Second Bout Of Exercise Research Articles

Physiological, Performance and Perceptual Effects of Acute Intake of an L-Arginine and L-Citrulline Beverage Prior to a Repeated Bout of Intensive Running Among University Soccer Players

The purpose of this study was to determine whether a combined L-arginine and L-citrulline beverage can enhance total nitric oxide (NOx), as well as physiological (cardiopulmonary metrics) and perceptual (rate of perceived exertion) responses to a repeated bout of high-intensity exercise among university soccer players. Thirty male soccer players were included in a randomized double-blind, placebo-controlled, parallel design. Participants performed two bouts of high-intensity running, spaced two hours apart. Forty minutes before the second bout only, participants consumed a 500 mL beverage containing 6 g L-arginine and 6 g L-citrulline (n = 15) or placebo (n = 15). Blood NOx concentration was measured immediately before and after both bouts. There was no significant increase in NOx or significant interaction effects for physiological, performance, or perceptual variables between the L-arginine/L-citrulline and placebo groups. The peak volume of oxygen uptake of the L-arginine/L-citrulline group was significantly higher in the second compared with the first exercise bout (54.92 ± 4.81 vs. 50.54 ± 9.22 mL/kg/min; p = 0.01). In the second bout of exercise, time to exhaustion in the L-arginine/L-citrulline group increased by 8.5% (~60 s) compared to the first. In conclusion, these results suggest that a single dose of L-arginine/L-citrulline beverage did not increase NOx yet seemed to impact aerobic metabolism in university soccer players.

The lactate response to a second bout of exercise is not reduced in a concurrent lower-limb exercise program

We aimed to evaluate the blood lactate level in response to two bouts of exercise. First, we hypothesized that blood lactate elevation in response to moderate-intensity aerobic exercise (MIAE) would be lower at the end of the second bout of MIAE than the first bout of MIAE. In this context, we also hypothesized that lactate accumulation at the end of resistance exercise (RE) would be reduced if MIAE is performed before RE (i.e., concurrent exercise; CE). If so, we hypothesized that the order of the CE (i.e., RE + MIAE vs. MIAE + RE) influences blood lactate kinetics. To test the hypotheses, forty-three healthy men participated in three studies. In study 1, 20 men (age 21 ± 2 years) performed two bouts of a 20-min MIAE separated by a 20-min rest interval. In study 2, 11 men (age 22 ± 1 years) performed RE only and CE (MIAE + RE; ARCE) with a 20-min rest interval in a crossover design. In study 3, 12 men (age 21 ± 2 years) performed both CEs, which were ARCE and RE + MIAE (RACE), with a 20-min rest interval in a crossover design. We measured blood lactate before and at the end of each exercise session. In study 1, the blood lactate response to the second bout of MIAE was lower than that of the first bout (P < 0.001, r = 0.68). However, the blood lactate response to the ARCE trial was not lower than the response to the RE trial in study 2 (P = 0.475, r = 0.22). The results of study 3 showed that the RACE and ARCE trials induced a similar lactate response (MIAE P = 0.423, r = 0.28; RE P = 0.766, d = 0.03). These observations indicate that whereas lactate accumulation might be diminished by a second bout of MIAE, a different type of exercise (i.e., aerobic/resistance) did not result in a diminished lactate accumulation in response to a second bout of exercise.

Continuous Monitoring of Interstitial Fluid Glucose Responses to Endurance Exercise with Different Levels of Carbohydrate Intake.

We compared the 24 h changes in interstitial fluid glucose concentration (IGC) following a simulated soccer match between subjects consuming a high-carbohydrate (HCHO; 8 g/kg BW/day) diet and those consuming a moderate-carbohydrate (MCHO; 4 g/kg BW/day) diet. Eight active healthy males participated in two different trials. The subjects were provided with the prescribed diets from days 1 to 3. On day 3, the subjects performed 90 min (2 bouts × 45 min) of exercise simulating a soccer match. The IGC of the upper arm was continuously monitored from days 1 to 4. No significant difference in the IGC was observed between trials during exercise. The total area under the curve (t-AUC) value during exercise did not significantly differ between the HCHO (9719 ± 305 mg/dL·90 min) and MCHO (9991 ± 140 mg/dL·90 min). Serum total ketone body and beta-hydroxybutyrate concentrations were significantly higher in the MCHO than in the HCHO after a second bout of exercise. No significant differences in the IGC were observed between trials at any time point during the night after exercise (0:00-7:00). In addition, t-AUC value during the night did not significantly differ between the HCHO (32,378 ± 873 mg/dL·420 min) and MCHO (31,749 ± 633 mg/dL·420 min). In conclusion, two days of consuming different carbohydrate intake levels did not significantly affect the IGC during a 90 min simulated soccer match. Moreover, the IGC during the night following the exercise did not significantly differ between the two trials despite the different carbohydrate intake levels (8 vs. 4 g/kg BW/day).

