Test-Retest Reliability of Running Economy and Metabolic and Cardiorespiratory Parameters During a Multistage Incremental Treadmill Test in Male Middle- and Long-Distance Runners.

This study investigated the test-retest reliability of running economy (RE) and metabolic and cardiorespiratory parameters related to endurance running performance using a multistage incremental treadmill test. On two occasions separated by 21-28 days, 12 male middle- and long-distance runners ran at 10, 11, 12, 13, and 14 km/hr for 8 min each stage, immediately followed by a ramp test to volitional exhaustion. Carbohydrate (10% maltodextrin solution) was consumed before and during the test to provide ∼1 g/min of exercise. RE, minute ventilation (V˙E), oxygen consumption (V˙O2), carbon dioxide production (V˙CO2), respiratory exchange ratio (RER), heart rate (HR), ratings of perceived exertion (RPE), and blood glucose and lactate concentrations were recorded for each stage and at volitional exhaustion. Time-to-exhaustion (TTE) and peak oxygen consumption (V˙O2peak) during the ramp test were also recorded. Absolute reliability, calculated as the coefficient of variation (CV) between repeated measures, ranged from 2.3% to 3.1% for RE, whereas relative reliability, calculated as the intraclass correlation coefficient (ICC), ranged from .42 to .79. V˙E, V˙O2, V˙O2peak, V˙CO2, RER, and HR had a CV of 1.1%-4.3% across all stages. TTE and RPE had a CV of 7.2% and 2.3%-10.8%, respectively, while glucose and lactate had a CV of 4.0%-17.8%. All other parameters, except for blood glucose, were demonstrated to have good-to-excellent relative reliability assessed by ICC. Measures of RE, V˙O2peak, and TTE were reliable during this two-phase multistage incremental treadmill test in a cohort of trained and highly trained male middle- and long-distance runners.

Effects of 3 days of citrulline malate supplementation on short-duration repeated sprint running performance in male team sport athletes.

Citrulline malate (CM) is purported to be an ergogenic aid during various types of exercise performance. However, the effects of CM on repeated sprint performance (RSP) are under-explored. In a placebo-controlled, double-blind, counterbalanced cross-over design, male university-level team sport athletes (n = 13) performed two familiarization trials, after which CM or placebo (PLA) (8 × 1 g tablets each day) were taken on the 2 days prior to, and with breakfast on the morning of, each main experimental trial. The main experimental trials employed a RSP protocol consisting of 10 repetitions of 40 m maximal shuttle run test (MST) with a 30 s interval between the start of each sprint. Sprint times and heart rate were recorded throughout the MST, and blood lactate concentrations were measured before, immediately after, and 5 min after completing the MST. CM resulted in better RSP compared to PLA, as indicated by a lower sprint performance decrement (Sdec: CM, 4.68% ± 1.82% vs. PLA, 6.10% ± 1.83%; p = 0.03; ES = 0.77), which was possibly influenced by the fastest sprint time being faster in CM (CM, 8.16 ± 0.34 s vs. PLA, 8.29 ± 0.39 s; p = 0.011; ES = 0.34). There were no differences between CM and PLA in average sprint time (p = 0.54), slowest sprint time (p = 0.48), blood lactate concentrations (p = 0.73) or heart rate (p = 0.18), nor was there a condition × time interaction effect across the 10 sprints (p = 0.166). Three days of CM supplementation (8 g daily) attenuated the sprint performance decrement during short-duration high-intensity exercise in the form of running RSP in male university-level team sport athletes.

Exercise induces tissue-specific adaptations to enhance cardiometabolic health.

The risk associated with multiple cancers, cardiovascular disease, diabetes, and all-cause mortality is decreased in individuals who meet the current recommendations for physical activity. Therefore, regular exercise remains a cornerstone in the prevention and treatment of non-communicable diseases. An acute bout of exercise results in the coordinated interaction between multiple tissues to meet the increased energy demand of exercise. Over time, the associated metabolic stress of each individual exercise bout provides the basis for long-term adaptations across tissues, including the cardiovascular system, skeletal muscle, adipose tissue, liver, pancreas, gut, and brain. Therefore, regular exercise is associated with a plethora of benefits throughout the whole body, including improved cardiorespiratory fitness, physical function, and glycemic control. Overall, we summarize the exercise-induced adaptations that occur within multiple tissues and how they converge to ultimately improve cardiometabolic health.

