The missing hydrogen ion, part-2: Where the evidence leads to.

The purpose of this manuscript was to present the evidence for why cells do not produce metabolic acids. In addition, evidence that opposes common viewpoints and arguments used to support the cellular production of lactic acid (HLa) or liver keto-acids have been provided. Organic chemistry reveals that many molecules involved in cellular energy catabolism contain functional groups classified as acids. The two main acidic functional groups of these molecules susceptible to ∼H+ release are the carboxyl and phosphoryl structures, though the biochemistry and organic chemistry of molecules having these structures reveal they are produced in a non-acidic ionic (negatively charged) structure, thereby preventing pH dependent ∼H+ release. Added evidence from the industrial production of HLa further reveals that lactate (La-) is produced followed by an acidification step that converts La- to HLa due to pH dependent ∼H+ association. Interestingly, there is a plentiful list of other molecules that are classified as acids and compared to HLa have similar values for their H+ dissociation constant (pKd). For many metabolic conditions, the cumulative turnover of these molecules is far higher than for La-. The collective evidence documents the non-empirical basis for the construct of the cellular production of HLa, or any other metabolic acid.

Validity of combined hydration self-assessment measurements to estimate a low vs. high urine concentration in a small sample of (tactical) athletes.

PURPOSE: Relationships between body weight, urine color (Uc), and thirst level (WUT) have been proposed as a simple and inexpensive self-assessment method to predict dehydration. This study aimed to determine if this method also allowed us to accurately identify a low vs. high urine concentration in (tactical) athletes. METHODS: A total of n = 19 Army Reserve Officer Training Corps cadets and club sports athletes (22.7 ± 3.8 years old, of which 13 male) were included in the analysis, providing morning body weight, thirst sensation, and Uc for five consecutive days. Each item received a score 0 or 1, resulting in a WUT score ranging from 0 (likely hydrated) to 3 (very likely dehydrated). WUT model and individual item outcomes were then compared with a ≥ 1.020 urine specific gravity (USG) cut-off indicating a high urine concentration, using descriptive comparisons, generalized linear mixed models, and logistic regression (to calculate the area under the curve (AUC)). RESULTS: WUT score was not significantly predictive of urine concentration, z = 1.59, p = 0.11. The AUC ranged from 0.54 to 0.77 for test days, suggesting a fair AUC on most days. Only Uc was significantly related to urine concentration, z = 2.49, p = 0.01. The accuracy of the WUT model for correctly classifying urine samples with a high concentration was 68% vs. 51% of samples with a low concentration, resulting in an average accuracy of 61%. CONCLUSION: This study shows that WUT scores were not predictive of urine concentration, and the method did not substantially outperform the accuracy of Uc scoring alone.

Mouth Rinsing and Ingestion of Unpleasant Salty or Bitter Solutions Does Not Improve Cycling Sprint Performance in Trained Cyclists.

The purpose of this study was to investigate the influence of mouth rinsing and ingesting unpleasant salty or bitter solutions on cycling sprint performance and knee extensor force characteristics. Eleven male and one female trained cyclists (age: 34 ± 9 years, maximal oxygen uptake 56.9 ± 3.9 ml·kg-1·min-1) completed a ramp test and familiarization followed by four experimental trials. In each trial, participants completed an all-out 30-s cycling sprint with knee extensor maximal voluntary contractions before and immediately after the sprint. In a randomized, counterbalanced, cross-over order, the four main trials were: a no solution control condition, water, salty (5.8%), or bitter (2 mM quinine) solutions that were mouth rinsed (10 s) and ingested immediately before the cycling sprint. There were no significant differences between conditions in mean power (mean ± SD, no solution: 822 ± 115 W, water: 818 ± 108 W, salt: 832 ± 111 W, bitter: 818 ± 105 W); peak power (no solution: 1,184 ± 205 W, water: 1,177 ± 207 W, salt: 1,195 ± 210 W, bitter: 1,184 ± 209 W); or fatigue index (no solution: 51.5% ± 5.7%, water: 50.8% ± 7.0%, salt: 51.1% ± 5.9%, bitter: 51.2% ± 7.1%) during the sprint. Maximal force and impulse declined postexercise; however, there were no significant differences between conditions in knee extensor force characteristics. The present data do not support the use of unpleasant salty or bitter solutions as an ergogenic aid to improve sprint exercise performance.

