Search

Background: Spiroergometry is important for modern performance diagnostics, and reference values have been evaluated for bicycle and treadmill ergometers. The aim of this study is to assess the comparability of bicycle and hand-crank spiroergometry and its associated parameters, as hand-crank spiroergometry can be used during rehabilitation in patients with definitive or temporally impairment of the lower extremity. Methods: Thirty-seven healthy volunteers completed 2 exhausting performance diagnostics on hand-crank and bicycle spiroergometry. Participants' anthropometric characteristics, maximum power, multiple exertion criteria, maximum aerobic capacity, and maximum heart rate were detected, and ventilatory and metabolic thresholds were determined. Results: The maximum power, maximum heart rate, maximum aerobic capacity, and ventilatory thresholds were significant higher on the bicycle ergometer (P <.001). The metabolic thresholds occurred on higher lactate values on the hand-crank ergometer. Equations for calculating maximum aerobic capacity from the maximum power measured in either hand-crank or bicycle ergometer could be found through regression analysis. Conclusions: Although there are problems in interpreting results of different ergometries due to severe physiology differences, the equations can be used for patients who are temporally unable to complete the established ergometry due to a deficit in the lower extremity. This could improve training recommendations for patients and para-athletes in particular. [ABSTRACT FROM AUTHOR]

This study investigated the test–retest reliability of running economy (RE) and metabolic and cardiorespiratory parameters related to endurance running performance using a multistage incremental treadmill test. On two occasions separated by 21–28 days, 12 male middle- and long-distance runners ran at 10, 11, 12, 13, and 14 km/hr for 8 min each stage, immediately followed by a ramp test to volitional exhaustion. Carbohydrate (10% maltodextrin solution) was consumed before and during the test to provide ∼1 g/min of exercise. RE, minute ventilation ( V ˙ E), oxygen consumption ( V ˙ O 2 ), carbon dioxide production ( V ˙ CO 2 ), respiratory exchange ratio (RER), heart rate (HR), ratings of perceived exertion (RPE), and blood glucose and lactate concentrations were recorded for each stage and at volitional exhaustion. Time-to-exhaustion (TTE) and peak oxygen consumption ( V ˙ O 2 peak) during the ramp test were also recorded. Absolute reliability, calculated as the coefficient of variation (CV) between repeated measures, ranged from 2.3% to 3.1% for RE, whereas relative reliability, calculated as the intraclass correlation coefficient (ICC), ranged from.42 to.79. V ˙ E , V ˙ O 2 , V ˙ O 2 peak , V ˙ CO 2 , RER, and HR had a CV of 1.1%–4.3% across all stages. TTE and RPE had a CV of 7.2% and 2.3%–10.8%, respectively, while glucose and lactate had a CV of 4.0%–17.8%. All other parameters, except for blood glucose, were demonstrated to have good-to-excellent relative reliability assessed by ICC. Measures of RE, V ˙ O 2 peak , and TTE were reliable during this two-phase multistage incremental treadmill test in a cohort of trained and highly trained male middle- and long-distance runners. [ABSTRACT FROM AUTHOR]

Purpose: We examined changes in stride temporal parameters and spring-mass model characteristics during repeated sprints following a 3-week period of "live high–train low and high" (LHTLH) altitude training in team-sport players. Methods: While residing under normobaric hypoxia (≥14 h/d; inspired oxygen fraction [FiO2] 14.5%–14.2%) for 14 days, elite field hockey players performed, in addition to their regular field hockey practice in normoxia, 6 sessions (4 × 5 × 5-s maximal sprints; 25-s passive recovery; 5-min rest) under either normobaric hypoxia (LHTLH; FiO2 ∼14.5%, n = 11) or normoxia (live high–train low; FiO2 20.9%, n = 12). A control group (live low–train low; FiO2 ∼20.9%, n = 9) residing in normoxia without additional repeated-sprint training was included. Before (Pre) and a few days (Post-1) and 3 weeks (Post-2) after the intervention, stride mechanics were assessed during an overground repeated-sprint test (8 × 20 m, 20-s recovery). Two-way repeated-measures analysis of variance (time [Pre, Post-1, and Post-2] × condition [LHTLH, live high–train low, and live low–train low]) were conducted. Results: Peak sprinting speed increased in LHTLH from Pre to Post-1 (+2.2% [2.0%]; P =.002) and Post-2 (+2.0% [2.4%]; P =.025), with no significant changes in live high–train low and live low–train low. There was no main effect of time (all P ≥.062), condition (all P ≥.771), or a significant time × condition interaction (all P ≥.230) for any stride temporal variable (contact time, flight time, stride frequency, and stride length) or spring-mass model characteristics (vertical and leg stiffness). Conclusions: Peak sprinting speed improved in elite field hockey players following LHTLH altitude training, while stride mechanical adjustments to repeated overground sprints remained unchanged for at least 3 weeks postintervention. [ABSTRACT FROM AUTHOR]

Purpose: To compare the standard Yo-Yo intermittent recovery (IR) test and an agility Yo-Yo IR test with a higher number of change-of-direction movements to cardiorespiratory match performance. Methods: The study included 11 professional male handball players (age 24.5 [4.6] y) of a German second-league team. The performance parameters of the players of the seasons 2016–17 to 2018–19 were analyzed. The Yo-Yo IR test was compared to a Yo-Yo IR test with multiple multidirectional changes of direction in response to visual stimuli, which was conducted on a SpeedCourt (Yo-Yo SC IR). Peak oxygen uptake (VO2peak) and maximum heart rate (HRmax) were measured. Between-methods differences of individual athletes were quantified with Bland–Altman plots. Results: HRmax was not statistically different during the Yo-Yo SC IR test compared to the Yo-Yo IR test (181 [10] vs 188 [8] beats·min−1; P =.16). Agreement between the 2 tests was moderate for HRmax and good for heart rates >180 beats·min−1. Mean average VO2peak was 51.7 (3.9) and 50.9 (2.8) mL·min–1·kg–1 for the Yo-Yo SC IR test and the Yo-Yo IR test (P =.693), respectively. Conclusions: A Yo-Yo test with multidirectional changes of direction in response to visual stimuli yielded good agreement with the frequently used linear running tests and can be used to assess players' VO2peak. The HRmax achieved during this test should be used with caution. [ABSTRACT FROM AUTHOR]

Objective: To (1) establish extensive physiological profiles of highly trained CrossFit® athletes using gold-standard tests and (2) investigate which physiological markers best correlate with CrossFit Open performance. Methods: This study encompassed 60 participants (30 men and 30 women), all within the top 5% of the CrossFit Open, including 7 CrossFit semifinalists and 3 CrossFit Games finalists. Isokinetic dynamometers were employed to measure maximum isometric and isokinetic leg and trunk strength. Countermovement-jump height and maximum isometric midthigh-pull strength were assessed on a force plate. Peak oxygen uptake (VO2peak) was measured by a cardiopulmonary exercise test, and critical power and W′ were evaluated during a 3-minute all-out test, both on a cycle ergometer. Results: Male and female athletes' median (interquartile range) VO2peak was 4.64 (4.43, 4.80) and 3.21 (3.10, 3.29) L·min−1, critical power 314.5 (285.9, 343.6) and 221.3 (200.9, 238.9) W, and midthigh pull 3158 (2690, 3462) and 2035 (1728, 2347) N. Linear-regression analysis showed strong evidence for associations between different anthropometric variables and CrossFit Open performance in men and women, whereas for markers of cardiorespiratory fitness such as VO2peak, this was only true for women but not men. Conventional laboratory evaluations of strength, however, manifested minimal evidence for associations with CrossFit Open performance across both sexes. Conclusions: This study provides the first detailed insights into the physiology of high-performing CrossFit athletes and informs training optimization. Furthermore, the results emphasize the advantage of athletes with shorter limbs and suggest potential modifications to CrossFit Open workout designs to level the playing field for athletes across different anthropometric characteristics. [ABSTRACT FROM AUTHOR]

