Intermittent Running Research Articles

A comparative analysis of physical fitness characteristics and rugby-specific game skills of schoolboy players by playing standards: Implications for talent identification programs in resource-constrained settings

Background: Rugby has not grown extensively in Africa compared to other continents, necessitating talent identification (TID) programs to recruit junior talent. However, it is unclear which physical characteristics and rugby-specific game skills to base the objective recruitment of potentially talented young players. Objectives: This study profiled the physical fitness characteristics and rugby-specific game skills of schoolboy rugby players by playing standards to identify variables differentiating elite from sub-elite players from Under 16 (U16) to U19 age categories. The study further compared Zimbabwean cohort data with similar data from international/regional countries. Methods: A cross-sectional design was utilised with 158 Zimbabwean schoolboy players playing competitive (elite) and non-competitive (sub-elite) rugby. The participants were measured for anthropometrics, speed, agility, upper-and-lower-muscular strength/power, muscle flexibility, prolonged high-intensity intermittent running ability, repeated high-intensity exercise performance ability, tackling, passing, and catching abilities. Results: For U16s, Vertical Jump (VJ), 2kg Medicine Ball Chest Throw (2kg MBCT), Wall-Sit-Leg Strength (WSLS), Yo-Yo Intermittent Recovery Level 1 (Yo-Yo IRL1), Tackling and Catching Ability tests discriminated elite from sub-elite players. Among U19s, the following tests differentiated elite from sub-elite players: VJ, 2kg MBCT, WSLS, 20-m/40-m linear speed, 60-s Push Up, One-Repetition Maximum Back Squat (IRM BS), 1RM Bench Press (BP), Repeated High-Intensity Exercise (RHIE), Tackling and Passing Ability. Elite Zimbabwean schoolboy rugby players were significantly leaner, slower, and “weaker” than their international/regional counterparts. Conclusion: The results suggest important physical fitness characteristics and rugby-specific game skills for future identification of potentially talented players at U16/U19 categories.

Effects of high-intensity intermittent cross-training on maximal oxygen uptake

We investigated the effects of high-intensity intermittent cross-training (HIICT) on maximal oxygen uptake (・VO2max). The HIICT consisted of alternating intermittent 20-s treadmill running (1st, 3rd, 5th, and 7th bouts) and 20-s bicycle exercise (2nd, 4th, and 6th bouts) with a 10-s rest period. Each intensity for running and bicycling of the HIICT corresponded to an oxygen demand of ∼160% and ∼170% of the O2max, respectively. Fifteen healthy young males (aged [24 ± 1] yrs) were randomly assigned to training (TG, n = 8) and non-training control (CG, n = 7) groups. The TG completed this HIICT daily 4 days/week for 6 weeks. Significant group × time interactions were observed for both the running and bicycling O2max (p < 0.001 each). After the training, the ・VO2max for both running ([57.4 ± 4.8] mL·kg−1·min−1) and bicycling ([50.6 ± 3.7] mL·kg−1·min−1) in the TG were significantly higher than those for running ( [50.1 ± 3.1] mL·kg−1·min−1) and bicycling ( [43.7 ± 3.6] mL·kg−1·min−1) in the CG, respectively (p < 0.01 each). Post-hoc tests revealed a significant increase in ・VO2max for running and bicycling in the TG after the HIICT (p < 0.001 each) but no significant difference in the CG. These results demonstrated that the newly developed HIICT increases the ・VO2max for both running and bicycling.

The Effect of a Synthetic-Grass Sport Surface on Physiology and Perception During Intermittent Exercise in Hot Conditions.

The current study aimed to determine the effect of a synthetic-grass sport surface on core body temperature, skin temperature, heart rate, thermal sensation, thermal comfort, and rating of perceived exertion (RPE)during intermittent exercise in hot conditions. Using a randomized crossover design, 13 trained/developmental team-sport athletes completed two 50-minute standardized intermittent running protocols on a synthetic and anatural-grass surface, on separate days (control-condition air temperature 32.6 °C [1.3 °C], relative humidity 43.2% [5.3%]). Final skin temperature was significantly higher on synthetic compared with natural grass at the calf (40.1 °C [2.5 °C] vs 33.4 °C [0.6 °C]; P < .001), shoulder (36.6 °C [1.7 °C] vs 33.7 °C [0.7 °C]; P < .001), and chest (33.2 °C [1.1 °C] vs 31.8 °C [1.2 °C]; P = .02). Thermal sensation (median: 2.3; interquartile range [0.5] vs 2.2 [0.5], P = .03) and sweat rate (1.5 [0.4]L·h-1 vs 1.2 [0.3]L·h-1; P = .02) were also significantly higher on synthetic grass. While final core body temperature was significantly higher on the natural than synthetic grass (38.4 °C [0.3 °C] vs 38.2 °C [0.4 °C]),there were no significant differences in delta core temperature, as well as heart rate, thermal comfort, or RPE. Higher skin temperatures, thermal sensation, and sweat rates suggest that exercising on synthetic grass in hot conditions may increase some markers of heat strain during exercise. However, delta core body temperature, heart rate, thermal comfort, and RPE remained unaffected.

