Modelling inter-individual variability in acute and adaptive responses to interval training: insights into exercise intensity normalisation.

PURPOSE: To investigate the influence of exercise intensity normalisation on intra- and inter-individual acute and adaptive responses to an interval training programme. METHODS: Nineteen cyclists were split in two groups differing (only) in how exercise intensity was normalised: 80% of the maximal work rate achieved in an incremental test (% W ˙ max) vs. maximal sustainable work rate in a self-paced interval training session (% W ˙ max-SP). Testing duplicates were conducted before and after an initial control phase, during the training intervention, and at the end, enabling the estimation of inter-individual variability in adaptive responses devoid of intra-individual variability. RESULTS: Due to premature exhaustion, the median training completion rate was 88.8% for the % W ˙ max group, but 100% for the % W ˙ max-SP the group. Ratings of perceived exertion and heart rates were not sensitive to how intensity was normalised, manifesting similar inter-individual variability, although intra-individual variability was minimised for the % W ˙ max-SP group. Amongst six adaptive response variables, there was evidence of individual response for only maximal oxygen uptake (standard deviation: 0.027 L·min-1·week-1) and self-paced interval training performance (standard deviation: 1.451 W·week-1). However, inter-individual variability magnitudes were similar between groups. Average adaptive responses were also similar between groups across all variables. CONCLUSIONS: To normalise completion rates of interval training, % W ˙ max-SP should be used to prescribe relative intensity. However, the variability in adaptive responses to training may not reflect how exercise intensity is normalised, underlining the complexity of the exercise dose-adaptation relationship. True inter-individual variability in adaptive responses cannot always be identified when intra-individual variability is accounted for.

Conventional methods to prescribe exercise intensity are ineffective for exhaustive interval training.

PURPOSE: To compare methods of relative intensity prescription for their ability to normalise performance (i.e., time to exhaustion), physiological, and perceptual responses to high-intensity interval training (HIIT) between individuals. METHODS: Sixteen male and two female cyclists (age: 38 ± 11 years, height: 177 ± 7 cm, body mass: 71.6 ± 7.9 kg, maximal oxygen uptake ([Formula: see text]O2max): 54.3 ± 8.9 ml·kg-1 min-1) initially undertook an incremental test to exhaustion, a 3 min all-out test, and a 20 min time-trial to determine prescription benchmarks. Then, four HIIT sessions (4 min on, 2 min off) were each performed to exhaustion at: the work rate associated with the gas exchange threshold ([Formula: see text]GET) plus 70% of the difference between [Formula: see text]GET and the work rate associated with [Formula: see text]O2max; 85% of the maximal work rate of the incremental test (85%[Formula: see text]max); 120% of the mean work rate of the 20 min time-trial (120%TT); and the work rate predicted to expend, in 4 min, 80% of the work capacity above critical power. Acute HIIT responses were modelled with participant as a random effect to provide estimates of inter-individual variability. RESULTS: For all dependent variables, the magnitude of inter-individual variability was high, and confidence intervals overlapped substantially, indicating that the relative intensity normalisation methods were similarly poor. Inter-individual coefficients of variation for time to exhaustion varied from 44.2% (85%[Formula: see text]max) to 59.1% (120%TT), making it difficult to predict acute HIIT responses for an individual. CONCLUSION: The present study suggests that the methods of intensity prescription investigated do not normalise acute responses to HIIT between individuals.

Inter-day reliability of heart rate complexity and variability metrics in healthy highly active younger and older adults.

