Constant-load Trials Research Articles

Effects of Cryo-Facial Mask on Running Performance in Amateur Middle-Distance Runners

The excess heat accumulated during exercise can lead to stress-induced fatigue, possibly impairing athletic performance. Various precooling techniques have been applied to enhance thermal comfort, reduce perception of effort, and improve endurance. In this randomized crossover study, twelve male amateur middle-distance runners (age: 33.69 ± 5.9 years; body mass: 71.9 ± 4.4 kg; height: 178.4 ± 5.6 cm; O2 peak: 63.3 ± 5.6 mL·min-1·kg-1) wore a facial cooling mask before a time-to-exhaustion (TTE) test on a treadmill, under cryostimulation or control conditions. The running performance comprised also two constant load trials, one conducted before and another after wearing the mask, both performed at the velocity of the first ventilatory threshold. Under cryostimulation condition, the TTE was 13% higher than the control condition (p = 0.0049; d = -0.19) with a significant main effect of time for both ratings of perceived exertion (F1, 22 = 50.10; p < 0.0001; η2p = 0.69) and heart rate (F1, 22 = 31.53; p < 0.0001; η2p = 0.59). A significant interaction “condition × time” was found for facial skin temperature (F2, 44 = 36.93; p < 0.0001; η2p = 0.63) and for heart rate during the constant load trial after wearing the mask (F1, 22 = 5.90; p = 0.0238; η2p = 0.21). The localized cryostimulation provided by the mask lowered the skin temperature on the face, potentially mitigating the negative effects of heat stress during running. Incorporating the cryo-facial mask as part of a pre-exercise routine for runners may offer a practical and convenient method to optimize performance and enhance overall training outcomes.

Characterizing the Exponential Profile of W' Recovery Following Partial Depletion.

The aim of this study was to characterize W' recovery kinetics in response to a partial W' depletion. We hypothesized that W' recovery following a partial depletion would be better described by a biexponential than by a monoexponential model. Nine healthy men performed a ramp incremental exercise test, three to five constant load trials to determine critical power and W', and 10 experimental trials to quantify W' depletion. Each experimental trial consisted of two constant load work bouts (WB1 and WB2) interspersed by a recovery interval. WB1 was designed to evoke a 25% or 75% W' depletion (DEP 25% and DEP 75% ). Subsequently, participants recovered for 30, 60, 120, 300, or 600 s and then performed WB2 to exhaustion to calculate the observed W' recovery (W' OBS ). W' OBS data were fitted using monoexponential and biexponential models, both with a variable and with a fixed model amplitude. Root mean square error and Akaike information criterion (AIC c ) were calculated to evaluate the models' goodness-of-fit. The biexponential model fits were associated with overall lower root mean square error values (0.4% to 5.0%) when compared with the monoexponential models (2.9% to 8.0%). However, ΔAIC c resulted in negative values (-15.5 and -23.3) for the model fits where the amplitude was kept free, thereby favoring the use of a monoexponential model for both depletion conditions. For the model fits where the amplitude was fixed at 100%, ΔAIC c was negative for DEP 25% (-15.0) but positive for DEP 75% (11.2). W' OBS values were strongly correlated between both depletion conditions ( r = 0.92) and positively associated with V̇O 2peak , critical power, and gas exchange threshold ( r = 0.67 to 0.77). The present study results did not provide evidence in favor of a biexponential modeling technique to characterize W' recovery following a partial depletion. Moreover, we demonstrated that fixed time constants were insufficient to model W' recovery across different depletion levels, and that W' recovery was positively associated with aerobic fitness. These findings underline the importance of employing variable and individualized time constants in future predictive W' models.

THE PHYSIOLOGICAL VALIDITY OF CRITICAL SPEED DERIVED FROM A 3-MINUTE ALL-OUT SWIM TEST

INTRODUCTION AND AIMS The boundary between heavy and severe exercise domains is one of the most consistent predictors of swimming performance. The gold standard approach to assessing this physiological threshold (numerous 30-minute constant-load trials) is complex and time-consuming, leading practitioners to explore other methodologies, which has left coaches questioning the validity of testing outcomes and reducing testing implementation. The recent proposal of a modified 3-minute all-out swim test has produced reliable estimates of critical speed (CS), however the estimates have not been validated against physiological measures. The aim of this study was to establish the physiological validity of CS derived from the modified 3-minute all-out swim test in elite swimmers. METHODS 16 elite swimmers completed a 3-minute test consisting of 12 maximal 25-m efforts separated by 5s of rest. CS was calculated as the average speed of the slowest two 25-m efforts from the last four completed. To identify MLSS, swimmers completed a 30-minute trial broken into 6 x 5-minute intervals. Blood lactate concentration collected at each interval determined the subsequent interval speed. Over two additional visits, participants completed a 30-minute constant speed trial – at 2% above and 2% below CS to determine the physiology surrounding CS. Statistical analyses were conducted to compare CS and MLSS and determine their association, and to compare physiological measures within the two constant load trials. RESULTS MLSS and CS were not statistically different (p&amp;gt;0.05) and had a strong positive correlation (r=0.98). A physiological steady state was verified in the below CS trial (p&amp;gt;0.05). A physiological steady state was not obtained in the above CS trial (p&amp;lt;0.05). CONCLUSIONS These findings suggest the modified 3-minute all-out swim test as a valid methodology to assess the CS of elite swimmers. Implementation of this methodology could enable critical insight into how athletes are adapting to training and contribute significantly to swimming talent identification.