Purpose: To develop and evaluate a theory on the frequent observation that cyclists prefer cadences (RPMs) higher than those considered most economical at submaximal exercise intensities via modeling and simulation of its mathematical description. Methods: The theory combines the parabolic power-to-velocity (v) relationship, where v is defined by crank length, RPM-dependent ankle velocity, and gear ratio, RPM effects on the maximal lactate steady state (MLSS), and lactate-dependent carbohydrate oxidation (CHO). It was tested against recent experimental results of 12 healthy male recreational cyclists determining the v-dependent peak oxygen uptake (VO2PEAKv), MLSS (MLSSv), corresponding power output (PMLSSv), oxygen uptake at PMLSSv (VO2MLSSv), and CHOMLSSv-management at 100 versus 50 per minute, respectively. Maximum RPM (RPMMAX) attained at minimized pedal torque was measured. RPM-specific maximum sprint power output (PMAXv) was estimated at RPMs of 100 and 50, respectively. Results: Modeling identified that MLSSv and PMLSSv related to PMAXv (IPMLSSv) promote CHO and that VO2MLSSv related to VO2PEAKv inhibits CHO. It shows that cycling at higher RPM reduces IPMLSSv. It suggests that high cycling RPMs minimize differences in the reliance on CHO at MLSSv between athletes with high versus low RPMMAX. Conclusions: The present theory-guided modeling approach is exclusively based on data routinely measured in high-performance testing. It implies a higher performance reserve above IPMLSSv at higher RPM. Cyclists may prefer high cycling RPMs because they appear to minimize differences in the reliance on CHO at MLSSv between athletes with high versus low RPMMAX. [ABSTRACT FROM AUTHOR]

Purpose: Determine the effects of advanced footwear technology (AFT) in track spikes and road-racing shoes on running economy (RE). Methods: Four racing shoes (3 AFT and 1 control) and 3 track spikes (2 AFT and 1 control) were tested in 9 male distance runners on 2 visits. Shoes were tested in a random sequence over 5-minute trials on visit 1 (7 trials at 16 km·h−1; 5-min rest between trials) and in the reverse/mirrored order on visit 2. Metabolic data were collected and averaged across visits. Results: There were significant differences across footwear conditions for oxygen consumption (F = 13.046; P <.001) and energy expenditure (F = 14.710; P <.001). Oxygen consumption (in milliliters per kilogram per minute) in both the first AFT spike (49.1 [1.7]; P <.001; dz = 2.1) and the other AFT spike (49.3 [1.7]; P <.001; dz = 1.7) was significantly lower than the control spike (50.2 [1.6]), which represented a 2.1% (1.0%) and 1.8% (1.0%) improvement in RE, respectively, for the AFT spikes. When comparing the subjects' most economic shoe by oxygen consumption (49.0 [1.5]) against their most economic spike (49.0 [1.8]), there were no statistical differences (P =.82). Similar statistical conclusions were made when comparing energy expenditure (in watts per kilogram). Conclusions: AFT track spikes improved RE ∼2% relative to a traditional spike. Despite their heavier mass, AFT shoes resulted in similar RE as AFT spikes. This could make the AFT shoe an attractive option for longer track races, particularly in National Collegiate Athletic Association and high school athletics, where there are no stack-height rules. [ABSTRACT FROM AUTHOR]

Purpose: Long-distance running performance has been reported to be associated with sprint performance in highly trained distance runners. Therefore, we hypothesized that sprint training could enhance distance running and sprint performance in long-distance runners. This study examined the effect of 6-week sprint training on long-distance running and sprint performance in highly trained distance runners. Methods: Nineteen college runners were divided into control (n = 8) and training (n = 11) groups. Participants in the training group performed 12 sprint training sessions in 6 weeks, while those in the control group performed 12 distance training sessions. Before and after the interventions, maximal oxygen uptake ( V ˙ O 2 max), O2 cost during submaximal running (290 m·min−1 and 310 m·min−1 of running velocity), and time to exhaustion (starting at 290 m·min–1 and increased 10 m·min–1 every minute) were assessed on a treadmill. Additionally, the 100-m and 400-m sprinting times and 3000-m running time were determined on an all-weather track. Results: In the control group, no measurements significantly changed after the intervention. In the training group, the time to exhaustion, 100-m and 400-m sprinting times, and 3000-m running time improved significantly, while V ˙ O 2 max and O2 cost did not change. Conclusions: These results showed that 6-week sprint training improved both sprint and long-distance running performance in highly trained distance runners without a change in aerobic capacity. Improvement in the time to exhaustion without a change in V ˙ O 2 max suggests that the enhancement of long-distance running performance could be attributable to improved anaerobic capacity. [ABSTRACT FROM AUTHOR]

Insomnia treatment among individuals with comorbid insomnia and obstructive sleep apnea is suboptimal. In a pilot randomized controlled trial, 19 individuals with comorbid insomnia and obstructive sleep apnea were allocated to one of two arms: EX + EX, consisting of two 8-week phases of exercise training (EX), or RE + CBTiEX, encompassing 8 weeks of relaxation training (RE) followed by 8 weeks of combined cognitive-behavioral therapy and exercise (CBTiEX). Outcomes included Insomnia Severity Index (ISI), polysomnography, and cardiorespiratory fitness measures. A mixed-model analysis of variance revealed a Group × Time interaction on peak oxygen consumption change, F(1, 14) = 10.1, p =.007, and EX increased peak oxygen consumption (p =.03, g′ = −0.41) and reduced ISI (p =.001, g′ = 0.82) compared with RE (p =.49, g = 0.16) post-8 weeks. Post-16 weeks, there was a significant Group × Time interaction (p =.014) driven by RE + CBTiEX yielding a larger improvement in ISI (p =.023, g′ = 1.48) than EX + EX (p =.88, g′ < 0.1). Objective sleep was unchanged. This study showed promising effects of regular EX alone and combined with cognitive-behavioral therapy for insomnia on ISI in comorbid insomnia and obstructive sleep apnea. [ABSTRACT FROM AUTHOR]

Purpose: This study aimed to cross-validate a recently proposed equation for the prediction of maximal oxygen uptake ( V ˙ O 2 max) in cycling exercise by using the average power output normalized by the body mass from a 5-minute time trial (RPO5-min) as the independent variable. Further, the study aimed to update the predictive equation using Bayesian informative prior distributions and meta-analysis. Methods: On different days, 49 male cyclists performed an incremental graded exercise test until exhaustion and a 5-minute time trial on a stationary cycle ergometer. We compared the actual V ˙ O 2 max with the predicted value obtained from the RPO5-min, using a modified Bayesian Bland–Altman agreement analysis. In addition, this study updated the data on the linear regression between V ˙ O 2 max and RPO5-min, by incorporating information from a previous study as a Bayesian informative prior distribution or via meta-analysis. Results: On average, the predicted V ˙ O 2 max using RPO5-min underestimated the actual V ˙ O 2 max by −6.6 mL·kg–1·min–1 (95% credible interval, −8.6 to −4.7 mL·kg–1·min–1). The lower and upper 95% limits of agreement were −17.2 (−22.7 to −12.3) and 3.8 (−1.0 to 9.5) mL·kg–1·min–1, respectively. When the current study's data were analyzed using the previously published data as a Bayesian informative prior distribution, the accuracy of predicting sample means was found to be better when compared with the data combined via meta-analyses. Conclusions: The proposed equation presented systematic bias in our sample, in which the prediction underestimated the actual V ˙ O 2 max. We provide an updated equation using the previous one as the prior distribution, which could be generalized to a greater audience of cyclists. [ABSTRACT FROM AUTHOR]