Scheduling Concurrent Training 48 versus 72 h after Simulated Match Play: Effects on Neuromuscular Function and Fatigue.

INTRODUCTION: Scheduling concurrent training (CT) during the in-season microcycle in field-based team sport is driven by prematch and postmatch recovery. This study examined the neuromuscular function, fatigue, and soreness responses to CT administered 48 h (match day (MD) + 2) versus 72 h (MD + 3) after match. METHODS: Ten male recreational-level team sport athletes were monitored daily during two 5-d microcycles, which began with a simulated match (Soccer-specific Aerobic Field Test (SAFT90)) and CT performed either 48 or 72 h after match. Maximal voluntary force, quadriceps maximum EMG, voluntary activation, muscle contractile function (evoked twitch responses), muscle soreness, and fatigue were assessed immediately before and after the SAFT90, and every 24 up to 96 h after match. Outcome measures were also assessed immediately after CT. The CT consisted of an intermittent sprint protocol and a lower limb resistance training session separated by 1 h. RESULTS: Immediately after the SAFT90 in both conditions, maximal voluntary force was below baseline (mean change (Δ), -14.6% ± 10.0%; P = 0.03), recovering 48 h post. Quadriceps contractile function (Δ, -31.5% ± 11.4%; P = 0.003) and voluntary activation (Δ, -8.9 ± 6.2%; P = 0.003) were also hampered after the SAFT90, recovering 24 h post in both conditions. In addition, the SAFT90 elicited elevated levels of fatigue and muscle soreness that recovered 24 h after the SAFT90 before increasing at 72 and 96 h post in the MD + 2 and MD + 3 conditions, respectively. CONCLUSIONS: Recovery of fatigue was only observed at the end of the microcycle when CT was prescribed on MD + 2. Therefore, CT scheduled early (MD + 2) in the microcycle might avoid compromising forthcoming match preparation.

Mouth rinsing and ingesting salty or bitter solutions does not influence corticomotor excitability or neuromuscular function.

PURPOSE: To explore the effect of tasting unpleasant salty or bitter solutions on lower limb corticomotor excitability and neuromuscular function. METHODS: Nine females and eleven males participated (age: 27 ± 7 years, BMI: 25.3 ± 4.0 kg m-2). Unpleasant salty (1 M) and bitter (2 mM quinine) solutions were compared to water, sweetened water, and no solution, which functioned as control conditions. In a non-blinded randomized cross-over order, each solution was mouth rinsed (10 s) and ingested before perceptual responses, instantaneous heart rate (a marker of autonomic nervous system activation), quadricep corticomotor excitability (motor-evoked potential amplitude) and neuromuscular function during a maximal voluntary contraction (maximum voluntary force, resting twitch force, voluntary activation, 0-50 ms impulse, 0-100 impulse, 100-200 ms impulse) were measured. RESULTS: Hedonic value (water: 47 ± 8%, sweet: 23 ± 17%, salt: 71 ± 8%, bitter: 80 ± 10%), taste intensity, unpleasantness and increases in heart rate (no solution: 14 ± 5 bpm, water: 18 ± 5 bpm, sweet: 20 ± 5 bpm, salt: 24 ± 7 bpm, bitter: 23 ± 6 bpm) were significantly higher in the salty and bitter conditions compared to control conditions. Nausea was low in all conditions (< 15%) but was significantly higher in salty and bitter conditions compared to water (water: 3 ± 5%, sweet: 6 ± 13%, salt: 7 ± 9%, bitter: 14 ± 16%). There was no significant difference between conditions in neuromuscular function or corticomotor excitability variables. CONCLUSION: At rest, unpleasant tastes appear to have no influence on quadricep corticomotor excitability or neuromuscular function. These data question the mechanisms via which unpleasant tastes are proposed to influence exercise performance.