PURPOSE: To investigate the inter-day reliability of time-domain, frequency-domain, and nonlinear HRV metrics in healthy highly active younger and older adults. The study also assessed the effect of age on the HRV metrics. METHODS: Forty-four older adults (34 M, 10F; 59 ± 5 years; [Formula: see text] = 40.9 ± 7.6 ml kg-1 min-1) and twenty-two younger adults (16 M, 6F; 22 ± 4 years; [Formula: see text] = 47.2 ± 12.8 ml kg-1 min-1) attended the laboratory. Visit one assessed aerobic fitness through an exercise test. In visits two and three, participants completed a 30-min supine RR interval measurement to derive the HRV metrics. RESULTS: The younger group (YG) and older group (OG) demonstrated poor to good day-to-day relative and absolute reliability for all HRV metrics (OG, ICCs = 0.33 to 0.69 and between day CVs = 3.8 to 29.2%; YG, ICCs = 0.37 to 0.93 and between day CVs = 3.5 to 36.5%). There was a significant reduction in ApEn (P < 0.001), SampEn (P = 0.031), RMSSD (P < 0.001), SDNN (P < 0.001), LF power (P < 0.001) and HF power (P < 0.001), HRV metrics with ageing. There was no significant effect of age the complexity metrics DFA α1 (P = 0.107), α2 (P = 0.147) and CI-8 (P = 0.493). CONCLUSION: HRV metrics are reproducible between days in both healthy highly active younger and older adults. There is a decline in linear and nonlinear HRV metrics with age, albeit there being no age-related change in the nonlinear metrics, DFA α1, α2 and CI-8.

Adding Intermittent Vibration to Varied-intensity Work Intervals: No Extra Benefit.

Varied-intensity work intervals have been shown to induce higher fractions of maximal oxygen uptake during high-intensity interval training compared with constant-intensity work intervals. We assessed whether varied-intensity work intervals combined with intermittent vibration could further increase cyclists' fraction of maximal oxygen uptake to potentially optimise adaptive stimulus. Thirteen cyclists (V̇O2max: 69.7±7.1 ml·kg-1·min-1) underwent a performance assessment and two high-intensity interval training sessions. Both comprised six 5-minute varied-intensity work intervals within which the work rate was alternated between 100% (3×30-second blocks, with or without vibration) and 77% of maximal aerobic power (always without vibration). Adding vibration to varied-intensity work intervals did not elicit a longer time above ninety percent of maximal oxygen uptake (415±221 versus 399±209 seconds, P=0.69). Heart rate- and perceptual-based training-load metrics were also not affected (all P≥0.59). When considering individual work intervals, no between-condition differences were found (fraction of maximal oxygen uptake, P=0.34; total oxygen uptake, P=0.053; mean minute ventilation, P=0.079; mean heart rate, P=0.88; blood lactate concentration, P=0.53; ratings of perceived exertion, P=0.29). Adding intermittent vibration to varied-intensity work intervals does not increase the fraction of maximal oxygen uptake elicited. Whether intermittent exposure to vibration can enhance cyclists' adaptive stimulus triggered by high-intensity interval training remains to be determined.

Functional threshold power and the (manufactured) critical power controversy.

We read with concern yet another communication from Dotan regarding the critical power (CP) concept which contains a litany of factual errors, false statements, and dated physiological interpretations. Space does not permit us to rebut every incorrect point made about our work (Wong et al., 2022) and the wider field in which it sits, but we will address what we consider to be some of the more egregious errors in his letter. We would first note, however, that our paper was not actually focused on the critical power concept.

Ischemic preconditioning of the muscle reduces the metaboreflex response of the knee extensors.