Effects of a Single Dose of Dietary Nitrate via Beetroot Crystals on High-Intensity Intermittent Exercise Performance in Recreational Collegiate Athletes

Abstract: Endurance and high-intensity intermittent exercise are paramount in the pursuit of optimal athletic performance. Nitrate (NO₃⁻) supplementation has emerged as a promising avenue for enhancing these aspects. Prior studies underscore the beneficial role of nitrate supplementation in augmenting endurance and high-intensity intermittent exercise. The current study probes the immediate effects of nitrate supplementation, specifically beetroot crystals (BRC), on high-intensity intermittent running performance in recreational collegiate athletes. In a randomized, cross-over, placebo-controlled, double-blind investigation, fourteen male athletes consumed either an acute dose of BRC (25 g·day⁻¹, containing ~8.1 mmol of NO₃⁻) or a placebo (PLA; 25 g·day⁻¹ of maltodextrin) 1.5 hours prior to undergoing a high-intensity intermittent exercise test in a controlled laboratory setting. Results elucidated that BRC supplementation improved high-intensity intermittent exercise performance (BRC: 270.5 ± 138.5 s vs. PLA: 231.7 ± 141.5 s; p &lt; 0.05) and elevated plasma NO₃⁻ and NO₂⁻ concentrations compared to the placebo group (p &lt; 0.05). Nonetheless, blood pressure, muscle oxygenation, plasma lactate, and glucose levels did not reveal any significant differences (p &gt; 0.05). Crucially, this study stands as the first to identify BRC as a significant enhancer of intermittent cycling performance in a controlled laboratory setting. These findings underscore the potential of acute BRC supplementation in boosting high-intensity intermittent exercise performance in recreational collegiate athletes, thereby prompting further investigation into its potential usage in sports and exercise scenarios. Keywords: endurance exercise, ergogenic aids, nitric oxide, recreational sports

Exploring the ergogenic potential of carbohydrate-caffeine combined mouth rinse on exercise and cognitive performance: a systematic review.

Carbohydrate (CHO) and caffeine (CAF) mouth rinsing have been independently reported to benefit sport performance. The proposed mechanisms by which mouth rinsing CHO exerts an influence are reported to be different from those for mouth rinsing CAF. However, the potential ergogenic effects of combining CHO and CAF in a single mouth rinse solution, are unclear. This study aimed to review the available evidence of CHO-CAF combined mouth rinse on exercise and cognitive performance in human participants. A systematic literature search was conducted using five databases until April 2024, following the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) recommendations. Among the nine randomized crossover studies included, only one study showed significant improvements in lower-body muscular endurance with CHO-CAF mouth rinse (effect size (ES): 0.48; p<0.05), while two studies reported non-statistically significant improvements in repeated sprint performance compared to other mouth rinse and placebo conditions (ES: 0.20-0.81; p=0.07-0.18). However, for other performance measures, including repeated jumps, upper-body strength and endurance, endurance cycling, and intermittent recovery run, most evidence (five studies) did not demonstrate significant ergogenic effects. Notably, of the two studies that examined cognitive performance, both reported significant improvements with CHO-CAF mouth rinse compared with the placebo condition (ES: 0.45-3.45; p<0.05). Overall, a synergistic influence of CHO-CAF mouth rinse on physical exercise performance is not evident, but preliminary evidence suggests potential benefits on cognitive performance. Future studies are required to address various methodological issues identified in this review, while practitioners and athletes should exercise caution when considering this novel nutritional strategy.