The repeated bout effect influences lower-extremity biomechanics during a 30-min downhill run

ABSTRACT The repeated bout effect in eccentric-biased exercises is a well-known phenomenon, wherein a second bout of exercise results in attenuated strength loss and soreness compared to the first bout. We sought to determine if the repeated bout effect influences changes in lower-extremity biomechanics over the course of a 30-min downhill run. Eleven male participants completed two bouts of 30-min downhill running (DR1 and DR2) at 2.8 m.s−1 and −11.3° on an instrumented treadmill. Three-dimensional kinematics and ground reaction forces were recorded and used to quantify changes in spatiotemporal parameters, external work, leg stiffness, and lower extremity joint-quasi-stiffness throughout the 30-min run. Maximum voluntary isometric contraction (MVIC) and perceived quadriceps pain were assessed before-after, and throughout the run, respectively. DR2 resulted in attenuated loss of MVIC (P = 0.004), and perceived quadriceps pain (P < 0.001) compared to DR1. In general, participants ran with an increased duty factor towards the end of each running bout; however, increases in duty factor during DR2 (+5.4%) were less than during DR1 (+8.8%, P < 0.035). Significant reductions in leg stiffness (−11.7%, P = 0.002) and joint quasi-stiffness (up to −25.4%, all P < 0.001) were observed during DR1 but not during DR2. Furthermore, DR2 was associated with less energy absorption and energy generation than DR1 (P < 0.004). To summarize, the repeated bout effect significantly influenced lower-extremity biomechanics over the course of a downhill run. Although the mechanism(s) underlying these observations remain(s) speculative, strength loss and/or perceived muscle pain are likely to play a key role. Highlights A 30-min downhill running bout increased contact time and reduced flight time transitioning to an increased duty factor. Lower-extremity stiffness also decreased and mechanical energy absorption increased over the course of the first 30-min downhill running bout. When the same bout of 30-min downhill running was performed three weeks later, the observed changes to lower extremity biomechanics were significantly attenuated. The findings from this study demonstrated, for this first time, a repeated bout effect for lower extremity biomechanics associated with downhill running.

Salutary Acute Effects of Exercise on Central Hemodynamics in Heart Failure With Preserved Ejection Fraction

BackgroundA warmup period of priming exercise has been shown to improve peripheral oxygen transport in older adults. We sought to determine the acute effects of priming exercise on central hemodynamics at rest and during a repeat exercise in heart failure with preserved ejection fraction (HFpEF). Methods and ResultsThis is a post hoc analysis from 3 studies. Patients with HFpEF (n = 42) underwent cardiac catheterization with simultaneous expired gas analysis at rest and during exercise (20 W for 5 minutes, priming exercise). Measurements were then repeated at rest and during a second bout of exercise at a 20-W workload (second exercise). During the priming exercise, patients with HFpEF displayed dramatic increases in biventricular filling pressures and exercise-induced pulmonary hypertension. After the priming exercise at rest, biventricular filling pressures and pulmonary artery (PA) pressures were lower and lung tidal volume was increased. During the second bout of exercise, biventricular filling (PA wedge pressure, 29 ± 8 mm Hg at second exercise vs 32 ± 7 mm Hg at first exercise, P = .0003) and PA pressures were lower, and PA compliance increased. ConclusionsThis study shows that short duration, submaximal priming exercise attenuates the pathologic increases in filling pressures, improving pulmonary vascular hemodynamics at rest and during repeat exercise in patients with HFpEF.