PURPOSE: This study investigated the effect of ischemic preconditioning (IP) on metaboreflex activation following dynamic leg extension exercise in a group of healthy participants. METHOD: Seventeen healthy participants were recruited. IP and SHAM treatments (3 × 5 min cuff occlusion at 220 mmHg or 20 mmHg, respectively) were administered in a randomized order to the upper part of exercising leg's thigh only. Muscle pain intensity (MP) and pain pressure threshold (PPT) were monitored while administrating IP and SHAM treatments. After 3 min of leg extension exercise at 70% of the maximal workload, a post-exercise muscle ischemia (PEMI) was performed to monitor the discharge group III/IV muscle afferents via metaboreflex activation. Hemodynamics were continuously recorded. MP was monitored during exercise and PEMI. RESULTS: IP significantly reduced mean arterial pressure compared to SHAM during metaboreflex activation (mean ± SD, 109.52 ± 7.25 vs. 102.36 ± 7.89 mmHg) which was probably the consequence of a reduced end diastolic volume (mean ± SD, 113.09 ± 14.25 vs. 102.42 ± 9.38 ml). MP was significantly higher during the IP compared to SHAM treatment, while no significant differences in PPT were found. MP did not change during exercise, but it was significantly lower during the PEMI following IP (5.10 ± 1.29 vs. 4.00 ± 1.54). CONCLUSION: Our study demonstrated that IP reduces hemodynamic response during metaboreflex activation, while no effect on MP and PPT were found. The reduction in hemodynamic response was likely the consequence of a blunted venous return.

Functional threshold power is not a valid marker of the maximal metabolic steady state.

Functional Threshold Power (FTP) has been considered a valid alternative to other performance markers that represent the upper boundary of the heavy intensity domain. However, such a claim has not been empirically examined from a physiological perspective.This study examined the blood lactate and VO2 response when exercising at and 15 W above the FTP (FTP+15W). Thirteen cyclists participated in the study. The VO2 was recorded continuously throughout FTP and FTP+15W, with blood lactate measured before the test, every 10 minutes and at task failure. Data were subsequently analysed using two-way ANOVA. The time to task failure at FTP and FTP+15W were 33.7 ± 7.6 and 22.0 ± 5.7 minutes (p < 0.001), respectively. The VO2peak was not attained when exercising at FTP+15W (VO2peak: 3.61 ± 0.81 vs FTP+15W 3.33 ± 0.68 L·min-1, p < 0.001). The VO2 stabilised during both intensities. However, the end test blood lactate corresponding to FTP and FTP+15W was significantly different (6.7 ± 2.1 mM vs 9.2 ± 2.9 mM; p < 0.05). The VO2 response corresponding to FTP and FTP+15W suggests that FTP should not be considered a threshold marker between heavy and severe intensity.

What Does It Take to Complete the Cape Epic?

ABSTRACT: Reinpõld, K, Bossi, AH, and Hopker, JG. What does it take to complete the cape epic? J Strength Cond Res 36(12): 3513-3520, 2022-This study aimed to describe the racing and training demands of the Cape Epic. Six male mountain bike riders (age: 39 ± 7 years, height: 181 ± 3 cm, and body mass: 78.7 ± 8.1 kg) trained for 4.5 months and took part in the Cape Epic. Training and racing data (prologue, stage 1, and 2) were analyzed, and riders were tested in the laboratory on 3 distinct occasions for maximal oxygen uptake (V̇O 2 max), maximal work rate (Wmax), and power output associated with the respiratory compensation point (RCP PO ). Statistical significance was set at p ≤ 0.05. With race durations of 1.5 ± 0.2, 6.5 ± 1.2, and 6.4 ± 1.4 hours for, respectively, prologue, stage 1, and 2, normalized power was higher in prologue (3.73 ± 0.72 W·kg -1 ) compared with stages 1 (3.06 ± 0.59 W·kg -1 , p < 0.001) and 2 (2.94 ± 0.69 W·kg -1 , p < 0.001). Riders spent more time in power zones 1 and 2 (as %RCP PO ) and less time in zones 4 and 5, during stage 2 compared with prologue (all zones p ≤ 0.028). Despite no changes in V̇O 2 max or Wmax, RCP PO increased from midtraining (3.89 ± 0.61 W·kg -1 ) to prerace testing (4.08 ± 0.64 W·kg -1 , p = 0.048). No differences were found between base and build training phases for time in power zones. In conclusion, the Cape Epic requires an ability to sustain high submaximal power outputs for several hours as well as an ability to repeat high-intensity efforts throughout the race. A well-balanced program, incorporating a pyramidal intensity distribution, may be used as a starting point for the design of optimal training approaches.

