The Effects of Caffeine on Heart Rate and Heart Rate Variability at Rest and During Submaximal Cycling Exercise.

The aim of this study was to investigate the effects of caffeine on heart rate and heart rate variability (HRV) at rest and during submaximal exercise. Using a balanced, double-blind, randomized, crossover design, 16 male cyclists (age: 37 ± 9 years; V˙O2max: 4.44 ± 0.67 L·min-1) completed three trials in an air-conditioned laboratory. In Trial 1, cyclists completed two incremental cycling tests to establish the V˙O2-power output relationship and V˙O2max. In trials 2 and 3, cyclists were evaluated for heart rate and HRV at rest, after which they ingested a capsule containing 5 mg·kg-1 of caffeine or placebo. Thirty-five minutes post-supplementation, additional resting heart rate and HRV readings were taken after which cyclists completed a submaximal incremental cycling test (6 min stages) at 40-80% of V˙O2max; with HR and HRV measurements taken in the last 5 min of each increment. HRV was determined from the root mean square of successive differences between R-R intervals. There were significant supplement × exercise intensity interactions on heart rate (p = .019) and HRV (p = .023), with post hoc tests on the latter showing that caffeine increased HRV at 40%, 50%, and 60% of V˙O2max by 3.6 ± 4.9, 2.6 ± 2.8, and 0.6 ± 1.7 ms, respectively. There was a supplement × time interaction effect on resting HRV (p < .001), but not on heart rate (p = .351). The results of this study support the suggestion that caffeine increases the parasympathetic modulation of heart rate.Clinical trial registration number: NCT05521386.

The Reliability of a Single-Trial Measurement of Maximal Accumulated Oxygen Deficit Determined via Perceptually-Regulated Exercise.

Purpose: The aim of this study was to evaluate the reliability of a single-trial determination of maximal accumulated oxygen deficit (MAOD) achieved via the aid of perceptually-regulated incremental exercise. Methods: 14 trained male cyclists (age: 45 ± 8 yrs; height: 1.82 ± 0.06 m; mass: 79.7 ± 6.7 kg; V˙O2max: 4.09 ± 0.57 L·min-1) performed three trials of a submaximal incremental cycling test followed by a test to exhaustion at 116% of predicted V˙O2max. The intensity for each stage of the incremental test was regulated by participants to elicit perceived exertion levels of 9-15 on the Borg (6-20) scale. Linear regression was used to estimate V˙O2max at a perceived exertion level of 19. MAOD was calculated from the difference between predicted and actual oxygen demand in the test to exhaustion, reported in oxygen equivalents (O2 eq). A separate incremental test was used to measure V˙O2max directly. Results: Correlation coefficients between perceived exertion and V˙O2 across trials were strong (r ≥0.99), and there were no between-trial differences in predicted V˙O2max (4.03 ± 1.04, 3.76 ± 0.53, and 3.69 ± 0.64 L·min-1, respectively; p = .142) or MAOD (2.75 ± 2.28, 2.50 ± 1.53, and 2.93 ± 1.40 L O2 eq, respectively; p = .633). Nevertheless, the coefficients of variation for predicted V˙O2max (14.2%) and MAOD (142.8%) were poor. Conclusions: The prediction of V˙O2max from perceptually-regulated exercise displays a level of test-retest reliability which prevents its use as a means of evaluating MAOD reliably in a single-trial.

The efficacy of genotype-based dietary or physical activity advice in changing behavior to reduce the risk of cardiovascular disease, type II diabetes mellitus or obesity: a systematic review and meta-analysis.

