High-intensity Interval Running Research Articles

Cool mama: Temperature regulation during high-intensity interval running in pregnant elite and recreational athletes

BackgroundRegular exercise during pregnancy is beneficial, but athletes often exceed the recommended 150 min of moderate-intensity activity, incorporate high-intensity exercises. The upper limit for exercise intensity and duration on fetal and maternal safety remains uncertain. A concern is a maternal core body temperature of >39.0 °C, potentially increase the risk of heat-related fetal malformations and complications during pregnancy. Blood flow redirection for thermoregulation could compromise fetal cardiovascular function, increasing the risk of miscarriage and preterm labor. This study evaluated whether pregnant women (gestational weeks 25–35) were at risk of exceeding a core body temperature of 39.0 °C during high-intensity running. We also investigated effects on skin temperature, fluid loss, and thermal sensation, comparing pregnant athletes to non-pregnant controls. MethodsIn this comparative cross-sectional study, 30 elite and recreational athletes (pregnant n = 15) completed up to five high-intensity treadmill-intervals. Core and skin temperature were continuously measured. Body weight was utilized to calculate the amount of fluid loss. ResultsHighest core body temperature were 38.76 °C and 39.56 °C in one pregnant and non-pregnant participant, respectively. Pregnant participants had lower core body temperatures (mean difference −0.47 °C, p ≤ 0.001) initially and a smaller increase (0.10 °C, p ≤ 0.003) during later intervals compared with the non-pregnant controls. Pregnant participants also showed a greater increase in skin temperature (4.08 ± 0.72 °C vs. 3.25 ± 0.86 °C, p = 0.008) and fluid loss (0.81 ± 0.19 L vs. 0.50 ± 0.12 L, p˂0.001). ConclusionPhysiological changes in pregnancy may enhance thermoregulation, indicating that high-intensity interval runs are unlikely to pose a risk of exceeding a core body temperature of 39 °C for pregnant athletes.

High-Intensity Interval Cycling and Running Yield a Similar Myokine and Osteokine Response in Young Adult Females

Background: The differential responses of the myokine irisin, in combination with changes in markers and regulators of bone remodeling to high-intensity interval exercise of high and low impact, were examined in 18 young adult females (22.5 ± 2.7 years). Methods: Participants performed two high-intensity interval exercise trials in random order: running on a treadmill and cycling on a cycle ergometer. Trials consisted of eight 1 min running or cycling intervals at ≥ 90% of maximal heart rate, separated by 1 min passive recovery intervals. Blood samples were collected at rest (pre-exercise) and 5 min, 1 h, and 24 h following each exercise trial. Irisin, osteocalcin, sclerostin, osteoprotegerin (OPG), receptor activator nuclear factor kappa-β ligand (RANKL), and parathyroid hormone (PTH) were analyzed in serum, with post-exercise concentrations being corrected for exercise-induced changes in plasma volume. Results: Irisin was elevated 24 h post-exercise compared to its resting values in both trials (20%, p < 0.05) and was higher after cycling compared to running (exercise mode effect, p < 0.05) with no interaction. Osteocalcin, sclerostin, PTH, and RANKL increased from pre- to 5 min post-exercise (18%, 37%, 83%, and 33%, respectively, p < 0.05), returning to baseline levels in 1 h, with no trial or interaction effects. OPG showed a time effect (p < 0.05), reflecting an overall increase at 5 min and 1 h post-exercise, which was not significant after the Bonferroni adjustment. Conclusions: In young adult females, high-intensity interval exercise induced an immediate response in markers and regulators of bone remodeling and a later response in irisin concentrations, which was independent of the gravitational impact.

Effects of aerobic exercise on metabolic indicators and physical performance in adult NAFLD patients: A systematic review and network meta-analysis.

