Validity, Reliability and Sensitivity of Measures of Sporting Performance

The effect of two β-alanine dosing strategies on 30-minute rowing performance: a randomized, controlled trial

Background

β-alanine (βA) supplementation has been shown to increase intramuscular carnosine content and subsequent high-intensity performance in events lasting < 4 minutes (min), which may be dependent on total, as opposed to daily, dose. The ergogenic effect of βA has also been demonstrated for 2000-m rowing performance prompting interest in whether βA may be beneficial for sustained aerobic exercise. This study therefore investigated the effect of two βA dosing strategies on 30-min rowing and subsequent sprint performance.

Methods

Following University Ethics approval, twenty-seven healthy, male rowers (age: 24 ± 2 years; body-height: 1.81 ± 0.02 m; body-mass: 82.3 ± 2.5 kg; body-fat: 14.2 ± 1.0%) were randomised in a double-blind manner to 4 weeks of: i) βA (2.4 g·d^− 1, βA1); ii) matched total βA (4.8 g on alternate days, βA2); or iii) cornflour placebo (2.4 g·d^− 1, PL). Participants completed a laboratory 30-min rowing time-trial, followed by 3x30-seconds (s) maximal sprint efforts at days 0, 14 and 28 (T1-T3). Total distance (m), average power (W), relative average power (W·kg^− 1), cardio-respiratory measures and perceived exertion were assessed for each 10-min split. Blood lactate ([La-]_b mmol·L^− 1) was monitored pre-post time-trial and following maximal sprint efforts. A 3-way repeated measures ANOVA was employed for main analyses, with Bonferonni post-hoc assessment (P ≤ 0.05).

Results

Total 30-min time-trial distance significantly increased from T1-T3 within βA1 only (7397 ± 195 m to 7580 ± 171 m, P = 0.002, ƞp² = 0.196), including absolute average power (194.8 ± 18.3 W to 204.2 ± 15.5 W, P = 0.04, ƞp² = 0.115) and relative average power output (2.28 ± 0.15 W·kg^− 1 to 2.41 ± 0.12 W·kg^− 1, P = 0.031, ƞp² = 0.122). These findings were potentially explained by within-group significance for the same variables for the first 10 min split (P ≤ 0.01), and for distance covered (P = 0.01) in the second 10-min split. However, no condition x time interactions were observed. No significant effects were found for sprint variables (P > 0.05) with comparable values at T3 for mean distance (βA1: 163.9 ± 3.8 m; βA2: 161.2 ± 3.5 m; PL: 162.7 ± 3.6 m), average power (βA1: 352.7 ± 14.5 W; βA2: 342.2 ± 13.5 W; PL: 348.2 ± 13.9 W) and lactate (βA1: 10.0 ± 0.9 mmol·L^− 1; βA2: 9.2 ± 1.1 mmol·L^− 1; PL: 8.7 ± 0.9 mmol·L^− 1).

Conclusions

Whilst daily βA may confer individual benefits, these results demonstrate limited impact of βA (irrespective of dosing strategy) on 30-min rowing or subsequent sprint performance. Further investigation of βA dosage > 2.4 g·d^− 1 and/or chronic intervention periods (> 4–8 weeks) may be warranted based on within-group observations.

Protein intake in the early recovery period after exhaustive exercise improves performance the following day

The aim of the present study was to investigate the effect of protein and carbohydrate ingestion during early recovery from exhaustive exercise on performance after 18-h recovery. Eight elite cyclists (V̇o2max: 74.0 ± 1.6 ml·kg−1·min−1) completed two exercise and diet interventions in a double-blinded, randomized, crossover design. Participants cycled first at 73% of V̇o2max (W73%) followed by 1-min intervals at 90% of V̇o2max until exhaustion. During the first 2 h of recovery, participants ingested either 1.2 g carbohydrate·kg−1·h−1 (CHO) or 0.8 g carbohydrate + 0.4 g protein·kg−1·h−1 (CHO + PROT). The diet during the remaining recovery period was similar for both interventions and adjusted to body weight. After an 18-h recovery, cycling performance was assessed with a 10-s sprint test, 30 min of cycling at W73%, and a cycling time trial (TT). The TT was 8.5% faster (41:53 ± 1:51 vs. 45:26 ± 1:32 min; P < 0.03) after CHO + PROT compared with CHO. Mean power output during the sprints was 3.7% higher in CHO + PROT compared with CHO (1,063 ± 54 vs. 1,026 ± 53 W; P = 0.01). Nitrogen balance in the recovery period was negative in CHO and neutral in CHO + PROT (−82.4 ± 11.5 vs. 7.0 ± 15.4 mg/kg; P < 0.01). In conclusion, TT and sprint performances were improved 18 h after exhaustive cycling by CHO + PROT supplementation during the first 2 h of recovery compared with isoenergetic CHO supplementation. Our results indicate that intake of carbohydrate plus protein after exhaustive endurance exercise more rapidly converts the body from a catabolic to an anabolic state than carbohydrate alone, thus speeding recovery and improving subsequent cycling performance.

NEW & NOTEWORTHY Prolonged high intensity endurance exercise depends on glycogen utilization and high oxidative capacity. Still, exhaustion develops and effective recovery strategies are required to compete in multiday stage races. We show that coingestion of protein and carbohydrate during the first 2 h of recovery is superior to isoenergetic intake of carbohydrate to stimulate recovery, and improves both endurance time-trial and 10-s sprint performance the following day in elite cyclists.

Reliability, usefulness and construct validity of the Combined Basketball Skill Test (CBST)

This study aimed to assess the reliability, usefulness and construct validity of the newly developed Combined Basketball Skill Test (CBST). Fifteen recreational (age = 22.8 ± 4.2 y, stature = 184.8 ± 6.5 cm, body mass = 81.6 ± 9.6 kg, training experience = 9.8 ± 5.3 y) and fifteen semiprofessional (age = 18.9 ± 3.3 y, stature = 190.5 ± 8.1 cm, body mass = 84.2 ± 11.2 kg, training experience = 11.1 ± 3.5 y) players volunteered to participate in this study. Test-retest reliability and usefulness were examined for recreational players, while construct validity was evaluated comparing the two player groups. The CBST is composed of 12 trials and its outcome measures include: completion time (sum of the 12 trial times); penalty time (sum of the times from the 12 trials); performance time (completion time + penalty time) and total number of errors. Relative reliability analysis showed acceptable ICC values (i.e. ≥0.70) in all the studied variables. Absolute reliability analysis showed a CV < 5% for completion (1.6%) and performance (2.0%) time, while a CV >5% is reported for the remaining variables. The usefulness of the test was considered "Marginal" and "Good" when comparing TE values with SWC₀₂ and SWC₀₅, respectively for all the studied variables. Likely and very likely differences were shown between recreational and semiprofessional players in all investigated variables. Results showed that the CBST is reliable, useful to detect moderate changes and valid to assess basketball skills.

Using Portable Force Plates to Assess Vertical Jump Performance: A Metrological Appraisal

The purpose of this study was to verify the metrological properties of portable force plates that are used to assess countermovement jump performance. While 88 participants (38 males, 50 females) were included in the agreement analyses, 84 participants (37 males and 47 females) completed the reliability part of the study. This randomized crossover design suggests that portable force plates could be used interchangeably with a reference system. Indeed, the differences between both devices were all considered trivial (effect size (ES) < 0.20), and the mean bias was never greater than 3.41% in comparison to the reference system. In addition, the absolute and relative reliability parameters were found to be acceptable for clinical use, even when used on different floor surfaces. However, it was found that the ratio between flight time and contraction time (FTCT) showed questionable reliability when tests were conducted on different surfaces (intraclass correlation coefficient = 0.49; coefficient of variation = 26.72%). Therefore, practitioners should be careful when installing the portable device on different floor surfaces in order to optimize the reliability and the ability to detect real change in the context of a countermovement jump monitoring process.

