Intermittent Running Protocol Research Articles

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.

Acute and prolonged effects of the simulated physical demands of a futsal match on lower limb muscle power and strength, sprint performance and muscle soreness

BACKGROUND: Prolonged fatigue effects may be a concern after futsal matches mainly because of the actions performed by futsal players (e.g., sprinting, jumping) that usually involve the stretch-shortening cycle (SSC). However, there no studies analyzed the prolonged effects of futsal-specific fatigue and how futsal players can recover from performance tasks. OBJECTIVE: To analyze the acute and prolonged effects of a protocol that simulates specific physical demands of futsal on countermovement-jump, sprint performance, muscle strength and muscle soreness. METHODS: Fifteen amateur futsal male athletes (18.3 ± 3.8 years) performed a futsal intermittent running protocol (FIRP) and were assessed for (moment production, sprint and jumping performance and muscle soreness) at pre, during half-time, immediately after, post 24 and 48 hours after the FIRP. Analysis of variance (repeated measures) was used to compare variable means over time. RESULTS: The main results indicated a decrement in the CMJ height (p= 0.03) and an increase of 10 m and 20 m sprint times (p= 0.01–p&lt; 0.01, respectively) during half-time and the post FIRP. There was a decrement in eccentric peak moment of the knee extensors (p= 0.02) and flexors (p&lt; 0.01) until 48h post protocol and a decrement in concentric peak moment of the flexors (p&lt; 0.01) post protocol. Athletes reported muscle soreness in the hamstrings (p= 0.03) post and 24 h after the FIRP. CONCLUSION: FIRP induced acute effects in the jump and sprint performances only. On the other hand, the knee moment production capability (mainly eccentric) suffered acute and also prolonged effects of the FIRP accompanied by delayed muscle soreness in the hamstring muscles.

Effects of Wearing a 50% Lower Jaw Advancement Splint on Biophysical and Perceptual Responses at Low to Severe Running Intensities.

Acute ergogenic effects of wearing occlusal splints have been reported for aerobic and anaerobic exercises, but the literature centered on performance improvement by using jaw repositioning splints is scarce. We aimed to analyze the effect of wearing a 50% lower jaw advancement splint on biophysical and perceptual responses at low to severe running intensities. Sixteen middle- and long-distance runners performed twice a 7 × 800 m intermittent running protocol (with 1 km·h−1 increments and 30 s rest periods) in an outdoor track field using two lower intraoral splints (a placebo and a lower jaw advancer). These devices were custom manufactured for each participant and a randomized and repeated measure design was used to compare conditions. No differences between placebo and lower jaw advancer were found (e.g., 52.1 ± 9.9 vs. 53.9 ± 10.7 mL·kg−1·min−1 of oxygen uptake, 3.30 ± 0.44 vs. 3.29 ± 0.43 m of stride length and 16 ± 3 vs. 16 ± 2 Borg scores), but small effects were sometimes observed (e.g., 109.2 ± 22.5 vs. 112.7 ± 25.2 L·min−1 of ventilation, ES = −0.42). Therefore, this jaw advancement splint had no substantial ergogenic effect on biophysical and perceptual responses when running at different intensities.

Effect of Different Running Exercise Modalities on Post-Exercise Oxidative Stress Markers in Trained Athletes.

The aim of this study was to examine the effect of running exercise modality on oxidative stress. Thirteen endurance athletes (age: 21.46 ± 0.66 years) performed three different running exercise modalities (Continuous running exercise (CR): continuous running exercise at 75% of VO2max for 25 min; intermittent running exercise #1 (15/15): intermittent running protocol, 15 s running at 75% of VO2max, 15 s passive recovery, performed for 50 min; intermittent running exercise #2 (30/30): intermittent running protocol, 30 s running at 75% of VO2max, 30 s passive recovery, performed for 50 min) in a randomized order. Blood samples were drawn at rest and immediately after each running exercise and assessed for malondialdehyde (MDA), advanced oxidation protein products (AOPP), superoxide dismutase(SOD), and glutathione peroxidase (GPX) activities. MDA increased by 55% following 30/30 exercise (p < 0.01), while it remained unchanged with CR and15/15 exercise. SOD increased after CR (+13.9%, p < 0.05), and also remained unchanged after 15/15 (p > 0.05) and decreased after 30/30 (−19.7% p < 0.05). GPX and AOPP did not change after exercise in all experimental sessions (p > 0.05). In conclusion, 30/30 intermittent running induced higher lipid damages than the 15/15 and CR exercise. 15/15 intermittent exercise promoted a better balance between free radicals production and antioxidant defense compared to continuous exercise and intermittent 30/30 exercise.