Microfluidic fabrication of compound microfibers encapsulating nano-enhanced phase change material (PCM) for thermal regulation

This study presents a microfluidic approach for fabrication of compound phase change fibers (CPCFs) encapsulating nano-enhanced phase change material (PCM), RT25, for thermal regulation. The produced fibers are flexible and have strong compatibility and durable stability, with their size and the proportion of PCM can be precisely controlled by the microfluidic approach. Especially, a hydroxy surface modification method was used to uniformly disperse SiO2 nanoparticles into the RT25, aiming to enhance the thermal regulation performance of the CPCFs. Thermal performance test was conducted and it indicated that, compared with the compound phase change fiber (CPCF) with pure RT25, the CPCF incorporated with 2 wt% SiO2 nanoparticles presented a notable increase in thermal conductivity by 46.52 % and 45.51 % for solid-state and liquid-state enclosed PCM with a limited reduction in both melting and solidification enthalpies by 9.21 % and 10.1 %, respectively. Moreover, an experiment simulating the heat dissipation scenario of the electronic cabinet under intermittent running with short operation and long rest was conducted by using the CPCFs. It showed that adding SiO2 nanoparticles can improve the heat absorption process (solid-to-liquid phase) via the CPCFs with a smaller temperature increase (i.e., the maximum temperature of simulated inner electronic device in the cabinet for the repeated intermittent running) and it is also able to make the CPCFs renew (liquid-to-solid phase) more quickly and ready for heat absorption process in the next cycle. These CPCFs offer a promising alternative for more efficient and sustainable thermal management of the electrical/electronic equipment.

The effect of a combined cooling intervention on cognitive function in the heat during an intermittent running protocol.

Despite optimal cognitive function being essential for performance, there is a lack of research on the effectiveness of combined cooling interventions on team sport athlete's cognitive function when exercising in the heat. In a randomised, crossover design, 12 unacclimatised men (age: 22.3±3.0years, body mass: 73.4±5.1kg, height: 181.0±5.3cm and max: 51.2±9.5mL/kg/min) participated in a control (CON) and combined cooling trial (ice slurry and ice collar; COOL). A battery of cognitive tests were completed prior to, during (at half-time) and following a 90-min intermittent running protocol in the heat (33°C, 50% relative humidity (RH)). Perceptual and physiological measures were taken throughout the protocol. In CON, response times were quicker on the Stroop task complex level (p=0.002) and the visual search test complex level at full-time (p=0.014) compared to COOL. During COOL, response times were quicker at half-time on the Stroop task complex level (p=0.024) compared to CON. Lower rectal temperatures were seen during COOL (CON: 37.44±0.65°C and COOL: 37.28±0.68°C) as well as lower skin, neck and forehead temperatures (main effect of trial, all p<0.05). Lower ratings of thermal sensation and perceived exertion and enhanced thermal comfort were recorded during COOL (main effect of trial, all p<0.05). Whilst minimal differences in cognitive function were found when using the combined cooling intervention, the findings highlight a practical and effective strategy to improving many physiological and perceptual responses to intermittent exercise in the heat.

Adaptive cognitive tasks for mental fatigue: An innovative paradigm for cognitive loading in human performance

ObjectivesMental fatigue (MF) can impair cognitive and physical performance in sport. We tested the hypothesis that a shorter adaptive Time Load Dual Back (TLDB) task induces MF faster than a longer Stroop; and subsequently impairs cognitive and intermittent running performance. DesignThis study employed a randomized within-participant design. Methods25 trained individuals performed a Yo-Yo test after one of four experimental conditions (30-min Stroop, 20-min and 10-min TLDB tasks, and active control). Cognitive performance was assessed using the Psychomotor Vigilance Task (PVT) before and after the experimental conditions. Measures of mood, workload, MF, RPE, heart rate (HR), heart rate variability (HRV) and blood lactate were collected. ANOVAs determined the effect of the 4 conditions. ResultsStroop and 20-min TLDB conditions impaired running performance similarly (p = .015), while no differences are reported for 10-min TLDB and Control. No significant differences in physiological parameters were reported during the Yo-Yo test although RPE was significantly higher in the Stroop and 20-min TLDB conditions (p = .014). Stroop and both TLDBs conditions impaired PVT's cognitive performance (p = .029), MF (p = .012), mental demand (p < .001), HR (p = .021) and HRV (p = .033); with 20-min TLDB task having the higher significant impact. Mood alterations were similar between Stroop and TLDB conditions. ConclusionsIntermittent running (Yo-Yo) and cognitive (PVT) performances, and subjective ratings were impaired by 30-min Stroop and 20-min TLDB tasks; while 10-min TLDB did not to impair performance. Shorter adaptive modes seem to be more effective in inducing MF and could have relevant clinical applications to assess conditions such as traumatic brain injury and concussion.