Time-trial performance is not impaired in either competitive athletes or untrained individuals following a prolonged cognitive task

It has been reported that mental fatigue decreases exercise performance during high-intensity constant-work-rate exercise (CWR) and self-paced time trials (TT) in recreationally-trained individuals. The purpose of this study was to determine whether performance is impaired following a prolonged cognitive task in individuals trained for competitive sport. Ten trained competitive athletes (ATH) and ten untrained healthy men (UNT) completed a 6-min severe-intensity CWR followed by a 6-min cycling TT immediately following cognitive tasks designed to either perturb (Stroop colour-word task and N-back task; PCT) or maintain a neutral (documentary watching; CON) mental state. UNT had a higher heart rate (75 ± 9 v. 69 ± 7 bpm; P = 0.002) and a lower positive affect PANAS score (19.9 ± 7.5 v. 24.3 ± 4.6; P = 0.036) for PCT compared to CON. ATH showed no difference in heart rate, but had a higher negative affect score for PCT compared to CON (15.1 ± 3.7 v. 12.2 ± 2.7; P = 0.029). Pulmonary O₂ uptake during CWR was not different between PCT and CON for ATH or UNT. Work completed during TT was not different between PCT and CON for ATH (PCT 103 ± 12 kJ; CON 102 ± 12 kJ; P > 0.05) or UNT (PCT 75 ± 11 kJ; CON 74 ± 12 kJ; P > 0.05). Compared to CON, during PCT, UNT showed unchanged psychological stress responses, whereas ATH demonstrated increased psychological stress responses. However, regardless of this distinction, exercise performance was not affected by PCT in either competitive athletes or untrained individuals.

Is the Functional Threshold Power a Valid Surrogate of the Lactate Threshold?

PURPOSE

To analyze the relationship between functional threshold power (FTP) and the lactate threshold (LT).

METHODS

A total of 20 male cyclists performed an incremental test in which LT was determined. At least 48 h later, they performed a 20-min time trial, and 95% of the mean power output was defined as FTP. Participants were divided into recreational (peak power output < 4.5 W·kg-1; n = 11) or trained cyclists (peak power output > 4.5 W·kg-1; n = 9) according to their fitness status.

RESULTS

The FTP (240 [35] W) was overall not significantly different (effect size = 0.20; limits of agreement = -2.4% [11.5%]) from the LT (246 [24] W), and both markers were strongly correlated (r = .95; P < .0001). Accounting for the participants' fitness status, no significant differences were found between FTP and LT (effect size = 0.22; limits of agreement =2.1% [7.8%]) in trained cyclists, but FTP was significantly lower than the LT (P = .0004, effect size = 0.81; limits of agreement =-6.5% [8.3%]) in recreational cyclists. A significant relationship was found between relative peak power output and the bias between FTP and the LT markers (r = .77; P < .0001).

CONCLUSIONS

FTP is a valid field test-based marker for the assessment of endurance fitness. However, caution should be taken when using FTP interchangeably with LT, as the bias between markers seems to depend on the athlete's fitness status. Whereas FTP provides a good estimate of LT in trained cyclists, in recreational cyclists, it may underestimate LT.

Supplemental Oxygen Does Not Influence Self-selected Work Rate at Moderate Altitude

INTRODUCTION

It is well known that supplemental oxygen can increase aerobic power output during high-intensity and/or maximal efforts at moderate altitude, yet the effects on self-selected work rate during lower-intensity, submaximal exercise are unknown. We reasoned that if the degree of arterial oxygen saturation (SaO2) influences teleoanticipatory regulation of power output, supplemental oxygen given at moderate altitude would increase average power output during exercise performed at self-selected work rates corresponding to RPE 9 (very light) and 13 (somewhat hard).

METHODS

Twenty-three subjects (17 males, 6 females) completed one familiarization [fraction of inspired O2 (FIO2) = 0.209] and two blinded, experimental trials (FIO2 = 0.209 and FIO2 = 0.267). In each trial, subjects self-regulated their work rate on a cycle ergometer to maintain RPE 9 for 5 min and RPE 13 for 10 min, before performing an incremental step test to exhaustion (25 W·min). Oxygen consumption (V˙O2) and SaO2 via pulse oximetry (SpO2) were continuously monitored. Subjects were asked to guess the experimental condition after each stage of the protocol.

RESULTS

Supplemental oxygen increased SpO2 throughout exercise (~4%; P < 0.001) and was associated with greater peak power output (4% ± 4%; P < 0.001) and V˙O2 (5% ± 10%; P = 0.010) during the incremental test, but did not increase average power output selected during exercise at RPE 9 (P = 0.235) or 13 (P = 0.992). Subjects were unable to perceive the difference in FIO2 at any stage (P > 0.14).

CONCLUSIONS

Small increases in inspired oxygen concentration at moderate altitude are imperceptible and do not appear to influence selection of submaximal work rates at RPE ≤ 13.

Effects of a single dose of beetroot juice on cycling time trial performance at ventilatory thresholds intensity in male triathletes

Background

Beetroot juice (BJ) is classified as a high-level supplement for improving sports performance. There is some controversy over the benefits of BJ supplementation for endurance exercise performance, especially when referring to well-trained athletes. This study examines the effects of acute BJ supplementation on cardioventilatory responses, exercise economy/efficiency, slow component of oxygen uptake, time trial performance, blood lactate, energy consumption, and carbohydrate and fat oxidation.

Methods

Twelve well-trained, male triathletes (aged 21–47 yr) were assigned in a randomized, double-blind, crossover design to receive 70 ml of BJ (6.5 mmol NO₃⁻) or placebo (PL). Three hours after taking the supplement, participants completed an endurance test on a cycle ergometer at a constant work rate (W) corresponding to first ventilatory threshold (VT1) (30 min) and second ventilatory threshold (VT2) time trial (~ 15 min).

Results

Maximal oxygen uptake was 54.78 ± 3.13 mL·min^− 1·kg^− 1, and gross efficiency was > 22% at each load intensity and experimental condition. No significant interaction effect (supplement*intensity) was observed on any of the cardioventilatory variables, efficiency/economy, VT2 time trial, energy expenditure, carbohydrate oxidation and fat oxidation (p > 0.05).

Conclusion

Our findings do not support an improvement in the variables examined in response to acute BJ supplementation. Probably, higher doses are needed for improving time trial performance in male triathletes during a cycle ergometer test conducted at a load intensity equivalent to the first and second ventilatory threshold.

Frequency Speed of Kick Test Performance Comparison Between Female Taekwondo Athletes of Different Competitive Levels

Santos, JFS and Franchini, E. Frequency speed of kick test performance comparison between female taekwondo athletes of different competitive levels. J Strength Cond Res 32(10): 2934-2938, 2018-Construct validity is a desirable characteristic in any performance test to differentiate athletes. However, no taekwondo-specific test was investigated with this purpose. The purpose of this study was to compare female taekwondo athletes grouped in different competitive levels. Forty-two female taekwondo athletes divided into International/National (median [interquartile range]; n = 21, age: 20 [18-25] years; body mass: 60 [53-72] kg; height: 164 [161-170] cm; and practice time: 8 [5-13] years) and State/Regional group (median [interquartile range]; n = 21; age: 18 [17-25] years; body mass: 57 [52-63] kg; height: 165 [160-172] cm; and practice time: 5 [2-8] years) volunteered to participate in this study. The female taekwondo athletes performed frequency speed of kick test (FSKT) with 10 seconds (FSKT10s) and intermittent 90 seconds (FSKTmult) during the competitive period. Differences between international/national and state/regional group were observed, with superiority to international/national group, for FSKT10s (U = 114.5, p = 0.007, ESr (effect size) = -0.42 [small]), FSKT1 (U = 127.0, p = 0.016, ESr = -0.37 [small]), FSKT2 (U = 108.5, p = 0.004, ESr = -0.45 [small]), FSKT3 (U = 127.0, p = 0.015, ESr = -0.37 [small]), and FSKTtotal (U = 124.0, p = 0.015, ESr = -0.38 [small]). Based on the results of this study, the FSKT seems to be a good tool to discriminate performance of female taekwondo athletes and could be used by coaches and athletes in their evaluation routines.

Effects of β-alanine and sodium bicarbonate supplementation on the estimated energy system contribution during high-intensity intermittent exercise

The effects of β-alanine (BA) and sodium bicarbonate (SB) on energy metabolism during work-matched high-intensity exercise and cycling time-trial performance were examined in 71 male cyclists. They were randomised to receive BA + placebo (BA, n = 18), placebo + SB (SB, n = 17), BA + SB (BASB, n = 19), or placebo + placebo (PLA, n = 18). BA was supplemented for 28 days (6.4 g day^-1) and SB (0.3 g kg^-1) ingested 60 min before exercise on the post-supplementation trial. Dextrose and calcium carbonate were placebos for BA and SB, respectively. Before (PRE) and after (POST) supplementation, participants performed a high-intensity intermittent cycling test (HICT-110%) consisting of four 60-s bouts at 110% of their maximal power output (60-s rest between bouts). The estimated contribution of the energy systems was calculated for each bout in 39 of the participants (BA: n = 9; SB: n = 10; BASB: n = 10, PLA: n = 10). Ten minutes after HICT-110%, cycling performance was determined in a 30-kJ time-trial test in all participants. Both groups receiving SB increased estimated glycolytic contribution in the overall HICT-110%, which approached significance (SB: + 23%, p = 0.068 vs. PRE; BASB: + 18%, p = 0.059 vs. PRE). No effects of supplementation were observed for the estimated oxidative and ATP-PCr systems. Time to complete 30 kJ was not significantly changed by any of the treatments, although a trend toward significance was shown in the BASB group (p = 0.06). We conclude that SB, but not BA, increases the estimated glycolytic contribution to high-intensity intermittent exercise when total work done is controlled and that BA and SB, either alone or in combination, do not improve short-duration cycling time-trial performance.