Partial body cryotherapy exposure drives acute redistribution of circulating lymphocytes: preliminary findings.

Partial body cryotherapy (PBC) is proposed to alleviate symptoms of exercise-induced muscle damage (EIMD) by reducing associated inflammation. No studies have assessed acute PBC exposure on peripheral blood mononuclear cell mobilisation or compared these with cold water immersion (CWI), which may inform how PBC impacts inflammatory processes. This trial examined the impact of a single PBC exposure on circulating peripheral blood mononuclear cells compared to CWI or a control. 26 males were randomised into either PBC (3 min at - 110 to - 140 °C), CWI (3 min at 9 °C), or control (3 min at 24 °C), with blood samples, heart rate, and blood pressure taken before and after exposure. Cytometric analysis determined that CD8+ T-cell populations were significantly elevated after treatments, with PBC increasing CD8+ T cells to a greater degree than either CWI or CON. Natural killer cell counts were also elevated after PBC, with the increase attributed specifically to the CD56loCD16+ cytotoxic subset. This provides the first evidence for the effect of PBC exposure on redistribution of immune cells. An increase in circulating leukocyte subsets such as CD8+ T cells and CD56loCD16+ natural killer cells suggests that PBC may induce a transient mobilisation of lymphocytes. PBC may thus enable a more efficient trafficking of these cells from the circulation to the site of initial cellular insult from exercise, potentially accelerating the process of cellular recovery. This provides novel evidence on the use of PBC as a recovery treatment and may also have applicability in other clinical settings involving the recovery of damaged skeletal muscle.

The missing hydrogen ion, part-1: Historical precedents vs. fundamental concepts.

The purpose of this review and commentary was to provide an historical and evidence-based account of organic acids and the biochemical and organic chemistry evidence for why cells do not produce metabolites that are acids. The scientific study of acids has a long history dating to the 16th and 17th centuries, and the definition of an acid was proposed in 1884 as a molecule that when in an aqueous solution releases a hydrogen ion (H+). There are three common ionizable functional groups for molecules classified as acids: 1) the carboxyl group, 2) the phosphoryl group and 3) the amine group. The propensity by which a cation will associate or dissociate with a negatively charged atom is quantified by the equilibrium constant (Keq) of the dissociation constant (Kd) of the ionization (Keq â€‹= â€‹Kd), which for lactic acid (HLa) vs. lactate (La-) is expressed as: Keq=Kd=[H+][La-][HLa]= 4 677.351 4 (ionic strength â€‹= â€‹0.01 Mol⋅L-1, T â€‹= â€‹25 â€‹°C). The negative log10 of the dissociation pKd reveals the pH at which half of the molecules are ionized, which for HLa â€‹= â€‹3.67. Thus, knowing the pKd and the pH of the solution at question will reveal the extent of the ionization vs. acidification of molecules that are classified as acids.

Acute Neuromuscular Response to Team Sports-Specific Running, Resistance, and Concurrent Training: A Crossover Study.

PURPOSE: This study aimed to examine the changes in muscle contractile function, voluntary activation, and muscle damage after lower limb resistance training (RT), intermittent sprint exercise, and concurrent training (CT). METHODS: Ten male, recreational team sport athletes with a history of RT participated in a randomized crossover study involving an intermittent sprint protocol (ISP), lower limb RT, and CT (ISP and RT separated by 1 h). Before (PRE), immediately after (POST), 24 h and 48 h after each exercise condition, quadriceps muscle activation, voluntary activation, muscle contractile function (evoked twitch responses), creatine kinase, muscle soreness, and Profile of Mood States (POMS)-fatigue were recorded. RESULTS: Quadriceps contractile function was hampered in all conditions, with a significantly greater decline observed POST RT (58.4% ± 18.0%) and CT (54.8% ± 8.6%) compared with ISP (35.9% ± 10.7%, P < 0.05), recovering at 48 h after all exercise conditions. POMS-fatigue ratings increased at POST in all conditions with CT and ISP eliciting the greatest increase, returning to baseline 48 h after all exercise conditions. Quadriceps muscle soreness remained elevated from PRE at 48 h after all exercise conditions. No changes across time were observed for voluntary activation and quadriceps surface EMG amplitude after any exercise condition. The volume and load lifted in the RT session was unaffected by previous intermittent exercise (ISP) in CT. CONCLUSIONS: RT impairs contractile function, which is not exacerbated when performed 1 h after the ISP. Contractile function after all exercise conditions displayed the same recovery profile (48 h) despite the postexercise decrement being smaller after the ISP compared with RT and CT. Previous intermittent sprint exercise does not negatively affect the volume of exercise performed in a lower limb RT session.