CONTEXT: Despite clear evidence that adherence to dietary and physical activity advice can reduce the risk of cardiometabolic disease, a significant proportion of the population do not follow recommendations. Personalized advice based on genetic variation has been proposed for motivating behavior change, although research on its benefits to date has been contradictory. OBJECTIVE: To evaluate the efficacy of genotype-based dietary or physical activity advice in changing behavior in the general population and in individuals who are at risk of cardiovascular disease (CVD) or type II diabetes mellitus (T2DM). DATA SOURCES: MEDLINE, EMBASE, PsycInfo, and the Cochrane Central Register of Controlled Trials (CENTRAL) were searched up to January 7, 2022. Randomized controlled trials of a genotype-based dietary and/or physical activity advice intervention that aimed to change dietary and/or physical activity behavior were included. DATA EXTRACTION: Abstracts of 7899 records were screened, and 14 reports from 11 studies met the inclusion criteria. DATA ANALYSIS: Genotype-based dietary or physical activity advice was found to have no effect on dietary behavior in any of the studies (standardized mean difference [SMD] .00 [-.11 to .11], P = .98), even when analyzed by subgroup: "at risk" (SMD .00 [-.16 to .16, P = .99]; general population (SMD .01 [-.14 to .16], P = .87). The physical activity behavior findings were similar for all studies (SMD -.01 [-.10 to .08], P = .88), even when analyzed by subgroup: "at risk" (SMD .07 [-.18 to .31], P = .59); general population (SMD -.02 [-.13 to .10], P = .77). The quality of the evidence for the dietary behavior outcome was low; for the physical activity behavior outcome it was moderate. CONCLUSIONS: Genotype-based advice does not affect dietary or physical activity behavior more than general advice or advice based on lifestyle or phenotypic measures. This was consistent in studies that recruited participants from the general population as well as in studies that had recruited participants from populations at risk of CVD or T2DM. SYSTEMATIC REVIEW REGISTRATION: PROSPERO registration no. CRD42021231147.

A cross-sectional retrospective survey of injury situation and prevalence in female recreational netball players with a focus on knee injuries.

OBJECTIVES: To examine situations of injury and injury prevalence in female adult recreational netball players with a focus on knee injuries. DESIGN: Cross sectional retrospective online survey. PARTICIPANTS: 193 female adult recreational netball players. MAIN OUTCOME MEASURES: Any injury sustained in the previous 12 months, situation of injury, any knee injuries sustained in the previous five years, the length of time unable to play netball, and knee injury management. RESULTS: In the previous 12 months, 61% of respondents sustained injury to the lower limb, and 27% to the upper limb. Lower limb injury situations were mostly landings (46%). Upper limb injury situations were mostly collisions with an opponent (27%). 46% reported sustaining a knee injury in the previous five years. Following knee injury, players were unable to play netball for 6.8 ± 7.0 months (training); and 8.2 ± 7.4 months (matches) respectively. CONCLUSIONS: Lower limb injury is more common than upper limb injury in recreational adult female adult netball players. Landing was the most common situation of injury for the lower limb including knee injuries. In the previous five years, nearly half of the players had sustained a knee injury resulting in more than six months out of the game.

Short-Term Creatine Supplementation and Repeated Sprint Ability-A Systematic Review and Meta-Analysis.

The aim of this study was to conduct a systematic review and meta-analysis of the effects of short-term creatine supplementation on repeated sprint ability. Fourteen studies met the inclusion criteria of adopting double-blind randomized placebo-controlled designs in which participants (age: 18-60 years) completed a repeated sprint test (number of sprints: 4 < n ≤ 20; sprint duration: ≤10 s; recovery duration: ≤90 s) before and after supplementing with creatine or placebo for 3-7 days in a dose of ∼20 g/day. No exclusion restrictions were placed on the mode of exercise. Meta-analyses were completed using random-effects models, with effects on measures of peak power output, mean power output, and fatigue (performance decline) during each repeated sprint test presented as standardized mean difference (δ), and with effects on body mass and posttest blood lactate concentration presented as raw mean difference (D). Relative to placebo, creatine resulted in a significant increase in body mass (D = 0.79 kg; p < .00001) and mean power output (δ = 0.61; p = .002). However, there was no effect of creatine on measures of peak power (δ = 0.41; p = .10), fatigue (δ = 0.08; p = .61), or posttest blood lactate concentration (D = 0.22 L/min; p = .60). In conclusion, creatine supplementation may increase mean power output during repeated sprint tests, although the absence of corresponding effects on peak power and fatigue means that more research, with measurements of intramuscular creatine content, is necessary to confirm.