Test-retest reliability of knee extensors endurance test with elastic resistance

Background

Reliable clinical tests capable of measuring resistance are important tools for rehabilitation. One alternative that has recently increased in popularity is the use of elastic tubes, which stand out for being easy to handle, low cost, practical, and feasible.

Objective

Analyze the test-retest reliability of the knee extensors muscle fatigue resistance test (FRT) with elastic tubes.

Methods

A total of 116 healthy young males, aged between 18 and 30 years old, participated in the study. Participants performed three pre-test stages: orientation, load presentation, and familiarization with equipment, lasting two weeks. Subsequently, they performed the FRT on two occasions (test and retest), with an interval of seven days. The reliability analyzes were performed using the intraclass correlation coefficient (ICC) with 95% confidence interval and typical measurement error (TME), also expressed as coefficient of variation (CV%).

Results

The findings regarding the reliability of the test demonstrated satisfactory values (time: ICC = 0.66; 95%CI [0.50; 0.76]; CV(%) = 9.34; repetition: ICC = 0.61; 95%CI [0.46; 0.73], CV(%) = 13.66; rhythm: ICC = 0.52; 95%CI [0.35; 0.67], CV(%) = 10.29.

Conclusion

From the findings presented, it is concluded that the proposed clinical test with elastic tubes demonstrates evidence of acceptable values.

Reproducibility of isokinetic strength assessment of knee muscle actions in adult athletes: Torques and antagonist-agonist ratios derived at the same angle position

The current study aimed to examine the reliability of the conventional and functional ratios derived from peak torques (PTs) and those obtained from the combination of knee flexors torque at the angle of knee extensors PT. Twenty-six male athletes (mean of 24.0±0.7 years) from different sports completed a test-to-test variation in isokinetic strength (Biodex, System 3) within a period of one week. Anthropometry and body composition assessed by Dual Energy X-ray Absorptiometry were also measured. The proposed isokinetic strength ratio measurements appeared to be highly reliable: conventional ratio at PT angle (intra-class correlation, ICC = 0.98; 95% confidence interval; 95%CI: 0.95 to 0.99); functional extension ratio at PT angle (ICC = 0.98; 95%CI: 0.96 to 0.99); and, functional flexion ratio at PT angle (ICC = 0.95; 95%CI: 0.89 to 0.98). Technical error of measurement (TEM) and associated percentage of the coefficient of variation (%CV) were as follows: conventional ratio at PT angle (TEM = 0.02; %CV = 4.1); functional extension ratio at PT angle (TEM = 0.02; %CV = 3.8); and, functional flexion ratio at PT angle (TEM = 0.03; %CV = 3.6). The current study demonstrated that the traditional and new obtained simple and combined isokinetic indicators seem highly reliable to assess muscle strength and function in adult male athletes. A single testing session seems to be sufficiently to obtain these isokinetic strength indicators.

Multiday Pomegranate Extract Supplementation Decreases Oxygen Uptake During Submaximal Cycling Exercise, but Cosupplementation With N-acetylcysteine Negates the Effect

Pomegranate extract (POMx) has been suggested as an ergogenic aid due to its rich concentration of polyphenols, which are proposed to enhance nitric oxide bioavailability, thereby improving the efficiency of oxygen usage and, consequently, endurance exercise performance. Although acute POMx supplementation improves aerobic exercise performance in untrained individuals, trained athletes appear to require chronic supplementation for a similar effect. Furthermore, the combination of POMx with a thiol antioxidant may prove more effective than POMx alone, due to the protective effects of thiols on nitric oxide. Thus, this study hypothesized that multiday POMx supplementation would decrease the oxygen uptake (VO₂) required by trained cyclists to perform submaximal exercise and increase performance during a time trial, and that thiol (N-acetylcysteine [NAC]) cosupplementation would enhance these effects. Eight cyclists completed four 8-day supplementation periods: POMx only, NAC only, POMx + NAC (BOTH), and placebo. Following supplementation, they performed submaximal cycling and a 5-min time trial, with VO₂ and muscle oxygen saturation (SmO₂) being recorded. A three-way (POMx × NAC × Intensity) repeated-measures analysis of variance with a Fisher's least significant difference post hoc assessment was performed for dependent variables (p ≤ .05). VO₂ during submaximal exercise was reduced with POMx versus placebo (-2.6 ml·min^-1·kg^-1, p = .009) and BOTH (-2.5 ml·min^-1·kg^-1, p < .05) and increased with NAC (+1.9 ml·min^-1·kg^-1, p < .03), despite no main effect of treatment on SmO₂ or performance. It appears that POMx's high polyphenol content reduced the VO₂ required during submaximal exercise. However, NAC cosupplementation annulled this effect; thus, NAC may interact with nitric oxide to reduce its bioavailability.

Early Adaptations to a Two-Week Uphill Run Sprint Interval Training and Cycle Sprint Interval Training

This study sought to compare early physiological and performance adaptations between a two-week cycle sprint interval training (SIT) and uphill run sprint training (UST) programs. Seventeen recreationally active adult males (age = 28 ± 5 years; body mass (BM) = 78 ± 9 kg) were assigned to either a control (n = 5), SIT (n = 6), or UST (n = 6) group. A discrete group of participants (n = 6, age = 33 ± 6 years, and body mass = 80 ± 9 kg) completed both training protocols to determine acute physiological responses. Intervention groups completed either a run or cycle peak oxygen uptake (VO₂peak) test (intervention type dependent) prior to and following two weeks of training. Training comprised of three sessions per week of 4 × 30-s “all-out” sprints with a four-minute active recovery between bouts on a cycle ergometer against 7.5% of body mass in the SIT group and on a 10% slope in the UST group. The VO₂peak values remained unchanged in both training groups, but time-to-exhaustion (TTE) was significantly increased only in the UST group (pre—495 ± 40 s, post—551 ± 15 s; p = 0.014) and not in the SIT group (pre—613 ± 130 s, post—634 ± 118 s, p = 0.07). Ventilatory threshold (VT) was significantly increased in both training groups (SIT group: pre—1.94 ± 0.45 L·min⁻¹, post—2.23 ± 0.42 L·min⁻¹; p < 0.005, UST group: pre—2.04 ± 0.40 L·min⁻¹, post—2.33 ± 0.34 L·min⁻¹, p < 0.005). These results indicate that UST may be an effective alternative to SIT in healthy individuals.

How to Construct, Conduct and Analyze an Exercise Training Study?

Randomized controlled trials (RCTs) can be regarded as gold standard in investigating dose-response and causal relationships in exercise science. Recommendations for exercise training routines and efficacy analyses of certain training regimen require valid data derived from robust RCTs. Moreover, meta-analyses rely on RCTs and both RCTs and meta-analyses are considered the highest level of scientific evidence. Beyond general study design a variety of methodological aspects and notable pitfalls has to be considered. Therefore, exercise training studies should be carefully constructed focusing on the consistency of the whole design "package" from an explicit hypothesis or research question over study design and methodology to data analysis and interpretation. The present scoping review covers all main aspects of planning, conducting, and analyzing exercise based RCTs. We aim to focus on relevant aspects regarding study design, statistical power, training planning and documentation as well as traditional and recent statistical approaches. We intend to provide a comprehensive hands-on paper for conceptualizing future exercise training studies and hope to stimulate and encourage researchers to conduct sound and valid RCTs in the field of exercise training.