Interactive effects of exercise intensity and recovery posture on postexercise hypotension.

Postexercise reduction in blood pressure, termed postexercise hypotension (PEH), is relevant for both acute and chronic health reasons and potentially for peripheral cardiovascular adaptations. We investigated the interactive effects of exercise intensity and recovery postures (seated, supine, and standing) on PEH. Thirteen normotensive men underwent a V̇o2max test on a cycle ergometer and five exhaustive constant load trials to determine critical power (CP) and the gas exchange threshold (GET). Subsequently, work-matched exercise trials were performed at two discrete exercise intensities (10% > CP and 10% < GET), with 1 h of recovery in each of the three postures. For both exercise intensities, standing posture resulted in a more substantial PEH (all P < 0.01). For both standing and seated recovery postures, the higher exercise intensity led to larger reductions in systolic [standing: -33 (11) vs. -21 (8) mmHg; seated: -34 (32) vs. -17 (37) mmHg, P < 0.01], diastolic [standing: -18 (7) vs. -8 (5) mmHg; seated: -10 (10) vs. -1 (4) mmHg, P < 0.01], and mean arterial pressures [-13 (8) vs. -2 (4) mmHg, P < 0.01], whereas in the supine recovery posture, the reduction in diastolic [-9 (9) vs. -4 (3) mmHg, P = 0.08) and mean arterial pressures [-7 (5) vs. -3 (4) mmHg, P = 0.06] was not consistently affected by prior exercise intensity. PEH is more pronounced during recovery from exercise performed above CP versus below GET. However, the effect of exercise intensity on PEH is largely abolished when recovery is performed in the supine posture.NEW & NOTEWORTHY The magnitude of postexercise hypotension is greater following the intensity above the critical power in a standing position.

Elite Cyclists with Type 1 Diabetes Show Acceptable Glycemic Excursions During a Time-Trial Performance Under High-Definition Transcranial Direct Current Stimulation

ObjectiveTo evaluate the effects of bilateral dorsolateral prefrontal cortex high-definition transcranial direct current stimulation (HD-tDCS) on glycemic excursions during a time-trial performance in elite cyclists with type 1 diabetes (T1D). MethodsIn a double-blind, randomized crossover order, 9 elite cyclists with T1D (no complications) underwent either HD-tDCS (F3 and F4) or control (SHAM) and completed a constant-load trial at 75% of the second ventilatory threshold plus a 15-km cycling time trial. ResultsReal-time continuous glucose monitoring revealed similar glycemic variability between the 2 conditions, showing a significant effect of time but no interaction (stimulation × time) or stimulation effect. ConclusionBecause glycemic control is crucial for both health and performance, these findings suggest that HD-tDCS could be safely used to enhance performance in athletes with T1D and potentially in a broader active T1D population.

Evaluation of the "Step-Ramp-Step" Protocol: Accurate Aerobic Exercise Prescription with Different Steps and Ramp Slopes.

To assess whether: i) a lower amplitude constant-load MOD is appropriate to determine the mean response time (MRT); ii) the method accurately corrects the dissociation in the V̇O 2 -PO relationship during ramp compared with constant-load exercise when using different ramp slopes. Eighteen participants (7 females) performed three SRS tests including: i) step-transitions into MOD from 20 to 50 W (MOD 50 ) and 80 W (MOD 80 ); and ii) slopes of 15, 30, and 45 W·min -1 . The V̇O 2 and PO at the gas exchange threshold (GET) and the corrected respiratory compensation point (RCP CORR ) were determined. Two to three 30-min constant-load trials evaluated the V̇O 2 and PO at the maximal metabolic steady state (MMSS). There were no differences in V̇O 2 at GET (1.97 ± 0.36, 1.99 ± 0.36, 1.95 ± 0.30 L·min -1 ), and RCP (2.81 ± 0.57, 2.86 ± 0.59, 2.84 ± 0.59) between 15, 30, and 45 W·min -1 ramps, respectively ( P > 0.05). The MRT in seconds was not affected by the amplitude of the MOD or the slope of the ramp (range 19 ± 10 s to 23 ± 20 s; P > 0.05). The mean PO at GET was not significantly affected by the amplitude of the MOD or the slope of the ramp (range 130 ± 30 W to 137 ± 30 W; P > 0.05). The PO at RCP CORR was similar for all conditions ((range 186 ± 43 W to 193 ± 47 W; P > 0.05). The SRS protocol accounts for the V̇O 2 MRT when using smaller amplitude steps, and for the V̇O 2 slow component when using different ramp slopes, allowing for accurate partitioning of the exercise intensity domains in a single test.