Does personalised nutrition advice based on apolipoprotein E and methylenetetrahydrofolate reductase genotype affect dietary behaviour?

Background: Dietary intake is linked to numerous modifiable risk factors of cardiovascular disease. Current dietary recommendations in the UK to reduce the risk of cardiovascular disease are not being met. A genotype-based personalised approach to dietary recommendations may motivate individuals to make positive changes in their dietary behaviour. Aim: To determine the effect of a personalised nutrition intervention, based on apolipoprotein E (ApoE, rs7412; rs429358) and methylenetetrahydrofolate reductase (MTHFR, rs1801133) genotype, on reported dietary intake of saturated fat and folate in participants informed of a risk genotype compared to those informed of non-risk genotype. Methods: Baseline data (n = 99) were collected to determine genotype (non-risk vs risk), dietary intake and cardiovascular risk (Q-Risk®2 cardiovascular risk calculator). Participants were provided with personalised nutrition advice via email based on their ApoE and MTHFR genotype and reported intake of folate and saturated fat. After 10 days, dietary intake data were reported for a second time. Results: Personalised nutrition advice led to favourable dietary changes, irrespective of genotype, in participants who were not meeting dietary recommendations at baseline for saturated fat (p < 0.001) and folate (p = 0.002). Only participants who were informed of a risk ApoE genotype met saturated fat recommendations following personalised nutrition advice. Conclusion: Incorporation of genotype-based personalised nutrition advice in a diet behaviour intervention may elicit favourable changes in dietary behaviour in participants informed of a risk genotype. Participants informed of a non-risk genotype also respond to personalised nutrition advice favourably but to a lesser extent.

Situations and mechanisms of non-contact knee injury in adult netball: A systematic review.

OBJECTIVES: Noncontact knee injuries in netball are a concern due to a range of negative consequences. To reduce the number of injuries, identifying the situation and mechanism of injury is important. This systematic review examined the literature reporting the situation and mechanism of noncontact knee injury in netball. DESIGN: Systematic Review. METHODS: PRISMA guidelines were followed and specific key-term combinations used to search databases. Descriptive and analytic-observational studies reporting the situation or mechanism of noncontact knee injury in females playing netball were included (evaluated using frequency counts). RESULTS: Six articles were included (combined sample 11,401). Players self-reported the situation of injury in five studies, only one study reported both the situation and mechanism of injury. Landing was the most reported situation of knee injury, representing 46.6% of all knee injuries whilst knee abduction (valgus) collapse was the most observed mechanism. Situation and mechanism of noncontact knee injury in netball were not adequately reported. CONCLUSIONS: Despite the variations in reporting methods, landing is the most common situation of injury. As only one study reported mechanism of injury, it is difficult to draw conclusions but the mechanism of noncontact knee injury in netball appears similar to those identified in other female athletes.

Caffeine, exercise physiology, and time-trial performance: no effect of ADORA2A or CYP1A2 genotypes.

The aim of this study was to investigate the influence of ADORA2A and CYP1A2 genotypes on the physiological and ergogenic effects of caffeine. Sixty-six male cyclists were screened for ADORA2A and CYP1A2 genotypes; with 40 taking part subsequently in a randomised, double-blind, placebo-controlled study. Trial 1 was used to establish the oxygen uptake-power output relationship and maximal oxygen uptake. In trials 2 and 3, participants ingested 5 mg·kg-1 of caffeine or placebo 1 h before completing a submaximal incremental cycling test, followed by a time-trial (∼30 min). Relative to placebo, caffeine led to a significant reduction in time to complete the time-trial (caffeine: 29.7 ± 1.8 min; placebo: 30.8 ± 2.3 min); but there was no effect of genotype. During submaximal exercise, caffeine reduced mean heart rate by 2.9 ± 3.7 beats·min-1, with effects dissipating as exercise intensity increased. Caffeine also significantly reduced perceived exertion by 0.5 ± 0.8, and increased blood lactate by 0.29 ± 0.42 mmol·L-1, respiratory exchange ratio by 0.013 ± 0.032, and minute ventilation by 3.1 ± 6.8 L·min-1. Nonetheless, there were no supplement × genotype interactions. In conclusion, caffeine influences physiological responses to submaximal exercise and improves time-trial performance irrespective of ADORA2A or CYP1A2 genotypes. Novelty: Caffeine affects physiological responses at rest and during submaximal exercise independent of ADORA2A or CYP1A2 genotypes. Variability in the effect of caffeine on time-trial performance is not explained by ADORA2A or CYP1A2 genotypes.