Acute physiological responses and performance following subsequent CrossFit ‘CINDY’ workout with Zea Mays juice

Purpose: The purpose of this study was to investigate the physiological responses and performance following subsequent repeated high intensity exercise with consumption of Zea may juice ( ZM ) Materials: Total of seventeen participants involved in the study. They were physically active who had cardio and strength training at least 3 times per week. The age of participants was 21.8±1.7 years old, body weight 65.4±11.2 kg and height 169.7±7.2 cm. Crossfit ‘CINDY’ exercise were repeated between two hours of rest. Treatment beverage of ( ZM ) juice vs Carbohydrate-electrolyte (CE) drinks were consumed immediately after exercise in double blind cross over manner. Number of complete set of exercise, heart rate, blood lactate and rate of perceived exhaustion (RPE) were recorded at the end of each exercise session. Results: Total number of complete ‘CINDY’ exercise significantly increased in ZM juice group during second bout of exercise compared to CE drink group. There were no significant difference in heart rate, blood lactate and RPE in both groups Conclusions: ZM juice has potentials an alternative recovery beverage to promote subsequent repeated exercise within short rest time.

Adaptations in antagonist co-activation: Role in the repeated-bout effect.

Eccentric exercise results in an adaptation which attenuates muscle damage from subsequent exercise—termed the “repeated-bout effect (RBE).” Purpose: Study examined antagonist co-activation and motor-unit recruitment strategy, assessed via dEMG, concomitant to the RBE. Methods: Nine participants performed 5 sub-maximal isometric trapezoid (ramp-up, hold, ramp-down) contractions at force levels corresponding to 50% and 80% of maximal isometric strength (MVC). Surface EMG signals of the biceps brachii were decomposed into individual motor-unit action potential trains. The relationship between mean firing rate (MFR) of each motor-unit and its recruitment threshold (RT) was examined using linear regression. Eccentric exercise was then performed until biceps brachii MVC had decreased by ~40%. Surface EMG of the biceps and triceps were collected during eccentric exercise. MVC, range-of-motion (ROM), and delayed onset muscle soreness (DOMS) were measured 24-hours, 72-hours, and 1-week following eccentric exercise. Three weeks later all procedures were repeated. Results: Changes in MVC (-32±14% vs -25±10%; p = 0.034), ROM (-11% vs 6%; p = 0.01), and DOMS (31.0±19mm vs 19±12mm; p = 0.015) were attenuated following the second bout of exercise. Triceps EMG was reduced (16.8±9.5% vs. 12.6±7.2%; p = 0.03) during the second bout of eccentric exercise. The slope (-0.60±0.13 vs -0.70±0.18; p = 0.029) and y-intercept (46.5±8.3 vs 53.3±8.8; p = 0.020) of the MFR vs. RT relationship was altered during contractions at 80% of MVC prior to the second bout of eccentric exercise. No changes were observed at 50% of MVC. Conclusion: A reduction in antagonist co-activation during the second bout of eccentric exercise suggests less total force was required to move an identical external load. This finding is supported by the increased negative slope coefficient and an increased y-intercept of the linear relationship between RT and MFR.

Iron Supplementation During 3 Consecutive Days Of Endurance Training Augmented Hepcidin Concentration

PURPOSE: Several physiological mechanisms have been proposed to explain impaired iron status, such as gastrointestinal bleeding, hemolysis, lack of iron in dietary diet and losses in sweat. However, detailed mechanisms underlying exercise-induced iron deficiency among athletes remain unclear. Hepcidin, the 25-amino acid peptide hormone, is a key mediator of iron homeostasis and it may represent another mechanism for iron deficiency in response to exercise training.The present study was designed to investigate impact of consecutive days of strenuous endurance training on hepcidin concentration. The influence of iron supplementation during training period was also determined. METHODS: Fourteen male endurance athletes (long distance runners, triathletes) participated (mean ± standard error, age: 19-22 yrs ; height: 1.68 ± 0.01m ; body mass: 57.3 ± 1.6 kg; maximal oxygen uptake (VO2max): 59.6 ± 0.8 ml/kg/min). Subjects were randomly assigned to either an iron treatment group (Fe group, n=7) or a placebo group (CON group, n=7). All subjects completed 3 consecutive days of endurance training, consisting of two bouts of 75 min of treadmill running at 75 % of VO2max, separated with 3h of rest between bouts. In the Fe group, 12 mg of iron was provided using flavor drink twice a day (24 mg/day), whereas the subjects in the CON group took the same flavor drink without iron. Venous blood samples were collected in early morning on days1-4 and 3h after second bout of exercise on day1. Serum hepcidin, ferritin, iron, myoglobin and plasma IL-6 concentrations were evaluated. RESULTS: The Fe and CON groups showed acute elevations of serum hepcidin, myoglobin and plasma IL-6 concentrations 3h after exercise (P < 0.05 vs. baseline). After 3 days of training period (day4), serum hepcidin concentration was significantly higher in Fe group than in CON group (11.0 ± 2.5 ng/mL vs. 5.9 ± 1.6 ng/mL, P < 0.05). Moreover, serum iron concentration was decreased only in Fe group on day 4 (91.3 ± 13.5 in the Fe group vs. 129.7 ± 7.4 μg/dL in the CON group). CONCLUSIONS: Three consecutive days of endurance training increased hepcidin concentration at baseline when the iron was supplemented.