nonalcoholic fatty liver disease (NAFLD) is characterized by excessive accumulation of fat in the liver without alcoholism. We conducted a systematic review and meta-analysis to elucidate the efficacy of aerobic exercise on metabolic indicators and physical performance of adult patients with NAFLD. To conduct the systematic review and network meta-analysis, 2 researchers searched PubMed, EBSCO, and Web of science databases to identify randomized clinical trials of aerobic exercise interventions for adults with NAFLD published between inception and July 2022. We assessed the methodological quality of the included literature using the Cochrane Risk Assessment Scale and the PEDro Scale. Relevant data were extracted, variables were converted to the same units, and meta-analysis was performed using RevMan 5.4 software. We compared mean differences (MD) between experimental and control groups. For each outcome analyzed, we expressed data as MD with 95% CI to compare metabolic markers and exercise capacity between the experimental and control NAFLD patients. Eleven randomized clinical trials with a total of 491 individuals with NAFLD were included in accordance with the criteria of this study. Types of aerobic exercise include moderate or high-intensity interval running, cycling, Nordic walking, equipment training, etc; Training duration 4 to 16 weeks, 30 to 60 minutes 3 or more times a week. Compared with the control group, aerobic exercise group had reduced weight of patients, (MD) 1.20 kg (95% CI: -1.38 to -1.01 kg, P < .00001). Seven studies confirmed that aerobic exercise significantly reduced triglycerides, (MD) 3.00 mg/dL (95% CI: -5.80 to -0.21 mg/dL, P = .04); increased high density lipoproteins (MD) 5.96 mg/dL (95% CI: 2.95 to 8.96 mg/dL, P = .0001) and reduced low-density lipoproteins (MD) 6.45 mg/dL (95% CI: -8.53 to -4.37 mg/dL, P < .00001); the study also showed that aerobic exercise reduced the liver enzymes aspartate aminotransferase and alanine aminotransferase to varying degrees. Aerobic exercise can improve physical performance and increase peak oxygen consumption of (MD) 6.29 mL/Kg*minutes, (95% CI: 3.05-9.53mL/Kg*minutes, P = .0001). Aerobic exercise significantly reduced weight and improved metabolic index and physical performance. Impacted by the limitations of various regimens, doses, duration, center settings, populations enrolled, the study had certain limitations. The randomized controlled trials with larger sample sizes, multiple centers, and high quality should be conducted to validate the above conclusion. Further studies will be required to focus on the total duration of the intervention, duration and frequency of sessions, and intensity that are optimal for the promotion of physical performance and metabolic capacity in this population.

Can the high intensity interval running in slope affect concurrently explosive strength performance?

Background: Physical exercise programs are typically composed of activities directed to the development of different physical abilities, usually stimulated in the same session. Objective: The aim of the study was to determine the effect of one session of aerobic exercise at high intensity to 1% and 10% gradient on the height (HJump) and kinematics of the depth jump (PExc - eccentric, concentric phase PCon, and contact time – CT). Methods: Twenty-five moderately trained men (VO2Max 53.2 ± 4.3 mL.kg-1.min-1) attended five visits in the laboratory. Familiarity with the procedures in depth jump, VO2Max measures and their velocity associated (VVO2Max), and time to exhaustion performance (TLim) were performed at two initial visits. Results: On the three subsequent visits, the volunteers were subjected to three maximum depth jumps before and 10 min after the following conditions: (1) running intervals at high intensity of 10% gradient (R10%), (2) at 1% gradient (R1%), and control condition (CON). The order of conditions was determined randomly. A running condition did not induce significant changes from HJump (R1% 1.1% vs 1.0% R10%) when expressed as percentage difference from the CON condition. The PExc, PCon, and CT also did not change after running sessions (P&gt; 0.05). None of the intervals running strategies were able to generate significant change in height and kinematics of the vertical depth jump. Conclusion: The prescription of the running at VVO2Max in 1% or 10% gradient does not seem to lead to concurrent effect, is suggested to ensure the concomitant development of maximal aerobic power and explosive strength.

An Acute Bout of Exercise Suppresses Appetite via Central Lactate Metabolism

Exercise has been reported to elicit a transient suppression of appetite. Plasma lactate, which is produced by exercising muscle, is believed to have a critical effect on exercise-induced appetite suppression. However, the underlying mechanisms and signaling steps of central lactate metabolism remain unexplored. After central oxamate administration, C57BL/6J male mice performed 10 high-intensity interval running at 90% Vmax for 4 minutes each, which separated by 2 minutes at 12 m/min. Food intake and the expression of hypothalamic appetite-regulating neuropeptides including proopiomelanocortin (POMC) and neuropeptide Y (NPY) were investigated following exercise training. Janus kinase 2 (Jak2)-signal transducer and activator of transcription 3 (STAT3) signaling pathway was also determined by Western blot. In addition, hypoxia-inducible factor-1α (HIF-1α) was investigated to explore the effect of central lactate metabolism following exercise. We found that central oxamate administration reversed exercise-induced suppression of food intake, and as well as changes in the expression of POMC and NPY. Moreover, acute exercise led to an increase in the phosphorylation of Jak2 and STAT3 in the hypothalamus, while central lactate inhibition significantly blunted this effect. In addition, HIF-1α expression increased obviously after exercise, while it was attenuated by central oxamate administration. Collectively, our data reveal that central lactate metabolism mediates exercise-induced suppression of appetite and changes in neuropeptides, possibly through enhanced Jak2-STAT3 signaling.