The effect of the menstrual cycle on running economy.

BACKGROUND: The aim of this study was to examine the effect of the menstrual cycle on running economy (RE). METHODS: Using a repeated-measures design, ten eumenorrheic, trained female runners (age: 32±6 yrs, V̇O2max: 59.7±4.7 mL·kg-1·min-1) completed four, weekly, identical sub-maximal and maximal incremental step tests on a treadmill to measure physiological responses across a full menstrual cycle. For phase comparison, the results from the trials that fell in the early follicular (low estrogen, low progesterone), late follicular (high estrogen, low progesterone) and mid-luteal (high estrogen, high progesterone) phases were used. RESULTS: There was a significant effect of menstrual cycle phase on RE (P=0.001), with RE in the mid-luteal (ML) phase being worse than that of the early follicular (EF) (+2.33 mL·kg-1·min-1; P=0.026) and late follicular (LF) (+2.17 mL·kg-1·min-1; P=0.011) phases. The ML phase also resulted in elevated core temperature versus the EF (+0.51 ºC; P=0.001) and LF (+0.66 ºC; P=0.037) phases, and elevated minute ventilation versus the EF phase (+3.83 L·min-1; P=0.003). No significant effects of menstrual cycle phase were found on body mass, heart rate, ratings of perceived exertion, time-to-exhaustion, maximal oxygen consumption, or blood lactate concentration. CONCLUSIONS: In the ML phase, which causes increased core temperature and minute ventilation, RE is impaired at exercise intensities that are applicable to training and performance. In physiologically stressful environments, this impairment in RE may have a significant impact on training and performance.

The effects of acute static and dynamic stretching on spring-mass leg stiffness.

OBJECTIVE: This study investigated the effect of brief static and dynamic stretching on spring-mass leg stiffness in a vertical bilateral hopping task. METHOD: 38 men and 18 women were randomly assigned to either a natural (NAT; n = 27), or maximal (MAX; n = 29) hopping group. NAT bounced at their self-selected stiffness and MAX were instructed to bounce as stiffly as possible. Hopping was performed at 2.2 Hz on a force plate. After each of four treatment conditions (no stretch, 30 s stretch, multiple (4 × ) 30 s stretch, and dynamic stretch), subjects completed three × 30 s bouts (2 min rest periods) of hopping, in a counterbalanced crossover design. Stretches were performed on: gluteals, hamstrings, quadriceps and calves. Spring-mass leg stiffness was calculated as the ratio of peak vertical force to vertical displacement during ground contact. RESULTS: The results revealed that men displayed greater leg stiffness than women (mean difference: 6.04 kN m-1; 95% likely range: 1.94-10.13 kN m-1), and that MAX produced higher stiffness values than NAT (mean difference: 10.93 kN m-1; 95% likely range: 6.84-15.03 kN m-1). Although there were no significant effects of treatment (p = 0.85) or time (p = 0.54) on leg stiffness, there was a significant treatment × time interaction (p = 0.015). Nevertheless, post hoc analyses were unable to identify where those differences were. CONCLUSION: Relative to controls, the results of this study showed that brief static stretching or non task-specific dynamic stretching does not affect spring-mass leg stiffness during vertical bilateral hopping.

The Effects of Sodium Phosphate Supplementation on Physiological Responses to Submaximal Exercise and 20 km Cycling Time-Trial Performance.