Running mechanics adjustments to perceptually-regulated interval runs in hypoxia and normoxia

ObjectivesWe determined whether perceptually-regulated, high-intensity intermittent runs in hypoxia and normoxia induce similar running mechanics adjustments within and between intervals. DesignWithin-participants repeated measures. MethodsNineteen trained runners completed a high-intensity intermittent running protocol (4×4-min intervals at a perceived rating exertion of 16 on the 6–20 Borg scale, 3-min passive recoveries) in either hypoxic (FiO2=0.15) or normoxic (FiO2=0.21) conditions. Running mechanics were collected over 10 consecutive steps, at constant velocity (∼15.0±2.0km.h−1), at the beginning and the end of each 4-min interval. Repeated measure ANOVA were used to assess within intervals (onset vs. end of each interval), between intervals (interval 1, 2, 3 vs. 4) and FiO2 (0.15 vs. 0.21) main effects and any potential interaction. ResultsParticipants progressively reduced running velocity from interval 1–4, and more so in hypoxia compared to normoxia for intervals 2, 3 and 4 (P<0.01). There were no between intervals (across all intervals P>0.298) and FiO2 (across all intervals P>0.082) main effects or any significant between intervals×within intervals×FiO2 interactions (all P>0.098) for any running mechanics variables. Irrespective of interval number or FiO2, peak loading rate (+10.6±7.7%; P<0.001) and duration of push-off phase (+2.0±3.1%; P=0.001) increased from the onset to the end of 4-min intervals, whereas peak push-off force decreased (−4.0±4.0%; P<0.001). ConclusionsWhen carrying out perceptually-regulated interval treadmill runs, runners adjust to progressively slower velocities in hypoxia compared to normoxia. However, only subtle constant-velocity modifications of their mechanical behaviour occurred within each set, independently of FiO2 or interval number.

Low Doses of Caffeine: Enhancement of Physical Performance in Elite Adolescent Male Soccer Players.

Context: High doses of ∼6mg·kg-1 body mass have improved performance during intermittent running, jumping, and agility protocols. However, there are sparse data on low doses of caffeine, especially in elite adolescent soccer players. Methods: A total of 15 elite youth soccer players (177.3 [4.8]cm, 66.9 [7.9]kg, and 16 [1]y) participated in the study, consuming 1, 2, or 3 mg·kg-1 caffeine in a gelatin capsule or a 2-mg·kg-1 placebo in a single-blind, randomized, crossover study design. Testing consisted of a 20-m sprint, arrowhead agility (change of direction [CoD] right or left), countermovement jump (CMJ), and Yo-Yo Intermittent Recovery Test Level 1 (Yo-Yo IR1). Postexercise CMJ performance was assessed as participants exited the Yo-Yo IR1. Data were analyzed using a Bayesian multilevel regression model to provide explained variance and probabilities of improvement (P = %). Results: Compared with placebo, 3 mg·kg-1 caffeine presented the highest probabilities of change across a range of tests (mean[SD], P = %). Times for 20-m sprint were 3.15 (0.10)s vs 3.18 (0.09)s (P = 73%), CoD-right times were 8.43 (0.24)s vs 8.55 (0.25)s (P = 99%), CoD-left times were 8.44 (0.22)s vs 8.52 (0.18)s (P = 85%), Yo-Yo IR1 distance was 2440 (531)m vs 2308 (540)m (P = 15%), and preexercise CMJ height was 41.6 (7.2)cm vs 38 (8.5)cm (P = 96%). Postexercise CMJ was higher with 3mg·kg-1 than with placebo (42.3 [8]cm vs 36.6 [8]cm; P = 100%). Doses of 1 or 2 mg·kg-1 caffeine also demonstrated the ability to enhance performance but were task dependent. Conclusion: Low doses of caffeine improve performance but are dose and task dependent. A dose of 3 mg·kg-1 caffeine improved performance across the majority of tests with potential to further improve postexercise CMJ height.