Critical power is a key threshold determining the magnitude of post-exercise hypotension in non-hypertensive young males.

The effect of different exercise intensities on the magnitude of post-exercise hypotension has not been rigorously clarified with respect to the metabolic thresholds that partition discrete exercise intensity domains (i.e., critical power and the gas exchange threshold (GET)). We hypothesized that the magnitude of post-exercise hypotension would be greater following isocaloric exercise performed above versus below critical power. Twelve non-hypertensive men completed a ramp incremental exercise test to determine maximal oxygen uptake and the GET, followed by five exhaustive constant load trials to determine critical power and W' (work available above critical power). Subsequently, criterion trials were performed at four discrete intensities matched for total work performed (i.e., isocaloric) to determine the impact of exercise intensity on post-exercise hypotension: 10% above critical power (10%>CP), 10% below critical power (10%<CP), 10% above GET (10%>GET) and 10% below GET (10%<GET). The post-exercise decrease (i.e., the minimum post-exercise values) in mean arterial (10%>CP: -12.7±8.3 vs. 10%<CP: v3.5±2.9mmHg), diastolic (10%>CP: -9.6±9.8 vs. 10%<CP: -1.4±5.0mmHg) and systolic (10%>CP: -23.8±7.0 vs. 10%<CP: -9.9±4.3mmHg) blood pressures were greater following exercise performed 10%>CP compared to all other trials (all P<0.01). No effects of exercise intensity on the magnitude of post-exercise hypotension were observed during exercise performed below critical power (all P>0.05). Critical power represents a threshold above which the magnitude of post-exercise hypotension is greatly augmented. NEW FINDINGS: What is the central questions of this study? What is the influence of exercise intensity on the magnitude of post-exercise hypotension with respect to metabolic thresholds? What is the main finding and its importance? The magnitude of post-exercise hypotension is greatly increased following exercise performed above critical power. However, below critical power, there was no clear effect of exercise intensity on the magnitude of post-exercise hypotension.

591-P: Elite Cyclists with Type 1 Diabetes (T1D) Show Acceptable Glycemic Excursions during a Time-Trial Performance under High-Definition Transcranial Direct-Current Stimulation (HD-tDCS)

Patients with T1D are typically challenged by glycemic fluctuations during exercise. We recently applied HD-tDCS - a neuromodulation enhancer - both in healthy and T1D elite cyclists to improve endurance performance. Here, in a double-blind, counterbalanced, randomized order, nine elite cyclists (28 ± 3.5 years; BMI: 20.8 ± 1.3 kg/m2; VO2peak: 65.3 ± 1.7 mL/min/kg) with T1D (no complications) underwent either HD-tDCS (F3, F4) or control (SHAM) and completed a constant-load trial (CLT) at 75% of the 2nd ventilatory threshold plus a 15-km cycling time-trial (TT). Comparing the two conditions by real-time continuous glucose monitoring (CGM), subjects showed similar glycemic variability in any part of the session (Figure: bold line = mean; dotted lines = min &amp; max), with a significant effect of time (F=26.32; P&amp;lt;0.0001), but no interaction stimulation x time (F=0.08; P&amp;gt;0.99) nor effect of stimulation (F=0.077; P=0.79). Further, CGM data were stable for the 3 days preceding and following the tests. Given that glycemic control becomes of critical interest not only for health but also for performance goals, these findings suggest that HD-tDCS can be safely used as a performance improvement device in athletes with T1D, and possibly in a wider population of active T1D-subjects. Disclosure R.Codella: None. G.Gallo: None. A.Meloni: None. L.Luzi: Advisory Panel; Eli Lilly and Company, Medtronic, Research Support; Gelesis, Speaker's Bureau; A. Menarini Diagnostics, Amgen Inc., Boehringer Ingelheim and Eli Lilly Alliance, Eli Lilly and Company, Novo Nordisk, Novartis. L.Filipas: None.

Can We Accurately Predict Critical Power and W' from a Single Ramp Incremental Exercise Test?