Hypoglycemia during moderate intensity exercise reduces counterregulatory responses to subsequent hypoglycemia.

Hypoglycemia, which occurs commonly during and following exercise in people with diabetes, is thought to be due to attenuated counterregulation in the setting of therapeutic insulin excess. To better understand the pathophysiology of counterregulation, we aimed to determine if dextrose administration to maintain euglycemia during moderate intensity exercise alters the attenuation of counterregulatory responses to subsequent hypoglycemia in healthy adults. Counterregulatory responses to hypoglycemia were assessed in 18 healthy adults after bed rest and following exercise with (n = 9) and without (n = 9) dextrose infusion. Responses were measured during a stepped euglycemic‐hypoglycemic clamp 24 h after either bed rest or two 90‐min bouts of exercise at 70% peak oxygen uptake. Hypoglycemia occurred during the second bout of exercise without dextrose infusion. Plasma glucagon and epinephrine responses to stepped hypoglycemia after antecedent exercise without dextrose infusion were significantly lower at the 45 mg/dL glycemic level compared to after bed rest. However, no attenuation of the counterregulatory responses to hypoglycemia was evident after antecedent exercise when dextrose was infused. This study suggests that the attenuation of the counterregulatory responses during hypoglycemia after exercise is likely due to the hypoglycemia that occurs during moderate prolonged exercise and not solely due to exercise or its intensity.

Timing of carbohydrate ingestion did not affect inflammatory response and exercise performance during prolonged intermittent running.

BackgroundCarbohydrate ingestion during exercise is known to attenuate exercise-induced elevation of plasma IL-6 concentration. However, the influence of timing of carbohydrate ingestion remains unclear.PurposeThe present study investigated the influence of different timing of carbohydrate ingestion during a simulated soccer game on exercise performance, metabolic and inflammatory responses.MethodsSeven active males performed 3 exercise trials in a randomized order. The exercise consisted of two consecutive bouts of 45 min running (4–16 km/h), separated with 15 min rest period between bouts. The subjects ingested carbohydrate gel (1.0 g/kg) immediately before the first bout of exercise (ONE), immediately before first and second bouts of exercise (0.5 g/kg for each ingestion) (TWO) or placebo immediately before exercise (PLA) Time course changes of maximal jump height, peak power output during 6-s maximal pedaling, perceived fatigue and heart rate (HR) were monitored. Blood samples were also drawn to determine blood glucose, serum insulin, free fatty acid (FFA), myoglobin (Mb), creatine kinase (CK) and plasma IL-6 concentrations.ResultsBlood glucose and serum insulin concentrations were significantly higher in the ONE trial after first bout of 45 min exercise compared with PLA trial (P < 0.05), while serum FFA concentration was significantly elevated in PLA compared with ONE and TWO trials after second bout of exercise (P < 0.05). However, changes of jump height, peak power output during 6-s maximal pedaling, perceived fatigue, HR, or indirect muscle damage (Mb, CK) and inflammatory (IL-6) markers were not significantly different among three trials (P > 0.05).ConclusionsThe timing of carbohydrate ingestion did not affect exercise performance, exercise-induced muscle damage or inflammatory response during a simulated soccer game.

