Mean Power Output Research Articles

The reliability and validity of repeat power ability assessments and measurement indices in loaded vertical jumps.

Repeat power ability (RPA) assessments are a valuable evaluation of an athlete's ability to repeatedly perform high intensity movements. Establishing the most reliable and valid loaded jump RPA assessment and method to quantify RPA has yet to be determined. This study aimed to compare the reliability and validity of an RPA assessment performed with loaded squat jumps (SJ) or countermovement jumps (CMJ) using force-time derived mean and peak power output. RPA was quantified using calculations of average power output, a fatigue index and a percent decrement score for all repetitions and with the first and last repetitions removed. Validity was established by comparing to a 30 second Bosco repeated jump test (30BJT). Eleven well-trained male field hockey players performed one set of 20 repetitions of both SJs (20SJ) and CMJs (20CMJ) on separate occasions using a 30% one repetition maximum half squat load. These assessments were repeated 7 days apart to establish inter-test reliability. On a separate occasion, each participant performed the 30BJT. The reliability of average peak power for 20SJ and 20CMJ was acceptable (CV < 5%; ICC > 0.9), while average mean power reliability for 20CMJ (CV < 5%; ICC > 0.9) was better than 20SJ (CV > 5%; ICC > 0.8). Percent decrement of 20CMJ peak power, with the first and final jump removed from the percent decrement calculation (PD%CMJpeak18), was the most reliable measurement of power output decline (CV < 5 %; ICC > 0.8). Average mean and peak power for both RPA protocols had moderate to strong correlations with 30BJT average mean and peak power (r = 0.5-0.8; p< 0.05-0.01). No RPA measurements of power decline were significantly related to BJT measurements of power decline. These findings indicate that PD%CMJpeak18 is the most reliable measure of RPA power decline. The lack of relationship between power decline in the loaded RPA and the 30BJT assessment suggest that each assessment may be measuring a different physical quality. These results provide sport science practitioners with additional methods to assess RPA and provide useful information on the reliability and validity of these outcome measures. Additional research needs to be performed to examine the reliability and validity of the novel RPA assessments in other athletic populations and to determine the sensitivity of these measurements to training and injury.

Intra- and Inter-Day Reliability of Inertial Loads with Cluster Sets When Performed during a Quarter Squat on a Flywheel Device.

The aims of this study were to (i) estimate the intra- and inter-day reliability of mean concentric (CON) and eccentric (ECC) power at different inertial loads during a flywheel quarter-squat using a cluster set approach and (ii) to determine the acute effect of internal and external attentional focus on mean power when performing the flywheel quarter squat. Twelve collegiate field sport male athletes (age 22.4 ± 3.2 years, weight 81.4 ± 10.3 kg, height 1.81 ± 0.06 m) attended four cluster set testing sessions separated by 7 days. Sessions consisted of 4 sets of 15 repetitions using 4 inertial loads (0.025, 0.050, 0.075, and 0.100 kg·m2). A cluster block consisted of 5 repetitions, including "momentum repetitions" (4 × 5 + 5 + 5). Mean power (MP), CON power, ECC power, and ECC overload were recorded for both internal and external attentional focus groups. The external instructional group attained familiarization after two flywheel sessions (ES = 0.03-0.15) with little volatility between performance measures (CV% = 3.39-9.22). The internal instructional group showed large differences in MP output from session 2 to session 3 for all loads (ES = 0.59-1.25). In conclusion, the flywheel cluster set approach is a reliable training modality for maintaining MP output during all repetitions.

Repeated-sprint training in hypoxia boosts up team-sport-specific repeated-sprint ability: 2-week vs 5-week training regimen.