Purpose: To assess (1) whether and how a higher maximal lactate steady state (MLSS) at higher cycling cadence (RPM) comes along with higher absolute and/or fractional carbohydrate combustion (CHOMLSS), respectively, and (2) whether there is an interrelation between potential RPM-dependent MLSS effects and the maximally achievable RPM (RPMMAX). Methods: Twelve healthy males performed incremental load tests to determine peak power, peak oxygen uptake, and 30-minute MLSS tests at 50 and 100 per minute, respectively, to assess RPM-dependent MLSS, corresponding power output, CHOMLSS responses, and 6-second sprints to measure RPMMAX. Results: Peak power, peak carbon dioxide production, and power output at MLSS were lower (P =.000, ω2 = 0.922; P =.044, ω2 > 0.275; and P =.016, ω2 = 0.373) at 100 per minute than at 50 per minute. With 6.0 (1.5) versus 3.8 (1.2) mmol·L−1, MLSS was higher (P =.000, ω2 = 0.771) at 100 per minute than at 50 per minute. No corresponding RPM-dependent differences were found in oxygen uptake at MLSS, carbon dioxide production at MLSS, respiratory exchange ratio at MLSS, CHOMLSS, or fraction of oxygen uptake used for CHO at MLSS, respectively. There was no correlation between the RPM-dependent difference in MLSS and RPMMAX. Conclusions: The present study extends the previous finding of a consistently higher MLSS at higher RPM by indicating (1) that at fully established MLSS conditions, respiration and CHOMLSS management do not differ significantly between 100 per minute and 50 per minute, and (2) that linear correlation models did not identify linear interdependencies between RPM-dependent MLSS conditions and RPMMAX. [ABSTRACT FROM AUTHOR]

This study sought to investigate the effect of cold ambient temperature on subcutaneous abdominal adipose tissue (SCAAT) lipolysis and blood flow during steady-state endurance exercise in endurance-trained cyclists. Ten males (age: 23 ± 3 years; peak oxygen consumption: 60.60 ± 4.84 ml·kg−1·min−1; body fat: 18.4% ± 3.5%) participated in baseline lactate threshold (LT) and peak oxygen consumption testing, two familiarization trials, and two experimental trials. Experimental trials consisted of cycling in COLD (3 °C; 42% relative humidity) and neutral (NEU; 19 °C; 39% relative humidity) temperatures. Exercise consisted of 25 min cycling at 70% LT and 25 min at 90% LT. In situ SCAAT lipolysis and blood flow were measured via microdialysis. Heart rate, core temperature, carbohydrate and fat oxidation, blood glucose, and blood lactate were also measured. Heart rate, core temperature, oxygen consumption, and blood lactate increased with exercise but were not different between COLD and NEU. SCAAT blood flow did not change from rest to exercise or between COLD and NEU. Interstitial glycerol increased during exercise (p <.001) with no difference between COLD and NEU. Fat oxidation increased (p <.001) at the onset of exercise and remained elevated thereafter with no difference between COLD and NEU. Carbohydrate oxidation increased with increasing exercise intensity and was greater at 70% LT in COLD compared to NEU (p =.030). No differences were observed between conditions for any other variable. Cycling exercise increased SCAAT lipolysis but not blood flow. Ambient temperature did not alter SCAAT metabolism, SCAAT blood flow, or fat oxidation in well-trained cyclists, though cold exposure increased whole-body carbohydrate oxidation at lower exercise intensities. [ABSTRACT FROM AUTHOR]

Purpose: The aim of this study was to describe the day-by-day training and racing characteristics in preparation for the Giro d'Italia of 1 world-class road cyclist who achieved a place on the podium in the final general classification of the Giro d'Italia. Methods: Day-by-day power meter training and racing data of 1 study subject (road cyclist; age 25 y; relative maximum oxygen consumption 81 mL·min−1·kg−1; relative 20-min record power output 6.6 W·kg−1) covering the 152 days leading up to the podium in the Giro d'Italia final general classification were retrospectively analyzed. Daily load, daily volume, and intensity distribution were considered. Results: During training a pattern alternating "hard days" versus "easy days" was observed, as significant amounts of medium or high intensity, or load, were not performed for more than 2 consecutive days This pattern was achieved combining high volume (>4 h) with a significant amount of medium and high intensity within the same training sessions. During training, when training load and intensity increased, the density of "easy days" augmented. In 1-week stage races and the Giro d'Italia, 3 to 8 consecutive days with significant amounts of medium and high intensity were performed. A high number of training sessions with small amounts of medium- and high-intensity volume was observed: 38 days accumulating 3 to 10 minutes at medium intensity and 29 days spending 1 to 9 minutes at high intensity. Conclusion: These data provide novel insights about the day-by-day periodization strategies leading to a top 3 in the Giro d'Italia general classification. [ABSTRACT FROM AUTHOR]

Purpose: We compared the adaptive responses to supramaximal high-intensity interval training (HIIT) individualized according to anaerobic speed reserve (ASR), the 30-15 Intermittent Fitness Test (VIFT), and velocity associated with maximum oxygen uptake (MAS) to determine which approach facilitates more identical adaptations across athletes with different profiles. Methods: Thirty national-level basketball players (age = 28.4 [5] y; body mass = 88.9 [6.3] kg; height = 190 [4.8] cm) were randomly assigned to 3 training groups performing 2 sets of 4, 6, 8, 6, 8, and 10-minute runs (from first to sixth week, respectively), consisting of 15-second running at Δ%20ASR (MAS + 0.2 × ASR), 95%VIFT, and 120%MAS, with 15 seconds recovery between efforts and a 3-minute relief between sets. Results: All 3 interval interventions significantly (P <.05) enhanced maximum oxygen uptake ( V ˙ O 2 max), oxygen pulse ( V ˙ O 2 / HR), first and second ventilatory threshold (VT1 and VT2), cardiac output ( Q ˙ max ), stroke volume, peak and average power output, testosterone levels, and testosterone-to-cortisol ratio following the training period. Different values of interindividual variability (coefficient of variation) for the percentage changes of the measured variables were observed in response to HIITASR, HIITvIFT, and HIITMAS for V ˙ O 2 max (8.7%, 18.8%, 34.6%, respectively), V ˙ O 2 / HR (9.5%, 15.0%, 28.6%), VT1 (9.6%, 19.6%, 34.6%), VT2 (21.8%, 32.4%, 56.7%), Q ˙ max (8.2%, 16.9%, 28.8%), stroke volume (7.9%, 15.2%, 23.5%), peak power output (20%, 22%, 37.3%), average power output (21.1%, 21.3%, 32.5%), testosterone (52.9%, 61.6%, 59.9%), and testosterone-to-cortisol ratio (55.1%, 59.5%, 57.8%). Conclusions: Supramaximal HIIT performed at Δ%20ASR resulted in more uniform physiological adaptations than HIIT interventions prescribed using VIFT or MAS. Although hormonal changes do not follow this approach, all the approaches induced an anabolic effect. [ABSTRACT FROM AUTHOR]

