Effect of ACTN3 Polymorphism on Self-reported Running Times.

Kreutzer, A, Martinez, CA, Kreutzer, M, Stone, JD, Mitchell, JB, and Oliver, JM. Effect of ACTN3 polymorphism on self-reported running times. J Strength Cond Res 33(1): 80-88, 2019-This investigation examined the effect of ACTN3 genotype on self-reported distance running personal records (PRs). Of 94 (n = 94) recreationally active men and women, 82 (f = 42, m = 40; age: 22.6 ± 4.5 years; body mass index [BMI]: 23.5 ± 3.4 kg·m) reported 1-mile running PRs, whereas 57 (f = 33, m = 24; age: 23.4 ± 5.3 years; BMI: 22.9 ± 9.3 kg·m) reported 5K running PRs. Subjects were grouped by the presence (ACTN3) or absence (ACTN3) of α-actinin-3, as well as by individual genotype (RR, RX, and XX). Among female participants, ACTN3 reported 64.5 seconds faster (p = 0.048) 1-mile PRs compared with their ACTN3 counterparts. No differences were observed when comparing 5K PRs between genotypes. Two one-sided test equivalence testing revealed that none of the effects observed when comparing ACTN3 and ACTN3 were equivalent to zero. Our study confirms a reportedly greater prevalence of XX benefits for endurance performance in females when compared with males but fails to strongly link ACTN3 genotype to endurance performance. Practitioners should continue to be cautious when using genetic information for talent identification and sport selection.

Velocity Drives Greater Power Observed During Back Squat Using Cluster Sets.

This investigation compared the kinetics and kinematics of cluster sets (CLU) and traditional sets (TRD) during back squat in trained (RT) and untrained (UT) men. Twenty-four participants (RT = 12, 25 ± 1 year, 179.1 ± 2.2 cm, 84.6 ± 2.1 kg; UT = 12, 25 ± 1 year, 180.1 ± 1.8 cm, 85.4 ± 3.8 kg) performed TRD (4 × 10, 120-second rest) and CLU (4 × (2 × 5) 30 seconds between clusters; 90 seconds between sets) with 70% one repetition maximum, randomly. Kinematics and kinetics were sampled through force plate and linear position transducers. Resistance-trained produced greater overall force, velocity, and power; however, similar patterns were observed in all variables when comparing conditions. Cluster sets produced significantly greater force in isolated repetitions in sets 1-3, while consistently producing greater force due to a required reduction in load during set 4 resulting in greater total volume load (CLU, 3302.4 ± 102.7 kg; TRD, 3274.8 ± 102.8 kg). Velocity loss was lessened in CLU resulting in significantly higher velocities in sets 2 through 4. Furthermore, higher velocities were produced by CLU during later repetitions of each set. Cluster sets produced greater power output for an increasing number of repetitions in each set (set 1, 5 repetitions; sets 2 and 3, 6 repetitions; set 4, 8 repetitions), and the difference between conditions increased over subsequent sets. Time under tension increased over each set and was greater in TRD. This study demonstrates greater power output is driven by greater velocity when back squatting during CLU; therefore, velocity may be a useful measure by which to assess power.

Acute response to cluster sets in trained and untrained men.

PURPOSE: In traditional sets (TRD) repetitions are performed continuously, whereas cluster sets (CLU) allow a brief rest between groups of repetitions. We investigated the acute mechanical, metabolic, and hormonal response to CLU in men. METHODS: Twelve resistance-trained (RT) and 11 untrained (UT) men performed TRD (4 × 10 repetitions with 2 min rest) and CLU [4 × (2 × 5) with 1.5 min rest between sets 30 s rest between clusters] at 70 % 1RM back squat in random order. Seven days separated trials. Average power and time under tension (TUT) were calculated. Blood was sampled pre, sets 1, 2, and 3; immediate post-exercise, 5, 15, 30, 60 min post-exercise for blood lactate, total testosterone (TT), free testosterone (FT), growth hormone (GH), and cortisol. RESULTS: CLU produced greater average power at an increasing number of repetitions over each set with greater total volume load. TUT was shorter for RT and lower for CLU in repetitions 1, 6, 7, 8. Blood lactate was higher Set 2 through 30 min in TRD. RT had higher TT; however, the time course was similar between RT and UT. TT and FT increased immediate post-exercise and remained elevated 30 min in both conditions. GH was significantly greater during TRD with a similar pattern observed in both conditions. Cortisol was significantly lower at 30 min in CLU. CONCLUSION: CLU allowed greater total volume load, shorter TUT, greater average power, similar anabolic hormonal response, and less metabolic stress. The acute response was similar despite training status.

