividual variability of the drug's ergogenic properties.