Acute Ingestion of a Ketone Monoester without Co-ingestion of Carbohydrate Improves Running Economy in Male Endurance Runners.

PURPOSE: Acute ingestion of a ketone monoester, with and without co-ingestion of carbohydrate, was investigated for effects on running economy (RE), time to exhaustion (TTE), and other related indices of endurance running performance. METHODS: Using a three condition, placebo-controlled, randomized crossover design, 11 male middle- and long-distance runners ran at five submaximal speeds (10-14 km·h -1 ) on a motorized treadmill for 8 min each, immediately followed by a ramp test to volitional exhaustion. Participants consumed either a 10% carbohydrate solution (CHO), a 10% carbohydrate solution with 750 mg·kg -1 body mass of an ( R )-3-hydroxybutyl ( R )-3-hydroxybutyrate ketone monoester (CHO + KE), or 750 mg·kg -1 body mass of the ketone monoester in flavored water (KE) before (two-thirds of the dose) and during (one-third of the dose) exercise. RESULTS: ß-hydroxybutyrate concentration averaged 1.8 ± 0.3 and 2.1 ± 0.3 mM during exercise in CHO + KE and KE, respectively. RE was lower at each submaximal running speed (effect size = 0.48-0.98) by an average of 4.1% in KE compared with CHO, but not between CHO + KE and CHO. TTE did not differ between CHO (369 ± 116 s), CHO + KE (342 ± 99 s), or KE (333 ± 106 s) ( P = 0.093). CONCLUSIONS: Acute ingestion of a ketone monoester without carbohydrate, but not when coingested with carbohydrate, improved RE in middle- and long-distance runners at a range of submaximal running speeds and did not alter TTE in a short-duration ramp test to volitional exhaustion. Further investigation is required to examine if these differences translate into positive performance outcomes over longer durations of exercise.

The Effect of Hormonal Contraceptive Use on Skeletal Muscle Hypertrophy, Power and Strength Adaptations to Resistance Exercise Training: A Systematic Review and Multilevel Meta-analysis.

BACKGROUND: Resistance exercise training is widely used by general and athletic populations to increase skeletal muscle hypertrophy, power and strength. Endogenous sex hormones influence various bodily functions, including possibly exercise performance, and may influence adaptive changes in response to exercise training. Hormonal contraceptive (HC) use modulates the profile of endogenous sex hormones, and therefore, there is increasing interest in the impact, if any, of HC use on adaptive responses to resistance exercise training. OBJECTIVE: Our aim is to provide a quantitative synthesis of the effect of HC use on skeletal muscle hypertrophy, power and strength adaptations in response to resistance exercise training. METHODS: A systematic review with meta-analysis was conducted on experimental studies which directly compared skeletal muscle hypertrophy, power and strength adaptations following resistance exercise training in hormonal contraceptive users and non-users conducted before July 2023. The search using the online databases PUBMED, SPORTDiscus, Web of Science, Embase and other supplementary search strategies yielded 4669 articles, with 8 articles (54 effects and 325 participants) meeting the inclusion criteria. The methodological quality of the included studies was assessed using the "Tool for the assessment of study quality and reporting in exercise". RESULTS: All included studies investigated the influence of oral contraceptive pills (OCP), with no study including participants using other forms of HC. The articles were analysed using a meta-analytic multilevel maximum likelihood estimator model. The results indicate that OCP use does not have a significant effect on hypertrophy [0.01, 95% confidence interval (CI) [- 0.11, 0.13], t = 0.14, p = 0.90), power (- 0.04, 95% CI [- 0.93, 0.84], t = - 0.29, p = 0.80) or strength (0.10, 95% CI [- 0.08, 0.28], t = 1.48, p = 0.20). DISCUSSION: Based on the present analysis, there is no evidence-based rationale to advocate for or against the use of OCPs in females partaking in resistance exercise training to increase hypertrophy, power and/or strength. Rather, an individualised approach considering an individual's response to OCPs, their reasons for use and menstrual cycle history may be more appropriate. REGISTRATION: The review protocol was registered on PROSPERO (ID number and hyperlink: CRD42022365677).