Temperature Measurement Inside Protective Headgear: Comparison With Core Temperatures and Indicators of Physiological Strain During Exercise in a Hot Environment.

Non-invasive temperature monitoring with a sensor inside protective headgear may be effective in detecting temperatures that are associated with heat illness. The purpose was to establish the relationship between in-hardhat temperatures (Tih) and core temperature (Tc) as measured by rectal (Tre) and esophageal (Tes) probes. Thirty males (age 24.57 ± 4.32 yrs.) completed two trials: continuous submaximal exercise (CSE) and a series of high intensity 30-s sprints (HIE) with a one-minute rest between each. Exercise in both conditions was in a 36(°)C environment (40% RH) while wearing a standard hardhat with sensors mounted on the forehead that were monitored remotely. Exercise continued until voluntary termination or until Tc reached 39.5(°)C. Temperatures, heart rate, cardiorespiratory, and perceptual responses were monitored throughout. A physiological strain index (PSI) was calculated from Tc and HR. The final temperatures in the CSE condition were 38.77 ± 0.41, 38.90 ± 0.49 and 39.29 ± 0.58(°)C and in the HIE condition, final temperatures were 38.76 ± 0.37, 38.91 ± 0.47, and 39.19 ± 0.57 f (o)C for Tih, Tre, and Tes, respectively. The PSI in CSE was 9.62 ± 062, 9.18 ± 1.11, and 10.04 ± 1.05, and in the HIE condition 9.67 ± 068, 9.29 ± 0.99. and 9.86 ± 1.02 based on Tih, Tre and Tes, respectively. The general agreement between the Tih and other temperature measures along with the consistency as indicated by a low coefficient of variation (approx. 1%) in the recordings of the Tih sensors at the point of termination suggest that this device, or similar devices, may have application as a warning system for impending heat-related problems.

The effects of elapsed time after warm-up on subsequent exercise performance in a cold environment.

Athletes often compete in cold environments and may face delays because of weather or race logistics between performance of a warm-up and the start of the race. This study sought to determine, (a) whether a delay after warm-up affects subsequent time trial (TT) performance and (b) if exposure to a cold environment has an additive effect. We hypothesized that after a warm-up, 30 minutes of rest in a cold environment would negatively affect subsequent rowing and running performance. In a temperate (temp; 24° C) or cold (cold; 5° C) environment, 5 rowers (33 ± 10 years; 83 ± 12 kg) and 5 runners (23 ± 2 years; 65 ± 8 kg) performed a 15-minute standardized warm-up followed by a 5- or 30-minute rest and then performed a 2-km rowing or 2.4 km running TT. The 5-minute rest following warm-up in the temperate environment (5Temp) served as the control trial to which the other experimental trials (5Cold; 30Temp; and 30Cold) were compared. Heart rate, lactate, and esophageal (Tes) and skin (Tsk) temperatures were measured throughout. Postrest and post-TT, Tes, and Tsk were lowest in the 30Cold trials. The greatest decrement in TT performance vs. 5Temp occurred in 30Cold (-4.0%; difference of 20 seconds). This difference is considered to have practical importance, as it was greater than the reported day-to-day variation for events of this type. We conclude that longer elapsed time following warm-up, combined with cold air exposure, results in potentially important reductions in exercise performance. Athletes should consider the appropriate timing of warm-up. In addition, performance may be preserved by maintaining skin and core temperatures following a warm-up, via clothing or other means.

Fatigue during high-intensity endurance exercise: the interaction between metabolic factors and thermal stress.