Purpose: We examined the effects of increasing hypoxia severity on oxygenation kinetics in the vastus lateralis muscle during repeated treadmill sprints, using statistical parametric mapping (SPM). Methods: Ten physically active males completed 8 sprints of 5 seconds each (recovery = 25 s) on a motorized sprint treadmill in normoxia (sea level; inspired oxygen fraction = 0.21), moderate hypoxia (inspired oxygen fraction = 0.17), and severe hypoxia (SH; inspired oxygen fraction = 0.13). Continuous assessment of tissue saturation index (TSI) in the vastus lateralis muscle was conducted using near-infrared spectroscopy. Subsequently, TSI data were averaged for the sprint–recovery cycle of all sprints and compared between conditions. Results: The SPM analysis revealed no discernible difference in TSI signal amplitude between conditions during the actual 5-second sprint phase. However, during the latter portion of the 25-second recovery phase, TSI values were lower in SH compared with both sea level (from 22 to 30 s; P =.003) and moderate hypoxia (from 16 to 30 s; P =.001). The mean distance covered at sea level (22.9 [1.0] m) was greater than for both moderate hypoxia (22.5 [1.2] m; P =.045) and SH (22.3 [1.4] m; P =.043). Conclusions: The application of SPM demonstrated that only SH reduced muscle oxygenation levels during the late portion of the passive (recovery) phase and not the active (sprint) phase during repeated treadmill sprints. These findings underscore the usefulness of SPM for assessing muscle oxygenation differences due to hypoxic exposure and the importance of the duration of the between-sprints recovery period. [ABSTRACT FROM AUTHOR]

With ascent to high altitude (HA), compensatory increases in cerebral blood flow and oxygen delivery must occur to preserve cerebral metabolism and consciousness. We hypothesized that this compensation in cerebral blood flow and oxygen delivery preserves tolerance to simulated hemorrhage (via lower body negative pressure, LBNP), such that tolerance is similar during sustained exposure to HA vs. low altitude (LA). Healthy humans (4F/4 M) participated in LBNP protocols to presyncope at LA (1130 m) and 5-7 days following ascent to HA (3800 m). Internal carotid artery (ICA) blood flow, cerebral delivery of oxygen (CDO2) through the ICA, and cerebral tissue oxygen saturation (ScO2) were determined. LBNP tolerance was similar between conditions (LA: 1276 ± 304 s vs. HA: 1208 ± 306 s; P = 0.58). Overall, ICA blood flow and CDO2 were elevated at HA vs. LA (P ≤ 0.01) and decreased with LBNP under both conditions (P

Purpose: Fran is one of the most popular CrossFit benchmark workouts used to control CrossFitters' improvements. Detailed physiological characterization of Fran is needed for a more specific evaluation of CrossFitters' training performance improvements. The aim of the study was to analyze the oxygen uptake ( V ˙ O 2 ) kinetics and characterize the energy system contributions and the degree of postexercise fatigue of the unbroken Fran. Methods: Twenty trained CrossFitters performed Fran at maximal exertion. V ˙ O 2 and heart-rate kinetics were assessed at baseline and during and post-Fran. Blood lactate and glucose concentrations and muscular fatigue were measured at baseline and in the recovery period. Results: A marked increase in V ˙ O 2 kinetics was observed at the beginning of Fran, remaining elevated until the end (V ˙ O 2 peak : 49.2 [3.7] mL·kg−1·min−1, V ˙ O 2 amplitude: 35.8 [5.2] mL·kg−1·min−1, time delay: 4.7 [2.5] s and time constant: 23.7 [11.1] s; mean [SD]). Aerobic, anaerobic lactic, and alactic pathways accounted for 62% (4%), 26% (4%), and 12% (2%) of energy contribution. Reduction in muscle function in jumping ability (jump height: 8% [6%], peak force: 6% [4%], and maximum velocity: 4% [2%]) and plank prone test (46% [20%]) was observed in the recovery period. Conclusions: The Fran unbroken workout is a high-intensity effort associated with an elevated metabolic response. This pattern of energy response highlights the primary contribution of aerobic energy metabolism, even during short and very intense CrossFit workouts, and that recovery can take >24 hours due to cumulative fatigue. [ABSTRACT FROM AUTHOR]

Purpose: This study compared the effects of individualizing supramaximal interval rowing interventions using anaerobic power reserve (APR [high-intensity interval training (HIIT) prescribed according to individual APR (HIITAPR)]) and power associated with maximal oxygen uptake ( W V ˙ O 2 max [HIIT prescribed based on the individual W V ˙ O 2 max (HIITW)]) on the homogeneity of physiological and performance adaptations. Methods: Twenty-four well-trained rowers (age 24.8 [4.3] y, stature 182.5 [3] cm, body mass 86.1 [4.3]) were randomized into interventions consisting of 4 × 30-second intervals at 130%APR ( W V ˙ O 2 max + 0.3 × maximal sprint power) with weekly progression by increasing the number of repetitions per set (5, 6, 7, 8, 9, and 10, from first to sixth session) and the same sets and repetitions with the intensity described as 130% W V ˙ O 2 max. The work-to-recovery ratio was 1:1 for repetitions and 3 minutes between sets. Responses of aerobic fitness indices, power output, cardiac hemodynamics, locomotor abilities, and time-trial performance were examined. Results: Both HIITAPR and HIITW interventions significantly improved V ˙ O 2 max , lactate threshold, cardiac hemodynamics, and 2000-m performance, with no between-groups difference in changes over time. However, HIITAPR resulted in a lower interindividual variability in adaptations in V ˙ O 2 max and related physiological parameters, but this is not the case for athletic performance, which can depend on a multitude of factors beyond physiological parameters. Conclusions: Results demonstrated that expressing supramaximal interval intensity as a proportion of APR facilitates imposing the same degrees of homeostatic stress and leads to more homogeneous physiological adaptations in maximal variables when compared to prescribing a supramaximal HIIT intervention using W V ˙ O 2 max. However, lower interindividual variability would be seen in submaximal variables if HIIT interventions were prescribed using W V ˙ O 2 max. [ABSTRACT FROM AUTHOR]

Purpose: To investigate the effect of personalized sweat sodium replacement on drinking behavior, sodium and water balance, and thermophysiological responses during and after ultraendurance running in hot conditions. Methods: Nine participants (7 male, 2 female) completed two 5-hour treadmill runs (60% maximum oxygen uptake, 30°C ambient temperature), in a double-blind randomized crossover design, consuming sodium chloride (SODIUM) capsules to replace 100% of previously assessed losses or placebo (PLACEBO). Fluid was consumed ad libitum. Results: No effect of SODIUM was observed for ad libitum fluid intake or net fluid balance (P >.05). Plasma sodium concentration increased in both trials, but to a greater extent in SODIUM at 2.5 hours (mean [SD]: 4 [4] mmol·L−1 vs 1 [5] mmol·L−1; P <.05) and postexercise (4 [3] mmol·L−1 vs 1 [5] mmol·L−1; P <.05). Plasma volume change was not different between trials (P >.05) but was strongly correlated with sodium balance in SODIUM (r =.880, P <.01). No effect of sodium replacement was observed for heart rate, rectal temperature, thermal comfort, perceived exertion, or physiological strain index. During the 24 hours postexercise, ad libitum fluid intake was greater following SODIUM (2541 [711] mL vs 1998 [727] mL; P =.04), as was urinary sodium excretion (NaCl: 66 [35] mmol, Pl: 21 [12] mmol; P <.01). Conclusions: Personalized sweat sodium replacement during ultraendurance running in hot conditions, with ad libitum fluid intake, exacerbated the rise in plasma sodium concentration compared to no sodium replacement but did not substantially influence overall body-water balance or thermophysiological strain. A large sodium deficit incurred during exercise leads to substantial renal sodium conservation postexercise. [ABSTRACT FROM AUTHOR]