The purpose of this study was to examine the suitability of a single ramp incremental test to predict critical power (CP) and W' . We hypothesized that CP would correspond to the corrected power output (PO) at the respiratory compensation point (RCP) and W' would be calculable from the work done above RCP. One hundred fifty-three healthy young people (26 ± 4 yr, 51.4 ± 7.6 mL·min -1 ·kg -1 ) performed a maximal ramp test (20, 25, or 30 W·min -1 ), followed by three to five constant load trials to determine CP and W' . CP and W' were estimated using a "best individual fit" approach, selecting the mathematical model with the smallest total error. The RCP was identified by means of gas exchange analysis and then translated into its appropriate PO by applying a correction strategy in order to account for the gap in the V̇O 2 /PO relationship between ramp and constant load exercise. We evaluated the agreement between CP and the PO at RCP, and between W' and the total work done above CP ( W'RAMP > CP ) and above RCP ( W'RAMP > RCP ) during the ramp test. The CP was significantly higher than the PO at RCP (Δ = 8 ± 16 W, P < 0.001). W'RAMP > CP was significantly lower than W' (Δ = 1.9 ± 3.3 kJ, P < 0.001), whereas W'RAMP > RCP and W' did not differ from each other (Δ = -0.6 ± 5.8 kJ, P = 0.21). Despite the fact that CP and RCP occurred in close proximity, the estimation of W' from ramp exercise may be problematic given the likelihood of underestimation and considering the large variability. Therefore, we do not recommend the interchangeable use of CP and W' values derived from constant load versus ramp exercise, in particular, when the goal is to obtain accurate estimates or to predict performance capacity.

Effects of bilateral dorsolateral prefrontal cortex high-definition transcranial direct-current stimulation on time-trial performance in cyclists with type 1 diabetes mellitus

BackgroundHD-tDCS is capable to increase the focality of neuromodulation and has been recently applied to improve endurance performance in healthy subjects. Objective/hypothesisWhether these putative advantages could be exploited in active subjects with type 1 diabetes mellitus (T1D) remains questionable. MethodsIn a double-blind, randomized crossover order, 11 high-level cyclists (27 ± 4.3 years; weight: 65.5 ± 8.6 kg; height: 180 ± 8 cm; VO2peak: 67.5 ± 2.9 mL min−1 kg−1) with T1D underwent either HD-tDCS (F3, F4) or control (SHAM) and completed a constant-load trial (CLT) at 75% of the 2nd ventilatory threshold plus a 15-km cycling time-trial (TT). ResultsAfter HD-tDCS, the total time to cover the TT was 3.8% faster (P < 0.01), associated with a higher mean power output (P < 0.01), and a higher rate of power/perception of effort (P < 0.01) and power/heart rate at iso-time (P < 0.05) than the SHAM condition. Physiological parameters during CLT and TT did not differ in both conditions. ConclusionsThese findings suggest that upregulation of the prefrontal cortex could enhance endurance performance in high-level cyclists with T1D, without altering physiological and perceptual responses at moderate intensity. Present data open to future applications of HD-tDCS to a wider population of active T1D-subjects.

Effects of Bilateral Dorsolateral Prefrontal Cortex High-Definition Transcranial Direct-Current Stimulation on Physiological and Performance Responses at Severe-Intensity Exercise Domain in Elite Road Cyclists.

To investigate the effects of bilateral dorsolateral prefrontal cortex high-definition transcranial direct-current stimulation (HD-tDCS) on physiological and performance responses during exercise at the upper limit of the severe-intensity exercise domain in elite-level road cyclists. Eleven elite-level road cyclists (VO2peak: 71.8 [3.1]mL·kg-1·min-1) underwent the HD-tDCS or SHAM condition in a double-blind, counterbalanced, and randomized order. After 20minutes of receiving either HD-tDCS on dorsolateral prefrontal cortex (F3 and F4) or SHAM stimulation, participants completed a 10-minute constant-load trial (CLT1) at 90% of the first ventilatory threshold and a 2-minute CLT (CLT2) at peak power output. Thereafter, they performed a simulated 2-km time trial (TT). Maximal oxygen uptake, respiratory exchange ratio, heart rate, and rating of perceived exertion were recorded during CLT1 and CLT2, whereas performance parameters were recorded during the TT. In 6 out of 11 cyclists, the total time to complete the TT was 3.0% faster in HD-tDCS compared to SHAM. Physiological and perceptual variables measured during CLT1 and CLT2 did not change between HD-tDCS and SHAM. HD-tDCS over the dorsolateral prefrontal cortex seemed to improve cycling TT performance within the upper limit of the severe-intensity exercise domain, suggesting that an upregulation of the prefrontal cortex could be critical even in this exercise intensity domain. However, the limited dimension and the high interindividual variability require further studies to test these putative ergogenic effects.