Selected Physiological, Perceptual, and Physical Performance Changes During Two Bouts of Prolonged High-Intensity Intermittent Running Separated by 72 Hours.

Dobbin, N, Lamb, KL, and Twist, C. Selected physiological, perceptual, and physical performance changes during two bouts of prolonged high-intensity intermittent running separated by 72 hours. J Strength Cond Res 31(12): 3474-3481, 2017-This study investigated the effects of performing a second 90-minute intermittent running protocol 72 hours after an initial trial on selected physiological, perceptual, and sprint running measures. Eight subelite soccer players provided measures of isokinetic muscle function, countermovement jump (CMJ), 10-m sprinting, and muscle soreness before, and at 0, 24, 48, and 72 hours after a 90-minute intermittent high-intensity running bout (IHIR-1). A second 90-minute IHIR bout (IHIR-2) was performed 72 hours after the first. Heart rates, ratings of perceived exertion (RPE), blood lactate concentration [Bla], and 10-m sprint times were recorded periodically during both IHIR. Analysis of effects revealed that in the 72-hour period after IHIR-1, there were most likely increases in muscle soreness and likely to very likely deteriorations in CMJ, 10-m sprint, and isokinetic muscle function. During IHIR-2, heart rates (possibly to likely) and [Bla] (possibly to very likely) were lower than IHIR-1, whereas RPE remained unchanged. Sprint times during IHIR-2 were also likely to very likely higher than in IHIR-1. It was evident that these team sport players exposed to repeat bouts of prolonged high-intensity running within 72 hours downregulated their sprint performances in the second bout despite no change in perceived effort. These findings have implications for managing training and match loads during periods of intense scheduling.

Passive and post-exercise cold-water immersion augments PGC-1α and VEGF expression in human skeletal muscle.

PurposeWe tested the hypothesis that both post-exercise and passive cold water immersion (CWI) increases PGC-1α and VEGF mRNA expression in human skeletal muscle.Method Study 1 Nine males completed an intermittent running protocol (8 × 3-min bouts at 90 % dot{V}{text{O}}_{2} hbox{max}, interspersed with 3-min active recovery (1.5-min at 25 % and 1.5-min at 50 % dot{V}{text{O}}_{2} hbox{max}) before undergoing CWI (10 min at 8 °C) or seated rest (CONT) in a counterbalanced, randomised manner. Study 2 Ten males underwent an identical CWI protocol under passive conditions.Results Study 1 PGC-1α mRNA increased in CONT (~3.4-fold; P < 0.001) and CWI (~5.9-fold; P < 0.001) at 3 h post-exercise with a greater increase observed in CWI (P < 0.001). VEGFtotal mRNA increased after CWI only (~2.4-fold) compared with CONT (~1.1-fold) at 3 h post-exercise (P < 0.01). Study 2 Following CWI, PGC-1α mRNA expression was significantly increased ~1.3-fold (P = 0.001) and 1.4-fold (P = 0.0004) at 3 and 6 h, respectively. Similarly, VEGF165 mRNA was significantly increased in CWI ~1.9-fold (P = 0.03) and 2.2-fold (P = 0.009) at 3 and 6 h post-immersion.ConclusionsData confirm post-exercise CWI augments the acute exercise-induced expression of PGC-1α mRNA in human skeletal muscle compared to exercise per se. Additionally CWI per se mediates the activation of PGC-1α and VEGF mRNA expression in human skeletal muscle. Cold water may therefore enhance the adaptive response to acute exercise.

Assessing Overreaching With Heart-Rate Recovery: What Is the Minimal Exercise Intensity Required?