The acute physiological and perceptual effects of recovery interval intensity during cycling-based high-intensity interval training.

PURPOSE: The current study sought to investigate the role of recovery intensity on the physiological and perceptual responses during cycling-based aerobic high-intensity interval training. METHODS: Fourteen well-trained cyclists ([Formula: see text]: 62 ± 9 mL kg-1 min-1) completed seven laboratory visits. At visit 1, the participants' peak oxygen consumption ([Formula: see text]) and lactate thresholds were determined. At visits 2-7, participants completed either a 6 × 4 min or 3 × 8 min high-intensity interval training (HIIT) protocol with one of three recovery intensity prescriptions: passive (PA) recovery, active recovery at 80% of lactate threshold (80A) or active recovery at 110% of lactate threshold (110A). RESULTS: The time spent at > 80%, > 90% and > 95% of maximal minute power during the work intervals was significantly increased with PA recovery, when compared to both 80A and 110A, during both HIIT protocols (all P ≤ 0.001). However, recovery intensity had no effect on the time spent at > 90% [Formula: see text] (P = 0.11) or > 95% [Formula: see text] (P = 0.50) during the work intervals of both HIIT protocols. Session RPE was significantly higher following the 110A recovery, when compared to the PA and 80A recovery during both HIIT protocols (P < 0.001). CONCLUSION: Passive recovery facilitates a higher work interval PO and similar internal stress for a lower sRPE when compared to active recovery and therefore may be the efficacious recovery intensity prescription.

Novel evidence on the effect of tramadol on self-paced high-intensity cycling.

The use of tramadol is a controversial topic in cycling. In order to provide novel evidence on this issue, we tested 29 participants in a pre-loaded cycling time trial (TT; a 20-min TT preceded by 40-min of constant work-rate at 60% of the VO2max) after ingesting 100 mg of tramadol (vs placebo and paracetamol (1.5 g)). Participants performed the Psychomotor Vigilance Task (PVT) at rest and a Sustained Attention to Response Task (SART) during the 60 min of exercise. Oscillatory electroencephalography (EEG) activity was measured throughout the exercise. The results showed higher mean power output during the 20-min TT in the tramadol vs. paracetamol condition, but no reliable difference was reported between tramadol and placebo (nor paracetamol vs. placebo). Tramadol resulted in faster responses in the PVT and higher heart rate during exercise. The main effect of substance was reliable in the SART during the 40-min constant workload (no during the 20-min TT), with slower reaction time, but better accuracy for tramadol and paracetamol than for placebo. This study supports the increased behavioural and neural efficiency at rest for tramadol but not the proposed ergogenic or cognitive (harmful) effect of tramadol (vs. placebo) during self-paced high-intensity cycling.

The effect of mental fatigue on critical power during cycling exercise.

PURPOSE: Time to exhaustion (TTE) tests used in the determination of critical power (CP) and curvature constant (W') of the power-duration relationship are strongly influenced by the perception of effort (PE). This study aimed to investigate whether manipulation of the PE alters the CP and W'. METHODS: Eleven trained cyclists completed a series of TTE tests to establish CP and W' under two conditions, following a mentally fatiguing (MF), or a control (CON) task. Both cognitive tasks lasted 30 min followed by a TTE test. Ratings of PE and heart rate (HR) were measured during each TTE. Blood lactate was taken pre and post each TTE test. Ratings of perceived mental and physical fatigue were taken pre- and post-cognitive task, and following each TTE test. RESULTS: Perceived MF significantly increased as a result of the MF task compared to baseline and the CON task (P < 0.05), without a change in perceived physical fatigue (P > 0.05). PE was significantly higher during TTE in the MF condition (P < 0.05). Pre-post blood lactate accumulation was significantly lower after each TTE in MF condition (P < 0.05). HR was not significant different between conditions (P > 0.05). Neither cognitive task induced any change in CP (MF 253 ± 51 vs. CON 247 ± 58W; P > 0.05), although W' was significantly reduced in the MF condition (MF 22.8 ± 4.5 vs. CON 29.3 ± 6.3 kJ; P < 0.01). CONCLUSION: MF has no effect of CP, but reduces the W' in trained cyclists. Lower lactate accumulation during TTE tests following MF suggests that cyclists were not able to fully expend W' even though they exercised to volitional exhaustion.