Acute inorganic nitrate ingestion does not impact oral microbial composition, cognitive function, or high-intensity exercise performance in female team-sport athletes.

The purpose of this study was to investigate the effects of acute nitrate (NO3-)-rich beetroot juice ingestion on explosive and high-intensity exercise performance, oral microbiota composition, and cognitive flexibility (i.e., function), before and after maximal intermittent running exercise. Fifteen women team-sport athletes were assigned in a randomized, double-blind, crossover design to consume concentrated NO3--depleted beetroot juice (PL; 0.1mmol NO3-) and NO3--rich beetroot juice (BR; 12.0mmol NO3-) 2.5h prior to performing a battery of exercise performance tasks and cognitive testing before and after the Yo-Yo intermittent recovery level 1 (YYIR1) running test. Resting plasma [NO3-] and plasma nitrite ([NO2-]) were elevated following BR (P < 0.001). BR did not impact global composition or relative abundance of taxa in the oral microbiome (P > 0.05) or cognitive flexibility before or after exercise (P > 0.05). There was no significant difference in performance during 20-m (PRE, PL: 4.38 ± 0.27 vs. BR: 4.38 ± 0.32s; POST, PL: 4.45 ± 0.29 vs. BR: 4.43 ± 0.35s) and 10-m sprints (PRE, PL 2.78 ± 0.15 vs. BR 2.79 ± 0.18s; POST, PL: 2.82 ± 0.16 vs. BR: 2.81 ± 0.19s), isokinetic handgrip dynamometry, medicine ball throw, horizontal countermovement jump, or YYIR1 (PL: 355 ± 163m vs. BR: 368 ± 184m) between BR and PL (P > 0.05). These findings indicate that acute dietary NO3- may not influence the oral microbiome, explosive and high-intensity exercise performance, or cognitive function in women team-sport athletes.

Validity, reliability, and the contributing physical characteristics of a modified 15m prone Yo-Yo Intermittent Recovery Test Level-1 test in elite female rugby league players.

This study aims to establish the validity and reliability of the prone Yo-YoIRL1 in elite female rugby league players (part one) and determine the anthropometric and physical characteristics contributing to 15m prone Yo-YoIRL1 performance (part two). Part one, 21 subjects completed one Yo-YoIRL1, one 20m and two 15m prone Yo-YoIRL1 tests over four sessions, with 7-14 days in-between. Part two, ten subjects completed a testing battery, including body mass, height, dual-energy x-ray absorptiometry, isometric mid-thigh pull, isometric bench-press, 10m and 20m sprints and an incremental treadmill test ([Formula: see text]). The 15m prone YoYoIRL1 demonstrated poor reliability with a typical error of 68m (21%) and a smallest worthwhile change of 54m (9%). Validity analysis found the prone versions of the YoYoIRL1 were not sensitive measures of intermittent running performance. Both prone YoYoIRL1 test distances demonstrated large mean bias (76% and -37% respectively) and typical error of the estimate (19% and 21%, respectively) in comparison to the YoYoIRL1. Body mass (r = -0.89), lean mass (r = -0.64), body fat % (r = -0.68), [Formula: see text] (l∙min-1) (r = -0.64), IMTP (r = -0.69), IBP (r = -0.15), 10m (r = -0.77) and 20m (r = -0.72) momentum displayed large negative relationships with 15m prone Yo-YoIRL1 performance. Due to the poor validity of the 20m prone YoYoIRL1, the poor validity and reliability of the 15m prone YoYoIRL1, and the anthropometric and physical characteristics which negatively impact performance, practitioners should reconsider the use of the prone YoYoIRL1 test to monitor high intensity intermittent running performance.

Evaluation of bone marrow glucose uptake and adiposity in male rats after diet and exercise interventions.