Faster heart-rate recovery (HRR) after high to maximal exercise (≥90% of maximal heart rate) has been reported in athletes suspected of functional overreaching (f-OR). This study investigated whether this response would also occur at lower exercise intensity. Responses of HRR and rating of perceived exertion (RPE) were compared during an incremental intermittent running protocol to exhaustion in 20 experienced male triathletes (8 control subjects and 13 overload subjects led to f-OR) before and immediately after an overload training period and after a 1-wk taper. Both groups demonstrated an increase in HRR values immediately after the training period, but this change was very likely to almost certainly larger in the f-OR group at all running intensities (large to very large differences, eg, +16 ± 7 vs +3 ± 5 beats/min, in the f-OR and control groups at 11 km/h, respectively). The highest between-groups differences in changes in HRR were reported at 11 km/h (13 ± 4 beats/min) and 12 km/h (10 ± 6 beats/min). A concomitant increase in RPE at all intensities was reported only in the f-OR group (large to extremely large differences, +2.1 ± 1.5 to +0.7 ± 1.5 arbitrary units). These findings confirm that faster HRR does not systematically predict better physical performance. However, when interpreted in the context of the athletes' fatigue state and training phase, HRR after submaximal exercise may be more discriminant than HRR measures taken after maximal exercise for monitoring f-OR. These findings may be applied in practice by regularly assessing HRR after submaximal exercise (ie, warm-up) for monitoring endurance athletes' responses to training.

The Correlation Between Blood Lactate And Cardiac Troponin I following A Set Of Intermittent Running

Exercise intensity is considered to be a key factor affecting the release of cardiac troponin (cTn). However, most of the studies focus on responses of endurance sports or exercise. The experimental data of cTn and other biomarkers responses to intermittent exercise is still limited. PURPOSE: To determine the correlations between plasma cardiac troponin I (cTnI) and blood lactate, body mass index (BMI), as well as physiological characteristics after intermittent running. METHODS: Eighteen healthy, physically active collegiate males performed a graded exercise test to determine their VO2max and completed the intermittent running protocol 48 h later. This exercise protocol consisted of six 4-min running bouts and separated by 3 min of rest. Running velocity was set at an average of 90% VO2max. Capillary blood samples were drawn before and immediately after exercise for measuring lactate. Venous blood samples were collected at pre- and 3 h post-exercise for measuring cTnI. The nonparametric Spearman’s rank order correlation coefficient was used for statistic analysis. RESULTS: Plasma cTnI concentration was significantly increased following exercise. The delta cTnI was positively correlated with delta lactate (p = .013, rho = .57). However, no significant correlations were found between cTnI and body mass index, VO2max, as well as running velocity. CONCLUSION: The intermittent running protocol of this study induced the elevation in cTnI. The release of cTnI was associated with blood lactate level. As endurance sports, the intensity of intermittent exercise might be a factor affecting the release of cTn.

The influence of caffeine ingestion on strength and power performance in female team-sport players.

BackgroundThe aim of this study was to examine the influence of caffeine supplementation on knee flexor and knee extensor strength before, during and after intermittent running exercise in female team-sport players taking oral contraceptive steroids (OCS).MethodTen healthy females (24 ± 4 years; 59.7 ± 3.5 kg; undertaking 2–6 training sessions per week) taking low-dose monophasic oral contraceptives of the same hormonal composition took part in a randomised, double-blind, placebo-controlled crossover-design trial. Sixty minutes following the ingestion of a capsule containing 6 mg∙kg−1 body mass anhydrous caffeine or artificial sweetener (placebo), participants completed a 90-min intermittent treadmill-running protocol. Isometric strength performance and eccentric and concentric strength and power of the knee flexors and knee extensors (using isokinetic dynamometer), as well as countermovement jump (CMJ), was measured before, during and after the exercise protocol, as well as ~12 h post-exercise. Blood samples were taken before, during and post-exercise to measure glucose, insulin and free fatty acids (FFA).ResultsCaffeine supplementation significantly increased eccentric strength of the knee flexors (P < 0.05) and eccentric power of both the knee flexors (P < 0.05) and extensors (P < 0.05). However, there was no effect on isometric or concentric parameters, or CMJ performance. FFA was elevated with caffeine supplementation over time (P < 0.05) while levels of glucose and insulin were not affected by caffeine intake.ConclusionCaffeine supplementation increased eccentric strength and power in female team-sport players taking OCS both during an intermittent running protocol and the following morning.

Mental Fatigue Impairs Intermittent Running Performance.