The Hyperhydration Potential of Sodium Bicarbonate and Sodium Citrate.

Buffering agents have not been comprehensively profiled in terms of their capacity to influence water retention prior to exercise. The purpose of this investigation was to profile the fluid retention characteristics of sodium bicarbonate (BIC) and sodium citrate (CIT) to determine the efficacy of these buffering mediums as hyperhydrating agents. Nineteen volunteers (13 males and six females; age = 28.3 ± 4.9 years) completed three trials (randomized and cross-over design). For each trial, a baseline measurement of body mass, capillary blood, and urine was collected prior to ingestion of their respective condition (control condition [CON] = 25 ml/kg artificially sweetened water; BIC condition = CON + 7.5 g/L of sodium in the form of BIC; CIT condition = CON + 7.5 g/L of sodium in the form of CIT). The fluid loads were consumed in four equal aliquots (0, 20, 40 and 60 min; fluid intake was 1.972 ± 361 ml [CON]; 1.977 ± 360 ml [BIC]; 1.953 ± 352 ml [CIT]). Samples were recorded at 20 (body mass and urine) and 60 min (blood) intervals for 180 min. Blood buffering capacity (HCO3-) was elevated (p < .001) in both BIC (32.1 ± 2.2 mmol/L) and CIT (28.9 ± 3.8 mmol/L) at 180 min compared with CON (25.1 ± 1.8 mmol/L). Plasma volume expansion was greater (p < .001) in both BIC (8.1 ± 1.3%) and CIT (5.9 ± 1.8%) compared with CON (-1.1 ± 1.4%); whereas, total urine production was lower in BIC and CIT at 180 min (BIC vs. CON, mean difference of 370 ± 85 ml; p < .001; CIT vs. CON, mean difference of 239 ± 102 ml; p = .05). There were no increases observed in body mass (p = .9). Under resting conditions, these data suggest BIC and CIT induce a greater plasma hypervolemic response as compared with water alone.

Considerations in interpreting neuromuscular state in elite level Australian Rules football players.

OBJECTIVES: Examine the influence of test modality, season stage, match load and physical qualities on the interpretation of neuromuscular function (NF) post Australian Rules Football (ARF) matches. DESIGN: Repeated measures design. METHODS: Thirty-two elite ARF players' NF was assessed 72h following competitive matches (7±2) via the counter movement jump (CMJ) and isometric mid-thigh pull (IMTP). Influence of season stage, external load parameters (GPS; 10Hz) and moderating influences of lower body strength (LBS), lower body power (LBP) and intermittent exercise capacity upon NF recovery were assessed using linear mixed effects models. RESULTS: Moderate negative seasonal trends were evident for both rate of force development (RFD) 0-100ms (d=-0.86, 95%, CI: ±0.57) and 0-200ms (d=-0.76, CI: ±0.64). Significant but trivial effects of match load were observed between one standardised unit increase in high speed running (HSR) versus CMJ: Force at zero velocity (d=0.12, CI: ±0.12), and sum of high intensity accelerations and CMJ: Eccentric deceleration RFD (d=-0.18, CI: ±0.14). Accounting for baseline LBS better explained (weight of evidence: W=87%) seasonal trends observed in IMTP: peak force, with lower LBS showing greater capacity for improvement. Positive moderating influences were observed with baseline LBS and LBP (W=91 & 75%) on CMJ: eccentric mean power responses to HSR, and CMJ: jump height responses to very-HSR, respectively. CONCLUSIONS: Interpretation of athlete NF responses is complicated by the inconsistent and interacting influence of contextual factors (assessment modality, stage of season, load), in-particular higher baseline LBS and LBP may improve acute load related responses of NF.