Obesity impairs bone marrow (BM) glucose metabolism. Adult BM constitutes mostly of adipocytes that respond to changes in energy metabolism by modulating their morphology and number. Here we evaluated whether diet or exercise intervention could improve the high-fat diet (HFD) associated impairment in BM glucose uptake (BMGU) and whether this associates with the morphology of BM adipocytes (BMAds) in rats. Eight-week-old male Sprague-Dawley rats were fed ad libitum either HFD or chow diet for 24 weeks. Additionally after 12 weeks, HFD-fed rats switched either to chow diet, voluntary intermittent running exercise, or both for another 12 weeks. BMAd morphology was assessed by perilipin-1 immunofluorescence staining in formalin-fixed paraffin-embedded tibial sections. Insulin-stimulated sternal and humeral BMGU were measured using [18F]FDG-PET/CT. Tibial microarchitecture and mineral density were measured with microCT. HFD rats had significantly higher whole-body fat percentage compared to the chow group (17% vs 13%, respectively; p = 0.004) and larger median size of BMAds in the proximal tibia (815 µm2 vs 592 µm2, respectively; p = 0.03) but not in the distal tibia. Switch to chow diet combined with running exercise normalized whole-body fat percentage (p < 0.001) but not the BMAd size. At 32 weeks of age, there was no significant difference in insulin-stimulated BMGU between the study groups. However, BMGU was significantly higher in sternum compared to humerus (p < 0.001) and higher in 8-week-old compared to 32-week-old rats (p < 0.001). BMAd size in proximal tibia correlated positively with whole-body fat percentage (r = 0.48, p = 0.005) and negatively with humeral BMGU (r = -0.63, p = 0.02). HFD significantly reduced trabecular number (p < 0.001) compared to the chow group. Switch to chow diet reversed this as the trabecular number was significantly higher (p = 0.008) than in the HFD group. In this study we showed that insulin-stimulated BMGU is age- and site-dependent. BMGU was not affected by the study interventions. HFD increased whole-body fat percentage and the size of BMAds in proximal tibia. Switching from HFD to a chow diet and running exercise improved glucose homeostasis and normalized the HFD-induced increase in body fat but not the hypertrophy of BMAds.

Assessment of Maximum Oxygen Uptake in Elite Youth Soccer Players: A Comparative Analysis of Smartwatch Technology, Yoyo Intermittent Recovery Test 2, and Respiratory Gas Analysis.

The maximum oxygen uptake (VO2max) is a critical factor for endurance performance in soccer. Novel wearable technology may allow frequent assessment of V̇O2max during non-fatiguing warm-up runs of soccer players with minimal interference to soccer practice. The aim of this study was to assess the validity of VO2max provided by a consumer grade smartwatch (Garmin Forerunner 245, Garmin, Olathe, USA, Software:13.00) and the YoYo Intermittent Recovery Run 2 (YYIR2) by comparing it with respiratory gas analysis. 24 trained male youth soccer players performed different tests to assess VO2max: i) a treadmill test employing respiratory gas analysis, ii) YYIR2 and iii) during a non-fatiguing warm-up run of 10 min wearing a smartwatch as recommended by the device-manufacturer on 3 different days within 2 weeks. As the device-manufacturer indicates that validity of smartwatch-derived VO2max may differ with an increase in runs, 16 players performed a second run with the smartwatch to test this claim. The main evidence revealed that the smartwatch showed an ICC of 0.37 [95% CI: -0.25; 0.71] a mean absolute percentage error (MAPE) of 5.58% after one run, as well as an ICC of 0.54 [95% CI: -0.3; 8.4] and a MAPE of 1.06% after the second run with the smartwatch. The YYIR2 showed an ICC of 0.17 [95% CI: -5.7; 0.6]; and MAPE of 4.2%. When using the smartwatch for VO2max assessment in a non-fatiguing run as a warm-up, as suggested by the device manufacturer before soccer practice, the MAPE diminishes after two runs. Therefore, for more accurate VO2max assessment with the smartwatch, we recommend to perform at least two runs to reduce the MAPE and enhance the validity of the findings.

Variability of External Load Measures During Soccer Match Play: Influence of Player Fitness or Pacing?

The aims of this study were to examine the variability of selected external load metrics within 15-minute intervals during soccer match play and examine their relationship with players' high-intensity intermittent fitness. A total of 18 male soccer players were monitored for their external load metrics during 26 matches, which included total distance, high-metabolic-load distance, and mechanical work (defined as the sum of accelerations and decelerations >3m2). Additionally, players completed the 30-15 Intermittent Fitness Test. Total distance had lower coefficients of variation than high-metabolic-load distance and mechanical work (effect size [ES]: 5.2 to 6.4; very large). Within-player Δ-15min showed moderate to large decreases (ES: -0.7 to -1.6) and increases (ES: 0.9 to 1.8) in absolute and coefficient-of-variation values, respectively. Large relationships (r = .55 to .61) were observed between the Intermittent Fitness Test and 15-minmean and 15-minbest in all selected external load metrics. However, small to moderate (0.27 to 0.41) associations were observed between the Intermittent Fitness Test and Δ-15min in selected external load metrics. These findings suggest that players with relatively lower intermittent running capacity might show lower variability during matches, as evidenced by smaller reductions in high-intensity actions during the final 15minutes. We attribute these observations to players' possessing better pacing strategies.