242-OR: Bilateral Dorsolateral Prefrontal Cortex High-Definition Transcranial Direct-Current Stimulation (HD-tDCS) Improves Time-Trial Performance in Elite Cyclists with Type 1 Diabetes (T1D)

HD-tDCS is capable to increase the focality of neuromodulation and has been recently applied to improve endurance performance in healthy subjects. Here, in a double-blind, counterbalanced, randomized order, elite cyclists (27 ± 4.3 years; BMI: 20.2 ± 1.2 kg/m2; VO2peak: 67.5 ± 1.2 mL/min/kg) with T1D (no complications) underwent either HD-tDCS (F3, F4) or control (SHAM) and completed a constant-load trial at 75% of the 2nd ventilatory threshold plus a 15-km cycling time-trial (TT) . After HD-tDCS, the total time to cover the TT was 3.8 % faster (P&amp;lt;.01) and associated with higher mean power output (P&amp;lt;.01) and a lower rate of perceived exertion/power at iso-time (F=5.7; P&amp;lt;.01) than the SHAM condition. Cadence, lactate, glycemia, heart rate did not differ in both conditions. These findings suggest that upregulation of the prefrontal cortex could safely enhance endurance performance in elite cyclists with T1D, without altering physiological and perceptual responses at moderate intensity. Present data open to future applications of HD-tDCS to a wider population of active T1D-subjects. Disclosure R.Codella: None. L.Filipas: None. G.Gallo: None. L.Luzi: Advisory Panel; Eli Lilly and Company, Speaker's Bureau; Eli Lilly and Company, Novo Nordisk.

Metabolic, hormonal and performance effects of isomaltulose ingestion before prolonged aerobic exercise: a double-blind, randomised, cross-over trial

BackgroundIsomaltulose has been discussed as a low glycaemic carbohydrate but evidence concerning performance benefits and physiological responses has produced varying results. Therefore, we primarily aimed to investigate the effects of isomaltulose ingestion compared to glucose and maltodextrin on fat and carbohydrate oxidation rates, blood glucose levels and serum hormone concentrations of insulin and glucose-dependent insulinotropic polypeptide (GIP). As secondary aims, we assessed running performance and gastrointestinal discomfort.MethodsTwenty-one male recreational endurance runners performed a 70-min constant load trial at 70% maximal running speed (Vmax), followed by a time to exhaustion (TTE) test at 85% Vmax after ingesting either 50 g isomaltulose, maltodextrin or glucose. Fat and carbohydrate oxidation rates were calculated from spiroergometric data. Venous blood samples for measurement of GIP and insulin were drawn before, after the constant load trial and after the TTE. Capillary blood samples for glucose concentrations and subjective feeling of gastrointestinal discomfort were collected every 10 min during the constant load trial.ResultsNo between-condition differences were observed in the area under the curve analysis of fat (p = 0.576) and carbohydrate oxidation rates (p = 0.887). Isomaltulose ingestion led to lower baseline postprandial concentrations of blood glucose compared to maltodextrin (percent change [95% confidence interval], − 16.7% [− 21.8,-11.6], p < 0.001) and glucose (− 11.5% [− 17.3,-5.7], p = 0.001). Similarly, insulin and GIP concentrations were also lower following isomaltulose ingestion compared to maltodextrin (− 40.3% [− 50.5,-30.0], p = 0.001 and − 69.1% [− 74.3,-63.8], p < 0.001, respectively) and glucose (− 32.6% [− 43.9,-21.2], p = 0.012 and − 55.8% [− 70.7,-40.9], p < 0.001, respectively). Furthermore, glucose fluctuation was lower after isomaltulose ingestion compared to maltodextrin (− 26.0% [− 34.2,-17.8], p < 0.001) and glucose (− 17.4% [− 29.1,-5.6], p < 0.001). However, during and after exercise, no between-condition differences for glucose (p = 0.872), insulin (p = 0.503) and GIP (p = 0.244) were observed. No between-condition differences were found for TTE (p = 0.876) or gastrointestinal discomfort (p = 0.119).ConclusionIsomaltulose ingestion led to lower baseline postprandial concentrations of glucose, insulin and GIP compared to maltodextrin and glucose. Consequently, blood glucose fluctuations were lower during treadmill running after isomaltulose ingestion, while no between-condition differences were observed for CHO and fat oxidation rates, treadmill running performance and gastrointestinal discomfort. Further research is required to provide specific guidelines on supplementing isomaltulose in performance and health settings.

Bilateral Dorsolateral Prefrontal Cortex High-Definition Transcranial Direct-Current Stimulation Improves Time-Trial Performance in Elite Cyclists.