Purpose: To investigate performance-determining variables of an on-snow sprint cross-country skiing competition and the evolvement in their relationship with performance as the competition progresses from the individual time trial (TT) to the final. Methods: Sixteen national-level male junior skiers (mean [SD] age, 18.6 [0.8] y; peak oxygen uptake [VO2peak], 67.6 [5.5] mL·min−1·kg−1) performed a simulated sprint competition (1.3 km) in the skating style, comprising a TT followed by 3 finals (quarterfinals, semifinals, and final) completed by all skiers. In addition, submaximal and incremental roller-ski treadmill tests, on-snow maximal speed tests, and strength/power tests were performed. Results: VO2peak and peak treadmill speed during incremental testing and relative heart rate, rating of perceived exertion, blood lactate concentrations, and gross efficiency during submaximal testing were all significantly correlated with performance in the TT and subsequent finals (mean [range] r values:.67 [.53–.86], all P <.05). Relative VO2peak and submaximal relative heart rate and blood lactate concentration were more strongly correlated with performance in the semifinals and final compared with the TT (r values:.74 [.60–.83] vs 0.55 [.51–.60], all P <.05). Maximal speed in uphill and flat terrain was significantly correlated with performance in the TT and subsequent finals (r values:.63 [.38–.70], all P <.05), while strength/power tests did not correlate significantly with sprint performance. Conclusions: VO2peak and high-speed abilities were the most important determinants of sprint cross-country skiing performance, with an increased importance of VO2peak as the competition format progressed toward the final. [ABSTRACT FROM AUTHOR]

Purpose: To compare the energetic contribution and pacing in 2000- and 1500-m maximal rowing-ergometer performances. Methods: On separate visits (>48 h apart, random order), 18 trained junior (16.7 [0.4] y) male rowers completed 3 trials: a 7 × 4-minute graded exercise test, a 2000-m time trial (TT2000), and a 1500-m TT (TT1500). Respiratory gases were continuously measured throughout each trial. The submaximal power-to-oxygen-consumption relationship from the graded exercise test was used to determine the accumulated oxygen deficit for each TT. Differences in mean power output (MPO), relative anaerobic contribution, percentage of peak oxygen uptake, pacing index, maximum heart rate, rating of perceived exertion, and blood lactate concentration were assessed using linear mixed modeling. Results: Compared to TT2000 (324 [24] W), MPO was 5.2% (3.3%) higher in TT1500 (341 [29 W]; P <.001, η p 2 =.70). There was a 4.9% (3.3%) increase (P <.001, η p 2 =.71) in anaerobic contribution from 17.3% (3.3%) (TT2000) to 22.2% (4.3%) (TT1500). Compared to TT1500, maximum heart rate, rating of perceived exertion, and blood lactate concentration were all greater (P <.05) in TT2000. The pacing index was not different between trials. Percentage increase in MPO from TT2000 to TT1500 was negatively associated with pacing variance in TT1500 (R2 =.269, P =.027). Conclusions: Maximal ergometer performance over 1500 m requires a significantly greater anaerobic contribution compared with 2000 m. Junior male athletes adopt a consistent pacing strategy across both distances. However, those who experienced greater percentage increases in MPO over the shorter test adopted a more even pacing strategy. To prepare for 1500-m performance, greater emphasis should be placed on developing capacity for work in the severe domain and completing race simulations with a more even pacing strategy. [ABSTRACT FROM AUTHOR]

Purpose: Advanced footwear technology is prevalent in distance running, with research focusing on these "super shoes" in competitive athletes, with less understanding of their value for slower runners. The aim of this study was to compare physiological and biomechanical variables between a model of super shoes (Saucony Endorphin Speed 2) and regular running shoes (Saucony Cohesion 13) in recreational athletes. Methods: We measured peak oxygen uptake (VO2peak) in 10 runners before testing each subject 4 times in a randomly ordered crossover design (ie, Endorphin shoe or Cohesion shoe, running at 65% or 80% of velocity at VO2peak [vVO2peak]). We recorded video data using a high-speed camera (300 Hz) to calculate vertical and leg stiffnesses. Results: 65% vVO2peak was equivalent to a speed of 9.4 km·h−1 (0.4), whereas 80% vVO2peak was equivalent to 11.5 km·h−1 (0.5). Two-way mixed-design analysis of variance showed that oxygen consumption in the Endorphin shoe was 3.9% lower than in the Cohesion shoe at 65% vVO2peak, with an interaction between shoes and speed (P =.020) meaning an increased difference of 5.0% at 80% vVO2peak. There were small increases in vertical and leg stiffnesses in the Endorphin shoes (P <.001); the Endorphin shoe condition also showed trivial to moderate differences in step length, step rate, contact time, and flight time (P <.001). Conclusions: There was a physiological benefit to running in the super shoes even at the slower speed. There were also spatiotemporal and global stiffness improvements indicating that recreational runners benefit from wearing super shoes. [ABSTRACT FROM AUTHOR]

Purpose: The study examined the longitudinal interplay of anthropometric, metabolic, and neuromuscular development related to performance in adolescent national-level swimmers over 12 months. Methods: Seven male and 12 female swimmers (14.8 [1.3] y, FINA [International Swimming Federation] points 716 [51]) were tested before (T0) and after the preparation period (T1), at the season's peak (T2), and before the next season (T3). Anthropometric (eg, fat percentage) and neuromuscular parameters (squat and bench-press load-velocity profile) were assessed on dry land. Metabolic (cost of swimming [C], maximal oxygen uptake [ V ˙ O 2 peak ], and peak blood lactate [bLapeak]) and performance (sprinting speed [vsprint] and lactate thresholds [LT1 and 2]) factors were determined using a 500-m submaximal, 200-m all-out, 20-second sprint, and incremental test (+0.03 m·s−1, 3 min), respectively, in front-crawl swimming. Results: vsprint (+0.6%) and LT1 and 2 (+1.9–2.4%) increased trivially and slightly, respectively, from T0 to T2 following small to moderate strength increases (≥+10.2%) from T0 to T1 and V ˙ O 2 peak (+6.0%) from T1 to T2. Bench-press maximal strength and peak power correlated with vsprint from T0 to T2 (r ≥.54, P <.05) and LT2 at T1 (r ≥.47, P <.05). Changes in fat percentage and V ˙ O 2 peak (T2–T1 and T3–T2, r ≤ −.67, P <.01) and C and LT2 (T2–T0, r = −.52, P =.047) were also correlated. Conclusions: Increases in strength and V ˙ O 2 peak from preparation to the competition period resulted in improved sprint and endurance performance. Across the season, upper-body strength was associated with vsprint and LT2, although their changes were unrelated. [ABSTRACT FROM AUTHOR]

This study investigated the effects of an acute dose (900 mg) of New Zealand Blackcurrant (NZBC) extract on 5-km running performance, alongside associated physiological and metabolic responses. Sixteen trained male runners (age 26 ± 5 years, stature 173.4 ± 7.3 cm, body mass 73.7 ± 6.9 kg, maximal oxygen consumption [ V ˙ O 2 max ] 55.4 ± 6.1 ml·kg−1·min−1) ingested either capsules containing NZBC extract (3 × 300 mg CurraNZ, 315 mg anthocyanins) or a matched placebo (3 × 300 mg gluten-free flour) 2 hr before exercise in a double-blind, randomized, crossover design. Performance time, physiological, and metabolic responses were assessed in a 5-km time trial, preceded by 10-min exercise at the lactate threshold on a treadmill. NZBC extract did not alter the physiological or metabolic responses to exercise at the lactate threshold (oxygen uptake, respiratory exchange ratio, minute ventilation, carbohydrate oxidation, fat oxidation, heart rate, blood lactate, or rating of perceived exertion, p >.05). The 5-km time trial was completed in a faster time in the NZBC extract condition compared with placebo (NZBC: 1,308.96 ± 122.36 s, placebo: 1,346.33 ± 124.44, p =.001, d = −0.23, confidence interval range = [−0.46, 0.00 s]). No differences in physiological or metabolic responses were apparent between conditions for the 5-km time trial (p >.05). Ingesting 900 mg of NZBC extract as an acute dose improves performance in trained male runners without altering physiological or metabolic responses to exercise. Further research is needed to assess a wider range of possible mechanisms (e.g., cardiovascular function, metabolite profiles) to advance insight into improved performance following supplementation. [ABSTRACT FROM AUTHOR]