High-Intensity Interval Training Combined with High-Load Strength Training Improves Aerobic Fitness, Match Goals and Match Result during the In-Season Period in Under-19 Soccer Players.

This study compared the effects of adding a weekly session of either strength training followed by high-intensity interval training (HIIT) or high load plyometric training followed by small-sided games (SSG) on aerobic fitness, goals scored and conceded, and match results. Twenty-nine players from two youth elite teams competing in an under 19 (U19) first division league took part in the study. Of those, 16 players from one team followed the HIIT program (age: 17.8 ± 0.6 years) and 13 players from the other team trained once a week, following the SSG program (age: 18.0 ± 0.6 years). The training intervention lasted for 11 weeks and was applied once per week. For the HIIT team it included high-load strength training (80-95% of 1 RM) followed by high-intensity intermittent running, whereas for the SSG team (n = 13) it included plyometric exercises followed by SSG. Aerobic fitness was assessed before and after the intervention, while goals scored and conceded, as well as match results during the intervention period, were compared with the 11-week period preceding it. Only the HIIT team improved Yo-Yo IR2 performance (running distance: from 902.5 ± 147.5 to 1092.5 ± 155.8 m, p < 0.001) while there was no change for the SSG group. Moreover, during the 11-week intervention, the HIIT team improved the number of goals scored in the last 30 min of the game compared with the pre-intervention period (0.36 ± 0.50 to 1.27 ± 0.90 per match, p < 0.05) and the scored vs. conceded goals were higher in the second half (1.36 ± 1.03 vs. 0.27 ± 0.47, p < 0.05). No significant differences were found for these parameters in the SSG team. Regarding match result, the HIIT team increased the proportion of wins from 5 wins in 11 matches (or 45%) in the pre-intervention period to 9 wins in 11 matches (or 82%) during the intervention period, while this profile remained unchanged for the SSG team. In conclusion, the present study demonstrated that the HIIT program performed once per week was superior to SSG as it improves aerobic fitness, scored and conceded goals, and match result during the in-season period.

The Effects of Repeated-Sprint Training on Physical Fitness and Physiological Adaptation in Athletes: A Systematic Review and Meta-Analysis.

Repeated-sprint training (RST) is a common training method for enhancing physical fitness in athletes. To advance RST prescription, it is important to understand the effects of programming variables on physical fitness and physiological adaptation. This study (1) quantifies the pooled effects of running RST on changes in 10 and 20m sprint time, maximal oxygen consumption (VO2max), Yo-Yo Intermittent Recovery Test Level 1 (YYIR1) distance, repeated-sprint ability (RSA), countermovement jump (CMJ) height and change of direction (COD) ability in athletes, and (2) examines the moderating effects of program duration, training frequency, weekly volume, sprint modality, repetition distance, number of repetitions per set and number of sets per session on changes in these outcome measures. Pubmed, SPORTDiscus and Scopus databases were searched for original research articles up to 04 July 2023, investigating RST in healthy, able-bodied athletes, between 14 and 35years of age, and a performance calibre of trained or above. RST interventions were limited to repeated, maximal running (land-based) sprints of ≤ 10s duration, with ≤ 60s recovery, performed for 2-12weeks. A Downs and Black checklist was used to assess the methodological quality of the included studies. Eligible data were analysed using multi-level mixed-effects meta-analysis, with standardised mean changes determined for all outcomes. Standardised effects [Hedges G (G)] were evaluated based on coverage of their confidence (compatibility) intervals (CI) using a strength and conditioning specific reference value of G = 0.25 to declare an improvement (i.e. G > 0.25) or impairment (i.e. G < - 0.25) in outcome measures. Applying the same analysis, the effects of programming variables were then evaluated against a reference RST program, consisting of three sets of 6 × 30m straight-line sprints performed twice per week for 6weeks (1200m weekly volume). 40 publications were included in our investigation, with data from 48 RST groups (541 athletes) and 19 active control groups (213 athletes). Across all studies, the effects of RST were compatible with improvements in VO2max (G 0.56, 90% CI 0.32-0.80), YYIR1 distance (G 0.61, 90% CI 0.43-0.79), RSA decrement (G - 0.61, 90% CI - 0.85 to - 0.37), linear sprint times (10m: G - 0.35, 90% CI - 0.48 to - 0.22; 20m: G - 0.48, 90% CI - 0.69 to - 0.27), RSA average time (G - 0.34, 90% CI - 0.49 to - 0.18), CMJ height (G 0.26, 90% CI 0.13-0.39) and COD ability (G - 0.32, 90% CI - 0.52 to - 0.12). Compared with the reference RST program, the effects of manipulating training frequency (+ 1 session per week), program duration (+ 1 extra training week), RST volume (+ 200m per week), number of reps (+ 2 per set), number of sets per session (+ 1 set) or rep distance (+ 10m per rep) were either non-substantial or comparable with an impairment in at least one outcome measure per programming variable. Running-based RST improves speed, intermittent running performance, VO2max, RSA, COD ability and CMJ height in trained athletes. Performing three sets of 6 × 30m sprints, twice per week for 6weeks is effective for enhancing physical fitness and physiological adaptation. Additionally, since our findings do not provide conclusive support for the manipulation of RST variables, further work is needed to better understand how programming factors can be manipulated to augment training-induced adaptations. Open Science Framework registration https://doi.org/10.17605/OSF.IO/RVNDW .