To investigate (1) the boosting effects immediately and 4 weeks following 2-week, 6-session repeated-sprint training in hypoxia (RSH2-wk, n = 10) on the ability of team-sport players in performing repeated sprints (RSA) during a team-sport-specific intermittent exercise protocol (RSAIEP) by comparing with normoxic counterpart (CON2-wk, n = 12), and (2) the dose effects of the RSH by comparing the RSA alterations in RSH2-wk with those resulting from a 5-week, 15-session regimen (RSH5-wk, n = 10). Repeated-sprint training protocol consisted of 3 sets, 5 × 5-s all-out sprints on non-motorized treadmill interspersed with 25-s passive recovery under the hypoxia of 13.5% and normoxia, respectively. The within- (pre-, post-, 4-week post-intervention) and between- (RSH2-wk, RSH5-wk, CON2-wk) group differences in the performance of four sets of RSA tests held during the RSAIEP on the same treadmill were assessed. In comparison with pre-intervention, RSA variables, particularly the mean velocity, horizontal force, and power output during the RSAIEP enhanced significantly immediate post RSH in RSH2-wk (5.1-13.7%), while trivially in CON2-wk (2.1-6.2%). Nevertheless, the enhanced RSA in RSH2-wk diminished 4 weeks after the RSH (-3.17-0.37%). For the RSH5-wk, the enhancement of RSA immediately following the 5-week RSH (4.2-16.3%) did not differ from that of RSH2-wk, yet the enhanced RSA was well-maintained 4-week post-RSH (0.12-1.14%). Two-week and five-week RSH regimens could comparably boost up the effects of repeated-sprint training in normoxia, while dose effect detected on the RSA enhancement was minimal. Nevertheless, superior residual effects of the RSH on RSA appear to be associated with prolonged regimen.

Cold water immersion of the hand and forearm during half-time improves intermittent exercise performance in the heat

The present study aimed to investigate the effect of cold water immersion of the hand and forearm during half-time (HT) on intermittent exercise performance and thermoregulation by imitating intermittent athletic games in the heat. In a randomized crossover design, 11 physically active men performed the first half (first and second block) and second half (third and fourth block) intermittent cycling exercise protocol, which consisted of a 5-s maximal power pedalling (body weight × 0.075 kp) every minute separated by 25-s of unloaded pedalling and rest (30 s) in the heat (33°C, 50% relative humidity). The two-halves were separated by a 15-min HT. During HT, the participants were assigned to the CON (sedentary resting) or COOL (immersion of hands and forearms in cold water at 15–17°C) condition. The mean power output in the second half was significantly greater (third and fourth block:p&amp;lt; 0.05) in the COOL than in the CON condition. Moreover, there was a significant decrease in the rectal (0.54 ± 0.17°C,p&amp;lt; 0.001) and mean skin (1.86 ± 0.34°C,p&amp;lt; 0.05) temperatures of the COOL condition during HT. Furthermore, the heart rate (16 ± 7 bpm,p&amp;lt; 0.05) and skin blood flow (40.2 ± 10.5%,p&amp;lt; 0.001) decreased at the end of HT in the COOL condition. In the second half, thermal sensation was more comfortable in the COOL condition (p&amp;lt; 0.001). Cold water immersion of the hand and forearm during HT improved physiological and reduced perceived heat stress. Moreover, it prevented a reduction in intermittent exercise performance in the second half.

Repeated-Sprint Training at 5000-m Simulated Altitude in Preparation for the World Rugby Women's Sevens Series: Too High?

The objective of this study is to investigate the effectiveness of novel repeated-sprint training in hypoxia (RSH) protocol, likely maximizing hypoxic stimulus (higher than commonly used) while preserving training quality (interset rest in normoxia). Twenty-three world-class female rugby sevens players performed four repeated-sprint training sessions (4 sets of 5 × 5-s cycle sprints-25-s intersprint recovery and 3-min interset rest) under normobaric hypoxia (RSH, exercise and interset rest at FiO 2 of 10.6% and 20.9%, respectively; n = 12) or normoxia (repeated-sprint training in normoxia; exercise and interset rest at FiO 2 of 20.9%; n = 11) during a 9-d training camp before international competition. Repeated-sprint ability (8 × 5-s treadmill sprints-25-s recovery), on-field aerobic capacity, and brachial endothelial function were assessed pre- and postintervention. Arterial oxygen saturation (pooled data: 87.0% ± 3.1% vs 96.7% ± 2.9%, P < 0.001) and peak and mean power outputs (sets 1 to 4 average decrease: -21.7% ± 7.2% vs -12.0% ± 3.8% and -24.9% ± 8.1% vs -14.9% ± 3.5%; both P < 0.001) were lower in RSH versus repeated-sprint training in normoxia. The cumulated repeated-sprint distance covered significantly increased from pre- to postintervention (+1.9% ± 3.0%, P = 0.019), irrespective of the condition ( P = 0.149). On-field aerobic capacity did not change (all P > 0.45). There was no significant interaction (all P > 0.240) or condition main effect (all P > 0.074) for any brachial artery endothelial function variable. Only peak diameter increased ( P = 0.026), whereas baseline and peak shear stress decreased ( P = 0.014 and 0.019, respectively), from pre- to postintervention. In world-class female rugby sevens players, only four additional repeated-sprint sessions before competition improve repeated-sprint ability and brachial endothelial function. However, adding severe hypoxic stress during sets of repeated sprints only did not provide supplementary benefits.