Post-Exercise Blood Pressure Response to Repeated Bouts of Aquatic Treadmill Exercise

An acute bout of endurance exercise is known to elicit a post-exercise hypotensive response. PURPOSE: Determine the effect of repeated bouts of aquatic treadmill exercise on consecutive days in physically untrained, pre-hypertensive men. Five male subjects (SBP: 132 ± 10 mmHg; DBP: 79 ± 6 mmHG; 29 ± 7 years; 180 ± 8 cm; 89.7 ± 22.7 kg; 29 ± 12% Fat; 40 ± 7 ml·kg−1·min−1) completed an acute aquatic treadmill exercise session (60% VO2max; 300 kcal) on two consecutive days. While subjects were seated post-exercise, blood pressure and heart rate were measured automatically every 10-minutes from 20 to 60 minutes post. A dependent sample t-test was performed on the average values recorded during this time period. RESULTS: Both absolute and percent changes for individual subjects and for the group as a whole are displayed in the table below. While changes were not significant, there was a trend towards a greater reduction in all parameters for the second exercise session. CONCLUSION: Most subjects showed reduced blood pressure (DBP: 100% of subjects; SBP, MAP: 80%) and heart rate (80%) following the second bout of exercise. Given a larger sample size than this preliminary data set, there may be a significant cumulative effect of repeated exercise bouts on the post-exercise hypotension response.Table: No title available.

Acute Eccentric or Concentric Exercise Does Not Improve Antibody Responses to Ovalbumin Vaccination in Mice.

Several published reports suggest that acute eccentric exercise can improve vaccination responses in young and old adults, especially if they are sub-optimal (Pascoe et al. Brain Behav Imm, 2014). The mechanisms are unclear but hypothesized to occur due to an inflammation-induced adjuvant effect on the immune response. In order to understand the mechanisms responsible for this effect, verification of this potential beneficial effect needs to be replicated in an animal model. PURPOSE: To determine the effects of acute eccentric or concentric exercise on the antibody response to vaccination in mice. METHODS: Balb/c male mice, aged 6 weeks (n=20) were randomized into one of three groups: concentric exercise (CON, n=7), eccentric exercise (ECC, n=6) or sedentary (SED, n=7). Initially, for the CON group, mice were exercised at 17m/min speed at +5% grade for 60 minutes on a treadmill. No electrical shock was used. The ECC group exercised at the same speed and duration but at -20% grade. After 24 hours, another bout of exercise was repeated. We have shown that this ECC protocol induces muscle damage and local inflammation in mice (Boppart et al, Am J Physiol Cell Physiol, 2011). All mice were intramuscularly inoculated in the gastrocnemius with 25μg (suboptimal dose from prior titration) of ovalbumin (OVA) and 200 μg aluminum hydroxide as adjuvant in 50μl sterile saline immediately after the second bout of exercise. Blood was collected before (pre) and one, two and four weeks after vaccination from the retro-orbital vein. Plasma anti-ovalbumin IgG was determined using ELISA procedures. RESULTS: We found a significant time main effect (p<0.001) indicating a significant increase in anti-OVA IgG at 1, 2 and 4 weeks relative to pre-vaccination. Interestingly, we found a significant time x treatment interaction (p=0.04) and a trend towards a treatment main effect (p=0.08) indicating that ECC exercise responses were blunted when compared to CON and SED, especially at the 4 week time point. CONCLUSION: We conclude, given the parameters of our study, that acute ECC or CON exercise does not improve antibody responses to vaccination in young mice when administered immediately after exercise. Future experiments will address whether acute exercise can improve vaccine responses in animals exhibiting impaired immunity (e.g. aged).

Higher Fat Oxidation When Post-Meal Exercise Is Proceeded By Pre-Meal Exercise In Diabetes Patients

PURPOSE: The progression from obesity to IGT and type 2 diabetes has been associated with blunted increase in fat oxidation during exercise and an inability to switch to carbohydrate oxidation after meal consumption. In healthy individuals, it has been demonstrated that dividing the exercise session in smaller bouts increases fat oxidation during exercise. Our aim was to compare the fat oxidation rates during exercise performed close to a standard meal. Therefore, 40 minutes of moderate-intensity aerobic exercise were performed either in a single post-meal session (ContEx) or in split in two 20-minute bouts, one before and the other after standard lunch (SplitEx). METHODS: Nine type 2 diabetes patients underwent two different experimental sessions, ContEx and SplitEx. A portable metabolic cart was used to measure respiratory fluxes of O2 and CO2, and thus calculate respiratory exchange rate and fat oxidation rate. Exercise intensity was set at 50% of the heart rate reserve, for a total of 40 minutes accumulated in either a single bout after a standard lunch (55% CHO, 25% fat, 20% protein) or in two bouts before and after lunch. RESULTS: Fat oxidation rate was significantly higher during the SplitEx compared to the ContEx experimental session (.42 ± .26 g*min-1 vs .28 ± .20 g*min-1, P = .04). When dividing the 40-min sessions in two 20-min sessions, i.e. pre and post meal bouts of SplitEx, and first 20 min and second 20 min of ContEx, fat oxidation rate was significantly higher in the post meal bout of SplitEx compared to the pre meal Splitex and the first and second 20 minutes of ContEx (.46 ± .25 g*min-1 vs .37 ± .27 g*min-1 vs .27 ± .2 g*min-1 vs .28 ± .18 g*min-1, P < .05). CONCLUSIONS: Exercising before a meal improves fat oxidation of a second bout of exercise in diabetes patients. This priming effect of prior exercise appears to persist even when insulin levels are high, like the early postprandial state, time when fat oxidation is expected to be low.

