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Matthias Hovorka, Peter Leo, Dieter Simon, Clemens Rumpl, and Alfred Nimmerichter

Purpose: The purpose of the current investigation was to retrospectively assess possible differences in physiological performance characteristics between junior cyclists signing a contract with an under-23 (U23) development team versus those failing to sign such a contract. Methods: Twenty-five male junior cyclists (age: 18.1 [0.7] y, stature: 181.9 [6.0] cm, body mass: 69.1 [7.9] kg, peak oxygen uptake: 71.3 [6.2] mL·min−1·kg−1) were assigned to this investigation. Between September and October of the last year in the junior category, each cyclist performed a ramp incremental exercise test to determine certain physiological performance characteristics. Subsequently, participants were divided in 2 groups: (1) those signing a contract with a U23 development team (JUNIORU23) and (2) those failing to sign such a contract (JUNIORNON-U23). Unpaired t tests were used to assess possible between-groups differences in physiological performance characteristics. The level of statistical significance was set at P < .05 two tailed. Results: No significant between-groups differences in submaximal (ie, gas exchange threshold, respiratory compensation point) and maximal physiological performance characteristics (ie, peak work rate, peak oxygen uptake) expressed in absolute values (ie, L·min−1, W) were observed (P > .05). However, significant between-groups differences were observed when physiological performance characteristics were expressed relative to the cyclists’ body weights (P < .05). Conclusions: The current investigation showed that junior cyclists stepping up to a U23 development team might be retrospectively differentiated from junior cyclists not stepping up based on certain physiological performance characteristics, which might inform practitioners and/or federations working with young cyclists during the long-term athletic development process.

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Timothy D. Griest, Michael J. Saunders, Christopher J. Womack, and Nicholas D. Luden

Purpose: The primary objective was to assess the performance benefits of caffeine (CAF) supplementation in habitual users. Importantly, this investigation was designed to account for the potential confounding effects of CAF withdrawal (CAFW), which are inherent and common in previous work. Methods: Ten CAF-consuming (394 [146] mg·d−1) recreational cyclists (age 39.1 [14.9] y; maximum oxygen consumption 54.2 [6.2] mL·kg–1·min–1) completed four 10-km time trials (TTs) on a cycle ergometer. On each trial day, 8 hours before reporting to the laboratory, subjects consumed 1.5 mg·kg–1 CAF to prevent withdrawal (no withdrawal [N]) or a placebo (PLA; withdrawal [W]). Then, 1 hour prior to exercise, they received either 6 mg·kg–1 CAF or PLA. These protocols were repeated 4 times, employing all combinations of N/W and CAF/PLA. Results: CAFW did not impair TT power output (PLAW vs PLAN P = .13). However, preexercise CAF only improved TT performance when compared to PLA in the W condition (CAFN vs PLAW P = .008, CAFW vs PLAW P = .04), not when W was mitigated (PLAN vs CAFN P = .33). Conclusions: These data indicate that preexercise CAF only improves recreational cycling performance when compared to bouts preceded by CAF abstinence, suggesting that habitual users may not benefit from 6 mg·kg–1 of CAF and that previous work may have overstated the value of CAF supplementation for habitual users. Future work should examine higher doses of CAF for habitual users.

Open access

Ricardo J.S. Costa, Kayla Henningsen, Stephanie K. Gaskell, Rebekah Alcock, Alice Mika, Christopher Rauch, Samuel N. Cheuvront, Phil Blazy, and Robert Kenefick