Hematological, skeletal muscle fiber and exercise performance adaptations to heat training in elite female and male cyclists.

Heat exercise training may increase exercise performance in athletes. The underlying mechanisms remain partly unresolved, and it is unknown if female and male athletes may experience comparable gains. The aims were to investigate whether heat training (HEAT) increases hemoglobin mass (Hbmass), skeletal muscle fiber characteristics and thermoneutral exercise performance in elite female and male endurance athletes. Female (n=20; VO2max = 58.2 ± 6.7 ml.min.kg) and male (n=27; VO2max = 76.4 ± 7.8 ml.min.kg) cyclists were studied before and after five weeks of randomized control or HEAT training consisting of five weekly sessions each of 50 min duration which were included in their normal training regimes. Overall, the observed relative responses to HEAT were largely similar in female and male study participants. HEAT increased (P<0.05) Hbmass in female from 650 ± 77 to 675 ± 76 g (4.0 ± 1.6%) and from 1008 ± 155 to 1041 ± 147 g (3.5 ± 2.3%) in male. In contrast, skeletal muscle citrate synthase activity, fiber type distribution and capillary density remained unchanged with HEAT. Lactate threshold, VO2max and mean power output during 15 min all out testing were all enhanced (P<0.05) following HEAT in female and male study participants. In conclusion, five weeks of HEAT increases Hbmass in female and male elite cyclists and improves exercise performance in a thermoneutral environment. Based on this, heat training may be recommended to elite female and male athletes aiming to perform in a thermoneutral environment.

Effects of Dietary Nitrate Supplementation on Performance during Single and Repeated Bouts of Short-Duration High-Intensity Exercise: A Systematic Review and Meta-Analysis of Randomised Controlled Trials.

Inorganic nitrate (NO3-) has emerged as a potential ergogenic aid over the last couple of decades. While recent systematic reviews and meta-analyses have suggested some small positive effects of NO3- supplementation on performance across a range of exercise tasks, the effect of NO3- supplementation on performance during single and repeated bouts of short-duration, high-intensity exercise is unclear. This review was conducted following PRISMA guidelines. MEDLINE and SPORTDiscus were searched from inception to January 2023. A paired analysis model for cross-over trials was incorporated to perform a random effects meta-analysis for each performance outcome and to generate standardized mean differences (SMD) between the NO3- and placebo supplementation conditions. The systematic review and meta-analysis included 27 and 23 studies, respectively. Time to reach peak power (SMD: 0.75, p = 0.02), mean power output (SMD: 0.20, p = 0.02), and total distance covered in the Yo-Yo intermittent recovery level 1 test (SMD: 0.17, p < 0.0001) were all improved after NO3- supplementation. Dietary NO3- supplementation had small positive effects on some performance outcomes during single and repeated bouts of high-intensity exercise. Therefore, athletes competing in sports requiring single or repeated bouts of high-intensity exercise may benefit from NO3- supplementation.

Carbohydrate, but not fat, oxidation is reduced during moderate-intensity exercise performed in 33 vs. 18°C at matched heart rates.

Exposure to environmental heat stress increases carbohydrate oxidation and extracellular heat shock protein 70 (HSP70) concentrations during endurance exercise at matched absolute, external work rates. However, a reduction in absolute work rate typically occurs when unacclimated enduranceathletes train and/or compete in hot environments. We sought to determine the effect of environmental heat stress on carbohydrate oxidation rates and plasma HSP70 expression during exercise at matched heart rates (HR). Ten endurance-trained, male cyclists performed two experimental trials in an acute, randomised, counterbalanced cross-over design. Each trial involved a 90-min bout of cycling exercise at 95% of the HR associated with the first ventilatory threshold in either 18 (TEMP) or 33°C (HEAT), with ~ 60% relative humidity. Mean power output (17 ± 11%, P < 0.001) and whole-body energy expenditure (14 ± 8%, P < 0.001) were significantly lower in HEAT. Whole-body carbohydrate oxidation rates were significantly lower in HEAT (19 ± 11%, P = 0.002), while fat oxidation rates were not different between-trials. The heat stress-induced reduction in carbohydrate oxidation was associated with the observed reduction in power output (r = 0.64, 95% CI, 0.01, 0.91, P = 0.05) and augmented sweat rates (r = 0.85, 95% CI, 0.49, 0.96, P = 0.002). Plasma HSP70 and adrenaline concentrations were not increased with exercise in either environment. These data contribute to our understanding of how moderate environmental heat stress is likely to influence substrate oxidation and plasma HSP70 expression in an ecologically-valid model of endurance exercise.