Prescribing 6-weeks of running training using parameters from a self-paced maximal oxygen uptake protocol.

PURPOSE: The self-paced maximal oxygen uptake test (SPV) may offer effective training prescription metrics for athletes. This study aimed to examine whether SPV-derived data could be used for training prescription. METHODS: Twenty-four recreationally active male and female runners were randomly assigned between two training groups: (1) Standardised (STND) and (2) Self-Paced (S-P). Participants completed 4 running sessions a week using a global positioning system-enabled (GPS) watch: 2 × interval sessions; 1 × recovery run; and 1 × tempo run. STND had training prescribed via graded exercise test (GXT) data, whereas S-P had training prescribed via SPV data. In STND, intervals were prescribed as 6 × 60% of the time that velocity at [Formula: see text] ([Formula: see text]) could be maintained (Tmax). In S-P, intervals were prescribed as 7 × 120 s at the mean velocity of rating of perceived exertion 20 (vRPE20). Both groups used 1:2 work:recovery ratio. Maximal oxygen uptake ([Formula: see text]), [Formula: see text], Tmax, vRPE20, critical speed (CS), and lactate threshold (LT) were determined before and after the 6-week training. RESULTS: STND and S-P training significantly improved [Formula: see text] by 4 ± 8 and 6 ± 6%, CS by 7 ± 7 and 3 ± 3%; LT by 5 ± 4% and 7 ± 8%, respectively (all P < .05), with no differences observed between groups. CONCLUSIONS: Novel metrics obtained from the SPV can offer similar training prescription and improvement in [Formula: see text], CS and LT compared to training derived from a traditional GXT.

The effects of acute carbohydrate and caffeine feeding strategies on cycling efficiency.

To assess the effect of carbohydrate and caffeine on gross efficiency (GE), 14 cyclists (V̇O2max 57.6 ± 6.3 ml.kg-1.min-1) completed 4 × 2-hour tests at a submaximal exercise intensity (60% Maximal Minute Power). Using a randomized, counter-balanced crossover design, participants consumed a standardised diet in the 3-days preceding each test and subsequently ingested either caffeine (CAF), carbohydrate (CHO), caffeine+carbohydrate (CAF+CHO) or water (W) during exercise whilst GE and plasma glucose were assessed at regular intervals (~30 mins). GE progressively decreased in the W condition but, whilst caffeine had no effect, this was significantly attenuated in both trials that involved carbohydrate feedings (W = -1.78 ± 0.31%; CHO = -0.70 ± 0.25%, p = 0.008; CAF+CHO = -0.63 ± 0.27%, p = 0.023; CAF = -1.12 ± 0.24%, p = 0.077). Blood glucose levels were significantly higher in carbohydrate ingestion conditions (CHO = 4.79 ± 0.67 mmol·L-1, p < 0.001; CAF+CHO = 5.05 ± 0.81 mmol·L-1, p < 0.001; CAF = 4.46 ± 0.75 mmol·L-1; W = 4.20 ± 0.53 mmol·L-1). Carbohydrate ingestion has a small but significant effect on exercise-induced reductions in GE, indicating that cyclists' feeding strategy should be carefully monitored prior to and during assessment.

Age differences in physiological responses to self-paced and incremental [Formula: see text] testing.