Effects of High-Intensity Position-Specific Drills on Physical and Technical Skill Performance in Elite Youth Soccer Players.

Cuong Le, C, Ma'ayah, F, Nosaka, K, Hiscock, D, and Latella, C. Effects of high-intensity position-specific drills on physical and technical skill performance in elite youth soccer players. J Strength Cond Res 37(5): e332-e340, 2023-Soccer physical preparation has been extensively researched with previous emphasis on high-intensity interval running and small-sided games. However, neither approach considers positional differences. The purpose of this study was to investigate the feasibility and short-term effects of a novel position-specific conditioning training (PSCT) paradigm on physical and technical abilities of young soccer players. Fifteen male Vietnamese professional youth soccer players (16.1 ± 0.4 years, 171.7 ± 4.8 cm, 63.9 ± 3.8 kg) undertook a 3-week control period followed by a 3-week intervention with PSCT drills performed twice per week. Position-specific conditioning training comprised purposely designed drills for attackers, defenders, and wingers, respectively. The intensity and duration were the same for all drills (4 × 4 minutes at ∼90% heart rate maximum [HRmax], separated by a 4-minute recovery at 70% HRmax) but differed in the technical and tactical actions performed. Outcome measures included Yo-Yo intermittent recovery test level 1, repeated sprint ability, 10-m and 30-m sprint time, and the Loughborough Soccer Passing Test for technical skills in a fatigued and nonfatigued state. Position-specific conditioning training drills induced a desirable intensity for effective conditioning purpose (89.0 ± 2.1% HRmax) with low interplayer variability (coefficient of variation = 2.4%). Yo-Yo intermittent recovery test level 1 performance improved ( p < 0.05) after the control (Δ178.7 ± 203.3 m) and intervention (Δ176.0 ± 225.7 m) periods without a difference between. These results confirmed the feasibility of PSCT as a novel high-intensity training approach for soccer players. Improvements in aerobic capacity were noted, despite no effect on other physical and technical measures. PSCT may be suitable for individual training, return-to-play stages of rehabilitation, during off-season, or in academy settings when time is not a constraint.

Acute Effects of High-Intensity Interval Running on Lower-Body and Upper-Body Explosive Strength and Throwing Velocity in Handball Players.

Seipp, D, Feuerbacher, JF, Jacobs, MW, Dragutinovic, B, and Schumann, M. Acute effects of high-intensity interval running on lower-body and upper-body explosive strength and throwing velocity in handball players. J Strength Cond Res 36(11): 3167-3172, 2022-The purpose of this study was to determine the acute effects of handball-specific high-intensity interval training (HIIT) on explosive strength and throwing velocity, after varying periods of recovery. Fourteen highly trained male handball players (age: 25.4 (26.2 ± 4.2) performed HIIT consisting of repeated 15-second shuttle runs at 90% of final running speed (V IFT ) to exhaustion . Upper-body and lower-body explosive strength and throwing velocities were measured before and immediately after HIIT, as well as after 6 hours. These tests included 3 repetitions of both bench press and squat exercise at 60% of the 1 repetition maximum (1RM) as well as 3 repetitions of the set shot without run up and jump shot, respectively. Explosive squat performance was significantly reduced at post (-5.48%, p = 0.026) but not at 6 h (-0.24%, p = 1.000). Explosive bench press performance remained statistically unaltered at post (0.32%, p = 1.000) and at 6 hour (1.96%, p = 1.000). This was also observed in the subsequent throws both immediately after (-0.60%, p = 1.000) (-0.31%, p = 1.000) and at 6 h (-1.58%, p = 1.000) (1.51%, p = 0.647). Our data show a reduction in explosive strength of the lower but not upper extremities when preceded by running HIIT. Since throwing velocity was not affected by intense lower-body exercise, combining lower-body HIIT and throwing practice may be of no concern in highly trained handball players.

Impact of Treadmill Interval Running on the Appearance of Zinc Finger Protein FHL2 in Bone Marrow Cells in a Rat Model: A Pilot Study.