Cross-code verification of non-neutral ABL and single wind turbine wake modelling in LES

Large Eddy Simulations (LES) of atmospheric boundary layer (ABL) flow with the actuator disc (AD) for turbine modelling is a widely used method of simulating wind farm flows. Hence, it is important to understand the requirements for achieving a good comparison between ABL flow and turbine wakes between different research group setups, despite unavoidable differences which include LES numerical framework, sub-grid scale (SGS) model, and turbine modelling, and at grid resolutions achievable in large wind farm simulations. In this work, conventionally neutral (CNBL), stable (SBL) and convective (CBL) boundary layers, and single turbine wakes under these different conditions, are compared between the EPFL pseudo-spectral code WIRE LES and the DTU finite-volume code EllipSys3D. ABL profiles largely agree well with hub height velocity magnitudes agreeing to 0.7%, 3.8% and 0.5% for the CNBL, SBL and CBL respectively. The scale-dependent SGS model of WIRE LES results in reduced grid dependency, while EllipSys3D required higher grid resolution in the SBL. Wake flows show improved wake recovery and greater added turbulence intensity with increasing grid resolution, and good agreement is achieved with a radius R to cell size ratio of R/(dxdydz)1/3 ≥ 6.5. Trends in wake flow with different stability conditions, such as the influence of inflow turbulence intensity or shear, are well replicated between codes. Likewise, wake deficit and added TI profiles, and distributions of turbine power and thrust also agree well. Mean power output predictions match to 4.3%, 7.2% and 3.8% in the CNBL, SBL and CBL respectively between the two codes. Overall, these results demonstrate that good agreement is possible with aligned turbine data and sufficient grid resolution.

Acute performance, physiological, and perceptual changes in response to repeated cycling sprint exercise combined with systemic and local hypoxia in young males

This study investigated the acute performance, physiological, and perceptual changes during repeated sprint exercise (RSE) under normobaric hypoxia and with blood flow restriction (BFR). Fourteen active males completed standardized RSE (6 × 10 s cycling sprints with 30 s passive rest) in three randomized conditions: under normobaric hypoxia (FiO2 ∼ 14.4%, HYP), normoxia (FiO2 ∼ 20.9%, SHAM), and with BFR (40% arterial occlusion pressure). The percentage decrement score of power output (Sdec) was used to quantify motor performance fatigue. During RSE, muscle oxygenation (total and oxygenated hemoglobin) and activity of the right quadriceps were measured. Perceived motor fatigue, physical strain, affective valence, and arousal were queried after each sprint. Blood lactate concentration (BLC) and peripheral oxygenation (SpO2) were measured before and after RSE. Sdec was greater in HYP and BFR compared to SHAM (p ≤ 0.008). BFR decreased mean power output (p < 0.001) and muscle activity (p = 0.027) compared to SHAM. Decrease in muscle oxygenated hemoglobin was higher in BFR during each rest (p ≤ 0.005) and in HYP during rest 4 (p = 0.006) compared to SHAM. HYP increased BLC and decreased SpO2 compared to BFR (p < 0.001) and SHAM (p = 0.002). There were no differences between conditions for any rating scale (p ≥ 0.060). HYP and BFR increased motor performance fatigue but with different physiological responses, whereas perceptual responses were unaffected during RSE.