The purpose of the study was to investigate the effects of mental fatigue on intermittent running performance. Ten male intermittent team sports players performed two identical self-paced, intermittent running protocols. The two trials were separated by 7 d and preceded, in a randomized-counterbalanced order, by 90 min of either emotionally neutral documentaries (control) or the AX-continuous performance test (AX-CPT; mental fatigue). Subjective ratings of fatigue and vigor were measured before and after these treatments, and motivation was recorded before the intermittent running protocol. Velocity, heart rate, oxygen consumption, blood glucose and lactate concentrations, and ratings of perceived exertion (RPE) were measured throughout the 45-min intermittent running protocol. Session RPE was recorded 30 min after the intermittent running protocol. Subjective ratings of fatigue were higher after the AX-CPT (P = 0.005). This mental fatigue significantly reduced velocity at low intensities (1.28 ± 0.18 m·s vs 1.31 ± 0.17 m·s; P = 0.037), whereas high-intensity running and peak velocities were not significantly affected. Running velocity at all intensities significantly declined over time in both conditions (P < 0.001). Oxygen consumption was significantly lower in the mental fatigue condition (P = 0.007). Other physiological variables, vigor and motivation, were not significantly affected. Ratings of perceived exertion during the intermittent running protocol were not significantly different between conditions despite lower overall velocity in the mental fatigue condition. Session RPE was significantly higher in the mental fatigue condition (P = 0.013). Mental fatigue impairs intermittent running performance. This negative effect of mental fatigue seems to be mediated by higher perception of effort.

Development of a non-damaging high-intensity intermittent running protocol.

The aim of the present study was to devise a non-damaging high-intensity intermittent running protocol. Ten healthy active men completed high-intensity interval running (8× 3-min bouts at 90% of maximal oxygen uptake interspersed with 3-min recovery) on a motorized treadmill under normal laboratory temperatures. Mean heart rate and rating of perceived exertion significantly increased during the intermittent protocol (the first bout, 15.3± 1.2; the final bout, 18.6± 0.9; P< 0.001). Blood lactate concentrations were significantly elevated following bout 1 compared with resting values (1.2± 0.3 mmol/L vs 5.4± 2.4 mmol/L; P = 0.03). However, no significant reduction in maximal voluntary contraction was observed immediately after completing the last exercise bout (623.9± 143.6 N) or during the subsequent 7-d period compared to pre-exercise values (P = 0.59). Creatine kinase (CK) concentrations were not significantly increased following exercise or during the subsequent 7-d period (P = 0.96). Myoglobin (Mb) content was significantly increased following exercise (P = 0.01), however, values returned towards pre-exercise concentrations after 24 h. These results indicate that the high-intensity intermittent running protocol induced changes in physiological and subjective indices that are consistent with the effects of acute fatigue as opposed to those changes normally associated with exercise-induced muscle damage. This exercise protocol can therefore be used to investigate the influence of high-intensity exercise from physiological responses to molecular adaptation.

The Impact of Inhaled Salbutamol on Repeated Sprint Ability in Pre- Fatigued Soccer Players

Objectives: Investigate the ergogenic effect of inhaling up to 1600 μg of salbutamol on intermittent running performance in pre-fatigued soccer players. Methods: In a single blind randomised repeated measures design seven male and six female soccer players volunteered to participant. All participants were regularly playing competitive soccer and had no history of asthma. Following familiarisation sessions participants visited the exercise physiology laboratory on three occasions to complete an intermittent running protocol followed by twelve 17.5 m sprints. Prior to each trial participants inhaled either: placebo, 800 μg inhaled salbutamol (SAL800) or 1600 μg inhaled salbutamol (SAL1600). Following completion of the sprints a sample from the first urine passed was analysed for salbutamol concentration. A repeated measures ANOVA was used to compare the mean sprint time, maximal sprint power, peak blood lactate post sprints and post sprint salbutamol urine concentration between conditions. Results: Mean sprint time, maximum power, maximum velocity, peak HR and peak blood lactate during the 17.5 m sprints were not significantly different between treatments in soccer players. There was no significant difference between male and female players in urine drug concentration following SAL800 (mean + SD; 201.47 + 294.47 ng.ml-1 vs. 180.2 + 102.15 ng.ml-1) or SAL1600 (739.24 + 549.21 ng.ml-1 vs. 879.58 + 633.14 ng.ml-1). Three players urine drug concentrations were above the WADA decision limit set at 1200 ng.ml-1. Conclusions: Inhaling up to 1600 μg inhaled salbutamol did not significantly improve repeated sprint performance. However, inhalation of 1600 μg may result in a urine concentration above the current WADA upper limit and decision limit leading to a positive test. Athletes should ensure they use inhaled salbutamol at therapeutic doses to avoid the risk of breaching the WADA decision limit.