PURPOSE: A self-paced maximal exercise protocol has demonstrated higher [Formula: see text] values when compared against traditional tests. The aim was to compare physiological responses to this self-paced [Formula: see text] protocol (SPV) in comparison to a traditional ramp [Formula: see text] (RAMP) protocol in young (18-30 years) and old (50-75 years) participants. METHODS: Forty-four participants (22 young; 22 old) completed both protocols in a randomised, counter-balanced, crossover design. The SPV included 5 × 2 min stages, participants were able to self-regulate their power output (PO) by using incremental 'clamps' in ratings of perceived exertion. The RAMP consisted of either 15 or 20 W min-1. RESULTS: Expired gases, cardiac output (Q), stroke volume (SV), muscular deoxyhaemoglobin (deoxyHb) and electromyography (EMG) at the vastus lateralis were recorded throughout. Results demonstrated significantly higher [Formula: see text] in the SPV (49.68 ± 10.26 ml kg-1 min-1) vs. the RAMP (47.70 ± 9.98 ml kg-1 min-1) in the young, but not in the old group (>0.05). Q and SV were significantly higher in the SPV vs. the RAMP in the young (<0.05) but not in the old group (>0.05). No differences seen in deoxyHb and EMG for either age groups (>0.05). Peak PO was significantly higher in the SPV vs. the RAMP in both age groups (<0.05). CONCLUSION: Findings demonstrate that the SPV produces higher [Formula: see text], peak Q and SV values in the young group. However, older participants achieved similar [Formula: see text] values in both protocols, mostly likely due to age-related differences in cardiovascular responses to incremental exercise, despite them achieving a higher physiological workload in the SPV.

Reliability and Validity of a Self-paced Cardiopulmonary Exercise Test in Post-MI Patients.

A self-paced peak oxygen uptake (V̇O2peak) test (SPV) has been shown to produce higher V̇O2peak values compared to standard cardiopulmonary exercise tests (sCPET), but has not been tested on any clinical population. This study aimed to assess the reliability of the SPV in a healthy population (study 1), and the validity and reliability of the SPV in post-myocardial infarction (post-MI) patients (study 2). For study 1, 25 healthy participants completed 3 SPV's. For study 2, 28 post-MI patients completed one sCPET and 2 SPV's. The SPV consisted of 5×2-min stages where participants were able to self-regulate their effort by using incremental 'clamps' in ratings of perceived exertion. The sCPET consisted of a 20 W/min ramp. Results demonstrated the SPV to have a coefficient of variation for V̇O2peak of 4.7% for the healthy population, and 8.2% for the post-MI patients. Limits of agreement ranged between±4.22-5.86 ml·kg-1·min-1, with the intraclass correlation coefficient ranging between 0.89-0.95. In study 2, there was a significantly higher V̇O2peak achieved in the SPV (23.07±4.90 ml·kg-1·min-1) against the sCPET (21.29±4.93 ml·kg-1·min-1). It is concluded that these results provide initial evidence that the SPV may be a safe, valid and reliable method for determining exercise capacity in post-MI patients.

Laboratory predictors of uphill cycling performance in trained cyclists.

This study aimed to assess the relationship between an uphill time-trial (TT) performance and both aerobic and anaerobic parameters obtained from laboratory tests. Fifteen cyclists performed a Wingate anaerobic test, a graded exercise test (GXT) and a field-based 20-min TT with 2.7% mean gradient. After a 5-week non-supervised training period, 10 of them performed a second TT for analysis of pacing reproducibility. Stepwise multiple regressions demonstrated that 91% of TT mean power output variation (W kg-1) could be explained by peak oxygen uptake (ml kg-1.min-1) and the respiratory compensation point (W kg-1), with standardised beta coefficients of 0.64 and 0.39, respectively. The agreement between mean power output and power at respiratory compensation point showed a bias ± random error of 16.2 ± 51.8 W or 5.7 ± 19.7%. One-way repeated-measures analysis of variance revealed a significant effect of the time interval (123.1 ± 8.7; 97.8 ± 1.2 and 94.0 ± 7.2% of mean power output, for epochs 0-2, 2-18 and 18-20 min, respectively; P < 0.001), characterising a positive pacing profile. This study indicates that an uphill, 20-min TT-type performance is correlated to aerobic physiological GXT variables and that cyclists adopt reproducible pacing strategies when they are tested 5 weeks apart (coefficients of variation of 6.3; 1 and 4%, for 0-2, 2-18 and 18-20 min, respectively).