Experimental study on hydrodynamic behavior and energy conversion of multiple oscillating-water-column chamber in regular waves

An oscillating water column (OWC) device is a promising wave energy converter that uses ocean wave energy resources. The OWC chamber absorbs the energy of ocean waves and significantly affects energy conversion performance. In this study, the hydrodynamic performance of a multiple OWC chamber was investigated experimentally, emphasizing its hydrodynamic behavior and energy conversion characteristics. A series of regular wave tests were conducted for single-, triple-, and asymmetric triple OWC chambers in a two-dimensional wave tank. The same orifice ratio was applied to the single and triple chambers to induce an equivalent turbine-chamber interaction owing to the pressure drop. It was found that the triple OWC chamber contributes to an increase in the converted pneumatic power compared to the single OWC chamber due to reducing the sloshing motion of the internal fluid. Moreover, the temporal fluctuation of the overall output power was reduced because of the water column motion of each triple OWC chamber with a phase difference. The rear chamber of the asymmetric triple chamber traps the wave energy and contributes to not only increasing the output power but also the variability. Therefore, it can be observed that multiple OWC chambers improve energy conversion performance by increasing the mean power output and reducing temporal fluctuation.

Sleep restriction between consecutive days of exercise impairs sprint and endurance cycling performance.

The study aim was to determine the effect of sleep restriction (3 h) between consecutive days of exercise on sprint and endurance cycling performance, wellness, and mood. A total of 10 well-trained males performed 2 consecutive-day trials separated by a normal night sleep (control [CONT]; mean [SD] sleep duration 3.0[0.2]h) or sleep restriction (RES; mean [SD] sleep duration 3.0[0.2]h). Experimental trials included a 90-min fixed-paced cycling bout and the respective sleep conditions on Day 1, followed by two 6-s peak power (6-s PP) tests, a 4- and 20-min time trial (TT) on Day 2. Profile of Mood States (POMS) and wellness questionnaires were recorded on Day 1 and Day 2. Blood lactate and glucose, heart rate (HR), and rating of perceived exertion were recorded throughout Day 2. Power output (PO) was significantly reduced for RES in the 6-s PP trial (mean [SD] 1159[127]W for RES versus 1250[186]W for CONT; p=0.04) and mean PO during the 20-min TT (mean [SD] 237[59]W for RES versus 255[58]W for CONT; p=0.03). There were no differences for HR, lactate and glucose, or POMS between CONT and RES in all experimental trials (p=0.05-0.89). Participants reported a reduction in overall wellness prior to exercise on Day 2 following RES (mean [SD] 14.5[1.6]au) compared to CONT (mean [SD] 16[3.0]au; p=0.034). Sleep restriction and the associated reductions in wellness, reduce cycling performance during consecutive days of exercise in a range of cycling tests that are relevant to both track and road cyclists.

Influence of Air Velocity on Self-Paced Exercise Performance in Hot Conditions.

This study aimed to determine the effect of different air velocities on heat exchange and performance during prolonged self-paced exercise in the heat. Twelve male cyclists performed a 700-kJ time trial in four different air velocity conditions (still air, 16, 30, and 44 km·h -1 ) in 32°C and 40% relative humidity. Performance, thermal, cardiovascular, and perceptual responses were measured, and heat balance parameters were estimated using partitional calorimetry, including the maximum potential for sweat evaporation ( Emax ). Mean power output was lower in still air (232 ± 42 W) than 16 (247 ± 30 W), 30 (250 ± 32 W), and 44 km·h -1 (248 ± 32 W; all P < 0.001), but similar between the 16-, 30-, and 44-km·h -1 air velocity conditions ( P ≥ 0.275). Emax was lower in still air (160 ± 13 W·m -2 ) than 16 (298 ± 25 W·m -2 ), 30 (313 ± 23 W·m -2 ), and 44 km·h -1 (324 ± 31 W·m -2 ) and lower in 16 than 44 km·h -1 (all P < 0.001). Peak core temperature was higher in still air (39.4°C ± 0.7°C) than 16 (39.0°C ± 0.45°C), 30 (38.8°C ± 0.3°C), and 44 km·h -1 (38.8°C ± 0.5°C; all P ≤ 0.002). Mean skin temperature was lower with greater airflow ( P < 0.001) but similar in 30 and 40 km·h -1 ( P = 1.00). Mean heart rate was ~2 bpm higher in still air than 44 km·h -1 ( P = 0.035). RPE was greater in still air than 44 km·h -1 ( P = 0.017). Self-paced cycling in still air was associated with a lower Emax and subsequently higher thermal strain, along with a similar or greater cardiovascular strain, despite work rate being lower than in conditions with airflow. The similarity in performance between the 16-, 30-, and 44-km·h -1 air velocity conditions suggests that airflow ≥16 km·h -1 does not further benefit self-paced exercise performance in the heat because of modest improvements in evaporative efficiency.