LED therapy or cryotherapy between exercise intervals in Wistar rats: anti-inflammatory and ergogenic effects

The aim of this study was to test, between two bouts of exercise, the effects of light-emitting diode (LED) therapy and cryotherapy regarding muscle damage, inflammation, and performance. Male Wistar rats were allocated in four groups: control, passive recovery (PR), cryotherapy (Cryo), and LED therapy. The animals were submitted to 45min of swimming exercise followed by 25min of recovery and then a second bout of either 45min of exercise (muscle damage analysis) or time to exhaustion (performance). During the rest intervals, the rats were kept in passive rest (PR), submitted to cold water immersion (10min, 10°C) or LED therapy (940nm, 4J/cm(2)) of the gastrocnemius muscle. Blood samples were collected to analyze creatine kinase activity (CK), C-reactive protein (CRP), and leukocyte counts. The soleus muscles were evaluated histologically. Time to exhaustion was recorded during the second bout of exercise. After a second bout of 45min, the results demonstrated leukocytosis in the PR and Cryo groups. Neutrophil counts were increased in all test groups. CK levels were increased in the Cryo group. CRP was increased in PR animals. The PR group presented a high frequency of necrosis, but the LED group had fewer necrotic areas. Edema formation was prevented, and fewer areas of inflammatory cells were observed in the LED group. The time to exhaustion was greater in both the LED and Cryo groups, without differences in CK levels. CRP was decreased in LED animals. We conclude that LED therapy and cryotherapy can improve performance, although LED therapy is more efficient in preventing muscle damage and local and systemic inflammation.

Time Course of the Cross-Over Effect of Fatigue on the Contralateral Muscle after Unilateral Exercise

We investigated the cross-over effect of muscle fatigue and its time course on the non-exercising contralateral limb (NEL) after unilateral fatiguing contractions of the ipsilateral exercising limb (EL). For this purpose, 15 males performed two bouts of 100-second maximal isometric knee extensions with the exercising limb, and neuromuscular function of both the EL and NEL was assessed before (PRE), after a first fatiguing exercise (MID) and after a second fatiguing exercise (POST). Maximal voluntary isometric torque production declined in the EL after the first bout of exercise (−9.6%; p<0.001) while in the NEL, the decrease occurred after the second bout of exercise (−10.6%; p<0.001). At MID, torque decline of the EL was strictly associated to an alteration of the mechanical twitch properties evoked by neurostimulation of the femoral nerve (i.e., peak twitch torque, maximal rate of twitch development). According to these markers, we suggest that peripheral fatigue occurred. At POST, after the second bout of exercise, the voluntary activation level of the knee extensor muscles was altered from PRE (−9.1%; p<0.001), indicating an overall central failure in both the EL and NEL. These findings indicate that two bouts of unilateral fatiguing exercise were needed to induce a cross-over effect of muscle fatigue on the non-exercising contralateral limb. Differential adjustments of the motor pathway (peripheral fatigue vs. central fatigue) might contribute to the respective torque decline in the EL and the NEL. Given that our unilateral fatiguing exercise induced immediate maximal torque reduction in the EL and postponed the loss of torque production in the NEL, it is also concluded that the time course of muscle fatigue differed between limbs.