A Ketone Monoester with Carbohydrate Improves Cognitive Measures Postexercise, but Not Performance in Trained Females.

PURPOSE: The acute ingestion of a ketone monoester with the coingestion of a carbohydrate (KME + CHO) compared with carbohydrate (CHO) was investigated on cycling performance and cognitive performance in trained females. METHODS: Using a two condition, placebo-controlled, double-blinded and crossover design, 12 trained females (mean ± SD: age, 23 ± 3 yr; height, 1.64 ± 0.08 m; mass, 65.2 ± 12.7 kg) completed a baseline assessment of cognitive performance (psychomotor vigilance testing (PVT), task switching, and incongruent flanker), followed by 6 × 5-min intervals at 40%, 45%, 50%, 55%, 60%, and 65% of their maximal power output (W max ) and then a 10-km time trial, concluding with the same assessments of cognitive performance. Participants consumed either 375 mg·kg -1 body mass of KME with a 6% CHO solution (1 g·min -1 of exercise) or CHO alone, across three boluses (50:25:25). RESULTS: Blood ß-hydroxybutyrate concentrations averaged 1.80 ± 0.07 and 0.13 ± 0.01 mM during exercise in KME + CHO and CHO, respectively. Blood glucose decreased after drink 1 of KME + CHO (~15%; P = 0.01) but not CHO, and lactate concentrations were lower in KME + CHO at 50%, 55%, 60%, and 65% W max (all P < 0.05) compared with CHO. Despite these changes, no differences were found between conditions for time trial finishing times (KME + CHO, 29.7 ± 5.7 min; CHO, 29.6 ± 5.7 min; P = 0.92). However, only KME + CHO resulted in increases in psychomotor vigilance testing speed (~4%; P = 0.01) and faster reaction times (~14%; P < 0.01), speed (~15%; P < 0.01), and correct responses (~13%; P = 0.03) in the incongruent flanker during posttesting compared with CHO. CONCLUSIONS: The acute ingestion of a KME + CHO elevated blood ß-hydroxybutyrate and lowered glucose and lactate across multiple time points during exercise compared with CHO. Although these changes did not affect physical performance, several markers of cognitive performance were improved by the addition of a KME in trained females.

Functional assays reflective of cancer hallmarks in BT-549 cells are not impacted by media supplemented with exercise-trained plasma.

NEW FINDINGS: What is the central question of this study? Little is known regarding the effects of media supplemented with resting plasma from exercise-trained individuals, despite the established bioactive effects of acutely exercised samples. Does media supplemented with resting plasma from endurance-trained, strength-trained or recreationally active controls impact hallmarks of cancer in BT-549 cells? What is the main finding and its importance? Supplementing media with plasma from these trained athletes did not impact proliferation, migration, invasion or anoikis resistance compared to plasma from recreationally-active controls. These findings suggest that 'anti-cancer' effects of exercise are not present in resting blood samples of exercise-trained individuals. ABSTRACT: Media supplemented with sera from acutely exercised men has been shown to have 'anti-cancer' effects on prostate and breast cancer cell lines. This study investigated whether media supplemented with plasma samples taken at rest (≥30 h since the most recent exercise session) from men who were endurance-trained (END), strength-trained (STR) or recreationally active controls (CON) impacted the results of four assays that mimic hallmarks of cancer (proliferation, migration, extracellular matrix invasion and anoikis resistance) in the BT-549 breast cancer cell line. Compared to control conditions of either serum-free media or fetal bovine serum as appropriate, BT-549 cells cultured with plasma-supplemented media regardless of group resulted in greater cell proliferation (∼20-50%) and cell migration (∼15-20%), and lower extracellular matrix invasion (∼10-20%) and anoikis resistance (∼15-20%). Supplementing media with plasma from END or STR did not impact any outcomes of these assays compared to plasma from CON. Media supplemented with human plasma can impact functional assays reflective of cancer hallmarks in BT-549 cells, but effects of exercise on proliferation, migration, extracellular matrix invasion and anoikis resistance were not evident in resting blood samples of individuals with a prior history of exercise training.