Carbohydrate or Electrolyte Rehydration Recovers Plasma Volume but Not Post-immersion Performance Compared to Water After Immersion Diuresis.

We tested the hypothesis that a carbohydrate (CHO: 6.5%) or carbohydrate-electrolyte (CHO + E: 6.5% + 50 mmol/L NaCl) drink would better recover plasma volume (PV) and exercise performance compared to water (H2O) after immersion diuresis. Twelve men (24 ± 2 years; 82.4 ± 15.5 kg; and V̇O2max: 49.8 ± 5.1 mL · kg-1 · min-1) completed four experimental visits: a no-immersion control (CON) and three 4-h cold-water (18.0 °C) immersion trials (H2O, CHO, and CHO + E) followed by exercise in a warm environment (30 °C, 50% relative humidity). The exercise was a 60-minute loaded march (20.4 kg; 55% VO2max) followed by a 10-minute intermittent running protocol. After immersion, subjects were rehydrated with 100% of body mass loss from immersion diuresis during the ruck march. PV is reported as a percent change after immersion, after the ruck march, and after the intermittent running protocol. The intermittent running protocol distance provided an index of exercise performance. Data are reported as mean ± SD. After immersion, body mass loss was 2.3 ± 0.7%, 2.3 ± 0.5%, and 2.3 ± 0.6% for H2O, CHO, and CHO + E. PV loss after immersion was 19.8 ± 8.5% in H2O, 18.2 ± 7.0% in CHO, and 13.9 ± 9.3% in CHO + E, which was reduced after the ruck march to 14.7 ± 4.7% (P = .13) in H2O, 8.8 ± 8.3% (P < .01) in CHO, and 4.4 ± 10.9% (P = .02) in CHO + E. The intermittent running protocol distance was 1.4 ± 0.1 km in CON, 1.4 ± 0.2 km in H2O, 1.4 ± 0.1 km in CHO, and 1.4 ± 0.2 km in CHO + E (P = .28). Although CHO and CHO + E better restored PV after immersion, post-immersion exercise performance was not augmented compared to H2O, highlighting that fluid replacement following immersion diuresis should focus on restoring volume lost rather than fluid constituents.

Comparative effects of various running exercise modalities on femoral bone quality in rats.

It is now well established that physical exercise is an effective preventive method to reduce and treat certain chronic diseases, particularly musculoskeletal disorders. At the bone level, running exercise is well known for its positive effects on various parameters of bone quality. There is, however, no consensus regarding the effects of different running exercise modalities on bone quality. The objective of this study was to compare the effects of three treadmill running modalities: intermittent, moderate continuous, and a combination of both-on bone quality parameters in rats. Thirty-nine, 5-week-old, male Wistar rats were randomly divided in 4 groups: sedentary control (SED; n = 10), intermittent running exercise (IE; n = 10), continuous running exercise (CE; n = 10) and combined running exercise (COME; n = 9). Rats in running groups were exercised 45min/day, 5days/week, for 8 consecutive weeks. Femoral micro-architectural parameters were assessed by micro-CT; femoral osteocyte apoptosis, osteoclast resorption and bone histomorphometry were assessed by histology. Femoral trabecular thickness in the combined running group was increased (p < 0.0001) compared to respective results in the other running groups (0.13mm vs 0.11mm). The cortical thickness, osteocyte lacunae occupancy rate in the whole femur, numbers of apoptotic osteocytes and osteoclastic resorption surfaces were not significantly different between groups. Statistical differences were occasionally noted depending on the femoral anatomical region. These results suggest that the femur should not be considered as the better bone to study the effects of running protocols.