Carbohydrate beverages attenuate bone resorption markers in elite runners

ObjectiveWe evaluated the effects of carbohydrate (CHO) supplementation on markers of bone turnover in elite runners. DesignTwenty-four male runners were randomly assigned to two groups – a CHO and a control (CON) group – using a double-blind design. The participants were submitted to an overload training program (days 1–8), followed by a high-intensity intermittent running protocol (10×800m) on day 9. They received a maltodextrin solution (CHO group) or a placebo solution as the CON equivalent, before, during, and after these protocols. ResultsAfter 8days of intensive training, baseline levels of osteocalcin (OC) decreased in both CHO and CON groups (before: 28.8±3.6 and 26.6±2.4ng/ml, after: 24.8±3.0 and 21.9±1.6ng/ml, respectively, p<0.01). On day 9, at 80min of the recovery period, carboxy-terminal of telopeptide type I collagen (CTX) serum concentration was suppressed in the CHO group (0.3±0.1ng/ml) vs. 0.6±0.0ng/ml for the CON group (p<0.01). CHO supplementation was effective in decreasing CTX levels from baseline to recovery (0.5±0.1ng/mL to 0.3±0.1ng/mL, p<0.001), while an increase from 0.4±0.0ng/mL to 0.6±0.0ng/mL (p<0.001) was observed in the CON group. ConclusionCHO beverage ingestion attenuated the exercise-induced increase in CTX concentration, suggesting that CHO supplementation is a potential strategy to prevent bone damage in athletes.

Simulated games activity vs continuous running exercise: A novel comparison of the glycemic and metabolic responses in T1DM patients

To compare the glycemic and metabolic responses to simulated intermittent games activity and continuous running exercise in type 1 diabetes. Nine patients (seven male, two female; 35 ± 4 years; HbA1c 8.1 ± 0.2%/65 ± 2 mmol/mol) treated on a basal-bolus regimen completed two main trials, a continuous treadmill run (CON) or an intermittent running protocol (INT). Patients arrived to the laboratory fasted at ∼ 08:00 h, replicating their usual pre-exercise meal and administering a 50% reduced dose of rapid-acting insulin before exercising. Blood glucose (BG), K(+) , Na(++) , pH, triglycerides, serum cortisol and NEFA were measured at baseline and for 60 min post-exercise. Interstitial glucose was measured for a further 23 h under free-living conditions. Following exercise, BG declined under both conditions but was less under INT (INT -1.1 ± 1.4 vs CON -5.3 ± 0.4 mmol/L, P = 0.037), meaning more patients experienced hypoglycemia (BG ≤ 3.5 mmol/L; CON n = 3 vs INT n = 2) but less hyperglycemia (BG ≥ 10.9 mmol/L; CON n = 0 vs INT n = 6) under CON. Blood lactate was significantly greater, and pH lower, with a temporal delay in K(+) under INT (P < 0.05). No conditional differences were observed in other measures during this time, or in interstitial glucose concentrations during the remaining 23 h after exercise. Simulated games activity carries a lower risk of early, but not late-onset hypoglycemia than continuous running exercise in type 1 diabetes.