Although the benefits of physical exercise to preserve bone quality are now widely recognized, the intimate mechanisms leading to the underlying cell responses still require further investigations. Interval training running, for instance, appears as a generator of impacts on the skeleton, and particularly on the progenitor cells located in the bone marrow. Therefore, if this kind of stimulus initiates bone cell proliferation and differentiation, the activation of a devoted signaling pathway by mechano-transduction seems likely. This study aimed at investigating the effects of an interval running program on the appearance of the zinc finger protein FHL2 in bone cells and their anatomical location. Twelve 5-week-old male Wistar rats were randomly allocated to one of the following groups (n = 6 per group): sedentary control (SED) or high-intensity interval running (EX, 8 consecutive weeks). FHL2 identification in bone cells was performed by immuno-histochemistry on serial sections of radii. We hypothesized that impacts generated by running could activate, in vivo, a specific signaling pathway, through an integrin-mediated mechano-transductive process, leading to the synthesis of FHL2 in bone marrow cells. Our data demonstrated the systematic appearance of FHL2 (% labeled cells: 7.5%, p < 0.001) in bone marrow obtained from EX rats, whereas no FHL2 was revealed in SED rats. These results suggest that the mechanical impacts generated during high-intensity interval running activate a signaling pathway involving nuclear FHL2, such as that also observed with dexamethasone administration. Consequently, interval running could be proposed as a non-pharmacological strategy to contribute to bone marrow cell osteogenic differentiation.

Effect of High Intensity Interval Treadmill Exercise on Subsequent Lower and Upper Limb Strength Performance

ABSTRACT Purpose: The aim of this study was to analyze the acute effect of a treadmill high-intensity interval protocol on subsequent upper body and lower body strength exercise performance. Method: Sixteen young men had their maximal aerobic capacity and one-repetition maximum (1RM) determined and underwent four randomized conditions: a half-squat control session; a bench press control session; a treadmill interval protocol followed by a half-squat experimental session; and a treadmill interval protocol followed by a bench press experimental session. During the control sessions, four sets to failure for each exercise were performed at 80% of 1RM. In the experimental sessions, participants performed eight sprints of 40 s at 100% velocity of maximal oxygen uptake with 20 s of passive interval between them, followed by the same strength exercise protocol of the control sessions. The number of repetitions during each protocol and participants’ heart rate (HR),and blood lactate concentration ([lac]) were compared pre and post protocols and exercises. Results: Fewer repetitions were completed in the experimental session compared to the control sessions (p < .001). Moreover, the reduction in number of repetitions performed was more evident in half-squat compared to bench press (p = .018). HR was higher at the end of sessions with the interval protocol for both exercises (p < .001). The [lac] was higher at the end of session with the interval protocol for half-squat (p = .003). Conclusions: These findings suggest that previous high-intensity interval running may impair subsequent strength exercise performance, but the magnitude of the negative effect is greater in the lower limbs.

The Effect of Different Training Strategies Applied to Football Referees On Maxvo2 and Running Performance

Aim: In this study, the effects of high-intensity interval training and sprint training on amateur football referees running performances expressed by the FIFA Athletic Test, Cooper Test and MAXVO2 were investigated. Methods: Football referees average age (23.88±2.10); average height (181.16±1.99) cm; body weight (74.42±2.46) kg and body mass index (22.66±.62) kg/m2 calculated. They were applied high-intensity interval training and speed training 3 days a week for 16 weeks. FIFA Athletic Test and Cooper Test were applied in the pre-test and post-test to see the effect of the training process on the referees. SPSS package program was used to analyze the data. "Paired Sample t-Test" was used for the normally distributed data, and the "Wilcoxon Signed Rows Test", which is a nonparametric test, for non-normally distributed data, and the effect size was calculated. The results were evaluated according to the significance level "0.01" and "0.05". Results: When the FIFA Athletic Test, Cooper Test, body weight, and BMI pre-test and post-test values were compared in football referees, a statistically significant difference was found between the first measurement and the second measurement (p&lt;0.05). Conclusion: As a result of the study, it was observed that the training sessions had a positive effect on amateur football referees' running performances expressed by FIFA Athletic Test and Cooper Test and MAXVO2. This training program is recommended for the improvement of the degree-based running performances of amateur football referees. Keywords: Football referee, training, high-intensity interval running

The Effects of Running Compared with Functional High-Intensity Interval Training on Body Composition and Aerobic Fitness in Female University Students.