Coffee Ingestion Enhances 1-Mile Running Race Performance

Context: Caffeine, often in the form of coffee, is frequently used as a supplement by athletes in an attempt to facilitate improved performance during exercise. Purpose: To investigate the effectiveness of coffee ingestion as an ergogenic aid prior to a 1-mile (1609 m) race. Methods: In a double-blind, randomized, cross-over, and placebo-controlled design, 13 trained male runners completed a 1-mile race 60 minutes following the ingestion of 0.09 g·kg−1 coffee (COF), 0.09 g·kg−1 decaffeinated coffee (DEC), or a placebo (PLA). All trials were dissolved in 300 mL of hot water. Results: The race completion time was 1.3% faster following the ingestion of COF (04:35.37 [00:10.51] min:s.ms) compared with DEC (04:39.14 [00:11.21] min:s.ms; P = .018; 95% confidence interval [CI], −0.11 to −0.01; d = 0.32) and 1.9% faster compared with PLA (04:41.00 [00:09.57] min:s.ms; P = .006; 95% CI, −0.15 to −0.03; d = 0.51). A large trial and time interaction for salivary caffeine concentration was observed (P < .001; ), with a very large increase (6.40 [1.57] μg·mL−1; 95% CI, 5.5–7.3; d = 3.86) following the ingestion of COF. However, only a trivial difference between DEC and PLA was observed (P = .602; 95% CI, −0.09 to 0.03; d = 0.17). Furthermore, only trivial differences were observed for blood glucose (P = .839; ) and lactate (P = .096; ) and maximal heart rate (P = .286; ) between trials. Conclusions: The results of this study show that 60 minutes after ingesting 0.09 g·kg−1 of caffeinated coffee, 1-mile race performance was enhanced by 1.9% and 1.3% compared with placebo and decaffeinated coffee, respectively, in trained male runners.

Acute Effect of Oral N-Acetylcysteine on Muscle Soreness and Exercise Performance in Semi-Elite Rugby Players

N-acetylcysteine (NAC) supplementation may enhance performance and reduce soreness from acute, repeated-sprint, high-intensity exercise. Our aim was to investigate whether semi-elite rugby union athletes may benefit. In a randomized block design, 17 semi-elite male rugby players were assigned to receive either 1 g oral NAC (n = 8) or placebo (n = 9) for six days. The mean percentage effect of NAC on exercise performance was assessed through completion of a broken bronco exercise test on days 5 and 6 of supplementation. Players self-reported muscle soreness and tolerability to supplements using a modified Muscle Pain and Treatment Satisfaction Questionnaire throughout the supplement duration. NAC produced a likely beneficial performance effect on maximum shuttle sprint time (2.4%; 90% confidence limit ± 4.8%) but was unclear on total time during back-to-back broken bronco tests compared to placebo. NAC had a likely protective effect on subjective muscle soreness during days 1-4 of supplementation (-19% ± 27%) but a very likely harmful effect on days 5 and 6 of supplementation (71% ± 59%). Daily supplementation with 1 g of oral NAC for six days produced no adverse side effects, reduced muscle soreness after one bout of damaging exercise, but increased soreness following the second bout. The performance effects were generally unclear apart from maximal sprint time.

Assessing Cardiorespiratory Fitness of Soccer Players: Is Test Specificity the Issue?-A Review

It is important that players and coaches have access to objective information on soccer player’s physical status for team selection and training purposes. Physiological tests can provide this information. Physiological testing in laboratories and field settings are very common, but both methods have been questioned because of their specificity and accuracy respectively. Currently, football players have their direct aerobic fitness assessed in laboratories using treadmills or cycle ergometers, whilst indirect measures (using estimation of aerobic performance) are performed in the field, typically comprising multiple shuttle runs back and forth over a set distance. The purpose of this review is to discuss the applied techniques and technologies used for evaluating soccer players’ health and fitness variables with a specific focus on cardiorespiratory testing. A clear distinction of the functionality and the specificity between the field tests and laboratory tests is well established in the literature. The review findings prioritize field tests over laboratory tests, not only for commodity purpose but also for motivational and specificity reasons. Moreover, the research literature suggests a combination of various tests to provide a comprehensive assessment of the players. Finally, more research needs to be conducted to develop a specific and comprehensive test model through the combination of various exercise modes for soccer players.

Performance and Side Effects of Supplementation with N-Acetylcysteine: A Systematic Review and Meta-Analysis

BACKGROUND

N-Acetylcysteine (NAC) is a promising antioxidant supplement with potential as an acute strategy to enhance performance in elite sport, but there are concerns about its side effects with high doses.

OBJECTIVE

To review the current literature and evaluate the effects of NAC supplementation on sport performance and the risk of adverse effects.

METHODS

The literature up to May 2016 was searched on MEDLINE (PubMed), EMBASE, SPORTDiscus, Google Scholar and Scopus databases to identify all studies investigating the effects of NAC supplementation on exercise performance and/or side effects experienced. Performance outcomes from each study were converted to the percent effect equivalent to mean power output in a time trial. All pooled analyses were based on random-effects models generated by Review Manager (RevMan) [Computer program], version 5.3 (The Nordic Cochrane Centre, The Cochrane Collaboration, Copenhagen, 2014).

RESULTS

A total of seven studies met criteria for inclusion in the sport performance meta-analysis, and 17 for inclusion in the side effects meta-analysis. The typical daily dose of NAC reported was 5.8 g·d^-1; with a range between 1.2 and 20.0 g·d^-1. The mean increase in performance was 0.29% (95% confidence interval -0.67 to 1.25). The difference in the odds ratio of side effects on NAC compared with placebo was 1.11 (95% confidence interval 0.88-1.39). The sub-analysis of NAC dose suggested an increase in side effects as the dosage of NAC increased; however, this observation requires further investigation.

CONCLUSIONS

Despite initial research publications reporting positive performance effects with NAC, at this stage it cannot be recommended further. The risk of side effects from NAC supplementation also remains unclear owing to significant variations in effects. Suboptimal reporting and documentation in the literature creates difficulties when meta-analysing outcomes and generating conclusions.

The Effect of Dietary Nitrate Supplementation on Endurance Exercise Performance in Healthy Adults: A Systematic Review and Meta-Analysis

BACKGROUND

Recent research into the use of dietary nitrates and their role in vascular function has led to it becoming progressively more popular amongst athletes attempting to enhance performance.

OBJECTIVE

The objective of this review was to perform a systematic review and meta-analysis of the literature to evaluate the effect of dietary nitrate (NO₃^-) supplementation on endurance exercise performance. An additional aim was to determine whether the performance outcomes are affected by potential moderator variables.

DATA SOURCES

Relevant databases such as Cochrane Library, Embase, PubMed, Ovid, Scopus and Web of Science were searched for the following search terms 'nitrates OR nitrate OR beetroot OR table beet OR garden beet OR red beet AND exercise AND performance' from inception to October 2015.

STUDY SELECTION

Studies were included if a placebo versus dietary nitrate-only supplementation protocol was able to be compared, and if a quantifiable measure of exercise performance was ≥30 s (for a single bout of exercise or the combined total for multiple bouts).

STUDY APPRAISAL AND SYNTHESIS

The literature search identified 1038 studies, with 47 (76 trials) meeting the inclusion criteria. Data from the 76 trials were extracted for inclusion in the meta-analysis. A fixed-effects meta-analysis was conducted for time trial (TT) (n = 28), time to exhaustion (TTE) (n = 22) and graded-exercise test (GXT) (n = 8) protocols. Univariate meta-regression was used to assess potential moderator variables (exercise type, dose duration, NO₃^- type, study quality, fitness level and percentage nitrite change).

RESULTS

Pooled analysis identified a trivial but non-significant effect in favour of dietary NO₃^- supplementation [effect size (ES) = -0.10, 95 % Cl = -0.27 to 0.06, p > 0.05]. TTE trials had a small to moderate statistically significant effect in favour of dietary NO₃^- supplementation (ES = 0.33, 95 % Cl = 0.15-0.50, p < 0.01). GXT trials had a small but non-significant effect in favour of dietary NO₃^- supplementation in GXT performance measures (ES = 0.25, 95 % Cl = -0.06 to 0.56, p > 0.05). No significant heterogeneity was detected in the meta-analysis. No statistically significant effects were observed from the meta-regression analysis.

CONCLUSION

Dietary NO₃^- supplementation is likely to elicit a positive outcome when testing endurance exercise capacity, whereas dietary NO₃^- supplementation is less likely to be effective for time-trial performance. Further work is needed to understand the optimal dosing strategies, which population is most likely to benefit, and under which conditions dietary nitrates are likely to be most effective for performance.

Practical Cooling Strategies During Continuous Exercise in Hot Environments: A Systematic Review and Meta-Analysis

Background

Performing exercise in thermally stressful environments impairs exercise capacity and performance. Cooling during exercise has the potential to attenuate detrimental increases in body temperature and improve exercise capacity and performance.

Objective

The objective of this review was to assess the effectiveness of practical cooling strategies applied during continuous exercise in hot environments on body temperature, heart rate, whole body sweat production, rating of perceived exertion (RPE), thermal perception and exercise performance.