The study aimed to determine the effects of two differing amino acid beverage interventions on biomarkers of intestinal epithelial integrity and systemic inflammation in response to an exertional-heat stress challenge. One week after the initial assessment, participants (n = 20) were randomly allocated to complete two exertional-heat stress trials, with at least 1 week washout. Trials included a water control trial (CON), and one of two possible amino acid beverage intervention trials (VS001 or VS006). On VS001 (4.5 g/L) and VS006 (6.4 g/L), participants were asked to consume two 237-ml prefabricated doses daily for 7 days before the exertional-heat stress, and one 237-ml dose immediately before, and every 20 min during 2-hr running at 60% maximal oxygen uptake in 35 °C ambient conditions. A water volume equivalent was provided on CON. Whole blood samples were collected pre-, immediately post-, 1 and 2 hr postexercise, and analyzed for plasma concentrations of cortisol, intestinal fatty acid protein, soluble CD14, and immunoglobulin M (IgM) by ELISA, and systemic inflammatory cytokines by multiplex. Preexercise resting biomarker concentrations for all variables did not significantly differ between trials (p > .05). A lower response magnitude for intestinal fatty acid protein (mean [95% CI]: 249 [60, 437] pg/ml, 900 [464, 1,336] pg/ml), soluble CD14 (−93 [−458, 272] ng/ml, 12 [−174, 197] ng/ml), and IgM (−6.5 [−23.0, 9.9] MMU/ml, −10.4 [−16.2, 4.7] MMU/ml) were observed on VS001 and V006 compared with CON (p < .05), respectively. Systemic inflammatory response profile was lower on VS001, but not VS006, versus CON (p < .05). Total gastrointestinal symptoms did not significantly differ between trials. Amino acid beverages’ consumption (i.e., 4.5–6.4 g/L), twice daily for 7 days, immediately before, and during exertional-heat stress ameliorated intestinal epithelial integrity and systemic inflammatory perturbations associated with exercising in the heat, but without exacerbating gastrointestinal symptoms.

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Manoel Rios, Rodrigo Zacca, Rui Azevedo, Pedro Fonseca, David B. Pyne, Victor Machado Reis, Daniel Moreira-Gonçalves, and Ricardo J. Fernandes

Aim: To quantify the physiological demands and impact of muscle function t of the Fran workout, one of the most popular CrossFit benchmarks. Methods: Twenty experienced CrossFitters—16 male: 29 (6) years old and 4 female: 26 (5) years old— performed 3 rounds (with 30-s rests in between) of 21–21, 15–15, and 9–9 front squats to overhead press plus pull-up repetitions. Oxygen uptake and heart rate were measured at baseline, during the workout, and in the recovery period. Rating of perceived exertion, blood lactate, and glucose concentrations were assessed at rest, during the intervals, and in the recovery period. Muscular fatigue was also monitored at rest and at 5 minutes, 30 minutes, and 24 hours postexercise. Repeated-measures analysis of variance was performed to compare time points. Results: Aerobic (52%–29%) and anaerobic alactic (30%–23%) energy contributions decreased and the anaerobic lactic contribution increased (18%–48%) across the 3 rounds of the Fran workout. Countermovement jump height decreased by 8% (−12 to −3) mean change (95% CI), flight duration by 14% (−19 to −7), maximum velocity by 3% (−5 to −0.1), peak force 4% (−7 to −0.1), and physical performance (plank prone 47% [−54 to −38]) were observed. Conclusions: It appears that the Fran workout is a physically demanding activity that recruits energy from both aerobic and anaerobic systems. This severe-intensity workout evokes substantial postexercise fatigue and corresponding reduction in muscle function.