Comparison of inter-trial recovery times for the determination of critical power and W' in cycling.

Critical Power (CP) and W' are often determined using multi-day testing protocols. To investigate this cumbersome testing method, the purpose of this study was to compare the differences between the conventional use of a 24-h inter-trial recovery time with those of 3 h and 30 min for the determination of CP and W'. METHODS: 9 moderately trained cyclists performed an incremental test to exhaustion to establish the power output associated with the maximum oxygen uptake (p[Formula: see text]max), and 3 protocols requiring time-to-exhaustion trials at a constant work-rate performed at 80%, 100% and 105% of p[Formula: see text]max. Design: Protocol A utilised 24-h inter-trial recovery (CP24/W'24), protocol B utilised 3-h inter-trial recovery (CP3/W'3), and protocol C used 30-min inter-trial recovery period (CP0.5/W'0.5). CP and W' were calculated using the inverse time (1/t) versus power (P) relation (P = W'(1/t) + CP). RESULTS: 95% Limits of Agreement between protocol A and B were -9 to 15 W; -7.4 to 7.8 kJ (CP/W') and between protocol A and protocol C they were -27 to 22 W; -7.2 to 15.1 kJ (CP/W'). Compared to criterion protocol A, the average prediction error of protocol B was 2.5% (CP) and 25.6% (W'), whilst for protocol C it was 3.7% (CP) and 32.9% (W'). CONCLUSION: 3-h and 30-min inter-trial recovery time protocols provide valid methods of determining CP but not W' in cycling.

Central alterations of neuromuscular function and feedback from group III-IV muscle afferents following exhaustive high-intensity one-leg dynamic exercise.

The aims of this investigation were to describe the central alterations of neuromuscular function induced by exhaustive high-intensity one-leg dynamic exercise (OLDE, study 1) and to indirectly quantify feedback from group III-IV muscle afferents via muscle occlusion (MO, study 2) in healthy adult male humans. We hypothesized that these central alterations and their recovery are associated with changes in afferent feedback. Both studies consisted of two time-to-exhaustion tests at 85% peak power output. In study 1, voluntary activation level (VAL), M-wave, cervicomedullary motor evoked potential (CMEP), motor evoked potential (MEP), and MEP cortical silent period (CSP) of the knee extensor muscles were measured. In study 2, mean arterial pressure (MAP) and leg muscle pain were measured during MO. Measurements were performed preexercise, at exhaustion, and after 3 min recovery. Compared with preexercise values, VAL was lower at exhaustion (-13 ± 13%, P < 0.05) and after 3 min of recovery (-6 ± 6%, P = 0.05). CMEP area/M area was lower at exhaustion (-38 ± 13%, P < 0.01) and recovered after 3 min. MEP area/M area was higher at exhaustion (+25 ± 27%, P < 0.01) and after 3 min of recovery (+17 ± 20%, P < 0.01). CSP was higher (+19 ± 9%, P < 0.01) only at exhaustion and recovered after 3 min. Markers of afferent feedback (MAP and leg muscle pain during MO) were significantly higher only at exhaustion. These findings suggest that the alterations in spinal excitability and CSP induced by high-intensity OLDE are associated with an increase in afferent feedback at exhaustion, whereas central fatigue does not fully recover even when significant afferent feedback is no longer present.