Power Production and Blade Fatigue of a Wind Turbine Array Subjected to Active Yaw Control

This study investigated the power production and blade fatigue of a three-turbine array subjected to active yaw control (AYC) in full-wake and partial-wake configurations. A framework of a two-way coupled large eddy simulation (LES) and an aeroelastic blade simulation was applied to simulate the atmospheric boundary layer (ABL) flow through the turbines and the structural responses of the blades. The mean power outputs and blade fatigue loads were extracted from the simulation results. By exploring the feasible AYC decision space, we found that in the full-wake configuration, the local power-optimal AYC strategy with positive yaw angles endures less flapwise blade fatigue and more edgewise blade fatigue than the global power-optimal strategy. In the partial-wake configuration, applying positive AYC in certain inflow wind directions achieves higher optimal power gains than that in the full-wake scenario and reduces blade fatigue from the non-yawed benchmark. Using the blade element momentum (BEM) theory, we reveal that the aforementioned differences in flapwise blade fatigue are due to the differences in the azimuthal distributions of the local relative velocity on blade sections, resulting from the vertical wind shear and blade rotation. Furthermore, the difference in the blade force between the positively and negatively yawed front-row turbine induces different wake velocities and turbulence distributions, causing different fatigue loads on the downwind turbine exposed to the wake.

Phosphate Loading Does not Improve 30-km Cycling Time-Trial Performance in Trained Cyclists

Phosphate is integral to numerous metabolic processes, several of which strongly predict exercise performance (i.e.,cardiac function, oxygen transport, and oxidative metabolism). Evidence regarding phosphate loading is limited and equivocal, at least partly because studies have examined sodium phosphate supplements of varied molar mass (e.g.,mono/di/tribasic, dodecahydrate), thus delivering highly variable absolute quantities of phosphate. Within a randomized cross-over design and in a single-blind manner, 16 well-trained cyclists (age 38 ± 16years, mass 74.3 ± 10.8kg, training 340 ± 171min/week; mean ± SD) ingested either 3.5g/day of dibasic sodium phosphate (Na2HPO4: 24.7mmol/day phosphate; 49.4mmol/day sodium) or a sodium chloride placebo (NaCl: 49.4mmol/day sodium and chloride) for 4days prior to each of two 30-km time trials, separated by a washout interval of 14days. There was no evidence of any ergogenic benefit associated with phosphate loading. Time to complete the 30-km time trial did not differ following ingestion of sodium phosphate and sodium chloride (3,059 ± 531s vs. 2,995 ± 467s). Accordingly, neither absolute mean power output (221 ± 48 W vs. 226 ± 48W) nor relative mean power output (3.02 ± 0.78W/kg vs. 3.08 ± 0.71W/kg) differed meaningfully between the respective intervention and placebo conditions. Measures of cardiovascular strain and ratings of perceived exertion were very closely matched between treatments (i.e.,average heart rate 161 ± 11beats per minute vs. 159 ± 12 beats per minute; Δ2beats per minute; and ratings of perceived exertion 18 [14-20]units vs. 17 [14-20] units). In conclusion, supplementing with relatively high absolute doses of phosphate (i.e.,>10mmol daily for 4days) exerted no ergogenic effects on trained cyclists completing 30-km time trials.

High-Intensity Interval Training, Performance, and Oxygen Uptake Kinetics in Highly Trained Traditional Rowers.