The separation and identification of circulating small extracellular vesicles from endurance-trained, strength-trained and recreationally active men.

Small extracellular vesicles (EV) are membrane-encapsulated particles that carry bioactive cargoes, are released by all cell types and are present in all human biofluids. Changes in EV profiles and abundance occur in response to acute exercise, but this study investigated whether individuals with divergent histories of exercise training (recreationally active controls - CON; endurance-trained - END; strength-trained - STR) presented with varied abundances of small EVs in resting samples and whether the abundance of small EVs differed within each group across two measurement days. Participants (n = 38, all male; CON n = 12, END n = 13, STR n = 13) arrived at the lab on two separate occasions in a rested, overnight fasted state, with standardisation of time of day of sampling, recent dietary intake, time since last meal and time since last exercise training session (∼40 h). Whole blood samples were collected and separated into plasma from which small EVs were separated using size exclusion chromatography and identified in accordance with the Minimal Information For Studies of Extracellular Vesicles (MISEV) guidelines. No differences in the abundance of small EVs were observed within or between groups across multiple methods of small EV identification (nanoparticle tracking analysis, flow cytometry, immunoblot of specific EV markers). Targeted metabolomics of the small EV preparations identified 96 metabolites that were associated with the structure and function of small EVs, with no statistically significant differences in concentrations observed across groups. The results of the current study suggest that the abundance and metabolomic profile of small EVs derived from men with divergent histories of exercise training are similar to those in resting blood samples. KEY POINTS: Extracellular vesicles (EV) are membrane-encapsulated particles that are present in circulation and carry bioactive materials as 'cargo'. The abundance and profile of small EVs are responsive to acute exercise, but little is known about the relationship between small EVs and exercise training. This study examined the abundance, and a targeted metabolomic profile, of small EVs separated from the blood of endurance athletes, strength athletes and recreationally active controls at rest (∼40 h after the most recent exercise session) on two separate but identical lab visits. No differences were observed in the abundance or metabolomic profile of small EV preparations between the groups or between the lab visits within each group. Further research should determine whether the bioactive cargoes (e.g. RNA, protein and additional metabolites) carried within EVs are altered in individuals with divergent histories of exercise training or in response to exercise training interventions.

Prevalence and determinants of sarcopenia in community-dwelling older adults in Ireland.

BACKGROUND: Data on the prevalence of sarcopenia among older adults in Ireland are lacking. AIMS: To assess the prevalence and determinants of sarcopenia among community-dwelling older adults in Ireland. METHODS: This cross-sectional analysis involved n = 308 community-dwelling adults aged ≥ 65 y living in Ireland. Participants were recruited via recreational clubs and primary healthcare services. Sarcopenia was defined according to the 2019 European Working Group on Sarcopenia in Older People (EWGSOP2) criteria. Skeletal muscle mass was estimated using bioelectrical impedance analysis, strength was measured via handgrip dynamometry, and physical performance was assessed using the Short Physical Performance Battery. Detailed information was collected on demographics, health, and lifestyle. Dietary macronutrient intake was measured via a single 24 h recall. Binary logistic regression was used to examine potential demographic, health, lifestyle, and dietary determinants of sarcopenia (where both probable and confirmed sarcopenia were combined). RESULTS: The prevalence of EWGSOP2-defined probable sarcopenia was 20.8% and confirmed sarcopenia was 8.1% (5.8% had severe sarcopenia). Polypharmacy (OR 2.60, 95% confidence interval [CI] 1.3, 5.23), height (OR 0.95, 95% CI 0.91, 0.98), and Instrumental Activities Of Daily Living (IADL) score (OR 0.71, 95% CI 0.59, 0.86) were independently associated with sarcopenia (probable and confirmed combined). There were no independent associations between energy-adjusted macronutrient intakes, as determined by 24 h recall, and sarcopenia. CONCLUSION: Sarcopenia prevalence within this sample of community-dwelling older adults in Ireland is broadly similar to other European cohorts. Polypharmacy, lower height, and lower IADL score were independently associated with EWGSOP2-defined sarcopenia.