Determination of locomotor qualities in elite Australian Football: A pragmatic approach.

The study examined the utility of surrogate measures of athletic performance to determine locomotor qualities (maximal aerobic velocity and peak velocity) in elite Australian Football (AF). 29 professional AF players undertook aerobic fitness (3km time-trial [TT] and 30-15 Intermittent Fitness Test [30-15 IFT]) and peak velocity (PV; 50 m maximal sprints using 10Hz GPS) assessments in pre-season. Characteristics of TT performance (mean velocity, 500m and 1km splits) were compared with a surrogate for maximal aerobic velocity (MAV; 80% of 30-15 IFT final velocity). PVs derived from sprint tests were compared to those attained in AF matches (10 Hz GPS). Higher Pearson correlations were observed between MAV versus the fastest 500m (r = 0.74) and 1km (r = 0.75) of the 3km TT, but they were not superior to mean velocity (r = 0.72; p ≥ 0.30) which also demonstrated the lowest bias (p ≤ 0.01) and equivalent typical errors (0.16-0.17 m.s-1). Peak velocity was higher across match observations (0.28, CI: ± 0.17 m.s -1, p = 0.017) versus sprint tests. There was no impact of playing position on the determination of locomotor qualities using surrogate measures of locomotor qualities. Locomotor qualities can be determined practically using 10Hz GPS devices during 3km time-trials and competitive matches (assuming appropriate signal quality), without additional fitness assessments.

Effects of a Rugby League Match Simulation on Decision-Making in Elite Junior Rugby League.

ABSTRACT: Redman, K, Steel, K, Kelly, V, and Siegler, J. Effects of a rugby league match simulation on decision-making in elite junior rugby league. J Strength Cond Res 35(7): 1972-1980, 2021-The paucity of research on decision-making in Rugby league within the context of a match, and the potential for age and playing experience to influence decision-making ability, warrants further investigation. Therefore, the aim of this study was to determine the effects of a simulated rugby league match on decision-making in elite junior rugby league players. Twenty male junior rugby league players (age 15.9 ± 0.9 years, body mass 87.3 ± 14.3 kg, height 1.82 ± 0.07 m, playing experience 10.2 ± 2.4 years) completed a match simulation protocol that replicated the physiological demands of an elite junior rugby league match. Decision-making performance was measured prematch, midmatch, and postmatch simulation through a reactive agility test and video-based temporal occlusion task. Upper- and lower-body neuromuscular measures as well as ratings of perceived exertion were obtained before decision-making assessments to quantify fatigue. A 2-way mixed analysis of variance with Bonferroni corrections was used to assess changes during the simulation, and significance was accepted at p < 0.05. The main finding of this study was despite observing a decline in neuromuscular function during the match simulation protocol (countermovement jump declined 1.9 ± 0.6 cm [95% confidence intervals 0.4-3.5]; p < 0.05), this decline did not significantly affect decision-making performance (reactive agility test [p = 0.58]; temporal occlusion [p = 0.88]). These results suggest elite junior rugby league players are capable of sustaining performance during a progressively fatiguing match simulation.

The Impact of Individualizing Sodium Bicarbonate Supplementation Strategies on World-Class Rowing Performance.