The purpose of this study was to examine the effects of hot (37° C) and cool (10° C) environments on cycling time to exhaustion (TTE), pH, lactate, and core temperature (Tc). Eleven endurance-trained subjects completed 4 TTE trials: Hot 80% VO2max (H80), Cool 80% (C80), Hot 100% (H100), and Cool 100% VO2max (C100). Esophageal temperature and blood was sampled before, every 5 minutes, at exhaustion, and 3 minutes after exercise and analyzed for lactate, pH, and HCO3-. Multifactorial analysis of variance with repeated measures was used to determine differences between mean values (± SD). Time to exhaustion was shorter in H100 and C100 vs. H80 and C80 (5.64 ± 1.49 minutes, 5.83 ± 1.03 minutes, 12.82 ± 2.0 minutes, and 24.85 ± 6.0 minutes, respectively) and shorter in H80 vs. C80 (p < 0.01). The pH at exhaustion was different among all conditions (7.17 ± 0.06, 7.15 ± 0.07, 7.21 ± 0.04, and 7.24 ± 0.06 units for H100, C100, H80, and C80, respectively, p = 0.02). The Tc at exhaustion was lower in H100 and C100 (37.93 ± 0.67 and 37.62 ± 0.58° C) vs. H80 and C80 (38.54 ± 0.51° C and 38.53 ± 0.38° C) (p < 0.01). In H80 and C80, the higher Tc likely played a greater role in the termination of exercise, whereas, in H100 and C100, pH and metabolic changes may have been more important. Despite these differences, neither an upper limit for Tc nor a lower limit for pH was identified; thus, fatigue based entirely on peripheral factors was not supported, and a combination of peripheral and central processes must be considered. The practical implications of these findings are that aerobic exercise at or near VO2max may be impacted more by metabolic factors, whereas lower intensities (∼80% VO2max) may be affected more by heat stress; these differences should be considered when training for events of this type.

Preexercise energy drink consumption does not improve endurance cycling performance but increases lactate, monocyte, and interleukin-6 response.

The purpose of this study was to investigate the influence of an energy drink (ED) on cycling performance and immune-related variables. Eleven trained male cyclists (33.4 ± 8.9 years; 81 ± 7.6 kg; maximal VO2, 52 ± 3.4 ml·kg(-1)·min(-1)) consumed 500 ml of (a) ED (2.0 g taurine, 1.2 g glucuronolactone, 160 mg caffeine, 56 g carbohydrate [CHO], and B vitamins), (b) cola matched for caffeine and CHO (CC), or (c) flavored placebo (PL: sparking water and flavoring) 50 minutes before racing in a randomized, crossover design. Performance was measured as time to complete (TTC) a 25-mile simulated road race. Blood was collected at baseline, 30 minutes after drink consumption, during exercise at miles 5 (M5), 15 (M15), and immediately (POEX) and 30 minutes (30minPO) after exercise. TTC was not different (p > 0.05) among trials (ED, 68.6 ± 2.7; CC, 68.9 ± 3.8; PL, 69.6 ± 3.8 minutes). Consumption of CC and ED elicited a mild hypoglycemia elicited a mild hypoglycemia during cycling. POEX interleukin-6 (IL-6) was greatest after ED, whereas CC IL-6 was greater than PL (10.2 ± 1.6, 6.7 ± 0.6, and 4.8 ± 0.7 pg·ml(-1), respectively; p < 0.001). Cycling increased leukocyte number in all conditions with ED leukocyte number greater than that of PL at M15 (9.8 ± 0.6, 8.5 ± 0.3 × 10(6) cells·mL(-1)). Energy drink induced an earlier recruitment of monocytes to the blood stream than CC. Mean fat oxidation was greater in PL compared with CC (0.43 ± 0.06 and 0.28 ± 0.04 g·min(-1); p = 0.033) but did not differ between ED (0.32 ± 0.06) and PL. Lactate was higher in ED compared with CC and PL at M5 and M15 (p = 0.003), but there was no significant influence of either ED or CC on performance. Carbohydrate and caffeine consumption before endurance cycling significantly increased the IL-6 release and leukocytosis, and the additional ingredients in ED seem to have further augmented these responses.

Ingestion of carbohydrate during recovery in exercising people.