Purpose: One hundred years ago, Hill and Lupton introduced the concept of maximal oxygen uptake ( V ˙ O 2 max), which is regarded as "the principal progenitor of sports physiology." We provide a succinct overview of the evolvement of research on V ˙ O 2 max , from Hill and Lupton's initial findings to current debates on limiting factors for V ˙ O 2 max and the associated role of convective and diffusive components. Furthermore, we update the current use of V ˙ O 2 max in elite endurance sport and clinical settings. Practical Applications and Conclusions: V ˙ O 2 max is a healthy and active centenarian that remains a very important measure in elite endurance sports and additionally contributes as an important vital sign of cardiovascular function and fitness in clinical settings. Over the past 100 years, guidelines for the test protocols and exhaustion criteria, as well as the understanding of limiting factors for V ˙ O 2 max , have improved dramatically. Presently, possibilities of accurate and noninvasive determination of the convective versus diffusive components of V ˙ O 2 max by wearable sensors represent an important future application. V ˙ O 2 max is not only an indicator of cardiorespiratory function, fitness, and endurance performance but also represents an important biomarker of cardiovascular function and health to be included in routine assessment in clinical practice. [ABSTRACT FROM AUTHOR]

Purpose: Total hemoglobin mass (tHbmass) and blood volume (BV) are important determinants of maximal oxygen uptake and endurance capacity. Higher-caliber endurance athletes usually possess higher tHbmass and BV values. This study aimed to compare tHbmass and BV among swimmers of diverse competitive calibers and distances. Methods: Thirty swimmers (16 female and 14 male) participated in the study: 3 were tier 5, world class (869 [59] FINA points); 15 were tier 4, elite/international (853 [38] points); and 12 were tier 3, highly trained/national (808 [35] points). They specialized in competition distances ranging from 200 m to open-water 10 km. Between February 2019 and February 2020, all swimmers had their tHbmass and BV measured by carbon monoxide rebreathing 1 to 6 times and participated in multiple competitions and race events. Results: Relative tHbmass and BV were not different (P >.05) between tiers among women or among men (pooled tHbmass values 14.5 [0.5], 12.5 [1.5], 12.6 [2.3] g/kg for tier 5, tier 4, and tier 3, respectively). No differences were observed in relative tHbmass (P =.215) and BV (P =.458) between pool and open-water swimmers or between 200-, 400-, and 1500-m specialists (P >.05). No significant correlations were found between the highest measured absolute or relative tHbmass and BV and the highest FINA points scored over the follow-up period (R = −.42–.17, P =.256–.833), irrespective of competition distance. Conclusion: tHbmass and BV values did not differ between swimmers of different calibers or among competition distances. Furthermore, these values did not correlate with FINA points, either in males or in females. The present results indicate that hematological characteristics may have a lesser impact on swimming performance than on land-based endurance sports. [ABSTRACT FROM AUTHOR]

Purpose: To investigate differences in time to exhaustion (TTE), O2 uptake ( V ˙ O 2 ), and accumulated O2 deficit ( O 2 def ) between competitive and recreational cross-country (XC) skiers during an intermittent-interval protocol standardized for maximal aerobic power (MAP). Methods: Twelve competitive (maximal V ˙ O 2 [ V ˙ O 2 max ] = 76.5 ± 3.8 mL · kg − 1 · min − 1 ) and 10 recreational ( V ˙ O 2 max = 63.5 ± 6.3 mL · kg − 1 · min − 1 ) male XC skiers participated. All tests were performed on a rollerski treadmill in the V2 ski-skating technique. To quantify MAP and maximal accumulated oxygen deficit (MAOD), the skiers performed a steady-state submaximal test followed by a 1000-m time trial. After a 60-minute break, TTE, V ˙ O 2 , and accumulated O 2 def were measured during an intermittent-interval protocol (40-s work and 20-s recovery), which was individually tailored to 120% and 60% of each subject's MAP. Results: During the 1000-m time trial, the competitive skiers had 21% (95% CI, 12%–30%) shorter finish time and 24% (95% CI, 14%–34%) higher MAP (all P <.01) than the recreational skiers. No difference was observed in relative exercise intensity (average power/MAP; P =.28), MAOD (P =.18), or fractional utilization of V ˙ O 2 max. During the intermittent-interval protocol, the competitive skiers had 34% (95% CI, 3%–65%) longer TTE (P =.03) and accumulated 61% (95% CI, 27%–95%) more O 2 def (P =.001) than the recreational skiers during work phases. Conclusions: Competitive XC skiers have longer TTE and accumulate more O 2 def than recreational XC skiers during an intermittent-interval protocol at similar intensity relative to MAP. This implies that performance in intermittent endurance sports is related to the ability to repeatedly recharge fractions of MAOD. [ABSTRACT FROM AUTHOR]

Purpose: Laboratory-based indicators are commonly used for performance assessment in young cyclists. However, evidence supporting the use of these indicators mostly comes from cross-sectional research, and their validity as predictors of potential future performance remains unclear. We aimed to assess the role of laboratory variables for predicting transition from U23 (under 23 y) to professional category in young cyclists. Methods: Sixty-five U23 male road cyclists (19.6 [1.5] y) were studied. Endurance (maximal graded test and simulated 8-min time trial [TT]), muscle strength/power (squat, lunge, and hip thrust), and body composition (assessed with dual-energy X-ray absorptiometry) indicators were determined. Participants were subsequently followed and categorized attending to whether they had transitioned ("Pro") or not ("Non-Pro") to the professional category during the study period. Results: The median follow-up period was 3 years. Pro cyclists (n = 16) showed significantly higher values than Non-Pro riders (n = 49) for ventilatory thresholds, peak power output, peak oxygen uptake, and TT performance (all P <.05, effect size > 0.69) and lower levels of fat mass and bone mineral content/density (P <.05, effect size > 0.63). However, no significant differences were found for muscle strength/power indicators (P >.05, effect size < 49). The most accurate individual predictor was TT performance (overall predictive value = 76% for a cutoff value of 5.6 W·kg−1). However, some variables that did not reach statistical significance in univariate analyses contributed significantly to a multivariate model (R2 =.79, overall predictive value = 94%). Conclusions: Although different "classic" laboratory-based endurance indicators can predict the potential of reaching the professional category in U23 cyclists, a practical indicator such as 8-minute TT performance showed the highest prediction accuracy. [ABSTRACT FROM AUTHOR]

Purpose: Variable-speed control in the field is challenging for motion science. Tests were performed to evaluate speed, Froude number, and oxygen consumption if these varied when using the same frequency of steps. The objective of this study was to evaluate the use of auditory feedback to control variable speed on the treadmill and track during acceleration cycles around the transition speed. Methods: Twenty-four trained men participated. The protocol was based on 5 ramps of 50 seconds each around 80%, 90%, 100%, 110%, and 120% of the walking–running transition speed, recording the frequency of steps with a mobile phone during the treadmill test. The tests were replicated on the track using auditory feedback. Results: When evaluating each speed of the protocols separately for the same frequency of steps, the average speed on the track was always higher on average at 54.7% compared to the laboratory (P <.050), and on the track, it was 16.2% higher than in the laboratory (P >.050). Conclusions: It cannot be considered that the same frequency of steps is equivalent to the same speed in the laboratory and on the track. These results point to the importance of reliable speed control during open field tests. [ABSTRACT FROM AUTHOR]