The aim of this study was to examine the effects of sodium phosphate (SP) supplementation on physiological responses to submaximal exercise and 20 km cycling time-trial performance. Using a randomized, double-blind, crossover design, 20 endurance-trained male cyclists (age: 31 ± 6 years; height: 1.82 ± 0.07 m; body mass: 76.3 ± 7.0 kg; maximal oxygen uptake [V̇O2max]: 57.9 ± 5.5 mL·kg-1·min-1) completed two supplementation trials separated by a 14-day washout period. The trials consisted of 10 minutes of cycling at 65% V̇O2max followed by a 20 km time trial. Expired air was monitored throughout each trial for the evaluation of V̇O2, minute ventilation (V̇E), and respiratory exchange ratio (RER). Heart rate was monitored during each trial along with ratings of perceived exertion (RPE) and blood lactate concentration. For four days before each trial, participants ingested 50 mg·kg fat-free mass-1·day-1 of either SP or placebo. There were no effects (p ≥ .05) of supplementation on physiological responses during cycling at 65% V̇O2max. There were also no effects of supplementation on time-trial performance (placebo: 32.8 ± 2.2 min; SP: 32.8 ± 2.3 min). Nevertheless, relative to placebo, SP increased V̇E (mean difference: 3.81 L·min-1; 95% confidence interval: [0.16, 7.46 L·min-1]), RER (mean difference: 0.020; 95% confidence interval: [0.004, 0.036]), and RPE (mean difference: 0.39; 95% confidence interval: [0.04, 0.73]) during time trials, as well as post time-trial blood lactate concentration (mean difference: 1.06 mmol·L-1; 95% confidence interval: [0.31, 1.80 mmol·L-1]). In conclusion, SP supplementation has no significant effects on submaximal physiological responses or 20 km time-trial performance.

Caffeine and Sprint Cycling Performance: Effects of Torque Factor and Sprint Duration.

PURPOSE: To investigate the influence of torque factor and sprint duration on the effects of caffeine on sprint cycling performance. METHODS: Using a counterbalanced, randomized, double-blind, placebo-controlled design, 13 men completed 9 trials. In trial 1, participants completed a series of 6-s sprints at increasing torque factors to determine the torque factor, for each individual, that elicited the highest (Toptimal) peak power output (PPO). The remaining trials involved all combinations of torque factor (0.8 N·m-1·kg-1 vs Toptimal), sprint duration (10 s vs 30 s), and supplementation (caffeine [5 mg·kg-1] vs placebo). RESULTS: There was a significant effect of torque factor on PPO, with higher values at Toptimal (mean difference 168 W; 95% likely range 142-195 W). There was also a significant effect of sprint duration on PPO, with higher values in 10-s sprints (mean difference 52 W; 95% likely range 18-86 W). However, there was no effect of supplementation on PPO (P = .056). Nevertheless, there was a significant torque factor × sprint duration × supplement interaction (P = .036), with post hoc tests revealing that caffeine produced a higher PPO (mean difference 76 W; 95% likely range 19-133 W) when the sprint duration was 10 s and the torque factor was Toptimal. CONCLUSION: The results of this study show that when torque factor and sprint duration are optimized, to allow participants to express their highest PPO, there is a clear effect of caffeine on sprinting performance.

Methodological Approaches and Related Challenges Associated With the Determination of Critical Power and Curvature Constant.