High-intensity interval running (HIIT-R) and high-intensity functional training (HIFT) are two forms of HIIT exercise that are commonly used. The purpose of this study was to determine the effects of HIFT on aerobic capacity and body composition when compared to HIIT-R in females. Twenty healthy, untrained female university students (age 20.5 ± 0.7 year) were randomly assigned to a 12-week HIIT-R or HIFT intervention. The HIIT-R group involved a 30 s maximal shuttle run with a 30 s recovery period, whereas the HIFT involved multiple functional exercises with a 2:1 work-active recovery ratio. Body composition, VO2max, and muscle performance were measured before and post intervention. As a result, HIIT-R and HIIT-F stimulated similar improvements in VO2max (17.1% ± 5.6% and 12.7% ± 6.7%, respectively, p > 0.05). Only the HIIT-F group revealed significant improvements in muscle performance (sit-ups, 16.5% ± 3.1%, standing broad jump 5.1% ± 2.2%, p < 0.05). Body fat percentage decreased (17.1% ± 7.4% and 12.6% ± 5.1%, respectively, p < 0.05) in both HIIT-R and HIIT-F with no between-group differences. We concluded that HIFT was equally effective in promoting body composition and aerobic fitness compared to HIIT-R. HIFT resulted in improved muscle performance, whereas the HIIT-R protocol demonstrated no gains.

The Effect of Different Training Strategies Applied to Football Referees On Maxvo2 and Running Performance

Aim: In this study, the effects of high-intensity interval training and sprint training on amateur football referees running performances expressed by the FIFA Athletic Test, Cooper Test and MAXVO2 were investigated. Methods: Football referees average age (23.88±2.10); average height (181.16±1.99) cm; body weight (74.42±2.46) kg and body mass index (22.66±.62) kg/m2 calculated. They were applied high-intensity interval training and speed training 3 days a week for 16 weeks. FIFA Athletic Test and Cooper Test were applied in the pre-test and post-test to see the effect of the training process on the referees. SPSS package program was used to analyze the data. "Paired Sample t-Test" was used for the normally distributed data, and the "Wilcoxon Signed Rows Test", which is a nonparametric test, for non-normally distributed data, and the effect size was calculated. The results were evaluated according to the significance level "0.01" and "0.05". Results: When the FIFA Athletic Test, Cooper Test, body weight, and BMI pre-test and post-test values were compared in football referees, a statistically significant difference was found between the first measurement and the second measurement (p&lt;0.05). Conclusion: As a result of the study, it was observed that the training sessions had a positive effect on amateur football referees' running performances expressed by FIFA Athletic Test and Cooper Test and MAXVO2. This training program is recommended for the improvement of the degree-based running performances of amateur football referees. Keywords: Football referee, training, high-intensity interval running

A Comparison Of High-intensity Interval Running And Tabata On Post-exercise Metabolism: A Pilot Analysis

PURPOSE: Compare the metabolic rate following: 1) no exercise (rest), 2) completion of high-intensity interval running (HIIR) and 3) completion of Tabata. METHODS: Recreationally active individuals (n = 7; 6F, 1 M; age = 22.2 ± 2.1 yrs; body mass = 64.2 ± 12.0 kg; body fat% = 26.2 ± 3.1) performed each of the 3 bouts on separate days with at least 7 days in between each bout. Rest consisted of sitting for 25 minutes. Tabata was performed for 25 minutes and involved performing repeated cycles of body calisthenics at maximal effort for 20 seconds followed with 10 seconds of rest. HIIR was performed for 25 minutes with repeated cycles of running for 20 seconds followed with 10 seconds of rest. Both Tabata and HIIR were set up to be performed at the same heart rate (HR). Ten minutes following the completion of each bout, the participants’ metabolic rate (MR) was assessed in 10-minute intervals over the next hour. The MR assessment included the participants’ average VO2 (l/min), respiratory exchange ratio (RER), fat oxidation (total grams), and total energy expenditure (TEE). Significant differences (p < .05) between the bouts were determined using a one-way, repeated measures ANOVA and Bonferroni post-hoc test. RESULTS: Average HR (bpm) during Tabata (174.9 ± 5.2) was significantly higher (p = .027, ES = 1.2) compared to HIIR (166.4 ± 9.3). Average VO2 was unchanged between bouts (p = .62). TEE was unchanged between bouts (p = .28). RER was significantly lower following both HIIR (.75 ± .04, p = .002, ES = -1.8) and Tabata (.71 ± .02, p = .001, ES = -2.5) compared to rest (.83 ± .05) and there was no significant difference between exercises (p = .084). Fat oxidation was significantly higher following both HIIR (5.7 ± 1.5, p = .001; ES = 1.4) and Tabata (6.9 ± 1.4, p = .0004; ES = 2.2) compared to rest (3.7 ± 1.5) and Tabata was significantly higher than HIIR (p = .035, ES = .83). CONCLUSION: Despite the significant differences in heart rate between HIIR and Tabata both exercise bouts elicited similar changes in post-exercise metabolism when compared to rest. Both HIIR and Tabata might be lifestyle practices that promote healthy weight management; however, the small sample size and short metabolic assessment period limits the application of our results. A larger sample size and an expanded assessment period could better clarify the effectiveness of these exercises.