Free access

Colleen X. Muñoz and Michael F. Bergeron

First morning urine (FMU) assessment would be a practical and convenient solution for clinically acceptable detection of underhydration prior to competition/training, and for the general public. Thus, we thus sought to determine the diagnostic accuracy of FMU as a valid indicator of recent (previous 24 hr, 5 days average) hydration practices. For 5 consecutive days and one final morning, 67 healthy women (n = 38) and men (n = 29; age: 20 [1] years, body mass index: 25.9 [5.5]) completed 24-hr diet logs for total water intake (from beverages and foods, absolute and relative to body mass), 24-hr urine and FMU collection (last morning only) for osmolality (Osm), specific gravity (SG), and color (Col), and morning blood sampling for plasma osmolality and copeptin. Correlations determined significance and relationship strength among FMU and all other variables. Area under the receiver operating characteristic curves, sensitivity, specificity, and positive likelihood ratios were employed using previously reported values to indicate underhydration (total water intake < 30 ml/kg, osmolality > 500, and >800 mOsm/kg, specific gravity > 1.017, and copeptin > 6.93 pmol/L). FMU_Osm and FMU_SG were significantly correlated (p < .05) to all variables except the previous 5-day plasma osmolality. FMU_Col was only significantly correlated with other color time intervals and total water intake per gram. FMU_Osm held greatest utility (area under the receiver operating characteristic curve, sensitivity, and specificity >80%) overall, with the best outcome being FMU_Osm indicating a previous 24-hr osmolality threshold of 500 mOsm/kg (FMU_Osm criterion >710 mOsm/kg and positive likelihood ratio = 5.9). With less effort and cost restriction, FMU is a viable metric to assess underhydration.

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Sarah R. Jackman, Gareth A. Wallis, Jinglei Yu, Andrew Philp, Keith Baar, Kevin D. Tipton, and Oliver C. Witard

Branched-chain amino acids (BCAA) and carbohydrate (CHO) are commonly recommended postexercise supplements. However, no study has examined the interaction of CHO and BCAA ingestion on myofibrillar protein synthesis (MyoPS) rates following exercise. We aimed to determine the response of MyoPS to the co-ingestion of BCAA and CHO following an acute bout of resistance exercise. Ten resistance-trained young men completed two trials in counterbalanced order, ingesting isocaloric drinks containing either 30.6-g CHO plus 5.6-g BCAA (B + C) or 34.7-g CHO alone following a bout of unilateral, leg resistance exercise. MyoPS was measured postexercise with a primed, constant infusion of L-[ring13C6] phenylalanine and collection of muscle biopsies pre- and 4 hr postdrink ingestion. Blood samples were collected at time points before and after drink ingestion. Serum insulin concentrations increased to a similar extent in both trials (p > .05), peaking at 30 min postdrink ingestion. Plasma leucine (514 ± 34 nmol/L), isoleucine (282 ± 23 nmol/L), and valine (687 ± 33 nmol/L) concentrations peaked at 0.5 hr postdrink in B + C and remained elevated for 3 hr during exercise recovery. MyoPS was ∼15% greater (95% confidence interval [−0.002, 0.028], p = .039, Cohen’s d = 0.63) in B + C (0.128%/hr ± 0.011%/hr) than CHO alone (0.115%/hr ± 0.011%/hr) over the 4 hr postexercise period. Co-ingestion of BCAA and CHO augments the acute response of MyoPS to resistance exercise in trained young males.

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Craig A. Staunton, Erik P. Andersson, Glenn Björklund, and Marko S. Laaksonen

Purpose: To identify differences in heart rate (HR) and concentration of blood lactate ([La]) relationships between laboratory- and field-based skate-roller-skiing tests. Methods: Fourteen world-class biathletes (8 women, 6 men) completed a laboratory- and field-based roller-skiing test using the skate technique. The laboratory-based test comprised 5 to 7 submaximal steps at a fixed incline and speed on a roller-skiing treadmill. The field-based test comprised 5 steps on a course where the final hill was designed to mimic the conditions of the laboratory test. HR and [La] were measured for each step. The HR associated with 2 mmol·L−1 (HR@2 mmol) and 4 mmol·L−1 (HR@4 mmol) of [La] was calculated using an interpolation method. A 1-way analysis of variance and Bland–Altman analyses with 95% limits of agreement (LoA) were used to determine if test type influenced HR@2 mmol or HR@4 mmol. A second-order polynomial was fitted to group-level data to highlight the HR–[La] relationships for laboratory- and field-based tests. Results: HR@2 mmol was lower for field tests than for laboratory tests (mean bias: 1.9%HRmax; 95% LoA: −4.5 to +8.3%HRmax; P < .001). HR@4 mmol was also lower for field tests compared to laboratory tests (mean bias: 2.4%HRmax; 95% LoA: −1.2 to +6.0%HRmax; P < .001). On the group level, the lactate threshold occurred at a lower HR during roller skiing in the field compared to the laboratory. Conclusions: The findings from this study confirm that for a given HR, [La] was greater in field- compared with laboratory-based conditions. These results might have implications for how coaches define training-intensity “zones” during skate roller skiing based on laboratory tests.