Physical Match Demands of International Women's Rugby Union: A Three-Year Longitudinal Analysis of a Team Competing in The Women's Six Nations Championship.

There is a paucity of studies describing the physical match demands of elite international women's rugby union, which limits coaches' ability to effectively prepare players for the physical demands required to compete at the elite level. Global positioning system technologies were used to measure the physical match demands of 53 international female rugby union players during three consecutive Women's Six Nations Championships (2020-2022), resulting in 260 individual match performances. Mixed-linear modelling was used to investigate differences in physical match demands between positions. Significant effects (p < 0.05) of the position were observed for all variables, with the exception of relative distances (m.min-1) at velocities of 1.01-3.00 m·s-1 (p = 0.094) and 3.01-5.00 m·s-1 (p = 0.216). This study provides valuable data on the physical match demands of elite international women's rugby union match play that may aid practitioners in the physical preparation of players to compete at this level. Training methodologies for elite-level female rugby union players should consider the unique demands across positional groups with specific considerations of high-velocity running and collision frequency.

Within-Subject Variability and the Influence of Exercise Training History on the Resting Plasma Metabolome in Men.

This study investigated within-subject variability in the circulating metabolome under controlled conditions, and whether divergent exercise training backgrounds were associated with alterations in the circulating metabolome assessed in resting samples. Thirty-seven men comprising of endurance athletes (END; body mass, 71.0 ± 6.8 kg; fat-free mass index, 16.9 ± 1.1 kg/m2), strength athletes (STR; 94.5 ± 8.8 kg; 23.0 ± 1.8 kg/m2), and recreationally active controls (CON; 77.6 ± 7.7 kg; 18.1 ± 1.0 kg/m2) provided blood samples after an overnight fast on two separate occasions controlled for time of day of sampling, recent dietary intake, time since last meal, and time since last exercise training session. A targeted profile of metabolites, performed using liquid chromatography and mass spectrometry on plasma samples, identified 166 individual metabolites and metabolite features, which were analyzed with intraclass correlation coefficients, a multilevel principal component analysis, and univariate t tests adjusted for multiple comparisons. The median intraclass correlation coefficient was .49, with 46 metabolites displaying good reliability and 31 metabolites displaying excellent reliability. No difference in the abundance of any individual metabolite was identified within groups when compared between visits, but a combined total of 44 metabolites were significantly different (false discovery rate <0.05) between groups (END vs. CON, 42 metabolites; STR vs. CON, 10 metabolites; and END vs. STR, five metabolites). Under similar measurement conditions, the reliability of resting plasma metabolite concentrations varies largely at the level of individual metabolites with ∼48% of metabolites displaying good-to-excellent reliability. However, a history of exercise training was associated with alterations in the abundance of ∼28% of metabolites in the targeted profile employed in this study.

Prevalence of hormonal contraceptive use and reported side effects of the menstrual cycle and hormonal contraceptive use in powerlifting and rugby.

OBJECTIVES: The prevalence of hormonal contraceptive (HC) use and the associated symptomology of use or nonuse are under-studied in athletic populations, and in particular, in strength and collision sports. This study aimed to investigate the prevalence of hormonal contraceptive use and reported side effects of the menstrual cycle and hormonal contraceptive use in powerlifters and rugby players. METHODS: Competitive female powerlifters and rugby players (aged ≥18 y), representing a strength and a collision sport respectively, completed an anonymous online questionnaire for the purpose of assessing self-reported prevalence of HC use, and symptoms of the menstrual cycle and HC use. Athletes were categorized by sport (powerlifters, n = 149; rugby players, n = 135) in order to conduct a stratified analysis. For open-ended questions, a content analysis was conducted to categorize responses, and frequency analyses were performed. RESULTS: Current HC use was reported by 51.1% of athletes, with similar prevalence for the two sports (powerlifting, 48.3% vs. rugby, 54.1%, P = 0.34). Side effects of the menstrual cycle were reported in 83.5% of non-HC users, with the most common being unspecified cramping (42.4%), headache/migraine (24.5%), and fatigue (24.5%). Side effects were reported in 40.0% of HC users, with the most common being mood changes (17.9%), stomach pain (8.3%) and headaches/migraines (6.9%). CONCLUSION: A large proportion of HC users and nonusers in this study experience negative side effects of HC use and the menstrual cycle, respectively. The symptoms experienced by both groups are wide-ranging, with a high degree of variation between individuals. The negative side-effects experienced by HC users and nonusers may have an influence on athletic performance, and this requires future investigation.