BACKGROUND: Cardiac dysfunction from pulmonary vascular disease causes characteristic findings on cardiopulmonary exercise testing (CPET). We tested the accuracy of CPET for detecting inadequate stroke volume (SV) augmentation during exercise, a pivotal manifestation of cardiac limitation in patients with pulmonary vascular disease. METHODS: We reviewed patients with suspected pulmonary vascular disease in whom CPET and right heart catheterization (RHC) measurements were taken at rest and at anaerobic threshold (AT). We correlated CPET-determined O2·pulseAT/O2·pulserest with RHC-determined SVAT/SVrest. We evaluated the sensitivity and specificity of O2·pulseAT/O2·pulserest to detect SVAT/SVrest below the lower limit of normal (LLN). For comparison, we performed similar analyses comparing echocardiographically-measured peak tricuspid regurgitant velocity (TRVpeak) with SVAT/SVrest. RESULTS: From July 2018 through February 2023, 83 simultaneous RHC and CPET were performed. Thirty-six studies measured O2·pulse and SV at rest and at AT. O2·pulseAT/O2·pulserest correlated highly with SVAT/SVrest (r = 0.72, 95% CI 0.52, 0.85; p

Previous observations demonstrate New Zealand blackcurrant (NZBC) extract to alter cardiovascular responses at rest without prior exercise. However, the prolonged effects of NZBC on blood pressure and heart rate variability following exercise are not known. Participants (n15 [five women], age: 31 ± 9 years, maximal oxygen uptake: 44 ± 9 ml·kg−1·min−1) undertook a control condition of 2 hr of lying supine rest. Subsequently, in a double-blind, placebo (PLA)-controlled, randomized crossover design participants completed 1 hr of treadmill exercise at 50% maximal oxygen uptake followed by 2-hr supine rest with blood pressure and heart rate variability measurement following a 7-day intake of NZBC and PLA. With NZBC, there was an increase in average fat oxidation (NZBC: 0.24 ± 0.11 vs. PLA: 0.17 ± 0.11 g/min, p =.005), and larger high-frequency relative power during the exercise (p =.037). In the 2-hr rest period, delta change for systolic pressure was larger with NZBC than PLA (Control vs. NZBC: −5.6 ± 6.4, Control vs. PLA: −3.5 ± 6.0 mmHg, p =.033) but was not different for diastolic or mean arterial pressure. There were no alterations in heart rate variabilities during the 2 hr following the exercise with NZBC. A 7-day intake of NZBC causes a larger postexercise hypotension response in young, physically active men and women following 1 hr of treadmill exercise at 50% maximal oxygen uptake. [ABSTRACT FROM AUTHOR]

Background: Laboratory assessment of maximal oxygen uptake ( V ˙ O 2 max) is physically and mentally draining for the athlete and requires expensive laboratory equipment. Indirect measurement of V ˙ O 2 max could provide a practical alternative to laboratory testing. Purpose: To examine the relationship between the maximal power output (MPO) in an individualized 7 × 2-minute incremental test (INCR-test) and V ˙ O 2 max and to develop a regression equation to predict V ˙ O 2 max from MPO in female rowers. Methods: Twenty female club and Olympic rowers (development group) performed the INCR-test on a Concept2 rowing ergometer to determine V ˙ O 2 max and MPO. A linear regression analysis was used to develop a prediction of V ˙ O 2 max from MPO. Cross-validation analysis of the prediction equation was performed using an independent sample of 10 female rowers (validation group). Results: A high correlation coefficient (r =.94) was found between MPO and V ˙ O 2 max. The following prediction equation was developed: V ˙ O 2 max (mL·min−1) = 9.58 × MPO (W) + 958. No difference was found between the mean predicted V ˙ O 2 max in the INCR-test (3480 mL·min−1) and the measured V ˙ O 2 max (3530 mL·min−1). The standard error of estimate was 162 mL·min−1, and the percentage standard error of estimate was 4.6%. The prediction model only including MPO, determined during the INCR-test, explained 89% of the variability in V ˙ O 2 max. Conclusion: The INCR-test is a practical and accessible alternative to laboratory testing of V ˙ O 2 max. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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 PLANP =.13). However, preexercise CAF only improved TT performance when compared to PLA in the W condition (CAFN vs PLAWP =.008, CAFW vs PLAWP =.04), not when W was mitigated (PLAN vs CAFNP =.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. [ABSTRACT FROM AUTHOR]

Purpose: To determine whether competitive performance, as defined by International Biathlon Union (IBU) and International Ski Federation (FIS) points in biathlon and cross-country (XC) skiing, respectively, can be projected using a combination of anthropometric and physiological metrics. Shooting accuracy was also included in the biathlon models. Methods: Data were analyzed using multivariate methods from 45 (23 female and 22 male) biathletes and 202 (86 female and 116 male) XC skiers who were all members of senior national teams, national development teams, or ski-university or high school invite-only programs (age range: 16–36 y). Anthropometric and physiological characteristics were assessed via dual-energy X-ray absorptiometry and incremental roller-ski treadmill tests, respectively. Shooting accuracy was assessed via an outdoor standardized testing protocol. Results: Valid projective models were identified for female biathletes' IBU points (R2 =.80/Q2 =.65) and female XC skiers' FIS distance (R2 =.81/Q2 =.74) and sprint (R2 =.81/Q2 =.70) points. No valid models were identified for the men. The most important variables for the projection of IBU points were shooting accuracy, speeds at blood lactate concentrations of 4 and 2 mmol·L−1, peak aerobic power, and lean mass. The most important variables for the projection of FIS distance and sprint points were speeds at blood lactate concentrations of 4 and 2 mmol·L−1 and peak aerobic power. Conclusions: This study highlights the relative importance of specific anthropometric, physiological, and shooting-accuracy metrics in female biathletes and XC skiers. The data can help to identify the specific metrics that should be targeted when monitoring athletes' progression and designing training plans. [ABSTRACT FROM AUTHOR]

Acute ketone monoester (KE) supplementation can alter exercise responses, but the performance effect is unclear. The limited and equivocal data to date are likely related to factors including the KE dose, test conditions, and caliber of athletes studied. We tested the hypothesis that mean power output during a 20-min cycling time trial (TT) would be different after KE ingestion compared to a placebo (PL). A sample size of 22 was estimated to provide 80% power to detect an effect size dz of 0.63 at an alpha level of.05 with a two-tailed paired t test. This determination considered 2.0% as the minimal important difference in performance. Twenty-three trained cyclists (N = 23; peak oxygen uptake: 65 ± 12 ml·kg−1 min−1; M ± SD), who were regularly cycling >5 hr/week, completed a familiarization trial followed by two experimental trials. Participants self-selected and replicated their diet and exercise for ∼24 hr before each trial. Participants ingested either 0.35 g/kg body mass of (R)-3-hydroxybutyl (R)-3-hydroxybutyrate KE or a flavor-matched PL 30 min before exercise in a randomized, triple-blind, crossover manner. Exercise involved a 15-min warm-up followed by the 20-min TT on a cycle ergometer. The only feedback provided was time elapsed. Preexercise venous [β-hydroxybutyrate] was higher after KE versus PL (2.0 ± 0.6 vs. 0.2 ± 0.1 mM, p <.0001). Mean TT power output was 2.4% (0.6% to 4.1%; mean [95% confidence interval]) lower after KE versus PL (255 ± 54 vs. 261 ± 54 W, p <.01; dz = 0.60). The mechanistic basis for the impaired TT performance after KE ingestion under the present study conditions remains to be determined. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Purpose: The aim of the study was to analyze physiological and energetic demands of elite gymnasts during still-rings routines (SRRs). Methods: Eleven male gymnasts (mean [SD] 23.6 [3.9] y, 65.9 [5.6] kg, 171.1 [6.7] cm) performed a maximal graded exercise test and an individual SRR, during which respiratory gas and heart rate (HR) were measured using a mobile spiroergometer and a paired HR sensor. Metabolic energy and the energy contribution in terms of aerobic, anaerobic lactic, and anaerobic alactic were determined by oxygen uptake (VO2) during exercise, net lactate production, and the fast component of postexercise VO2 kinetics. Results: Mean routine duration of the SRRs was 48.3 (4.5) seconds. VO2 and HR during SRRs were shown to be 86.9% (5.9%) and 91.0% (3.3%), respectively, of the maximal values measured during the graded exercise test. The anaerobic alactic, aerobic, and anaerobic lactic systems provided 50.9% (6.6%), 28.6% (4.8%), and 20.5% (5.2%), respectively, of the total energy required during SRRs. The energy contribution of the anaerobic lactic system correlated negatively with individual anaerobic threshold (r = −.715) and maximal VO2 (r = −.682). Conclusions: The anaerobic alactic system is the predominant energy source for ATP resynthesis during SRRs. The high relative VO2 and HR values reached during SRRs show that these routines strongly stress the cardiovascular system. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the applicability of the Lactate Threshold (LT) to predict maximal oxygen uptake (˙VO2max) and demarcate the boundary between the moderate- to heavy- intensity domain (HRm-h) in old age in comparison to the most utilized methods. A cross-sectional validation study was conducted. Participants aged 61 to 77 performed a familiarization procedure, an incremental maximal exercise treadmill test (CPX) for ˙VO2max determination, the Six-minute Walk Test (6MWT), and a discontinuous incremental field test for LT determination. Lower (P<0.01) internal effort was required for LT testing (76±8%HRmax) compared to 6MWT (92±9%HRmax). The application of the 6MWT reference equations overestimated ˙VO2max by 10–23%. LTs better estimated the ˙VO2max (r ≈0.90, SEE: ≈3.0] compared to the 6MWT (r=0.68, SEE=5.5). HRm-h determined by the CPX differed (20%; P=0.001) from that obtained by LT. HRm-h stratification indicated participants fall into the very light to the vigorous intensity domains. LT testing is more submaximal than the 6MWT, and is a valuable tool to estimate the ˙VO2max in older male adults. Implementation of LT testing in physical activity programs might help improving the quality of aerobic exercise training in older men. [ABSTRACT FROM AUTHOR]