Physical exercise induces mental flow related to catecholamine levels in noncompetitive, but not competitive conditions in men

The study aimed to reveal physical exercise conditions and catecholamine response-dependent differences while an individual experiences a flow state (FS) following noncompetitive and competitive running drills. Urine laboratory catecholamine levels were measured using a standard clinical method during pre- and post-physical exercises. The noncompetitive task involved intermittent running drills, from an absolute beginning up through exhaustion. Initially, the drill is performed individually then later competing alongside other runners. Twenty-two males (mean age: 40.27; SD: 5.4; min–max: 31–49 years) were selected in accordance to the following criterion: healthy status without using medication, routine forms of training (running, cycling or swimming) ideally performed with regularity, at least three times per week, 45 min per session. During the noncompetitive task, a high FS experience was associated with a low level of catecholamines, (noradrenaline and adrenaline) while in parallel, the high FS was associated with a low concentration of homovallinic acid. During competitive conditions, the FS-related catecholamine level changes have not yet been found. In conclusion, the low concentration of the circulating catecholamines supports the transient hypofrontality hypothesis regarding the FS experiences. Furthermore, synchronized noradrenaline and adrenaline neurosecretion play an essential role in the manifestation and the prolongation of FS in noncompetitive exercise conditions.

Acute beetroot juice supplementation did not enhance intermittent running performance in trained rugby players

ABSTRACT Purpose: Since the effect of dietary nitrate (NO3 -) supplementation on rugby performance is unclear, the aim of the present study was to determine the effect of acute NO3 - supplementation, on the modified Yo-Yo intermittent recovery level 1 (IR1) performance test in trained male rugby players. Methods: In a randomised, counterbalanced, double-blind, placebo-controlled crossover design, 12 trained rugby union players performed two experimental trials three hours after supplementation of either 140 mL NO3 --rich (BRJ; ∼12.8 mmol NO3 -) or NO3 --depleted (PLA) BRJ. After blood sampling, players performed the modified Yo-Yo IR1 test. Countermovement jumps (CMJ) were also measured before (pre-CMJ) and after (post-CMJ) the prone Yo-Yo IR1 test. Results: Plasma NO3 - (BRJ: 570 ± 146 µM vs. PLA: 72 ± 23 µM) and nitrite (NO2 -) concentrations (BRJ: 320 ± 123 nM vs. PLA: 103 ± 57 nM) were increased after BRJ compared to PLA supplementation (both P < 0.001). Performance in the modified Yo-Yo IR1 test did not differ between BRJ (542 ± 209 m) and PLA (498 ± 185 m, P = 0.3). The jump height in pre-CMJ and in post-CMJ were similar between trials (both P > 0.05). Conclusions: Acute BRJ supplementation increased plasma NO3 - and NO2 - concentrations but had no benefit on an intermittent running test that reflects the demands of rugby performance, and CMJ performances. The findings do not support acute high-dose NO3 - supplementation as an ergogenic aid to enhance physical performance in trained male rugby players.

Investigating the effect of exercise on the expression of genes related to cardiac physiological hypertrophy.

Physiological hypertrophy of the heart is associated with an increase in the normal function of the heart, and it directly relates to regular exercise, especially among elite athletes. Researches about special signaling pathways that create physiological hypertrophy have recently received more attention. As a result, the present study was conducted to investigate the effect of aerobic exercise intensity on the expression of genes involved in heart physiological hypertrophy. For this purpose, 30 male Wistar rats were prepared and randomly divided into three groups: control, intense intermittent training, and submaximal continuous training. The intensive intermittent training protocol included 30 minutes of intermittent running, each interval including 4 minutes of running with an intensity of 85-90% VO2max and 2 minutes of active recovery with an intensity of 50-60% VO2max three days a week for 8 weeks. Also, the submaximal continuous exercise group had activity intensity equal to 50-55% of the maximum oxygen consumption. The expression of genes related to cardiac hypertrophy such as MMP-I, TGF-ß1, and TIMP was evaluated through real-time PCR technique. The results showed that the expression of studied genes in the three groups had significant differences (p<0.05). Both training methods led to a significant increase in TGF-ß1 and TIMP gene expression in the heart of rats. But the changes in MMP-I in the intermittent group were not significant compared to the control group. In general, it seems that exercise leads to the improvement of the factors involved in the physiological hypertrophy of the heart. Therefore, the findings of the current research are expressed with caution and more research is needed in the future.