Inflammatory markers CD11b, CD16, CD66b, CD68, myeloperoxidase and neutrophil elastase in eccentric exercised human skeletal muscles

The aim of the present study was to investigate leucocyte markers, CD11b, CD16, CD66b, CD68, myeloperoxidase and neutrophil elastase on skeletal muscle biopsies from biceps brachii after unaccustomed eccentric exercise followed by the second bout of exercise 3 weeks later. The subjects (10 subjects received COX-2 inhibitor (Celecoxib) and 13 subjects received placebo) were divided into three categories: mild, moderate and severe effect of eccentric exercise, according to the reduction and recovery of muscle force-generating capacity after performing 70 maximal eccentric actions with elbow flexors on an isokinetic dynamometer. The results showed that the CD66b antibody was applicable for localization of neutrophils in human skeletal muscle, whereas the other studied neutrophil markers recognized also other leucocytes than neutrophils. The number of CD66b positive cells in skeletal muscle was very low and was not affected by the exercise. The macrophage marker CD68 showed reactivity also against satellite cells and fibroblast-like cells in skeletal muscle and therefore cannot be applied as a quantitative value for inflammatory cells. Skeletal muscle fibre injury, shown as dystrophin negative fibres, was observed approximately in half of the biopsies at 4 and 7 days after the first exercise bout in the categories moderate and severe effect of eccentric exercise. These subjects represent the most prominent loss in muscle force-generating capacity both at the category and the individual levels. Furthermore, deformed skeletal muscle fibres were observed in five subjects in these categories after the second bout of exercise. The present results suggest that neutrophils are not involved in skeletal muscle fibre injury and the reduction in muscle force-generating capacity after a single bout of eccentric exercise is a good indirect indicator of muscle damage in humans. Furthermore, prolonged regeneration process could be one of the reasons for impaired peripheral muscle function after high-force eccentric exercise.

Decreased nerve growth factor upregulation is a mechanism for reduced mechanical hyperalgesia after the second bout of exercise in rats

Delayed onset muscle soreness (DOMS) is reduced when the same exercise is repeated after a certain interval. However, the mechanism for this adaptation, called a repeated bout effect, is still not well understood. Recently, we showed that upregulated nerve growth factor (NGF) triggered by B2 bradykinin receptor (B2R) activation in exercised muscle was responsible for DOMS. In this study, we investigated whether NGF upregulation was reduced after repeated bouts of exercise in rats, and if so, whether this change occurred upstream of B2R. A bout of 500 lengthening contractions (LC) was applied on day 0 and again 5 days later. DOMS was evaluated by the mechanical withdrawal threshold of the exercised extensor digitorum longus (EDL) muscle. Mechanical hyperalgesia and NGF mRNA upregulation in EDL were observed after the first LC, but not after the second LC. We then injected HOE140, a B2R antagonist with effects lasting only several hours, once before the first LC. This blocked the development of mechanical hyperalgesia and NGF mRNA upregulation not only after the first LC but also after the second LC. This suggests that adaptation occurred upstream of B2R, as the influence of the first LC was limited to that area by HOE140.

Effects of prior heavy-intensity exercise on oxygen uptake and muscle deoxygenation kinetics of a subsequent heavy-intensity cycling and knee-extension exercise

This study examined the effects of prior heavy-intensity exercise on the adjustment of pulmonary oxygen uptake (VO(2p)) and muscle deoxygenation Δ[HHb] during the transition to subsequent heavy-intensity cycling (CE) or knee-extension (KE) exercise. Nine young adults (aged 24 ± 5 years) performed 4 repetitions of repeated bouts of heavy-intensity exercise separated by light-intensity CE and KE, which included 6 min of baseline exercise, a 6-min step of heavy-intensity exercise (H1), 6-min recovery, and a 6-min step of heavy-intensity exercise (H2). Exercise was performed at 50 r·min(-1) or contractions per minute per leg. Oxygen uptake (VO(2)) mean response time was ∼20% faster (p < 0.05) during H2 compared with H1 in both modalities. Phase 2 time constants (τ) were not different between heavy bouts of CE (H1, 29.6 ± 6.5 s; H2, 28.0 ± 4.6 s) or KE exercise (H1, 31.6 ± 6.7 s; H2, 29.8 ± 5.6 s). The VO(2) slow component amplitude was lower (p < 0.05) in H2 in both modalities (CE, 0.19 ± 0.06 L·min(-1); KE, 0.12 ± 0.07 L·min(-1)) compared with H1 (CE, 0.29 ± 0.09 L·min(-1); KE, 0.18 ± 0.07 L·min(-1)), with the contribution of the slow component to the total VO(2) response reduced (p < 0.05) in H2 during both exercise modes. The effective τHHb was similar between bouts for CE (H1, 18.2 ± 3.0 s; H2, 18.0 ± 3.6 s) and KE exercise (H1, 26.0 ± 7.0 s; H2, 24.0 ± 5.8 s). The ΔHHb slow component was reduced during H2 in both CE and KE (p < 0.05). In conclusion, phase 2 VO(2p) was unchanged with priming exercise; however, a faster mean response time of VO(2p) during the heavy-intensity exercise preceded by a priming heavy-intensity exercise was attributed to a smaller slow component and reduced muscle deoxygenation indicative of improved muscle O(2) delivery during the second bout of exercise.