Effects of high-intensity interval exercise and moderate-intensity continuous exercise on executive function of healthy young males

PurposeThis study compared the executive function (EF) performance induced by moderate-intensity continuous exercise (MICE) versus high-intensity interval exercise (HIIE), under two exercise modalities (i.e., running vs. cycling), and explored whether the changes in EF performance were related to the hemodynamics response of the cerebral prefrontal area of the brain. MethodsIn a randomized cross-over design, 16 male participants completed 4 main trials, i.e., 40 min of moderate-intensity continuous running (MICR) or cycling (MICC) with 60% maximal oxygen consumption (VO2max), 33 min of high-intensity interval running (HIIR) or cycling (HIIC). For HIIR or HIIC trials, the exercise intensity was 60% VO2max for the first 5 min, followed by four 4-minute bouts of exercise at 90% VO2max, separated by 3-minute active recovery at 60% VO2max. EF was assessed via the Eriksen Flanker task (EFT) before (Pre), immediately after (Post 0), and 10 min after exercise (Post 10). Functional near-infrared spectroscopy (fNIRS) measured oxygenated hemoglobin (O2Hb) and deoxygenated hemoglobin (HHb) concentrations in the prefrontal area. Each main trial measured the concentrations of blood glucose and lactate, heart rate, and rate of perceived exertion. Results(1) Compared to the reaction time in EFT during the pretest, the corresponding reaction time was shorter at Post 10 (P < 0.01) but not at Post 0 (P = 0.06). Specifically, reaction time was shorter at Post 10 than in the pretest in HIIC (P = 0.04), MICC (P = 0.01), and HIIR (P < 0.01) but not MICR. (2) The fNIRS results revealed that O2Hb concentrations in the left dorsolateral prefrontal cortex area were much lower during Post 10 than during the pretest. (3) The blood lactate concentrations were not associated with EF performance regarding both accuracy and reaction time. ConclusionCompared to the pretest, EF was greater after the 10-minute rest during recovery but not immediately after exercise. The different HIIE or MICE protocols adopted in the present study may elicit minor differences regarding their effects on EF.

High-intensity interval running impairs subsequent upper limb strength performance.

This study compared the effect of treadmill running on subsequent upper limb exercise performance in young men. Seventeen young men (24.8±5.2 years) completed a: 1) bench press resistance exercise control session; 2) treadmill interval running protocol followed by the bench press session; and 3) treadmill continuous running protocol followed by the bench press session. Four sets of the bench press exercise were performed at 80% of 1RM up to volitional failure. In the interval protocol, eight sprints of 40s at 100% of the velocity of maximal oxygen uptake, with 20s of passive interval between them were performed, whereas in the continuous protocol 30-min of treadmill running at 90% of the heart rate corresponding to second ventilatory threshold was performed. The number of maximal repetitions completed in each set and condition was recorded and compared using a two-way repeated measures ANOVA. The interval protocol (18.7±4.9 repetitions) resulted in a reduction in the number of bench press repetitions compared to the control protocol (21.4±5.4 repetitions) (P=0.002); whereas continuous running did not affect the bench press performance (20.6±4.4 repetitions). The total number of repetitions reduced from set to set in all protocols (P<0.001). The results evidenced an impairment in the upper limb strength performance after high intensity interval, but not moderate intensity continuous running, which has implication for concurrent training planning and prescription.

The Effects of an Acute "Train-Low" Nutritional Protocol on Markers of Recovery Optimization in Endurance-Trained Male Athletes.