Methods

Electronic database searches of MEDLINE, SPORTDiscus, Scopus and Physiotherapy Evidence Database (PEDro) were conducted using medical subject headings, indexing terms and keywords. Studies were eligible if participants were defined as ‘healthy’, the exercise task was conducted in an environment ≥25 °C, it used a cooling strategy that would be practical for athletes to use during competition, cooling was applied during a self-paced or fixed-intensity trial, participants exercised continuously, and the study was a randomised controlled trial with the comparator either a thermoneutral equivalent or no cooling. Data for experimental and comparator groups were meta-analysed and expressed as a standardised mean difference and 95 % confidence interval.

Results

Fourteen studies including 135 participants met the eligibility criteria. Confidence intervals for meta-analysed data included beneficial and detrimental effects for cooling during exercise on core temperature, mean skin temperature, heart rate and sweat production during fixed-intensity exercise. Cooling benefited RPE and thermal perception during fixed-intensity exercise and improved self-paced exercise performance.

Conclusion

Cooling during fixed-intensity exercise, particularly before a self-paced exercise trial, improves endurance performance in hot environments by benefiting RPE and thermal perception, but does not appear to attenuate increases in body temperature.

The Critical Power Model as a Potential Tool for Anti-doping

Existing doping detection strategies rely on direct and indirect biochemical measurement methods focused on detecting banned substances, their metabolites, or biomarkers related to their use. However, the goal of doping is to improve performance, and yet evidence from performance data is not considered by these strategies. The emergence of portable sensors for measuring exercise intensities and of player tracking technologies may enable the widespread collection of performance data. How these data should be used for doping detection is an open question. Herein, we review the basis by which performance models could be used for doping detection, followed by critically reviewing the potential of the critical power (CP) model as a prototypical performance model that could be used in this regard. Performance models are mathematical representations of performance data specific to the athlete. Some models feature parameters with physiological interpretations, changes to which may provide clues regarding the specific doping method. The CP model is a simple model of the power-duration curve and features two physiologically interpretable parameters, CP and W′. We argue that the CP model could be useful for doping detection mainly based on the predictable sensitivities of its parameters to ergogenic aids and other performance-enhancing interventions. However, our argument is counterbalanced by the existence of important limitations and unresolved questions that need to be addressed before the model is used for doping detection. We conclude by providing a simple worked example showing how it could be used and propose recommendations for its implementation.

Acute Ingestion of Caffeinated Chewing Gum Improves Repeated Sprint Performance of Team Sport Athletes With Low Habitual Caffeine Consumption

The effects of acute ingestion of caffeine on short-duration high-intensity performance are equivocal, while studies of novel modes of delivery and the efficacy of low doses of caffeine are warranted. The aims of the present study were to investigate the effect of acute ingestion of caffeinated chewing gum on repeated sprint performance (RSP) in team sport athletes, and whether habitual caffeine consumption alters the ergogenic effect, if any, on RSP. A total of 18 male team sport athletes undertook four RSP trials using a 40-m maximum shuttle run test, which incorporates 10 × 40-m sprints with 30 s between the start of each sprint. Each participant completed two familiarization sessions, followed by caffeine (CAF; caffeinated chewing gum; 200 mg caffeine) and placebo (PLA; noncaffeinated chewing gum) trials in a randomized, double-blind manner. RSP, assessed by sprint performance decrement (%), did not differ (p = .209; effect size = 0.16; N = 18) between CAF (5.00 ± 2.84%) and PLA (5.43 ± 2.68%). Secondary analysis revealed that low habitual caffeine consumers (<40 mg/day, n = 10) experienced an attenuation of sprint performance decrement during CAF relative to PLA (5.53 ± 3.12% vs. 6.53 ± 2.91%, respectively; p = .049; effect size =0.33); an effect not observed in moderate/high habitual caffeine consumers (>130 mg/day, n = 6; 3.98 ± 2.57% vs. 3.80 ± 1.79%, respectively; p = .684; effect size = 0.08). The data suggest that a low dose of caffeine in the form of caffeinated chewing gum attenuates the sprint performance decrement during RSP by team sport athletes with low, but not moderate-to-high, habitual consumption of caffeine.

Recommendations for Assessment of the Reliability, Sensitivity, and Validity of Data Provided by Wearable Sensors Designed for Monitoring Physical Activity

Although it is becoming increasingly popular to monitor parameters related to training, recovery, and health with wearable sensor technology (wearables), scientific evaluation of the reliability, sensitivity, and validity of such data is limited and, where available, has involved a wide variety of approaches. To improve the trustworthiness of data collected by wearables and facilitate comparisons, we have outlined recommendations for standardized evaluation. We discuss the wearable devices themselves, as well as experimental and statistical considerations. Adherence to these recommendations should be beneficial not only for the individual, but also for regulatory organizations and insurance companies.

Tests for the Assessment of Sport-Specific Performance in Olympic Combat Sports: A Systematic Review With Practical Recommendations

The regular monitoring of physical fitness and sport-specific performance is important in elite sports to increase the likelihood of success in competition. This study aimed to systematically review and to critically appraise the methodological quality, validation data, and feasibility of the sport-specific performance assessment in Olympic combat sports like amateur boxing, fencing, judo, karate, taekwondo, and wrestling. A systematic search was conducted in the electronic databases PubMed, Google-Scholar, and Science-Direct up to October 2017. Studies in combat sports were included that reported validation data (e.g., reliability, validity, sensitivity) of sport-specific tests. Overall, 39 studies were eligible for inclusion in this review. The majority of studies (74%) contained sample sizes <30 subjects. Nearly, 1/3 of the reviewed studies lacked a sufficient description (e.g., anthropometrics, age, expertise level) of the included participants. Seventy-two percent of studies did not sufficiently report inclusion/exclusion criteria of their participants. In 62% of the included studies, the description and/or inclusion of a familiarization session (s) was either incomplete or not existent. Sixty-percent of studies did not report any details about the stability of testing conditions. Approximately half of the studies examined reliability measures of the included sport-specific tests (intraclass correlation coefficient [ICC] = 0.43–1.00). Content validity was addressed in all included studies, criterion validity (only the concurrent aspect of it) in approximately half of the studies with correlation coefficients ranging from r = −0.41 to 0.90. Construct validity was reported in 31% of the included studies and predictive validity in only one. Test sensitivity was addressed in 13% of the included studies. The majority of studies (64%) ignored and/or provided incomplete information on test feasibility and methodological limitations of the sport-specific test. In 28% of the included studies, insufficient information or a complete lack of information was provided in the respective field of the test application. Several methodological gaps exist in studies that used sport-specific performance tests in Olympic combat sports. Additional research should adopt more rigorous validation procedures in the application and description of sport-specific performance tests in Olympic combat sports.

Association between vitamin D status and testosterone and cortisol in ice hockey players

The identification of the vitamin D receptor in tissues related to testosterone and cortisol production, in conjunction with the observed correlations between vitamin D levels and these hormones in the general population, suggest vitamin D may influence testosterone and cortisol concentrations in athletes. A cross-sectional study design was used to evaluate the association between 25(OH)D and testosterone and cortisol concentrations in young male ice hockey players (n = 50). All athletes were recruited during October from the Sosnowiec area, Poland (50° N). Commercially available ELISA kits were used to determine total serum 25(OH)D, testosterone and cortisol concentrations. Serum 25(OH)D concentration was analyzed as both a continuous and dichotomous variable, binned at the criteria for deficiency (< 20 ng·ml^-1), to investigate a threshold effect. Neither continuous (r = 0.18, p = 0.20) nor dichotomous (r = 0.16, p = 0.27) 25(OH)D concentration was significantly correlated with testosterone concentration. A small, inverse correlation (r = -0.30, p = 0.04) was detected between 25(OH)D and cortisol concentrations when analyzed as a dichotomous variable only. Serum 25(OH)D concentration was neither associated with testosterone (p = 0.09) nor cortisol concentrations (p = 0.11) after adjusting for age, fat free mass and fat mass in sequential linear regression. The inability of vitamin D status to independently predict testosterone and cortisol concentrations suggests that any performance-enhancing effects of vitamin D in athletes are unlikely to be mediated primarily through these hormones, at least amongst young male ice-hockey players.

Making Decisions About Supplement Use

The use of dietary supplements is widespread among athletes in all sports and at all levels of competition, as it is in the general population. For the athlete training at the limits of what is sustainable, or for those seeking a shortcut to achieving their aims, supplements offer the prospect of bridging the gap between success and failure. Surveys show, however, that this is often not an informed choice and that the knowledge level among consumers is often low and that they are often influenced in their decisions by individuals with an equally inadequate understanding of the issues at stake. Supplement use may do more harm than good, unless it is based on a sound analysis of the evidence. Where a deficiency of an essential nutrient has been established by appropriate investigations, supplementation can provide a rapid and effective correction of the problem. Supplements can also provide a convenient and time-efficient solution to achieving the necessary intake of key nutrients such as protein and carbohydrate. Athletes contemplating the use of supplements should consider the potential for both positive and negative outcomes. Some ergogenic supplements may be of benefit to some athletes in some specific contexts, but many are less effective than is claimed. Some may be harmful to health of performance and some may contain agents prohibited by anti-doping regulations. Athletes should make informed choices that maximize the benefits while minimizing the risks.