Oxygen uptake kinetics (VO2kinetics) is a measure of an athlete's capacity to respond to variations in energy demands. Faster VO2kinetics is associated with better performance in endurance sports, but optimal training methods to improve VO2kinetics remain unclear. This study compared the effects of 2 high-intensity interval-training (HIIT) programs on traditional rowing performance and VO2kinetics. Twelve highly trained rowers performed one of two 6-week HIIT protocols: either 3-minute repetitions at 90% (HIIT90; n = 5) of peak aerobic power (PAP) or 90-second repetitions at 100% (HIIT100; n = 7) of PAP. Before (PRE) and after (POST) the training intervention, they performed an incremental test to exhaustion to determine the individual lactate threshold, onset of blood lactate accumulation and PAP, and two 6-minute rest-to-exercise transitions to determine VO2kinetics. No significant changes (P > .05) were observed for rowing ergometer power output at individual lactate threshold (HIIT90 PRE 255 [12], POST 264 [13]; HIIT100 247 [24], 266 [28]W), onset of blood lactate accumulation (279 [12], 291 [16]; 269 [23], 284 [32]W), or PAP (359 [13], 381 [15]; 351 [21], 363 [29]W) or for any parameters of VO2kinetics. No differences were observed between HIIT interventions. The HIIT interventions did not induce significant performance or VO2kinetics improvements, although mean power output at individual lactate threshold, onset of blood lactate accumulation, and PAP increased by 5.7%, 5.0%, and 4.5%, respectively. This suggests that the exact intensity and duration of HIIT sessions performed in the same intensity domain may be of lesser importance than other well-established influential factors (eg,training volume progression, training intensity distribution, altitude training) to develop aerobic qualities in endurance athletes.

Glucocorticoids Accelerate Erythropoiesis in Healthy Humans-Should the Use in Sports Be Reevaluated?

The World Anti-Doping Agency prohibits glucocorticoid administration in competition but not in periods out of competition. Glucocorticoid usage is controversial as it may improve performance, albeit debated. A hitherto undescribed but performance-relevant effect of glucocorticoids in healthy humans is accelerated erythropoiesis. We investigated whether a glucocorticoid injection accelerates erythropoiesis, increases total hemoglobin mass, and improves exercise performance. In a counterbalanced, randomized, double-blinded, placebo-controlled crossover design (3 months washout), 10 well-trained males (peak oxygen uptake, 60 ± 3 mL O 2 ·min -1 ·kg -1 ) were injected with 40 mg triamcinolone acetonide (glucocorticoid group) or saline (placebo group) in the gluteal muscles. Venous blood samples collected before and 7-10 h, 1, 3, 7, 14, and 21 d after treatment were analyzed for hemoglobin concentration and reticulocyte percentage. Hemoglobin mass and mean power output in a 450-kcal time trial were measured before as well as 1 and 3 wk after treatment. A higher reticulocyte percentage was evident 3 d (19% ± 30%, P < 0.05) and 7 d (48% ± 38%, P < 0.001) after glucocorticoid administration, compared with placebo, whereas hemoglobin concentration was similar between groups. Additionally, hemoglobin mass was higher ( P < 0.05) 7 d (glucocorticoid, 886 ± 104 g; placebo, 872 ± 103 g) and 21 d (glucocorticoid, 879 ± 111 g; placebo, 866 ± 103 g) after glucocorticoid administration compared with placebo. Mean power output was similar between groups 7 d (glucocorticoid, 278 ± 64 W; placebo, 275 ± 62 W) and 21 d (glucocorticoid, 274 ± 62 W; placebo, 275 ± 60 W) after treatment. Intramuscular injection of 40 mg triamcinolone acetonide accelerates erythropoiesis and increases hemoglobin mass but does not improve aerobic exercise performance in the present study. The results are important for sport physicians administering glucocorticoids and prompt a reconsideration of glucocorticoid usage in sport.

The effect of severe intensity bouts on muscle oxygen saturation responses in trained cyclists.