This study aimed to determine the effects of an acute "train-low" nutritional protocol on markers of recovery optimization compared to standard recovery nutrition protocol. After completing a 2-hour high-intensity interval running protocol, 8 male endurance athletes consumed a standard dairy milk recovery beverage (CHO; 1.2g/kg body mass [BM]of carbohydrate and 0.4g/kg BM of protein) and a low-carbohydrate (L-CHO; isovolumetric with 0.35g/kg BM of carbohydrate and 0.5g/kg BM of protein) dairy milk beverage in a double-blind randomized crossover design. Venous blood and breath samples, nude BM, body water, and gastrointestinal symptom measurements were collected preexercise and during recovery. Muscle biopsy was performed at 0hour and 2hours of recovery. Participants returned to the laboratory the following morning to measure energy substrate oxidation and perform a 1-hour distance test. The exercise protocol resulted in depletion of muscle glycogen stores (250mmol/kg dry weight) and mild body-water losses (BM loss = 1.8%). Neither recovery beverage replenished muscle glycogen stores (279mmol/kg dry weight) or prevented a decrease in bacterially stimulated neutrophil function (-21%). Both recovery beverages increased phosphorylation of mTORSer2448 (main effect of time = P < .001) and returned hydration status to baseline. A greater fold increase in p-GSK-3βSer9/total-GSK-3β occurred on CHO (P = .012). Blood glucose (P = .005) and insulin (P = .012) responses were significantly greater on CHO (618mmol/L per 2h and 3507μIU/mL per 2h, respectively) compared to L-CHO (559mmol/L per 2h and 1147μIU/mL per 2h, respectively). Rates of total fat oxidation were greater on CHO, but performance was not affected. A lower-carbohydrate recovery beverage consumed after exercise in a "train-low" nutritional protocol does not negatively impact recovery optimization outcomes.

The acute effect of high- and moderate-intensity interval exercise on vascular function before and after a glucose challenge in adolescents.

What is the central question of this study? What is the effect of high-intensity and moderate-intensity interval running on macro- and microvascular function in a fasted state and following a glucose challenge in adolescents? What is the main finding and its importance? Both macro- and microvascular function were improved after interval running independent of intensity. This finding shows that the intermittent exercise pattern and its associated effect on shear are important for vascular benefits. In adolescents, macrovascular function was enhanced after an acute glucose load. However, the effect of chronic glucose consumption on vascular function remains to be elucidated. Interventions targeting vascular function in youth are an important strategy for the primary prevention of cardiovascular diseases. This study examined, in adolescents, the effect of high-intensity interval running (HIIR) and moderate-intensity interval running (MIIR) on vascular function in a fasted state and postprandially after a glucose challenge. Fifteen adolescents (13 male, 13.9±0.6years) completed the following conditions on separate days in a counterbalanced order: (1) 8×1min HIIR interspersed with 75s recovery; (2) distance-matched amount of 1min MIIR interspersed with 75s recovery; and (3) rest (CON). Macro- (flow-mediated dilatation, FMD) and microvascular (peak reactive hyperaemia, PRH) function were assessed immediately before and 90min after exercise/rest. Participants underwent an oral glucose tolerance test (OGTT) 2h after exercise/rest before another assessment of vascular function 90min after the OGTT. Following exercise, both HIIR and MIIR increased FMD (P=0.02 and P=0.03, respectively) and PRH (P=0.04, and P=0.01, respectively) with no change in CON (FMD: P=0.51; PRH: P=0.16) and no significant differences between exercise conditions. Following the OGTT, FMD increased in CON (P<0.01) with no changes in HIIR and MIIR (both P>0.59). There was no change in PRH after the OGTT (all P>0.40). In conclusion, vascular function is improved after interval running independent of intensity in adolescents. Acute hyperglycaemia increased FMD, but prior exercise did not change vascular function after the OGTT in youth.

Does the Nutritional Composition of Dairy Milk Based Recovery Beverages Influence Post-exercise Gastrointestinal and Immune Status, and Subsequent Markers of Recovery Optimisation in Response to High Intensity Interval Exercise?

This study aimed to determine the effects of flavored dairy milk based recovery beverages of different nutrition compositions on markers of gastrointestinal and immune status, and subsequent recovery optimisation markers. After completing 2 h high intensity interval running, participants (n = 9) consumed a whole food dairy milk recovery beverage (CM, 1.2 g/kg body mass (BM) carbohydrate and 0.4 g/kg BM protein) or a dairy milk based supplement beverage (MBSB, 2.2 g/kg BM carbohydrate and 0.8 g/kg BM protein) in a randomized crossover design. Venous blood samples, body mass, body water, and breath samples were collected, and gastrointestinal symptoms (GIS) were measured, pre- and post-exercise, and during recovery. Muscle biopsies were performed at 0 and 2 h of recovery. The following morning, participants returned to the laboratory to assess performance outcomes. In the recovery period, carbohydrate malabsorption (breath H2 peak: 49 vs. 24 ppm) occurred on MBSB compared to CM, with a trend toward greater gut discomfort. No difference in gastrointestinal integrity (i.e., I-FABP and sCD14) or immune response (i.e., circulating leukocyte trafficking, bacterially-stimulated neutrophil degranulation, and systemic inflammatory profile) markers were observed between CM and MBSB. Neither trial achieved a positive rate of muscle glycogen resynthesis [−25.8 (35.5) mmol/kg dw/h]. Both trials increased phosphorylation of intramuscular signaling proteins. Greater fluid retention (total body water: 86.9 vs. 81.9%) occurred on MBSB compared to CM. Performance outcomes did not differ between trials. The greater nutrient composition of MBSB induced greater gastrointestinal functional disturbance, did not prevent the post-exercise reduction in neutrophil function, and did not support greater overall acute recovery.