Contemporary meta-analyses have generally demonstrated a positive effect of sodium bicarbonate (NaHCO3) supplementation on exercise performance. However, despite these claims, there is limited data on contrasting individualized and standardized timing of NaHCO3 ingestion prior to exercise to further enhance performance outcomes. Purpose: To determine whether NaHCO3 ingestion timing impacts 2,000-m rowing time-trial (TT) performance in elite-level rowers (Senior National team including Olympic/World Championships level) adhering to their own individualized pre-race strategies (e.g. nutrition, warm-up, etc.). Methods: Twenty three (n = 23) rowers across two research centers (using the exact same methods/protocols) completed three trials: NaHCO3 loading profile at rest to determine the individual's time-to-peak bicarbonate concentration [ HCO 3 - ], followed by two randomized 0.3 g·kgBM-1 NaHCO3 supplementation experimental trials conducted at different time points [consensus timing (CON): TT performed 60 min post-NaHCO3 ingestion; and individualized peak (IP): TT performed at the rower's individual peak [ HCO 3 - ] determined from the profiling trial post-NaHCO3 ingestion]. Results: There was a significant mean difference of +2.9 [± 0.4 mmol·L-1 HCO 3 - for IP vs. CON (95% CI 2.0 to 3.8 mmol·L-1); p = 0.02; d = 1.08] at pre warm-up, but not immediately prior to the TT (post warm-up). Performance times were significantly different between IP (367.0 ± 10.5 s) vs. CON (369.0 ± 10.3 s); p = 0.007; d = 0.15). Conclusions: The present study demonstrated a small but significant performance effect of an individualized NaHCO3 ingestion strategy. Similarities after warm-up between pre-TT sHCO 3 - values (CON ~ + 5.5 mmol·L-1; IP ~ + 6 mmol·L-1), however, would suggest this effect was not a result of any meaningful differences in blood alkalinity.

Use of Numerically Blinded Ratings of Perceived Exertion in Soccer: Assessing Concurrent and Construct Validity.

PURPOSE: To examine the concurrent and construct validity of numerically blinded ratings of perceived exertion (RPEs). METHODS: A total of 30 elite male youth soccer players (age 16.7 [0.5] y) were monitored during training and matches over a 17-wk in-season period. The players' external loads were determined via raw 10-Hz global positioning system. Heart rate (HR) was collected continuously and expressed as Bannister and Edwards training impulses, and minutes >80% of the players predetermined the maximum HR by the Yo-Yo Intermittent Recovery Test Level 1. RPE was collected confidentially 10 to 15 min after training/matches using 2 methods: (1) a traditional verbal response to the 0 to 100 category-ratio "centiMax" scale (RPE) and (2) numerically blinded RPE centiMax scale (RPEblind) with the response selected manually via a 5 × 7-in tablet "slider." The RPE and RPEblind were divided by 10 and multiplied by the duration to derive the sessional RPE. Linear mixed models compared ratings, and within-subject repeated-measures correlations assessed the sessional RPE versus HR and external load associations. RESULTS: There were no differences between the RPE and RPEblind (0.19; 95% confidence intervals, -0.59 to 0.20 au, P = .326) or their session values (13.5; 95% confidence intervals, -17.0 to 44.0 au, P = .386), and the ratings were nearly perfectly correlated (r = .96). The associations between the sessional RPE versus HR and external load metrics were large to very large (r = .65-.81), with no differences between the RPE methods (P ≥ .50). The RPEblind also reduced verbal anchor clustering and integer bias by 11% and 50%, respectively. CONCLUSIONS: RPEblind demonstrated concurrent and construct validity versus the traditional method, and may be used in situations where practitioners have concerns regarding the authenticity of athlete ratings.

Topical Sodium Bicarbonate: No Improvement in Blood Buffering Capacity or Exercise Performance.

PURPOSE: To assess the efficacy of a topical sodium bicarbonate (0.3 g/kg body weight NaHCO3) application (PR lotion; Amp Human) on blood buffering capacity and performance in recreationally active participants (study A) and moderately trained athletes (study B). METHODS: In Study A, 10 participants completed 2 experimental trials: oral NaHCO3 (0.3 g/kg body weight + placebo lotion) or PR lotion (0.9036 g/kg body weight + oral placebo) applied 90 minutes prior to a cycling task to exhaustion (30-s sprints at 120% peak power output with 30-s rest). Capillary blood was collected and analyzed for pH, bicarbonate, and lactate every 10 minutes throughout the 90-minute loading period and postexercise at 5, 10, and 15 minutes. In Study B, 10 cyclists/triathletes completed 2 experimental trials, applying either PR or placebo lotion 30 minutes prior to a cycling performance task (3 × 30-s maximal sprints with 90-s recovery). Capillary blood samples were collected at baseline, preexercise, and postexercise and analyzed as per study A. RESULTS: In Study A, pH and bicarbonate were significantly elevated from baseline after 10 minutes in the oral NaHCO3 condition and throughout recovery compared with no elevation in the PR lotion condition (P < .001). No differences in cycling time occurred between PR lotion (349 [119] s) and oral NaHCO3 (363 [80] s; P = .697). In Study B, no differences in blood parameters, mean power (P = .108), or peak power (P = .448) were observed between conditions. CONCLUSIONS: PR lotion was ineffective in altering blood buffering capacity or enhancing performance in either trained or untrained individuals.