PURPOSE OF REVIEW: The primary focus of this brief review is to describe the effect of carbohydrate (CHO) supplementation alone or in combination with protein on two responses during postexercise recovery that are not specifically related to the usual emphasis on glycogen resynthesis; that is, rapid postexercise rehydration, and recovery from exercise-induced muscle damage. RECENT FINDINGS: Evidence from postexercise rapid rehydration studies suggests that the addition of CHO to a rehydration solution may increase the rate of fluid restoration compared with water placebo. Adding protein to a CHO solution may further accentuate the beneficial effects. An additional postexercise concern for active individuals is the development of postexercise muscle soreness, a response that is pronounced with novel, eccentric exercise. Ingestion of CHO supplements, especially those combined with protein may help to minimize the exercise-induced muscle damage that is accompanied by muscle soreness, and reduced muscle function. SUMMARY: The practical implications of these findings are that CHO supplementation, especially in combination with protein, can enhance the rate of recovery relative to fluid balance and muscle damage; thus, these nutritional interventions should be considered for purposes in addition to the usual focus on glycogen resynthesis.

Exercise-associated hyponatremia: the influence of pre-exercise carbohydrate status combined with high volume fluid intake on sodium concentrations and fluid balance.

To evaluate the effect of hydration and carbohydrate (CHO) status on plasma sodium, fluid balance, and regulatory factors (IL-6 & ADH) during and after exercise; 10 males completed the following conditions: low CHO, euhydrated (fluid intake = sweat loss) (LCEH); low CHO, dehydrated (no fluid) (LCDH); high CHO, euhydrated (HCEH); and high CHO, dehydrated (HCDH). Each trial consisted of 90-min cycling at 60% VO(2) max in a 35°C environment followed by 3-h rehydration (RH). During RH, subjects received either 150% of sweat loss (LCDH & HCDH) or an additional 50% of sweat loss (LCEH and HCEH). Blood was analyzed for glucose, IL-6, ADH, and Na(+). Post-exercise Na(+) was greater (p < 0.001) for LCDH and HCDH (141.7 + 0.72 and 141.6 + 0.4 mM) versus LCEH and HCEH (136.4 + 0.6 and 135.9 + 0.3 mM). Post-exercise IL-6 was similar in all conditions, and post-exercise ADH was greater (p = 0.01) in dehydrated versus euhydrated conditions. The rate of urine production was greater in HCEH (7.59 + 3.0 mL/min) compared to all other conditions (3.86 + 2.2, 5.29 + 3.1, and 2.96 + 1.1 mL/min for LCDH, LCEH, and HCDH, respectively). Despite CHO and hydration manipulations, no regulatory effects of IL-6 and ADH on plasma [Na(+)] were observed. With euhydration during exercise and additional fluid consumed during recovery, a high-CHO status increased urinary output during recovery, and it decreased the frequency of hyponatremia (Na(+) < 135 mM). Therefore, a high-CHO status may provide some protection against exercise-associated hyponatremia.

Resistance and aerobic exercise: the influence of mode on the relationship between IL-6 and glucose tolerance in young men who are obese.

Regular exercise lowers indicators of disease risk including some inflammatory cytokines; however, the relationship between different modes of acute exercise, cytokine levels, and subsequent glucose tolerance is unclear. The purpose was to determine the effects of resistance (RES) and aerobic (AER) exercises on interleukin-6 (IL-6) and its association with glucose tolerance 24 hours after exercise. After testing for 1 repetition maximum (1RM) and VO2peak, 10 obese (body mass index > 30 kg · m(-2)), untrained men aged 18-26 years completed 3 protocols: 60 minutes of RES, AER, and a resting (CON) condition. The RES was 2 sets of 8 repetitions and a third set to fatigue at 80% 1RM of 8 lifts using all major muscle groups. The AER was 60 minutes of cycling at 70% of VO2peak. On day 1, subjects completed the 60-minute exercise or resting protocol, and on day 2, they completed an oral glucose tolerance test (OGTT). Blood was collected before and after exercise, at 2 and 7 hour postexercise, and before and every 30 minutes during the OGTT and was analyzed for IL-6, glucose and insulin. Postexercise IL-6 was greater in RES (8.01 ± 2.08 pg · mL(-1)) vs. in AER (4.26 ± 0.27 pg · mL(-1)), and both were greater than in CON (1.61 ± 0.18 pg · mL(-1)). During the OGTT, there were no differences in glucose or insulin between conditions for single time points or as area under the curve. The RES caused greater IL-6 levels immediately after exercise that may be related to the greater active muscle mass compared to AER. Neither exercise produced enhanced glucose removal compared to control; thus, despite the greater elevation in IL-6 in RES, for these exercise conditions and this population, this cytokine did not influence glucose tolerance.