Effect of Caffeine on Reactive Agility Time When Fresh and Fatigued

This study examined the effects of acute caffeine ingestion on agility performance and decision-making accuracy after simulated team-sport exercise. Using a randomized, double-blinded, counterbalanced design, 10 moderately trained male team-sport athletes ingested either caffeine (6 mg·kg(-1)) or placebo (dextrose) 60 min before completing an 80-min (4 × 20 min) simulated team-game, intermittent running protocol. Interspersed between each exercise quarter was a reactive agility test (RAT) consisting of five trials where measures of total time (TT), reactive agility (RA) time, decision time (DT), movement time (MT), and decision-making accuracy were obtained. Although there were no significant differences between trials for TT (P = 0.54), RA time (P = 0.84), MT (P = 0.89), or DT (P = 0.91), caffeine ingestion resulted in consistently faster TT (2.3%), RA time (3.9%), MT (2.7%), and DT (9.3%) scores compared with placebo (significant main effect for condition for RA time, TT, DT, and MT; P < 0.05). These faster times were supported by qualitative analyses of "almost certain benefit" and large effect size (ES) for RA (quarter 3) and "likely" to "very likely benefits" and moderate to large ES for TT (precircuit and quarters 1, 2, and 4) and RA time (precircuit and quarters 1, 2 and 4). A "likely benefit" and moderate ES was found for MT (quarters 1 and 3), but the effect of caffeine on DT was largely "unclear," with small ES and only a "likely" chance of benefit (quarters 2 and 3). Improved decision-making accuracy (3.8%) after caffeine ingestion was supported by a "likely benefit" (quarter 1) and large ES (quarters 1 and 4). Caffeine ingestion may be beneficial to RA performance when athletes are fresh and fatigued.

Carbohydrate supplementation delays DNA damage in elite runners during intensive microcycle training

The aim of this study was to evaluate the effect of carbohydrate supplementation on free plasma DNA and conventional markers of training and tissue damage in long-distance runners undergoing an overload training program. Twenty-four male runners were randomly assigned to two groups (CHO group and control group). The participants were submitted to an overload training program (days 1-8), followed by a high-intensity intermittent running protocol (10 × 800 m) on day 9. The runners received maltodextrin solution (CHO group) or zero energy placebo solution as the control equivalent before, during, and after this protocol. After 8 days of intensive training, baseline LDH levels remained constant in the CHO group (before: 449.1 ± 18.2, after: 474.3 ± 22.8 U/L) and increased in the control group (from 413.5 ± 23.0 to 501.8 ± 24.1 U/L, p < 0.05). On day 9, LDH concentrations were lower in the CHO group (509.2 ± 23.1 U/L) than in the control group (643.3 ± 32.9 U/L, p < 0.01) post-intermittent running. Carbohydrate ingestion attenuated the increase of free plasma DNA post-intermittent running (48,240.3 ± 5,431.8 alleles/mL) when compared to the control group (73,751.8 ± 11,546.6 alleles/mL, p < 0.01). Leukocyte counts were lower in the CHO group than in the control group post-intermittent running (9.1 ± 0.1 vs. 12.2 ± 0.7 cells/µL; p < 0.01) and at 80 min of recovery (10.6 ± 0.1 vs. 13.9 ± 1.1 cells/µL; p < 0.01). Cortisol levels were positively correlated with free plasma DNA, leukocytes, and LDH (all r > 0.4 and p < 0.001). The results showed that ingestion of a carbohydrate beverage resulted in less DNA damage and attenuated the acute post-exercise inflammation response, providing better recovery during intense training.

Development of laboratory-based intermittent running protocols that are matched for various physiological parameters

Data from cycling based protocols demonstrate that high-intensity interval training (HIT) is a more efficient mode of exercise training compared with traditional moderate-intensity continuous (CONT) approaches. The use of cycling...

Previous‐day hypohydration impairs skill performance in elite female field hockey players

The purpose of this study was to determine the effects of 2% hypohydration on skill performance in elite female field hockey players following intermittent exercise in the heat. Eight elite female field hockey players performed 50 min of a field hockey-specific intermittent treadmill running protocol (FHITP) in hot environmental conditions (33 °C, 60% relative humidity) in different hydration states: euhydrated (EUH) and hypohydrated by 2% body mass (HYPO). Hydration status was manipulated via a period (121±10 min) of passive hyperthermia (40 °C, 75% relative humidity) and controlled fluid intake 1 day preceding testing. Ad libitum fluid intake was permitted throughout both trials. Field hockey skill tests were performed pre- and post-FHITP. Skill performance time increased (P=0.029) in the HYPO trial compared with the EUH trial, which may be attributed to an increase in penalty time (P=0.024). Decision-making time increased (P=0.008) in the HYPO trial and was significantly impaired compared with EUH (P=0.016) pre-FHITP. Ad libitum drinking appeared to be sufficient to maintain decision-making performance as no interaction effects were evident post-FHITP. Players who commence match-play in a state of hypohydration may be susceptible to decrements in skill and decision-making performance.