The effects of anodal transcranial direct-current stimulation (tDCS) on endurance exercise performance are not yet fully understood. Different stimulated areas and low focality of classical tDCS technique may have led to discordant results. This study investigated the effect of a bilateral anodal high-definition tDCS (HD-tDCS) of the dorsolateral prefrontal cortex on the cycling time-trial (TT) performance and physiological and perceptual response at moderate intensity in elite cyclists. A total of 8 elite cyclists (maximal oxygen consumption: 72.2 [4.3]mL·min-1·kg-1) underwent in a double-blind, counterbalanced, and randomized order the experimental treatment (HD-tDCS) or control treatment (SHAM). After 20minutes of receiving either HD-tDCS on the dorsolateral prefrontal cortex (F3 and F4) or SHAM stimulation, the participants completed a constant-load trial (CLT) at 75% of the second ventilatory threshold. Thereafter, they performed a simulated 15-km TT. The ratings of perceived exertion, heart rate, cadence, oxygen consumption, and respiratory exchange ratio were recorded during the CLT; the ratings of perceived exertion and heart rate were recorded during the TT. The total time to complete the TT was 1.3% faster (HD-tDCS: 1212 [52]s vs SHAM: 1228 [56]s; P = .04) and associated with a higher heart rate (P < .001) and a tendency toward higher mean power output (P = .05). None of the physiological and perceptual variables measured during the CLT highlighted differences between the HD-tDCS and SHAM condition. The findings suggest that bilateral HD-tDCS on the dorsolateral prefrontal cortex improves cycling TT performance without altering the physiological and perceptual response at moderate intensity, indicating that an upregulation of the prefrontal cortex could enhance endurance exercise performance.

Bioenergetics of the VO2 slow component between exercise intensity domains

During heavy and severe constant-load exercise, VO2 displays a slow component (VO2sc) typically interpreted as a loss of efficiency of locomotion. In the ongoing debate on the underpinnings of the VO2sc, recent studies suggested that VO2sc could be attributed to a prolonged shift in energetic sources rather than loss of efficiency. We tested the hypothesis that the total cost of cycling, accounting for aerobic and anaerobic energy sources, is affected by time during metabolic transitions in different intensity domains. Eight active men performed 3 constant load trials of 3, 6, and 9 min in the moderate, heavy, and severe domains (i.e., respectively below, between, and above the two ventilatory thresholds). VO2, VO2 of ventilation and lactate accumulation ([La−]) were quantified to calculate the adjusted oxygen cost of exercise (AdjO2Eq, i.e., measured VO2 − VO2 of ventilation + VO2 equivalent of [La−]) for the 0–3, 3–6, and 6–9 time segments at each intensity, and compared by a two-way RM-ANOVA (time × intensity). After the transient phase, AdjO2Eq was unaffected by time in moderate (ml*3 min−1 at 0–3, 0–6, 0–9 min: 2126 ± 939 < 2687 ± 1036, 2731 ± 1035) and heavy (4278 ± 1074 < 5121 ± 1268, 5225 ± 1123) while a significant effect of time was detected in the severe only (5863 ± 1413 < 7061 ± 1516 < 7372 ± 1443). The emergence of the VO2sc was explained by a prolonged shift between aerobic and anaerobic energy sources in heavy (VO2 − VO2 of ventilation: ml*3 min−1 at 0–3, 0–6, 0–9 min: 3769 ± 1128 < 4938 ± 1256, 5091 ± 1123, [La−]: 452 ± 254 < 128 ± 169, 79 ± 135), while a prolonged metabolic shift and a true loss of efficiency explained the emergence of the VO2sc in severe.

Grey Zone: A Gap Between Heavy and Severe Exercise Domain.