Muniz-Pumares, D, Karsten, B, Triska, C, and Glaister, M. Methodological approaches and related challenges associated with the determination of critical power and W'. J Strength Cond Res 33(2): 584-596, 2019-The relationship between exercise intensity and time to task failure (P-T relationship) is hyperbolic, and characterized by its asymptote (critical power [CP]) and curvature constant (W'). The determination of these parameters is of interest for researchers and practitioners, but the testing protocol for CP and W' determination has not yet been standardized. Conventionally, a series of constant work rate (CWR) tests to task failure have been used to construct the P-T relationship. However, the duration, number, and recovery between predictive CWR and the mathematical model (hyperbolic or derived linear models) are known to affect CP and W'. Moreover, repeating CWR may be deemed as a cumbersome and impractical protocol. Recently, CP and W' have been determined in field and laboratory settings using time trials, but the validity of these methods has raised concerns. Alternatively, a 3-minute all-out test (3MT) has been suggested, as it provides a simpler method for the determination of CP and W', whereby power output at the end of the test represents CP, and the amount of work performed above this end-test power equates to W'. However, the 3MT still requires an initial incremental test and may overestimate CP. The aim of this review is, therefore, to appraise current methods to estimate CP and W', providing guidelines and suggestions for future research where appropriate.

Moderate-Intensity Oxygen Uptake Kinetics: Is a Mono-Exponential Function Always Appropriate to Model the Response?

PURPOSE: This study investigated the existence of the oxygen uptake ([Formula: see text]) overshoot and the effects of exercise intensity and fitness status on the [Formula: see text] response during moderate-intensity exercise. METHODS: Twelve "high-fitness" (Mage = 26 ± 5 years; Mheight = 184.1 ± 5.4 cm; Mbody mass = 76.6 ± 8.9 kg; mean peak oxygen uptake ([Formula: see text]peak) = 59.0 ± 3.3 mL·kg-1·min·-1) and 11 "moderate-fitness" (Mage = 29 ± 5 years; Mheight = 178.7 ± 7.5 cm; Mbody mass = 81.7 ± 10.9 kg; MV̇O2peak = 45.2 ± 3.1 mL·kg-1·min·-1) participants performed square-wave transitions from unloaded cycling to 3 different intensities (70%, 82.5%, and 95% of the gas exchange threshold). The data were modeled using both a mono-exponential function (Model 1) and a function that included a switch-on component (Model 2). The overshoot was computed by subtracting the steady state from the peak of the modeled response and by calculating the area of the curve that was above steady state. RESULTS: The goodness of fit was affected by model type (p = .002) and exercise intensity (p < .001). High-fitness participants displayed a smaller τ (p < .05) and a larger amplitude (p < .05) and were more likely to overshoot the steady state (p = .035). However, while exercise intensity did affect the amplitude (p < .001), it did not affect τ (p ≥ .05) or the likelihood of an overshoot occurring (p = .389). CONCLUSION: While exercise intensity did not alter the [Formula: see text] response, fitness status affected τ and the likelihood of an overshoot occurring. The overshoot questions the traditional approach to modeling moderate-intensity [Formula: see text] data.

Caffeine and Physiological Responses to Submaximal Exercise: A Meta-Analysis.

The aim of this study was to carry out a systematic review and meta-analysis of the effects of caffeine supplementation on physiological responses to submaximal exercise. A total of 26 studies met the inclusion criteria of adopting double-blind, randomized crossover designs that included a sustained (5-30 min) fixed-intensity bout of submaximal exercise (constrained to 60-85% maximal rate of oxygen consumption) using a standard caffeine dose of 3-6 mg·kg-1 administered 30-90 min prior to exercise. Meta-analyses were completed using a random-effects model, and data are presented as raw mean difference (D) with associated 95% confidence limits (CLs). Relative to placebo, caffeine led to significant increases in submaximal measures of minute ventilation (D = 3.36 L·min-1; 95% CL, 1.63-5.08; P = .0001; n = 73), blood lactate (D = 0.69 mmol·L-1; 95% CL, 0.46-0.93; P < .00001; n = 208), and blood glucose (D = 0.42 mmol·L-1; 95% CL, 0.29-0.55; P < .00001; n = 129). In contrast, caffeine had a suppressive effect on ratings of perceived exertion (D = -0.8; 95% CL, -1.1 to -0.6; P < .00001; n = 147). Caffeine had no effect on measures of heart rate (P = .99; n = 207), respiratory exchange ratio (P = .18; n = 181), or oxygen consumption (P = .92; n = 203). The positive effects of caffeine supplementation on sustained high-intensity exercise performance are widely accepted, although the mechanisms to explain that response are currently unresolved. This meta-analysis has revealed clear effects of caffeine on various physiological responses during submaximal exercise, which may help explain its ergogenic action.