Near-infrared spectroscopy (NIRS) quantifies muscle oxygenation (SmO2) during exercise. Muscle oxygenation response to self-paced, severe-intensity cycling remains unclear. Observing SmO2 can provide cycling professionals with the ability to assess muscular response, helping optimize decision-making. We aimed to describe the effect of self-paced severe intensity bouts on SmO2, measured noninvasively by a wearable NIRS sensor on the vastus lateralis (VL) muscle, and examine its reliability. We hypothesized a greater desaturation response with each bout, whereas, between trials, good reliability would be observed. Fourteen recreationally trained, and trained cyclists completed a ramp test to determine the power output (PO) at the respiratory compensation point (RCP). Athletes completed two subsequent visits of 50-minute sessions that included four severe-intensity bouts done at 5% above RCP PO. Muscle oxygenation in the VL was monitored using a wearable NIRS device. Measures included mean PO, heart-rate (HR), cadence, and SmO2 at bout onset, during work (work SmO2), and ΔSmO2. The bouts were compared using a one-way repeated measures ANOVA. For significant differences, a Fisher's least square difference post-hoc analysis was used. A two-way repeated measures ANOVA was used using trial and bout as main factors. Intraclass correlations (ICC) were used to quantify relative reliability for mean work, and standard error of the measurement (SEM) was used to quantify absolute agreement of mean work SmO2. Both PO and cadence showed no effect of bout or trial. Heart-rate at bout 2 (168 ± 8 bpm) and 4 (170 ± 7 bpm) were higher than bout 1 (160 ± 6 bpm). Onset SmO2 (%) response significantly increased in the final two bouts of the session. Mean work SmO2 increased across bouts, with the highest value displayed in bout 4 (36 ± 22%). ΔSmO2 showed a smaller desaturation response during bout 4 (27 ± 10%) compared to bout 3 (31 ± 10%). Mean work SmO2 ICC showed good reliability (ICC = 0.87), and SEM was 12% (CI 9-15%). We concluded that a non-invasive, affordable, wearable NIRS sensor demonstrated the heterogeneous muscle oxygenation response during severe intensity cycling bouts with good reliability in trained cyclists.

Music Alters Conscious Distance Monitoring without Changing Pacing and Performance during a Cycling Time Trial.

Athletes use their own perception to monitor distance and regulate their pace during exercise, avoiding premature fatigue before the endpoint. On the other hand, they may also listen to music while training and exercising. Given the potential role of music as a distractor, we verified if music influenced the athletes' ability to monitor the distance covered during a 20-km cycling time trial (TT20km). We hypothesized that music would elongate cyclists' perceived distance due to reduced attentional focus on exercise-derived signals, which would also change their ratings of perceived exertion (RPE). We also expected that the motivational role of music would also be beneficial in pacing and performance. After familiarization sessions, ten recreational cyclists performed an in-laboratory TT20km while either listening to music or not (control). They reported their RPE, associative thoughts to exercise (ATE), and motivation when they each perceived they had completed 2-km. Power output and heart rate (HR) were continuously recorded. Cyclists elongated their distance perception with music, increasing the distance covered for each perceived 2 km (p = 0.003). However, music reduced the error of conscious distance monitoring (p = 0.021), pushing the perceived distance towards the actual distance. Music increased the actual distance-RPE relationship (p = 0.004) and reduced ATE (p < 0.001). However, music affected neither performance assessed as mean power output (p = 0.564) and time (p = 0.524) nor psychophysiological responses such as HR (p = 0.066), RPE (p = 0.069), and motivation (p = 0.515). Cyclists elongated their distance perception during the TT20km and changed the actual distance-RPE relationship, which is likely due to a music-distractive effect. Although there was a reduced error of conscious distance monitoring, music affected neither pacing nor performance.

Effect of varying recovery intensities on power outputs during severe intensity intervals in trained cyclists during the Covid-19 pandemic

PurposeThe study aimed to investigate the effects of different recovery intensities on the power outputs of repeated severe intensity intervals and the implications for W′ reconstitution in trained cyclists.MethodsEighteen trained cyclists (FTP 258.0 ± 42.7 W; weekly training 8.6 ± 1.7 h∙week−1) familiar with interval training, use of the Zwift® platform throughout the Covid-19 pandemic, and previously established FTP (95% of mean power output from a 20-min test), performed 5 × 3-min severe intensity efforts interspersed with 2-min recoveries. Recovery intensities were: 50 W (LOW), 50% of functional threshold power (MOD), and self-selected power output (SELF).ResultsWhilst power outputs declined as the session progressed, mean power outputs during the severe intervals across the conditions were not different to each other (LOW 300.1 ± 48.1 W; MOD: 296.9 ± 50.4 W; SELF: 298.8 ± 53.3 W) despite the different recovery conditions. Mean power outputs of the self-selected recovery periods were 121.7 ± 26.2 W. However, intensity varied during the self-selected recovery periods, with values in the last 15 s being greater than the first 15 s (p < 0.001) and decreasing throughout the session (128.7 ± 25.4 W to 113.9 ± 29.3 W).ConclusionReducing recovery intensities below 50% of FTP failed to enhance subsequent severe intensity intervals, suggesting that a lower limit for optimal W′ reconstitution had been reached. As self-selected recoveries were seen to adapt to maintain the severe intensity power output as the session progressed, adopting such a strategy might be preferential for interval training sessions.