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The purpose of this study was to examine the effects of non-contingent feedback in the form of heart rate (HR) on the incidence of plateau at V̇O2max. Ten physically active males (age 24.8 yrs ± 4.2; mass 81.4 ± 9.0 kg; stature 1.80 ± 0.11 m, V̇O2max 53.2 ± 5.8 ml·kg-1.min-1) who were V̇O2max testing naïve but were cognisant as to the heart rate responses to exercise completed four incremental tests to volitional exhaustion, separated by ~72 h for the determination of V̇O2max and gas exchange threshold. The first trial served as a familiarisation with the remaining three being experimental conditions where HR was presented in a screen projection as either the actual response (HR-A) or 10 b·min-1 higher than recorded (HR-H) or 10 b·min-1 lower (HR-L). Throughout all trials V̇O2 was recorded on a breath-by-breath basis with plateau criteria of ≤ 50 ml·min-1. RESULTS: A significant difference was observed for Δ V̇O2 over the final two consecutive 30s sampling periods between HR-A, both HR-L and HR-H (p = 0.049) and for the incidence of plateau response between condition (p = 0.021). An additional significant difference was observed for sub-maximal Δ V̇O2 responses between HR-A and HR-H (p = 0.049) and HR-A and HR-L (p = 0.006). Non-significant differences were observed for all other criteria. These data indicate that when presented with non-contingent feedback in the form of HR, that the perceptually orientated pacing schema becomes disrupted promoting a sparing of the finite anaerobic capacity to compensate for the imbalance between the afferent signal and perception of effort. Key points The manifestation of the plateau at V̇O2max is disrupted (lower incidence rates) when participants are exposed to non-contingent feedback in the form of heart rate. Non-contingent feedback in the form of heart rate does not affect the V̇O2max score or associated cardio-respiratory parameters. Given the association between the V̇O2-plateau and the finite anaerobic capacity it is proposed that non-contingent feedback creates a sparing of this resource due to an imbalance between the perception of effort and the bio-feedback.

Beneficial use of probiotic (PRO) interventions on gastrointestinal endotoxemia (GE) prior to an ultra-endurance triathlon has been previously demonstrated. The prevalence of GE (and whether PRO strategies minimise gastrointestinal (GI) symptoms) relating to multi-day ultra-events is less known. Understanding if nutritional periodization strategies confer similar GI benefits also warrants investigation. \ud \ud PURPOSE: To assess the impact of probiotic supplementation and caloric periodization prior to an extreme ultra-marathon on GI symptoms and race performance. \ud \ud METHODS: Thirty-eight healthy participants were recruited from entrants of the 2015 Marathon Des Sables (age: 42±9yrs; weight: 77.71±10.31kg; VO2max: 52.58±8.66 mL·kg·min-1), and randomly assigned to either: PRO (100mg.d-1 capsulated Lactobacillus acidophilus); CP (caloric periodization of 500kcal above habitual intake on alternate days) or control (CON) for 12 weeks pre-race. Plasma lipopolysaccharides (LPS) via Limulus Amebocyte Lysate chromogenic endotoxin quantification were determined at baseline, pre and post-race. Participants graded duration and severity of GI symptoms through daily questionnaires. Performance times were obtained from accumulated race tracking. Data presented as mean ±SE. \ud \ud RESULTS: Race times (hrs:mins) were 41:28±2:31, 45:12±2:05 and 50:43 ±4:38 for PRO, CP and CON respectively (p>0.05). Overall LPS significantly increased from baseline (10.08±0.53pg.ml-1) to pre-race (13.12±0.74pg.ml-1; p=0.001). Delta LPS pre-race was not different between groups (PRO: 2.94±1.11pg.ml-1; CP: 3.71±1.28pg.ml-1; CON: 2.32±1.26pg.ml-1; p>0.05). Similarly, delta LPS post-race was not different, despite greater reductions in both intervention groups (PRO: -4.57±1.93pg.ml-1; CP: -6.95±1.84pg.ml-1; CON: -2.16±2.21pg.ml-1; p>0.05). GI symptom count favoured PRO (21.8%) compared with CP (41.6%) and CON (36.6%) respectively (p=0.001), although no differences for GI symptom index were reported between groups (p>0.05). \ud \ud CONCLUSIONS: Moderate GE was evident in a UK cohort undertaking a multi-day ultra-marathon. PRO use did not significantly impact on GE prevalence, despite evidence of reduced GI symptoms. Caloric periodization appeared to favour GE recovery post-race, but was not deemed significant.