Menopause Delays the Typical Recovery of Pre-Exercise Hepcidin Levels after High-Intensity Interval Running Exercise in Endurance-Trained Women.

Menopause commonly presents the gradual accumulation of iron in the body over the years, which is a risk factor for diseases such as cancer, osteoporosis, or cardiovascular diseases. Running exercise is known to acutely increase hepcidin levels, which reduces iron absorption and recycling. As this fact has not been studied in postmenopausal women, this study investigated the hepcidin response to running exercise in this population. Thirteen endurance-trained postmenopausal women (age: 51.5 ± 3.89 years; height: 161.8 ± 4.9 cm; body mass: 55.9 ± 3.6 kg; body fat: 24.7 ± 4.2%; peak oxygen consumption: 42.4 ± 4.0 mL·min−1·kg−1) performed a high-intensity interval running protocol, which consisted of 8 × 3 min bouts at 85% of the maximal aerobic speed with 90-s recovery. Blood samples were collected pre-exercise, 0, 3, and 24 h post-exercise. As expected, hepcidin exhibited higher values at 3 h post-exercise (3.69 ± 3.38 nmol/L), but also at 24 h post-exercise (3.25 ± 3.61 nmol/L), in comparison with pre-exercise (1.77 ± 1.74 nmol/L; p = 0.023 and p = 0.020, respectively) and 0 h post-exercise (2.05 ± 2.00 nmol/L; p = 0.021 and p = 0.032, respectively) concentrations. These differences were preceded by a significant increment of interleukin-6 at 0 h post-exercise (3.41 ± 1.60 pg/mL) compared to pre-exercise (1.65 ± 0.48 pg/m, p = 0.003), 3 h (1.50 ± 0.00 pg/mL, p = 0.002) and 24 h post-exercise (1.52 ± 0.07 pg/mL, p = 0.001). Hepcidin peaked at 3 h post-exercise as the literature described for premenopausal women but does not seem to be fully recovered to pre-exercise levels within 24 h post-exercise, as it would be expected. This suggests a slower recovery of basal hepcidin levels in postmenopausal women, suggesting interesting applications in order to modify iron homeostasis as appropriate, such as the prevention of iron accumulation or proper timing of iron supplementation.

Repeatability of training-induced skeletal muscle adaptations in active young males

ObjectivesMeasurements of protein content, enzymatic activity, and/or capillarization are frequently utilized as markers of skeletal muscle adaptation following exercise training. Whether changes in these markers of muscle adaptation are repeatable when individuals are repeatedly exposed to the same training stimulus is unknown. The purpose of this study was to test the repeatability of skeletal muscle adaptations to two identical training periods. MethodsTen active young males (age: 22 ± 2 years; VO2max: 57 ± 7 ml/kg/min) were exposed to two identical four-week periods of supervised high-intensity interval running (4 × 4 min at 90–95% of HRmax interspersed with 3-min at 70–75% HRmax) separated by a 3-month wash-out period. Vastus lateralis biopsies were obtained before and after each training period for the measurement of protein content, enzyme activity, and capillary density. ResultsTraining-induced changes in citrate synthase (CS) maximal activity, protein content (PGC-1α, OXPHOS, and LDH-A), and capillary density were not repeatable within individuals (r = −0.52–0.15; ICCs: −0.42–0.04; CVs: 11–67%). Several OXPHOS complex subunits also demonstrated dissimilar group-level adaptations (period × time interaction effects, p < 0.05) with large differences (ηp2 > 0.4) between training periods. A large (ηp2 = 0.65) increase in capillary density was apparent irrespective of training period (main effect of time, p = 0.05). ConclusionsAn individual (or a group of individuals) may exhibit dissimilar skeletal muscle adaptations when re-exposed to the same training stimulus. Our findings challenge the utility of classifying of individuals as high/low responders using measurements of mitochondrial protein content, CS activity and/or capillary density following a single training period.