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Cillian D. McGoldrick, Antonio Dello Iacono, Oliver J. Morgan, Jack Nayler, Janice Buchanan, Christopher McCart, and Viswanath B. Unnithan

Purpose: This study examined the interday reliability of a predetermined and a self-determined isometric-squat test among youth soccer players. Familiarization effects were evaluated to determine the minimum number of trials necessary to obtain consistent outputs. Finally, differences between protocols were evaluated. Methods: Thirty-one youth soccer players (mean [SD] age: 13.2 [1.0] y; body mass: 54.1 [3.4] kg; stature: 166.3 [11.2] cm; percentage of estimated adult height: 92.6% [3.6%]) from a top-tier professional academy completed 4 experimental sessions for each protocol: familiarization 1, familiarization 2, test, and retest sessions. Peak force; relative peak force; impulse from 0 to 50 milliseconds, 0 to 100 milliseconds, 0 to 150 milliseconds, and 0 to 200 milliseconds; and rate of force development from 0 to 50 milliseconds, 0 to 100 milliseconds, 0 to 150 milliseconds, and 0 to 200 milliseconds were measured. Results : Both protocols displayed acceptable (intraclass correlation coefficient ≥.75 and coefficient of variation ≤10%) reliability statistics for all metrics apart from rate of force development of any time epoch. Differences were found between familiarization 2 and both test and retest sessions for peak force (P = .034 and .021, respectively) and relative peak force (P = .035 and .005, respectively) across both protocols. Conclusions: The isometric-squat test is a reliable test among youth soccer players. Two familiarization sessions seem to be sufficient to ensure data stabilization. Outputs between the self-determined and predetermined are comparable; however, the latter seems preferable due to improved testing time efficiency.

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Tzlil Shushan, Dean Norris, Shaun J. McLaren, Martin Buchheit, Tannath J. Scott, Steve Barrett, Antonio Dello Iacono, and Ric Lovell

Purpose: To survey team-sport practitioners on current practices and perceptions of submaximal fitness tests (SMFTs). Methods: A convenience sample of team-sport practitioners completed an online survey (September to November 2021). Descriptive statistics were used to obtain information of frequencies. A mixed-model quantile (median) regression was employed to assess the differences between the perceived influence of extraneous factors. Results: A total of 66 practitioners (74 discrete protocols) from 24 countries completed the survey. Time-efficient and nonexhaustive nature were considered the most important features of implementation. Practitioners prescribed a range of SMFTs, administered mostly on a monthly or weekly basis, but scheduling strategies appeared to differ across SMFT categories. Cardiorespiratory/metabolic outcome measures were collected in most protocols (n = 61; 82%), with the majority monitoring heart-rate-derived indices. Subjective outcome measures (n = 33; 45%) were monitored exclusively using ratings of perceived exertion. Mechanical outcome measures (n = 19; 26%) included either a combination of locomotor outputs (eg, distance covered) or variables derived from microelectrical mechanical systems. The perceived influence of extraneous factors on measurement accuracy varied according to outcome measure, and there was a lack of consensus among practitioners. Conclusions: Our survey showcases the methodological frameworks, practices, and challenges of SMFTs in team sports. The most important features for implementation perhaps support the use of SMFTs as a feasible and sustainable tool for monitoring in team sports. The wide variety of protocols, scheduling strategies, and outcome measures, along with their associated collection and analytical techniques, may reflect the absence of robust evidence regarding the application of SMFTs in team sports.