Ingestion of carbohydrate or carbohydrate plus protein does not enhance performance during endurance exercise: a randomized crossover placebo-controlled clinical trial

A beverage containing protein (PRO) and carbohydrate (CHO) may have an ergogenic effect on endurance performance. However, evidence regarding its efficacy on similar conditions to athletes' race day is still lacking. The objective of this study was to compare the effects of 3 different nutritional supplementation strategies on performance and muscle recovery in a duathlon protocol. Thirteen male athletes (29.7 ± 7.7 years) participated in 3 simulated Olympic-distance duathlon trials (SDTs) under 3 different, randomly assigned supplementation regimens: CHO drink (75 g CHO), isocaloric CHO plus PRO drink (60.5 g CHO and 14.5 g PRO), and placebo drink (PLA). Supplements were offered during the cycling bout. Blood samples were collected before, immediately after, and 24 h after each SDT for creatine kinase (CK) analysis. Isometric peak torque (PT) was measured before and 24 h after each SDT. The primary outcome measure was the time to complete the 5-km running section (t_5km) at a self-selected pace. There was no difference in t_5km between CHO (1270.3 ± 130.5 s), CHO+PRO (1267.2 ± 138.9 s), and PLA (1275.4 ± 120 s); p = 0.87, effect size (ES) ≤ 0.1. Pre-post changes for PT and CK were not significant for any of the 3 conditions (PT: p = 0.24, ES ≤ 0.4; CK: p = 0.32, ES = 0.3-1.04). For endurance sports lasting up to 2 h, with a pre-exercise meal containing CHO at 1.5 g·kg^-1, supplementation with CHO or CHO+PRO does not offer additional benefits for performance and muscle recovery when compared with PLA.

Methodologies for Investigating Performance Changes With Supplement Use

Many expert sporting bodies now support a pragmatic acceptance of the use of performance supplements which have passed a risk:benefit analysis of being safe, effective, and permitted for use, while also being appropriate to the athlete's age and maturation in their sport. However, gaining evidence of the performance benefits of these supplements is a process challenged by the scarcity of research in relation to the number of available products, and the limitations of the poor quality of some studies. While meta-analyses and systematic reviews can help to provide information about the general use of performance supplements, the controlled scientific trial provides the basis on which these reviews are undertaken, as well as an opportunity to address more specific questions about supplement applications. Guidelines for the design of studies include the choice of well-trained athletes who are familiarized with performance tasks that have been chosen on their basis of their known reliability and validity. Supplement protocols should be chosen to maximize the likely benefits, and researchers should also make efforts to control confounding variables, while keeping conditions similar to real-life practices. Performance changes should be interpreted in light of what is meaningful to the outcomes of sporting competition. Issues that have been poorly addressed to date include the use of several supplements in combination and the use of the same supplement over successive events, both within a single, and across multiple competition days. Strategies to isolate and explain the variability of benefits to individuals are also a topic for future investigation.

Postmatch recovery of physical performance and biochemical markers in team ball sports: a systematic review

Background

Insufficient postmatch recovery in elite players may cause an increased risk of injuries, illnesses and non-functional over-reaching.

Objective

To evaluate postmatch recovery time courses of physical performance and biochemical markers in team ball sport players.

Study design

Systematic review.

Data sources

PubMed and Web of Science.

Eligibility criteria for selecting studies

This systematic review was conducted according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. The Critical Review Form for Quantitative Studies was used to evaluate quality. Studies were included if they met the following criteria: (1) original research evaluated players’ physical recovery postmatch; (2) team/intermittent sports; and (3) at least two postmeasurements were compared with baseline values.

Results

Twenty-eight studies were eligible. Mean methodological quality was 11.2±1.11. Most used performance tests and biochemical markers were the countermovement jump test, sprint tests and creatine kinase (CK), cortisol (C) and testosterone (T), respectively.

Summary/conclusions

The current evidence demonstrates that underlying mechanisms of muscle recovery are still in progress while performance recovery is already reached. CK recovery time courses are up to ≥72 hours. Soccer and rugby players need more time to recover for sprint performance, CK and C in comparison to other team ball sports. There are more high-quality studies needed regarding recovery in various team sports and recovery strategies on an individual level should be evaluated.

Clinical relevance

Ongoing insufficient recovery can be prevented by the use of the presented recovery time courses as specific practical recovery guidelines.

Predictive ability of a comprehensive incremental test in mountain bike marathon

Objectives

Traditional performance tests in mountain bike marathon (XCM) primarily quantify aerobic metabolism and may not describe the relevant capacities in XCM. We aimed to validate a comprehensive test protocol quantifying its intermittent demands.

Methods

Forty-nine athletes (38.8±9.1 years; 38 male; 11 female) performed a laboratory performance test, including an incremental test, to determine individual anaerobic threshold (IAT), peak power output (PPO) and three maximal efforts (10 s all-out sprint, 1 min maximal effort and 5 min maximal effort). Within 2 weeks, the athletes participated in one of three XCM races (n=15, n=9 and n=25). Correlations between test variables and race times were calculated separately. In addition, multiple regression models of the predictive value of laboratory outcomes were calculated for race 3 and across all races (z-transformed data).

Results

All variables were correlated with race times 1, 2 and 3: 10 s all-out sprint (r=−0.72; r=−0.59; r=−0.61), 1 min maximal effort (r=−0.85; r=−0.84; r=−0.82), 5 min maximal effort (r=−0.57; r=−0.85; r=−0.76), PPO (r=−0.77; r=−0.73; r=−0.76) and IAT (r=−0.71; r=−0.67; r=−0.68). The best-fitting multiple regression models for race 3 (r²=0.868) and across all races (r²=0.757) comprised 1 min maximal effort, IAT and body weight.

Conclusion

Aerobic and intermittent variables correlated least strongly with race times. Their use in a multiple regression model confirmed additional explanatory power to predict XCM performance. These findings underline the usefulness of the comprehensive incremental test to predict performance in that sport more precisely.

The Reliability and Sensitivity of Performance Measures in a Novel Pace-Bowling Test

OBJECTIVES

To evaluate the reliability and sensitivity of performance measures in a novel pace-bowling test.

METHODS

Thirteen male amateur-club fast bowlers completed a novel pace-bowling test on 2 separate occasions, 4-7 d apart. Participants delivered 48 balls (8 overs) at 5 targets on a suspended sheet situated behind a live batter, who stood in a right-handed and left-handed stance for an equal number of deliveries. Delivery instruction was frequently changed, with all deliveries executed in a preplanned sequence. Data on ball-release speed were captured by radar gun. A high-speed camera captured the moment of ball impact on the target sheet for assessment of radial error and bivariate variable error. Delivery rating of perceived exertion (0-100%) was collected as a measure of intensity.

RESULTS

Intraclass correlation coefficients and coefficients of variation revealed excellent reliability for peak and mean ball-release speed, acceptable reliability for delivery rating of perceived exertion, and poor reliability for mean radial error, bivariate variable error, and variability of ball-release speed. The smallest worthwhile change indicated high sensitivity with peak and mean ball-release speed and lower sensitivity with mean radial error and bivariate variable error.

CONCLUSIONS

The novel pace-bowling test incorporates improvements in ecological validity compared with its predecessors and can be used to provide a more comprehensive evaluation of pace-bowling performance. Data on the smallest worthwhile change can improve interpretation of pace-bowling research findings and may therefore influence recommendations for applied practice.

Effects of ambient particulate matter on aerobic exercise performance

Background/Objective

Wintertime thermal inversions in narrow mountain valleys create a ceiling effect, increasing concentration of small particulate matter (PM_2.5). Despite potential health risks, many people continue to exercise outdoors in thermal inversions. This study measured the effects of ambient PM_2.5 exposure associated with a typical thermal inversion on exercise performance, pulmonary function, and biological markers of inflammation.

Methods

Healthy, active adults (5 males, 11 females) performed two cycle ergometer time trials outdoors in a counterbalanced design: 1) low ambient PM_2.5 concentrations (<12 μg/m³), and 2) an air quality index (AQI) ranking of “yellow.” Variables of interest were exercise performance, exhaled nitric oxide (eNO), c-reactive protein (CRP), forced vital capacity (FVC), and forced expiratory volume in 1 s (FEV₁).