The Impact of Pulmonary and Peripheral Vascular Change from Particulate Matter Inhalation on Exercise Performance

Particulate matter (PM) inhalation has been associated with increased morbidity and mortality among susceptible populations, however, only recently has athletic performance among healthy subjects been investigated. PM inhalation has been shown to result in vasoconstriction of both the pulmonary and peripheral vasculature, yet no present study has investigated the effects of PM inhalation on both performance and the vasculature. PURPOSE: Examine the effect of PM inhalation on exercise performance, pulmonary arterial pressure (PAP), and flow-mediated vasodilation (FMD). METHODS: Sixteen volunteer participants were randomly assigned to two consecutive workouts (separated by 24 hr) in either high PM (HPM) (number count = 343,000 particles·cm3 ± 215,443; geometric mn = 26.6 nm ±7.44) or low PM (LPM) (number count = 2,170 particles·cm3 ± 2,066 conditions; geometric mn = 25.4 nm ± 6.61). HPM conditions were created through freshly generated PM from a 4-cycle gasoline engine. Following a seven day washout period, subjects returned to complete a second set of exercise bouts in a different condition. The participants' PAP and FMD were assessed before and after each exercise bout. RESULTS: Total work accumulated in HPM conditions decreased by 2.87% compared to LPM conditions (108.0 kJ ± 14.8 (LPM), 104.9 kJ ± 15.2 (HPM), p = 0.019). PAP was significantly increased (18.0 mmHg ± 1.39 pre, 18.8 mmHg ± 1.28 post, p = 0.043) after a single bout of exercise in HPM conditions among participants with baseline PAP exceeding 16.00 mmHg, while PAP was significantly greater (17.3 mmHg ± 1.80 pre, 18.9 mmHg ± 1.71 post, p < 0.001) among all participants after the second bout of exercise in HPM compared to the initial baseline measurement taken approximately 24 hr prior. FMD taken after the second bout of exercise in HPM was significantly decreased (9.37% ± 3.43 pre, 4.79% ± 3.01 post, p = 0.023) compared to the initial baseline. CONCLUSION: Exercise performance declined in HPM conditions. This appears to be due in part to impaired vasodilation in the pulmonary and peripheral vasculature which was most evident 24 hr. after exposure. It also appears that those with increased baseline PAP's are more susceptible to the effects of HPM inhalation.

The impact of different cooling modalities on the physiological responses in firefighters during strenuous work performed in high environmental temperatures

This study investigated the impact of ice vests and hand/forearm immersion on accelerating the physiological recovery between two bouts of strenuous exercise in the heat [mean (SD), 49.1(1.3)°C, RH 12 (1)]. On four occasions, eight firefighters completed two 20-min bouts of treadmill walking (5 km h, 7.5% gradient) while wearing standard firefighter protective clothing. Each bout was separated by a 15-min recovery period, during which one of four conditions were administered: ice vest (VEST), hand/forearm immersion (W), ice vest combined with hand/forearm immersion (VEST + W) and control (CON). Core temperature was significantly lower at the end of the recovery period in the VEST + W (37.97 ± 0.23°C) and W (37.96 ± 0.19°C) compared with the VEST (38.21 ± 0.12°C) and CON (38.29 ± 0.25°C) conditions and remained consistently lower throughout the second bout of exercise. Heart rate responses during the recovery period and bout 2 were similar between the VEST + W and W conditions which were significantly lower compared with the VEST and CON which did not differ from each other. Mean skin temperature was significantly lower at the start of bout 2 in the cooling conditions compared with CON; these differences reduced as exercise progressed. These findings demonstrate that hand/forearm immersion (~19°C) is more effective than ice vests in reducing the physiological strain when firefighters re-enter structural fires after short rest periods. Combining ice vests with hand/forearm immersion provides no additional benefit.