Ozkaya, O, Balci, GA, As, H, Cabuk, R, and Norouzi, M. Grey zone: A gap between heavy and severe exercise domain. J Strength Cond Res 36(1): 113-120, 2022-The aim of this study was to determine a critical threshold (CT) interpreted as "the highest exercise intensity where V̇o2 can be stabilized before reaching 95% of V̇o2max (V̇o2peak)" and compare it with commonly used anaerobic threshold indices. Ten well-trained male cyclists volunteered for this study. Ventilatory threshold (VT) was determined from incremental tests. Multisession constant-load trials were performed to reveal V̇o2max. Mathematically modeled critical power (CP) was estimated through the best individual fit parameter method. Maximal lactate steady state (MLSS) was detected by 30-minute constant-load exercises. The individual CT load of each cyclist was tested by constant-load exercises to exhaustion with +15 W intervals until minimal power output to elicit V̇o2peak. The results showed that work rate corresponding to CT (329.5 ± 41.5 W) was significantly greater than that of the MLSS (269.5 ± 38.5 W; p = 0.000), VT (279.6 ± 33 W; p = 0.000), and CP (306.3 ± 39.4 W; p = 0.000), and CP overestimated both VT and MLSS (p = 0.000). There was no significant V̇o2 difference between the 10th and 30th minute of MLSS and MLSS + 15 W exercise (0.36-0.13 ml·min-1·kg-1; p = 0.621). Exercising V̇o2 response of MLSS + 15 W could not exceed the level of 95% V̇o2max (57.02 ± 3.87 ml·min-1·kg-1 and 87.2 ± 3.1% of V̇o2max; p = 0.000), whereas V̇o2 responses greater than 95% of V̇o2max were always attained during exercises performed at CT + 15 W (64.52 ± 4.37 ml·min-1·kg-1 and 98.6 ± 1% of V̇o2max; p > 0.05). In conclusion, this study indicates that there is a "grey zone" between heavy and severe exercise domain. This information may play a key role in enhancing athletic performance by improving the quality of training programs.

Interlimb differences in parameters of aerobic function and local profiles of deoxygenation during double-leg and counterweighted single-leg cycling.

It is typically assumed that in the context of double-leg cycling, dominant (DOMLEG) and nondominant legs (NDOMLEG) have similar aerobic capacity and both contribute equally to the whole body physiological responses. However, there is a paucity of studies that have systematically investigated maximal and submaximal aerobic performance and characterized the profiles of local muscle deoxygenation in relation to leg dominance. Using counterweighted single-leg cycling, this study explored whether peak O2 consumption (V̇o2peak), maximal lactate steady-state (MLSSp), and profiles of local deoxygenation [HHb] would be different in the DOMLEG compared with the NDOMLEG. Twelve participants performed a series of double-leg and counterweighted single-leg DOMLEG and NDOMLEG ramp-exercise tests and 30-min constant-load trials. V̇o2peak was greater in the DOMLEG than in the NDOMLEG (2.87 ± 0.42 vs. 2.70 ± 0.39 L/min, P < 0.05). The difference in V̇o2peak persisted even after accounting for lean mass (P < 0.05). Similarly, MLSSp was greater in the DOMLEG than in the NDOMLEG (118 ± 31 vs. 109 ± 31 W; P < 0.05). Furthermore, the amplitude of the [HHb] signal during ramp exercise was larger in the DOMLEG than in the NDOMLEG during both double-leg (26.0 ± 8.4 vs. 20.2 ± 8.8 µM, P < 0.05) and counterweighted single-leg cycling (18.5 ± 7.9 vs. 14.9 ± 7.5 µM, P < 0.05). Additionally, the amplitudes of the [HHb] signal were highly to moderately correlated with the mode-specific V̇o2peak values (ranging from 0.91 to 0.54). These findings showed in a group of young men that maximal and submaximal aerobic capacities were greater in the DOMLEG than in the NDOMLEG and that superior peripheral adaptations of the DOMLEG may underpin these differences.NEW & NOTEWORTHY It is typically assumed that the dominant and nondominant legs contribute equally to the whole physiological responses. In this study, we found that the dominant leg achieved greater peak O2 uptake values, sustained greater power output while preserving whole body metabolic stability, and showed larger amplitudes of deoxygenation responses. These findings highlight heterogeneous aerobic capacities of the lower limbs, which have important implications when whole body physiological responses are examined.

Creatine supplementation improves performance above critical power but does not influence the magnitude of neuromuscular fatigue at task failure.

What is the central question of this study? Does the magnitude of neuromuscular fatigue depend on the amount of work done (W') at task failure when cycling above critical power (CP)? What is the main finding and its importance? Creatine supplementation increases W' and enhances supra-CP performance, but induces similar magnitudes of neuromuscular fatigue at task failure compared to placebo. Increased W' does not lead to higher levels of neuromuscular fatigue. This supports the notion of a critical level of neuromuscular fatigue at task failure and challenges a direct causative link between W' depletion and neuromuscular fatigue. The present study examined the effect of creatine supplementation on neuromuscular fatigue and exercise tolerance when cycling above critical power (CP). Eleven males performed an incremental cycling test with four to five constant-load trials to task failure (TTF) to obtain asymptote (CP) and curvature constant (W') of the power-duration relationship, followed by three constant-load supra-CP trials: (1) one TTF following placebo supplementation (PLA); (2) one TTF following creatine supplementation (CRE); and (3) one trial of equal duration to PLA following creatine supplementation (ISO). Neuromuscular assessment of the right knee extensors was performed pre- and post-exercise to measure maximal voluntary contraction (MVC), twitch forces evoked by single (Qpot ) and paired high- (PS100) and low- (PS10) frequency stimulations and voluntary activation. Creatine supplementation increased TTF in CRE vs. PLA by ∼11% (P=0.017) and work done above CP by ∼10% (P=0.015), with no difference (P>0.05) in reductions in MVC (-24±8%vs. -20±9%), Qpot (-39±13%vs. -32±14%), PS10 (-42±14%vs. -36±13%), PS100 (-25±10%vs. -18±12%) and voluntary activation (-7±8%vs. -5±7%). No significant difference was found between ISO and either PLA or CRE (P>0.05). These findings suggest similar levels of neuromuscular fatigue can be found following supra-CP cycling despite increases in performance time and amount of work done above CP, supporting the notion of a critical level of neuromuscular fatigue and challenging a direct causative link between W' depletion and neuromuscular fatigue.