Results

Despite a significant difference in mean PM_2.5 concentration of 9.3 ± 3.0 μg/m³ between trials (p < .001), there was no significant difference (p = .424) in the distance covered during low PM_2.5 conditions (9.9 ± 1.7 km) compared to high PM_2.5 conditions (10.1 ± 1.5 km). There were no clinically significant differences across time or between trials for eNO, CRP, FVC, or FEV₁. Additionally, there were no dose-response relationships (p > .05) for PM_2.5 concentration and the measured variables.

Conclusion

An acute bout of vigorous exercise during an AQI of “yellow” did not diminish exercise performance in healthy adults, nor did it have a negative effect on pulmonary function or biological health markers. These variables might not be sensitive to small changes from acute, mild PM_2.5 exposure.

Reliability and minimal detectable change of a new treadmill-based progressive workload incremental test to measure cardiorespiratory fitness in manual wheelchair users

BACKGROUND

Cardiorespiratory fitness training is commonly provided to manual wheelchair users (MWUs) in rehabilitation and physical activity programs, emphasizing the need for a reliable task-specific incremental wheelchair propulsion test.

OBJECTIVE

Quantifying test-retest reliability and minimal detectable change (MDC) of key cardiorespiratory fitness measures following performance of a newly developed continuous treadmill-based wheelchair propulsion test (WPT_Treadmill).

METHODS

Twenty-five MWUs completed the WPT_Treadmill on two separate occasions within one week. During these tests, participants continuously propelled their wheelchair on a motorized treadmill while the exercise intensity was gradually increased every minute until exhaustion by changing the slope and/or speed according to a standardized protocol. Peak oxygen consumption (VO_2peak), carbon dioxide production (VCO_2peak), respiratory exchange ratio (RER_peak), minute ventilation (VE_peak) and heart rate (HR_peak) were computed. Time to exhaustion (TTE) and number of increments completed were also measured. Intra-class correlation coefficients (ICC) were calculated to determine test-retest reliability. Standard error of measurement (SEM) and MDC_90% values were calculated.

RESULTS

Excellent test-retest reliability was reached for almost all outcome measures (ICC=0.91-0.76), except for RER_peak (ICC=0.58), which reached good reliability. TTE (ICC=0.89) and number of increments (ICC=0.91) also reached excellent test-retest reliability. For the main outcome measures (VO_2peak and TTE), absolute SEM was 2.27 mL/kg/min and 0.76 minutes, respectively and absolute MDC_90% was 5.30 mL/kg/min and 1.77 minutes, respectively.

CONCLUSION

The WPT_Treadmill is a reliable test to assess cardiorespiratory fitness among MWUs. TTE and number of increments could be used as reliable outcome measures when VO₂ measurement is not possible.

Reliable and sensitive physical testing of elite trapeze sailors

It was investigated whether a newly developed discipline-specific test for elite-level trapeze sailors is reliable and sensitive. Furthermore, the physical demands of trapeze sailing were examined. In part 1, 9 national team athletes were accustomed to a simulated sailing test, which subsequently was completed on 4 occasions to determine test reliability and sensitivity to manipulations in body weight. Rope-pulling mean power output (MPO), oxygen consumption (VO₂ ), heart rate (HR), and blood lactate values were acquired in all trials. In part 2, 6 sailors completed on-water racing with concurrent measurements of VO₂ , HR, and blood lactate. VO_2max was determined during an incremental treadmill running test. Typical error, minimal difference, and ICC for average MPO in the test were 1.3%, 1.7%, and 0.99%, respectively. Adding 4 kg of external body weight caused a decrease in average MPO (270 ± 45W vs 265 ± 45W, P < .05) and an increase in VO₂ (2.44 ± 0.23 L·min^-1 vs 2.55 ± 0.26 L·min^-1 , P < .01). VO₂ , HR, and blood lactate during on-water sailing were 54.5% ± 7.2% VO_2max , 75.1% ± 3.1% HR_max , and 5.8 ± 2.7 mmol·L^-1 , respectively. However, VO₂ and HR were substantially higher for periods of the race as peak values were 83.5% ± 11.4% and 89.9% ± 1.7% of max, respectively. In conclusion, the present test is reliable and sensitive, thus providing a sailing-specific alternative to traditional physical testing of elite trapeze sailors. Additionally, on-water racing requires moderate aerobic energy production, although oxygen consumption can approach maximal levels for short periods of time.

Fluid Balance in Team Sport Athletes and the Effect of Hypohydration on Cognitive, Technical, and Physical Performance

Sweat losses in team sports can be significant due to repeated bursts of high-intensity activity, as well as the large body size of athletes, equipment and uniform requirements, and environmental heat stress often present during training and competition. In this paper we aimed to: (1) describe sweat losses and fluid balance changes reported in team sport athletes, (2) review the literature assessing the impact of hypohydration on cognitive, technical, and physical performance in sports-specific studies, (3) briefly review the potential mechanisms by which hypohydration may impact team sport performance, and (4) discuss considerations for future directions. Significant hypohydration (mean body mass loss (BML) >2%) has been reported most consistently in soccer. Although American Football, rugby, basketball, tennis, and ice hockey have reported high sweating rates, fluid balance disturbances have generally been mild (mean BML <2%), suggesting that drinking opportunities were sufficient for most athletes to offset significant fluid losses. The effect of hydration status on team sport performance has been studied mostly in soccer, basketball, cricket, and baseball, with mixed results. Hypohydration typically impaired performance at higher levels of BML (3-4%) and when the method of dehydration involved heat stress. Increased subjective ratings of fatigue and perceived exertion consistently accompanied hypohydration and could explain, in part, the performance impairments reported in some studies. More research is needed to develop valid, reliable, and sensitive sport-specific protocols and should be used in future studies to determine the effects of hypohydration and modifying factors (e.g., age, sex, athlete caliber) on team sport performance.

Individual Endurance Training Prescription with Heart Rate Variability

INTRODUCTION

Measures of HR variability (HRV) have shown potential to be of use in training prescription.

PURPOSE

The aim of this study was to investigate the effectiveness of using HRV in endurance training prescription.

METHODS

Forty recreational endurance runners were divided into the HRV-guided experimental training group (EXP) and traditional predefined training group (TRAD). After a 4-wk preparation training period, TRAD trained according to a predefined training program including two to three moderate- (MOD) and high-intensity training (HIT) sessions per week during an 8-wk intensive training period. The timing of MOD and HIT sessions in EXP was based on HRV, measured every morning. The MOD/HIT session was programmed if HRV was within an individually determined smallest worthwhile change. Otherwise, low-intensity training was performed. Maximal oxygen consumption (V˙O2max) and 3000-m running performance (RS3000m) were measured before and after both training periods.

RESULTS

The number of MOD and HIT sessions was significantly lower (P = 0.021, effect size = 0.98) in EXP (13.2 ± 6.0 sessions) compared with TRAD (17.7 ± 2.5 sessions). No other differences in training were found between the groups. RS3000m improved in EXP (2.1% ± 2.0%, P = 0.004) but not in TRAD (1.1% ± 2.7%, P = 0.118) during the intensive training period. A small between-group difference (effect size = 0.42) was found in the change in RS3000m. V˙O2max improved in both groups (EXP: 3.7% ± 4.6%, P = 0.027; TRAD: 5.0% ± 5.2%, P = 0.002).

CONCLUSION

The results of the present study suggest the potential of resting HRV to prescribe endurance training by individualizing the timing of vigorous training sessions.

Reliability of the Maximal Resisted Sprint Load Test and Relationships With Performance Measures and Anthropometric Profile in Female Field Sport Athletes

Petrakos, G, Tynan, NC, Vallely-Farrell, AM, Kiely, C, Boudhar, A, and Egan, B. Reliability of the maximal resisted sprint load test and relationships with performance measures and anthropometric profile in female field sport athletes. J Strength Cond Res 33(6): 1704-1714, 2019-Resisted sled sprint (RSS) training is an effective modality for the improvement of linear sprint speed. Previous methods of RSS load prescription, e.g., an absolute load or as a percentage of body mass (%BM), do not account for interindividual differences in strength, power, or speed characteristics, although the "maximum resisted sled load" (MRSL) method of RSS load prescription may provide a solution. Maximum resisted sled load is defined as the final RSS load before an athlete can no longer accelerate between 2 phases (10-15 and 15-20 m) of a 20-m linear sprint. However, the MRSL test has not been analyzed for reliability. In addition, MRSL performance has not been compared with the outcome of other performance tests. The primary aim of this study was to investigate the reliability of the MRSL testing protocol in female field sport athletes. Participants (age, 20.8 ± 1.9 years; body mass, 64.3 ± 8.4 kg; height, 1.66 ± 0.65 m) tested for anthropometric measurements, strength and power performance testing, and twice for MRSL. Maximum resisted sled load values ranged from 20.7 to 58.9% BM. Maximum resisted sled load test-retest reliability intraclass correlation coefficient, confidence intervals, and coefficient of variations were 0.95, 0.85-0.98, and 7.6%, respectively. Maximum resisted sled load was"moderately" and "strongly" correlated with a number of anthropometric and performance tests (p ≤ 0.05), including percentage fat free mass, countermovement jump, loaded countermovement jump, rate of force development, horizontal jump, and horizontal bound performance. Maximum resisted sled load is a reliable measure for determining the RSS load at which an individual can no longer accelerate during a single RSS effort over 0-20 m. Maximum resisted sled load also accounts for interindividual variation in body composition, power, and speed characteristics of female field sport players.