Increased Lean Body Mass After Bodyweight-Based High Intensity Interval Training in Overweight and Obese Men.

Purpose: The effects of 8 weeks of bodyweight exercise-based, high-intensity interval training (BWHIIT) on body composition and blood-based markers of metabolic health were investigated in overweight and obese, sedentary young men. Methods: In a parallel group, PRE-POST design, n = 30 men (age, 25.7 ± 4.3 y; body mass index, 27.7 ± 2.1 kg m-2; 26.1 ± 5.2% body fat) were randomized to BWHIIT (n = 20) or a control group (CON; n = 10). BWHIIT consisted of supervised, group-based training sessions (~30 minutes) performed 3 times weekly. Each session consisted of 6 high-intensity bodyweight-based exercises, with each exercise being performed for 4 minutes in the manner of 8 sets of 20 seconds of exercise, 10 seconds of rest. Prior to commencing training (PRE), and 36 h after the final training session (POST), an overnight fasted blood sample was drawn, and body composition was assessed by dual-energy X-ray absorptiometry. Eighteen participants completed the intervention (CON, n = 9; BWHIIT, n = 9). Results: Lean body mass (LBM) was increased at POST in BWHIIT compared to CON (P = .011, η2p = .359), with the mean (95% confidence limits) increase in LBM from PRE to POST within BWHIIT being 1.23 (0.55, 1.92) kg. Body mass and fat mass were unchanged in both groups from PRE to POST. BWHIIT had no effect on serum concentrations of total cholesterol, HDL-C, LDL-C, triglycerides, NEFA, hsCRP, or glucose. Conclusion: Eight weeks of bodyweight exercise-based high intensity interval training by overweight and obese sedentary young men increased LBM by ~2%, but fat mass and blood-based markers of metabolic health were unchanged.

Dietary Intakes and the Risk of Low Energy Availability in Male and Female Advanced and Elite Rock Climbers.

ABSTRACT: Monedero, J, Duff, C, and Egan, B. Dietary intakes and the risk of low energy availability in male and female advanced and elite rock climbers. J Strength Cond Res 37(3): e8-e15, 2023-There is a culture among rock climbers of striving to maintain low body mass and percentage body fat to enhance performance. Diet practices based on this belief might lead to increased risk of low energy availability (LEA) or eating disorders (EDs). Twenty-five advanced or elite rock climbers (male, n = 14; female, n = 11) had body composition measured, completed 4-day food intake and physical activity diaries while wearing an accelerometer and heart rate monitor, and completed the Eating Attitudes Test (EAT)-26 and the Low Energy Availability in Females Questionnaire (LEAF-Q; n = 11 female subjects only). EAT-26 scores of 3.5 (1.8, 7.0) [median (IQR)] and 9.3 ± 6.4 (mean ± SD ) for male and female subjects, respectively, indicated low risk of ED in this cohort, but 4 female subjects were at high risk of LEA according to LEAF-Q scores. Suboptimal (<45 kcal·kg·FFM -1 ·d -1 ) and LEA (<30 kcal·kg·FFM -1 ·d -1 ) were evident in 88 and 28%, respectively, of climbers. However, only the female climbers had energy intakes (1775 ± 351 kcal·d -1 ) significantly lower than their calculated energy requirements (2056 ± 254 kcal·d -1 ; p = 0.006). In all subjects, carbohydrate intakes were lower (male subjects: 3.8 ± 1.2 g·kg -1 ·d -1 , p = 0.002; female subjects: 3.4 ± 0.7 g·kg -1 ·d -1 , p < 0.001), and fat intakes were higher (male subjects: 1.6 ± 0.5 g·kg -1 ·d -1 , p < 0.001; female subjects: 1.4 ± 0.4 g·kg -1 ·day -1 , p < 0.001) than current sports nutrition recommendations, and inadequate intakes of calcium, magnesium, and vitamin D were observed. Female subjects specifically had lower than recommended intakes of protein and iron. These results show that advanced and elite rock climbers have a high prevalence of LEA and have a risk of having nutritional deficiencies as result of their diet.