The effect of the oxygen uptake-power output relationship on the prediction of supramaximal oxygen demands.

BACKGROUND: The aim of this study was to investigate the relationship between oxygen uptake (V̇O2) and power output at intensities below and above the lactate threshold (LT) in cyclists; and to determine the reliability of supramaximal power outputs linearly projected from these relationships. METHODS: Nine male cyclists (mean±standard deviation age: 41±8 years; mass: 77±6 kg, height: 1.79±0.05 m and V̇O2max: 54±7 mL∙kg-1∙min-1) completed two cycling trials each consisting of a step test (10×3 min stages at submaximal incremental intensities) followed by a maximal test to exhaustion. The lines of best fit for V̇O2 and power output were determined for: the entire step test; stages below and above the LT, and from rolling clusters of five consecutive stages. Lines were projected to determine a power output predicted to elicit 110% peak V̇O2. RESULTS: There were strong linear correlations (r≥0.953; P<0.01) between V̇O2 and power output using the three approaches; with the slope, intercept, and projected values of these lines unaffected (P≥0.05) by intensity. The coefficient of variation of the predicted power output at 110% V̇O2max was 6.7% when using all ten submaximal stages. CONCLUSIONS: Cyclists exhibit a linear V̇O2 and power output relationship when determined using 3 min stages, which allows for prediction of a supramaximal intensity with acceptable reliability.

Accumulated Oxygen Deficit During Exercise to Exhaustion Determined at Different Supramaximal Work Rates.

PURPOSE: The aim of the study was to determine the effect of supramaximal exercise intensity during constant work-rate cycling to exhaustion on the accumulated oxygen deficit (AOD) and to determine the test-retest reliability of AOD. METHODS: Twenty-one trained male cyclists and triathletes (mean ± SD for age and maximal oxygen uptake [V̇O2max] were 41 ± 7 y and 4.53 ± 0.54 L/min, respectively) performed initial tests to determine the linear relationship between V̇O2 and power output, and V̇O2max. In subsequent trials, AOD was determined from exhaustive square-wave cycling trials at 105%, 112.5% (in duplicate), 120%, and 127.5% V̇O2max. RESULTS: Exercise intensity had an effect (P = .011) on the AOD (3.84 ± 1.11, 4.23 ± 0.96, 4.09 ± 0.87, and 3.93 ± 0.89 L at 105%, 112.5%, 120%, and 127.5% V̇O2max, respectively). Specifically, AOD at 112.5% V̇O2max was greater than at 105% V̇O2max (P = .033) and at 127.5% V̇O2max (P = .022), but there were no differences between the AOD at 112.5% and 120% V̇O2max. In 76% of the participants, the maximal AOD occurred at 112.5% or 120% V̇O2max. The reliability statistics of the AOD at 112.5% V̇O2max, determined as intraclass correlation coefficient and coefficient of variation, were .927 and 8.72%, respectively. CONCLUSIONS: The AOD, determined from square-wave cycling bouts to exhaustion, peaks at intensities of 112.5-120% V̇O2max. Moreover, the AOD at 112.5% V̇O2max exhibits an 8.72% test-retest reliability.

The effect of weightlifting shoes on the kinetics and kinematics of the back squat.

Weightlifting shoes (WS) are often used by athletes to facilitate their squat technique; however, the nature of these benefits is not well understood. In this study, the effects of footwear and load on the mechanics of squatting were assessed for 32 participants (age: 25.4 ± 4.4 years; mass 72.87 ± 11.35 kg) grouped by sex and experience. Participants completed loaded and unloaded back squats wearing both WS and athletic shoes (AS). Data were collected utilising a 3D motion capture system synchronised with a force platform and used to calculate kinematic and kinetic descriptors of squatting. For both load conditions, WS gave significantly (P < 0.05) reduced ankle flexion and increased knee flexion than AS, as well as a more upright trunk and greater knee moment for the unloaded condition. In addition, the experienced group experienced a significantly greater increase in knee and hip flexion with WS than the novices when unloaded. These results are consistent with the idea that WS permit a more knee flexed, upright posture during squatting, and provide preliminary evidence that experienced squatters are more able to exploit this effect. Decisions about footwear should recognise the effect of footwear on movement and reflect an athlete's movement capabilities and training objectives.