Dispelling the myth that habitual caffeine consumption influences the performance response to acute caffeine supplementation

This study investigates the influence of habitual caffeine intake on aerobic exercise-performance responses to acute caffeine supplementation. A double-blind, crossover, counterbalanced study was performed. Forty male endurance-trained cyclists were allocated into tertiles, according to their daily caffeine intake: low (58 ± 29 mg/d), moderate (143 ± 25 mg/d), and high (351 ± 139 mg/d) consumers. Participants completed three trials in which they performed simulated cycling time trials (TTs) in the fastest time possible following ingestion of the following: caffeine (CAF: 6 mg/kg body mass), placebo (PLA), and no supplement (CON). A mixed-model analysis revealed that TT performance was significantly improved in CAF compared with PLA and CON (29.92 ± 2.18 vs. 30.81 ± 2.67 and 31.14 ± 2.71 min, respectively; P = 0.0002). Analysis of covariance revealed no influence of habitual caffeine intake as a covariate on exercise performance ( P = 0.47). TT performance was not significantly different among tertiles ( P = 0.75). No correlation was observed between habitual caffeine intake and absolute changes (CAF − CON) in TT performance with caffeine ( P = 0.524). Individual analysis showed that eight, seven, and five individuals improved above the variation of the test in CAF in the low, moderate, and high tertiles, respectively. A Fisher’s exact test did not show any significant differences in the number of individuals who improved in CAF among the tertiles ( P > 0.05). Blood lactate and ratings of perceived exertion were not different between trials and tertiles ( P > 0.05). Performance effects of acute caffeine supplementation during an ~30-min cycling TT performance were not influenced by the level of habitual caffeine consumption.

NEW & NOTEWORTHY There has been a long-standing paradigm that habitual caffeine intake may influence the ergogenicity of caffeine supplementation. Low, moderate, and high caffeine consumers showed similar absolute and relative improvements in cycling time-trial performance following acute supplementation of 6 mg/kg body mass caffeine. Performance effects of acute caffeine were not influenced by the level of habitual caffeine consumption, suggesting that high habitual caffeine intake does not negate the benefits of acute caffeine supplementation.

Differential control of respiratory frequency and tidal volume during high-intensity interval training

NEW FINDINGS

What is the central question of this study? By manipulating recovery intensity and exercise duration during high-intensity interval training (HIIT), we tested the hypothesis that fast inputs contribute more than metabolic stimuli to respiratory frequency (f_R ) regulation. What is the main finding and its importance? Respiratory frequency, but not tidal volume, responded rapidly and in proportion to changes in workload during HIIT, and was dissociated from some markers of metabolic stimuli in response to both experimental manipulations, suggesting that fast inputs contribute more than metabolic stimuli to f_R regulation. Differentiating between f_R and tidal volume may help to unravel the mechanisms underlying exercise hyperpnoea. Given that respiratory frequency (f_R ) has been proposed as a good marker of physical effort, furthering the understanding of how f_R is regulated during exercise is of great importance. We manipulated recovery intensity and exercise duration during high-intensity interval training (HIIT) to test the hypothesis that fast inputs (including central command) contribute more than metabolic stimuli to f_R regulation. Seven male cyclists performed an incremental test, a 10 and a 20 min continuous time trial (TT) as preliminary tests. Subsequently, recovery intensity and exercise duration were manipulated during HIIT (30 s work and 30 s active recovery) by performing four 10 min and one 20 min trial (recovery intensities of 85, 70, 55 and 30% of the 10 min TT mean workload; and 85% of the 20 min TT mean workload). The work intensity of the HIIT sessions was self-paced by participants to achieve the best performance possible. When manipulating recovery intensity, f_R , but not tidal volume (V_T ), showed a fast response to the alternation of the work and recovery phases, proportional to the extent of workload variations. No association between f_R and gas exchange responses was observed. When manipulating exercise duration, f_R and rating of perceived exertion were dissociated from V_T , carbon dioxide output and oxygen uptake responses. Overall, the rating of perceived exertion was strongly correlated with f_R (r = 0.87; P < 0.001) but not with V_T . These findings may reveal a differential control of f_R and V_T during HIIT, with fast inputs appearing to contribute more than metabolic stimuli to f_R regulation. Differentiating between f_R and V_T may help to unravel the mechanisms underlying exercise hyperpnoea.

Validity and Reliability of a Portable Isometric Mid-Thigh Clean Pull

James, LP, Roberts, LA, Haff, GG, Kelly, VG, and Beckman, EM. Validity and reliability of a portable isometric mid-thigh clean pull. J Strength Cond Res 31(5): 1378-1386, 2017-This study investigated the test-retest reliability and criterion validity of force-time curve variables collected through a portable isometric mid-thigh clean pull (IMTP) device equipped with a single-axial load cell. Fifteen males with ≥6 months of resistance training experience attended two testing sessions. In each session, participants performed an IMTP in 2 separate conditions in a randomized counterbalanced manner. The criterion condition consisted of a closed-chain IMTP configured with a force plate (IMTPf), whereas the experimental test was undertaken using a portable IMTP with data acquired through a single-axial load cell (IMTPl). A very high reliability (coefficient of variation [CV] = 3.10, 90% confidence interval [CI]: 2.4-4.6%; intraclass correlation coefficient [ICC] = 0.96, 90% CI: 0.90-0.98) and acceptable validity (CV = 9.2, 90% CI: 7-14%; ICC = 0.88, 90% CI: 0.71-0.95) were found in the experimental condition for the measure of peak force. However, significant differences were present between the IMTPf and IMTPl (p < 0.0001). Alternate force-time curve variables did not reach acceptable levels of validity or reliability in the experimental condition. The IMTPl is a valid and highly reliable method for assessing peak force. This provides evidence supporting the use of an IMTPl as a cost-effective and portable alternative for those who wish to assess maximal force production in a similar fashion to a traditional IMTP. However, practitioners should be aware that these are slightly different tests.

Immersible ergocycle prescription as a function of relative exercise intensity

PURPOSE

The purpose of this study was to establish the relationship between various expressions of relative exercise intensity percentage of maximal oxygen uptake (%VO_2max), percentage of maximal heart rate (%HR_max), %VO₂ reserve (%VO₂R), and %HR reserve (%HRR)) in order to obtain the more appropriate method for exercise intensity prescription when using an immersible ergocycle (IE) and to propose a prediction equation to estimate oxygen consumption (VO₂) based on IE pedaling rate (rpm) for an individualized exercise training prescription.

METHODS

Thirty-three healthy participants performed incremental exercise tests on IE and dryland ergocycle (DE) at equal external power output (P_ext). Exercise on IE began at 40 rpm and was increased by 10 rpm until exhaustion. Exercise on DE began with an initial load of 25 W and increased by 25 W/min until exhaustion. VO₂ was measured with a portable gas analyzer (COSMED K4b²) during both incremental tests. On IE and DE, %VO₂R, %HR_max, and %HRR at equal P_ext did not differ (p > 0.05).

RESULTS

The %HRR vs. %VO₂R regression for both IE and DE did not differ from the identity line %VO₂R IE = 0.99 × HRR IE (%) + 0.01 (r ² = 0.91, SEE = 11%); %VO₂R DE = 0.94 × HRR DE (%) + 0.01 (r ² = 0.94, SEE = 8%). Similar mean values for %HR_max, %VO₂R, and %HRR at equal P_ext were observed on IE and DE. Predicted VO₂ obtained according to rpm on IE is represented by: VO₂ (L/min) = 0.000542 × rpm² - 0.026 × rpm + 0.739 (r = 0.91, SEE = 0.319 L/min).

CONCLUSION

The %HRR-%VO₂R relationship appears to be the most accurate for exercise training prescription on IE. This study offers new tools to better prescribe, control, and individualize exercise intensity on IE.