The Priming Effect of a Heavy or Very Heavy Resisted Sled Sprint-Based Conditioning Activity on Subsequent Unresisted Sprint Performance in Team Field Sport Athletes.

ABSTRACT: Monahan, M and Egan, B. The priming effect of a heavy or very heavy resisted sled sprint-based conditioning activity on subsequent unresisted sprint performance in team field sport athletes. J Strength Cond Res 37(1): 91-97, 2023-The effect of resisted sled sprinting (RSS) on postactivation performance enhancement (PAPE) was investigated in team field sport athletes (n = 28; m and female, 15 and 13; age, 22.1 ± 2.5 years; height, 1.77 ± 0.11 m; body mass [BM], 75.1 ± 16.4 kg). After a standardized warm-up, unresisted sprint (URS) performance was measured over 10- and 20-m (PRE) followed by a conditioning activity (CA) consisting of 3 × 20 m RSS. Unresisted sprint performance was then measured again at 30 seconds and 4, 8, 12, 16, 20, and 24 minutes after CA. The effect of heavy (H-RSS) or very heavy (VH-RSS) sled loads were compared during 2 separate visits using a randomized crossover design. Heavy-resisted sled sprinting and VH-RSS loads corresponded to a velocity decrement (Vdec) of 17.3 ± 3.6%Vdec (20.0 ± 2.3%BM) and 52.9 ± 3.8%Vdec (64.3 ± 7.0%BM), respectively. Unresisted sprint performance after CA was slower than PRE over 10- and 20-m (both p < 0.001 for time). The decline in URS performance over 20-m was greater in VH-RSS (time × sled load interaction, p = 0.033). However, after extraction of the fastest sprint times after CA, the fastest sprint time for 10-m improved after H-RSS by 0.026 (0.001, 0.050) seconds (p = 0.040; d = 0.21) but not after VH-RSS (p = 0.054; d = 0.14). The fastest sprint times for 20-m were similar to PRE after H-RSS and VH-RSS. No sex-specific differences were observed. Given the high intersubject variability in the magnitude of improvement, and for the time point at which the fastest sprint occurred, there remains questionable practical value to an RSS-based CA as a means to induce a PAPE for URS performance.

The resting serum metabolome in response to short-term sprint interval training.

PURPOSE: To investigate the response of a targeted fraction of (168 metabolites) of the resting serum metabolome to 9 sessions of sprint interval training (SIT). METHODS: Thirty-four recreationally active males provided resting blood samples before (baseline) and 48-72 h after (post) a short-term (9 sessions) cycle ergometer-based SIT intervention. A targeted analysis of 168 metabolites was performed on serum using liquid chromatography mass spectrometry (LC-MS). 160 distinct metabolites were identified and combined with 4 calculated metabolite sums and 3 calculated metabolite ratios creating a panel of 167 individual factors. Data were analysed using principal component analysis and univariate testing of all factors classified into 5 metabolite subgroups. RESULTS: SIT improved anaerobic capacity measured by average power output during a Wingate test (p < 0.01; mean difference = 38 W, 95% confidence interval [26, 51]) and aerobic capacity measured by average power output in a 20 min cycling test (p < 0.01; 17 W [12, 23]). Limited separation was discernible in the targeted serum metabolome between baseline and post-intervention when projected on the first and second principal component(s). However, univariate testing identified 11 fatty acids that had lower concentrations (false discovery rate < 0.05) in post-intervention samples. CONCLUSIONS: These findings demonstrate that this short-term SIT intervention had limited effect on the serum metabolome at rest, but a subfraction of fatty acids are potentially sensitive to short-term exercise training.

Molecular responses to acute exercise and their relevance for adaptations in skeletal muscle to exercise training.