UCI rule 1.3.013 limits the forward displacement of the nose of the saddle to 5cm rearward of the centre of the bottom-bracket. This study tests the effects of contravening this rule on 4km laboratory time trials and highlights biomechanical and physiological responses that could be of interest to coaches and bike fitters. Ten competitive male cyclists age 26±2 (mean±SD) yrs, height 180±5 cm, body mass 71±6 kg; V̇ O2max 70.9±8.6 ml·kg-1·min-1) completed 4km time trials and heavy intensity bouts. Riding posture was rotated forward where the nose of the saddle was 0, 2, 4, and 6cm to the rear of the bottom bracket (P0, P2, P4 and P6). End time, power, cardiorespiratory responses, lower appendage kinematics and crank torque kinetics were measured. There was no significant effect of position on 4 km time trials completion time or power. During 4 km time trials and heavy intensity bouts, gas exchange variables and lower limb range of motion were unchanged (P>0.05). Trunk lean angle, cardiac output and stroke volume were greater at P6 than other positions (P0.05). Results indicate, contravening rule 1.3.013 does not bring about improvements to 4km laboratory TTs. The rearward shift in peak crank torque most likely occurs as a function of altered muscle activation. Haemodynamic variations are possibly related to changes in peripheral resistance at the most forward position. Further work is necessary to allude to probable improvements in aerodynamics.

The purpose of this study was to assess the VO2max plateau response at VO2max during a series of pre-determined trials.Ten male well-trained athletes (age, 23.0 ± 3.2; height, 183.3 ± 5.5 cm; mass 77.5 ± 11.1 Kg; VO2max 66.5 ± 5.0 ml(.)kg(-1,)min(-1)), but who were VO2max testing naïve and with prior-knowledge of trial number completed four incremental tests to volitional exhaustion, separated by ~72-h for the determination of VO2max and gas exchange threshold. Throughout all trials VO2max was recorded on a breath-by-breath basis using a pre-calibrated metabolic cart, using a plateau criterion of Δ VO2 ≤1.5 ml(.)kg(-1.)min(-1) over the final 2 consecutive 30 s sampling periods. A significant difference was observed between trial-1 and trial-4 for plateau incidence (p = 0.0285) rising from 20% in trial-1 to a 70% response rate in trial-4. Furthermore a significant difference was observed for VO2dif (difference between criterion value and Δ VO2) in trial-1, 1.02 ± 1.69 ml(.)kg(-1.)min(-1) (p = 0.038), with non-significant differences observed for all other trials, despite a non-significant difference for VO2max across all trials (p0.05). Finally, a significant difference was observed for effort perception (RPE) at volitional exhaustion between trial-1 (17.7 ± 1.3) and trial-4 (19.0 ± 1.4) (p = 0.0052). These data indicate that prior-knowledge of trial number can influence the manifestation of the VO2 plateau in a group of well-trained male athletes, thereby suggesting that a form of effort control is established in order to preserve the finite anaerobic capacity. Key pointsIn well-trained athletes the incidence of plateau at VO2max increases in conjunction with an increase in trial number and the associated sensations of pain and fatigue.By informing the participant of the number of trials to be completed a closed-loop condition is developed whereby effort in all trials is compared to a perceptually developed template.Closed-loop condition leads to a sparing of the finite anaerobic capacity during incremental tests when the number of trials to be completed is known.