Changes in the quadriceps spinal reflex pathway after repeated sprint cycling are not influenced by ischemic preconditioning.

PURPOSE: We examined the effect of ischemic preconditioning (IPC) on changes in muscle force, activation, and the spinal reflex pathway during and after repeated sprint cycling. METHODS: Eight recreationally active men (high-intensity cardiorespiratory training > 3 times per week, > 6 months) completed two exercise sessions (5 sets of 5 cycling sprints, 150% max W), preceded by either IPC (3 × 5 min leg occlusions at 220 mmHg) or SHAM (3 × 5 min at 20 mmHg). Knee extensor maximal force and rate of force were measured before (PRE), immediately post (POST), 1H, and 24H after cycling. Twitch interpolation and resting potentiated twitches were applied to estimate voluntary activation and muscle contractility, respectively. Quadriceps H-reflex recruitment curves were collected at all time-points using 10 Hz doublet stimulation to allow estimation of H-reflex post-activation depression. Surface electromyograms and tissue oxygenation (via near-infrared spectroscopy) were continuously recorded during cycling. RESULTS: IPC did not affect any measure of neuromuscular function or performance during cycling. Maximal force and muscle contractility were significantly lower at POST and 1H compared to PRE and 24H by up to 50% (p < 0.01). Maximal force was lower than PRE at 24H by 8.7% (p = 0.028). Voluntary activation and rate of force were unchanged. A rightwards shift was observed for the H-reflex recruitment curve POST, and post-activation depression was higher than all other time-points at 24H (p < 0.05). Muscle activation and oxygenation decreased during cycling. CONCLUSIONS: IPC has a nominal effect on mechanisms associated with neuromuscular function during and after exercise in healthy populations.

Changes in Fatigue Are the Same for Trained Men and Women after Resistance Exercise.

PURPOSE: To measure changes in fatigue and knee-extensor torque in the 48 h after trained men and women completed a full-body resistance exercise session. METHODS: Eight trained women (mean ± SD: age, 25.6 ± 5.9 yr; height, 1.68 ± 0.06 m; mass, 71.0 ± 8.6 kg) and eight trained men (age, 25.5 ± 6.2 yr; height, 1.79 ± 0.05 m; mass, 86.4 ± 9.8 kg) performed a full-body resistance exercise session based on real-world athletic practice. Measurements were performed before and after the exercise session, as well as 1, 24, and 48 h after the session. Fatigue and pain were measured with standardized self-report measures. Maximal isometric contractions with the knee extensors and superimposed femoral nerve stimulation were performed to examine maximal torque, rate of torque development, voluntary activation, and muscle contractility. Two sets of 10 isokinetic contractions (60°·s) with the knee extensors were performed during the protocol with use of near-infrared spectroscopy to assess muscle oxygenation. EMG were recorded from two quadriceps muscles during all isometric and isokinetic contractions. RESULTS: Fatigue was increased from baseline for both sexes until 48 h after training (P < 0.001). Maximal torque and evoked twitch amplitudes were similarly reduced after exercise for men and women (P < 0.001). Voluntary activation and EMG amplitudes were unchanged after the training session. Muscle oxygenation was 13.3% ± 17.4% (P = 0.005) greater for women during the isokinetic repetitions, and the values were unchanged after the training session. CONCLUSIONS: This is the first study to show similar changes in the fatigue reported by trained men and women in the 48 h after a training session involving full-body resistance exercises. Sex differences in muscle oxygenation during exercise do not influence the reductions in muscle force, activation, or contractility after the training session.