Repeated, episodic bouts of skeletal muscle contraction undertaken frequently as structured exercise training are a potent stimulus for physiological adaptation in many organs. Specifically, in skeletal muscle, remarkable plasticity is demonstrated by the remodeling of muscle structure and function in terms of muscular size, force, endurance, and contractile velocity as a result of the functional demands induced by various types of exercise training. This plasticity, and the mechanistic basis for adaptations to skeletal muscle in response to exercise training, are underpinned by activation and/or repression of molecular pathways and processes in response to each individual acute exercise session. These pathways include the transduction of signals arising from neuronal, mechanical, metabolic, and hormonal stimuli through complex signal transduction networks, which are linked to a myriad of effector proteins involved in the regulation of pre- and posttranscriptional processes, and protein translation and degradation processes. This review therefore describes acute exercise-induced signal transduction and the molecular responses to acute exercise in skeletal muscle including emerging concepts such as epigenetic pre- and posttranscriptional regulation and the regulation of protein translation and degradation. A critical appraisal of methodological approaches and the current state of knowledge informs a series of recommendations offered as future directions in the field.

Exogenous Ketone Supplements in Athletic Contexts: Past, Present, and Future.

The ketone bodies acetoacetate (AcAc) and ß-hydroxybutyrate (ßHB) have pleiotropic effects in multiple organs including brain, heart, and skeletal muscle by serving as an alternative substrate for energy provision, and by modulating inflammation, oxidative stress, catabolic processes, and gene expression. Of particular relevance to athletes are the metabolic actions of ketone bodies to alter substrate utilisation through attenuating glucose utilisation in peripheral tissues, anti-lipolytic effects on adipose tissue, and attenuation of proteolysis in skeletal muscle. There has been long-standing interest in the development of ingestible forms of ketone bodies that has recently resulted in the commercial availability of exogenous ketone supplements (EKS). These supplements in the form of ketone salts and ketone esters, in addition to ketogenic compounds such as 1,3-butanediol and medium chain triglycerides, facilitate an acute transient increase in circulating AcAc and ßHB concentrations, which has been termed 'acute nutritional ketosis' or 'intermittent exogenous ketosis'. Some studies have suggested beneficial effects of EKS to endurance performance, recovery, and overreaching, although many studies have failed to observe benefits of acute nutritional ketosis on performance or recovery. The present review explores the rationale and historical development of EKS, the mechanistic basis for their proposed effects, both positive and negative, and evidence to date for their effects on exercise performance and recovery outcomes before concluding with a discussion of methodological considerations and future directions in this field.

Physiological and Perceptual Responses to a Single Session of Resisted Sled Sprint Training at Light or Heavy Sled Loads.

ABSTRACT: Monahan, M, Petrakos, G, and Egan, B. Physiological and perceptual responses to a single session of resisted sled sprint training at light or heavy sled loads. J Strength Cond Res 36(10): 2733-2740, 2022-The acute physiological and perceptual responses to a single session of resisted sled sprint (RSS) training are largely unexplored, nor have differences, if any, between male and female athletes been compared. Team field sport athletes (n = 27; male/female, 15/12; 21.1 ± 2.7 years) were assessed for Maximal Resisted Sled Load (MRSL) from which light (L-RSS, 30%MRSL) and heavy (H-RSS, 80%MRSL) sled loads were prescribed. On separate occasions in random order, 2 training sessions of 12 × 20 m RSS repetitions at either L- or H-RSS were performed, and assessments of physiological and perceptual responses were performed before (PRE), during, after (POST) and 24 hours after (+24 hours POST) each session. Compared to unresisted sprints, velocity decrements of 7.5 ± 2.2 and 22.7 ± 8.1% were produced by L-RSS and H-RSS, respectively. Heart rate, blood lactate, and ratings of perceived exertion were higher in H-RSS compared to L-RSS. Decrements in 20 m sprint and countermovement jump performance observed at POST had returned to PRE values at +24 hours POST. Except for a higher heart rate (∼7-12 b·min-1) in females during the respective sessions, responses to L- and H-RSS were generally similar between males and females. A single session of heavy RSS training is more demanding than light RSS training when matched for sprint number and distance, but measures of lower limb power and sprint performance return to pre-training levels within 24 hours regardless of sled load. Males and females respond similarly to a single session of RSS training when individualized, relative intensity sled loads are prescribed.