A comparison of methods to estimate anaerobic capacity: Accumulated oxygen deficit and W' during constant and all-out work-rate profiles.

This study investigated (i) whether the accumulated oxygen deficit (AOD) and curvature constant of the power-duration relationship (W') are different during constant work-rate to exhaustion (CWR) and 3-min all-out (3MT) tests and (ii) the relationship between AOD and W' during CWR and 3MT. Twenty-one male cyclists (age: 40 ± 6 years; maximal oxygen uptake [V̇O2max]: 58 ± 7 ml · kg-1 · min-1) completed preliminary tests to determine the V̇O2-power output relationship and V̇O2max. Subsequently, AOD and W' were determined as the difference between oxygen demand and oxygen uptake and work completed above critical power, respectively, in CWR and 3MT. There were no differences between tests for duration, work, or average power output (P ≥ 0.05). AOD was greater in the CWR test (4.18 ± 0.95 vs. 3.68 ± 0.98 L; P = 0.004), whereas W' was greater in 3MT (9.55 ± 4.00 vs. 11.37 ± 3.84 kJ; P = 0.010). AOD and W' were significantly correlated in both CWR (P < 0.001, r = 0.654) and 3MT (P < 0.001, r = 0.654). In conclusion, despite positive correlations between AOD and W' in CWR and 3MT, between-test differences in the magnitude of AOD and W', suggest that both measures have different underpinning mechanisms.

The Effects of Caffeine Supplementation on Physiological Responses to Submaximal Exercise in Endurance-Trained Men.

OBJECTIVES: The aim of this study was to evaluate the effects of caffeine on physiological responses to submaximal exercise, with a focus on blood lactate concentration ([BLa]). METHODS: Using a randomised, single-blind, crossover design; 16 endurance-trained, male cyclists (age: 38 ± 8 years; height: 1.80 ± 0.05 m; body mass: 76.6 ± 7.8 kg; [Formula: see text]: 4.3 ± 0.6 L∙min-1) completed four trials on an electromagnetically-braked cycle ergometer. Each trial consisted of a six-stage incremental test (3 minute stages) followed by 30 minutes of passive recovery. One hour before trials 2-4, participants ingested a capsule containing 5 mg∙kg-1 of either caffeine or placebo (maltodextrin). Trials 2 and 3 were designed to evaluate the effects of caffeine on various physiological responses during exercise and recovery. In contrast, Trial 4 was designed to evaluate the effects of caffeine on [BLa] during passive recovery from an end-exercise concentration of 4 mmol∙L-1. RESULTS: Relative to placebo, caffeine increased [BLa] during exercise, independent of exercise intensity (mean difference: 0.33 ± 0.41 mmol∙L-1; 95% likely range: 0.11 to 0.55 mmol∙L-1), but did not affect the time-course of [BLa] during recovery (p = 0.604). Caffeine reduced ratings of perceived exertion (mean difference: 0.5 ± 0.7; 95% likely range: 0.1 to 0.9) and heart rate (mean difference: 3.6 ± 4.2 b∙min-1; 95% likely range: 1.3 to 5.8 b∙min-1) during exercise, with the effect on the latter dissipating as exercise intensity increased. Supplement × exercise intensity interactions were observed for respiratory exchange ratio (p = 0.004) and minute ventilation (p = 0.034). CONCLUSIONS: The results of the present study illustrate the clear, though often subtle, effects of caffeine on physiological responses to submaximal exercise. Researchers should be aware of these responses, particularly when evaluating the physiological effects of various experimental interventions.