Physiological and psychological determinants of whole-body endurance exercise following short-term sustained operations with partial sleep deprivation

PurposeThe study examined the effects of short-term field-based military training with partial sleep deprivation on whole-body endurance performance in well-trained individuals.MethodsBefore and after a 2-day sustained operations (SUSOPS), 14 cadets performed a 15-min constant-load cycling at 65% of peak power output (PPO; CLT65), followed by an exhaustive constant-load trial at 85% of PPO (CLT85). Physiological [oxygen uptake (dot {V}O2), heart rate (HR), mean arterial pressure (MAP), cardiac output (CO), and regional oxygenation (TOI) in the frontal cerebral cortex and vastus lateralis muscle] and psychological [effort perception (RPE), affective valence (FS), and perceived activation (FAS)] variables were monitored during exercise.ResultsSUSOPS reduced time to exhaustion in CLT85 by 29.1% (p = 0.01). During the CLT65 trial, SUSOPS potentiated the exercise-induced elevations in dot {V}O2 and HR (p < 0.05), and blunted MAP (p = 0.001). CO did not differ between trials. Yet, towards the end of both CLT85 trials, CO tended to decline (p ≤ 0.08); a response that occurred at an earlier stage in the SUSOPS trial. During CLT65, SUSOPS altered neither cerebral nor muscle TOI. The SUSOPS CLT85 trial, however, was terminated at similar leg-muscle deoxygenation (p > 0.05) and lower prefrontal cortex deoxygenation (p < 0.01). SUSOPS increased RPE at submaximal intensities (p = 0.05), and suppressed FAS and FS throughout (p < 0.01).ConclusionsThe present findings indicate, therefore, that a brief period of military sustained operations with partial sleep deprivation augment cardiorespiratory and psychological strain, limiting high-intensity endurance capacity.

A Single Sub-maximal 3-min Test For Critical Power Estimation

Critical power (CP) demarcates heavy/sustainable from severe/unsustainable intensity exercise and is used for functional evaluation of exercise capacity and as a landmark for training design and exercise prescription. The gold standard measuring technique requires a physically demanding and time-consuming protocol (i.e., 3-5 constant-load trials to exhaustion) that may not be suitable in all contexts and populations. PURPOSE: We tested the hypothesis that CP can be accurately estimated based on blood lactate concentration ([LA]) determination at the third minute of a single submaximal non-exhausting cycle ergometer exercise. METHODS: Eight healthy men (26±2 years, 81±11 kg, 176±6 cm, 48±8 ml·Kg-1·min-1) performed five constant-power trials on a cycle ergometer, to the limit of intolerance, designed to generate a distribution of time-to-fatigue (tf) between ∼1 and 20 min. CP was calculated based on the individual watt–tf relationship. During each trial, [LA] was measure at rest and at 3 min from exercise onset and LA accumulation was calculated ([LA3min]) as the difference between 3-min and resting value. Based on individual trials >3 min in duration the [LA3min]–% of CP relationship was obtained and thereafter an estimate of CP (estCP) was computed. CP and estCP were compared by t-test, correlation, and Bland-Altman analysis. RESULTS: The group mean value of CP was 212 ± 37 watt. [LA3min] was a significant and linear function of the workload, expressed as % of CP (r2=0.82). estCP (212 ± 34 watt) was not significantly different from (p=0.90) and highly correlated with (r2=0.85) CP. The average difference (bias) between CP and estCP was -0.1 watt (not different from zero) with a precision of 14 watts. CONCLUSIONS: The data from this pilot study, on a small and homogeneous group of young men, indicate that CP can be accurately and precisely predicted based on a single submaximal non-exhausting trial and blood lactate concentration. Should these findings be confirmed in a larger and more heterogeneous population, they would offer a practical and valid alternative to direct CP determination. The knowledge of this functional parameter is of high practical utility as an indicator of the individual aerobic fitness as well as a quantitative instrument for exercise prescription.