Photodynamic therapy (PDT) utilizes reactive oxygen species (ROS) for eradication of cancer cells. Its effectiveness is governed by the oxygen content, which is scarce in the hypoxic tumor microenvironment. We report herein two zinc(II) phthalocyanines substituted with two or four nitric oxide (NO)‐releasing moieties, namely ZnPc‐2NO and ZnPc‐4NO, which can suppress the mitochondrial respiration, thereby sparing more intracellular oxygen for PDT. Using HT29 human colorectal adenocarcinoma cells and A549 human lung carcinoma cells, we have demonstrated that both conjugates release NO upon interaction with the intracellular glutathione, which can reduce the cellular oxygen consumption rate and adenosine triphosphate generation and alter the mitochondrial membrane potential. They can also relieve the hypoxic status of cancer cells and decrease the expression of hypoxia‐inducible factor protein HIF‐1α. Upon light irradiation, both conjugates can generate ROS and induce cytotoxicity even under a hypoxic condition, overcoming the oxygen‐dependent nature of PDT. Interestingly, the photodynamic action of ZnPc‐2NO elicits the release of damage‐associated molecular patterns, inducing the maturation of dendritic cells and triggering an antitumor immune response. The immunogenic cell death caused by this oxygen‐economized PDT has been demonstrated through a series of in vitro and in vivo experiments. [ABSTRACT FROM AUTHOR]

Accurate descriptions of the variability in single-cell oxygen consumption and its size-dependency are key to establishing more robust tissue models. By combining microfabricated devices with multiparameter identification algorithms, we demonstrate that single human hepatocytes exhibit an oxygen level-dependent consumption rate and that their maximal oxygen consumption rate is significantly lower than that of typical hepatic cell cultures. Moreover, we found that clusters of two or more cells competing for a limited oxygen supply reduced their maximal consumption rate, highlighting their ability to adapt to local resource availability and the presence of nearby cells. We used our approach to characterize the covariance of size and oxygen consumption rate within a cell population, showing that size matters, since oxygen metabolism covaries lognormally with cell size. Our study paves the way for linking the metabolic activity of single human hepatocytes to their tissue- or organ-level metabolism and describing its size-related variability through scaling laws. [ABSTRACT FROM AUTHOR]

Background: Various studies have shown that the type of intensity measure affects training intensity distribution (TID) computation. These conclusions arise from studies presenting data from meso- and macrocycles, while microcycles, e.g., high-intensity interval training shock microcycles (HIIT-SM) have been neglected so far. Previous literature has suggested that the time spent in the high-intensity zone, i.e., zone 3 (Z3) or the "red zone", during HIIT may be important to achieve improvements in endurance performance parameters. Therefore, this randomized controlled trial aimed to compare the TID based on running velocity (TIDV), running power (TIDP) and heart rate (TIDHR) during a 7-day HIIT-SM. Twenty-nine endurance-trained participant were allocated to a HIIT-SM consisting of 10 HIIT sessions without (HSM, n = 9) or with (HSM + LIT, n = 9) additional low-intensity training or a control group (n = 11). Moreover, we explored relationships between time spent in Z3 determined by running velocity (Z3V), running power (Z3P), heart rate (Z3HR), oxygen uptake ( Z 3 V ˙ O 2 ) and changes in endurance performance. Results: Both intervention groups revealed a polarized pattern for TIDV (HSM: Z1: 38 ± 17, Z2: 16 ± 17, Z3: 46 ± 2%; HSM + LIT: Z1: 59 ± 18, Z2: 14 ± 18, Z3: 27 ± 2%) and TIDP (Z1: 50 ± 8, Z2: 14 ± 11, Z3: 36 ± 7%; Z1: 62 ± 15, Z2: 12 ± 16, Z3: 26 ± 2%), while TIDHR (Z1: 48 ± 13, Z2: 26 ± 11, Z3: 26 ± 7%; Z1: 65 ± 17, Z2: 22 ± 18, Z3: 13 ± 4%) showed a pyramidal pattern. Time in Z3HR was significantly less compared to Z3V and Z3P in both intervention groups (all p < 0.01). There was a time x intensity measure interaction for time in Z3 across the 10 HIIT sessions for HSM + LIT (p < 0.001, pη2 = 0.30). Time in Z3V and Z3P within each single HIIT session remained stable over the training period for both intervention groups. Time in Z3HR declined in HSM from the first (47%) to the last (28%) session, which was more pronounced in HSM + LIT (45% to 16%). A moderate dose–response relationship was found for time in Z3V and changes in peak power output (rs = 0.52, p = 0.028) as well as time trial performance (rs = − 0.47, p = 0.049) with no such associations regarding time in Z3P, Z3HR, and Z 3 V ˙ O 2 . Conclusion: The present study reveals that the type of intensity measure strongly affects TID computation during a HIIT-SM. As heart rate tends to underestimate the intensity during HIIT-SM, heart rate-based training decisions should be made cautiously. In addition, time in Z3V was most closely associated with changes in endurance performance. Thus, for evaluating a HIIT-SM, we suggest integrating a comprehensive set of intensity measures. Trial Registration Trial register: Clinicaltrials.gov, registration number: NCT05067426. Key Points: Using heart rate, running velocity and running power as measures of intensity leads to different patterns of training intensity distribution during a 7-day HIIT shock microcycle. A polarized pattern was observed for velocity and power, whereas a more pyramidal distribution was found for heart rate. Additional low-intensity training volume during a HIIT shock microcycle led to a more pronounced decline in time in zone 3 measured with heart rate compared to a shock microcycle with HIIT sessions, only. A moderate dose–response relationship was observed between time in zone 3 measured by velocity and changes in peak power output as well as time-trial performance. No such correlation was found between time in zone 3 measured by power, heart rate, oxygen uptake, and changes in endurance performance parameters. [ABSTRACT FROM AUTHOR]