Influence of commonly employed resistance exercise protocols on circulating IL-6 and indices of insulin sensitivity.

The purpose of this project was to examine the influence of resistance exercise (RE) intensities, resulting in different total volume loads on circulating interleukin-6 (IL-6), insulin and glucose response (IGR) to a carbohydrate feeding (CHO), and whether RE-induced IL-6 was associated with postexercise IGR. Fourteen men (21.7 +/- 1.7 years, 83 +/- 14.2 kg), performed 2 RE sessions (low-intensity resulting in high volume [65% 1-repetition maximum (1RM)], LO; high intensity resulting in low volume [85% 1RM], HI); and a nonexercise control trial (CON). Resistance exercise included 3 sets (LO = 12 reps, 12 reps, and failure; HI = 8 reps, 8 reps, and failure) of 8 exercises. Blood was obtained pre- (PR) and post (PO) exercise, and 6 hours postexercise (6H). Twenty-three hours after RE or CON, participants consumed 100 g dextrose (CHO) beverage. Blood was collected before (0 minutes) and 60 minutes after CHO (n = 6, phase 1) or every 30 minutes for a 2-hour oral glucose tolerance test (n = 8; phase 2). Circulating IL-6, insulin, and glucose were analyzed via enzyme-linked immunosorbent assay, radioimmunoassay, and enzymatic methods, respectively. Total volume load was higher in LO (17,729 +/- 1,466 kg) compared with HI (13,160 +/- 1,097 kg; p < 0.001). Postexercise IL-6 was elevated (p = 0.003) in LO and HI compared with CON (7.4 +/- 1.3, 5.2 +/- 0.7, and 2.5 +/- 0.7 pg.mL, respectively), with LO IL-6 greater than HI. Areas under the curve for glucose (p = 0.081; CON: 741 +/- 46, LO: 690 +/- 28, and HI: 660 +/- 21 mM.min) and insulin (p = 0.075; CON: 6,818 +/- 1,018, LO: 5,056 +/- 869, and HI: 5,405 +/- 1,076 microIU.mL) were not different among trials (n = 8). When 0- and 60-minute values were compared (n = 14), insulin was lower at 60 minutes in LO and HI compared with CON (55 + 9.1, 83 +/- 13, 105 +/- 13 microIU.mL, respectively) with LO insulin being lower than HI (p < 0.001). No relationship was observed between PO IL-6 and IGR, but PR IL-6 was negatively related to both PR (r = -0.043, p < 0.05) and 60 minutes (r = -0.59, p < 0.01) glucose (n = 14). These results indicate that TVL contributes to RE-induced IL-6 release and that TVL may be more important than RE intensity when improvements in glucose tolerance or IS are the goal.

Behavioral immune system activity predicts downregulation of chronic basal inflammation.

Here, we present a mechanistically grounded theory detailing a novel function of the behavioral immune system (BIS), the psychological system that prompts pathogen avoidance behaviors. We propose that BIS activity allows the body to downregulate basal inflammation, preventing resultant oxidative damage to DNA and promoting longevity. Study 1 investigated the relationship between a trait measure of pathogen avoidance motivation and in vitro and in vivo proinflammatory cytokine production. Study 2 examined the relationship between this same predictor and DNA damage often associated with prolonged inflammation. Results revealed that greater trait pathogen avoidance motivation predicts a) lower levels of spontaneous (but not stimulated) proinflammatory cytokine release by peripheral blood mononuclear cells (PBMCs), b) lower plasma levels of the proinflammatory cytokine interleukin-6 (IL-6), and c) lower levels of oxidative DNA damage. Thus, the BIS may promote health by protecting the body from the deleterious effects of inflammation and oxidative stress.

Heat shock protein (HSP-72) levels in skeletal muscle following work in heat.

INTRODUCTION: Acute bouts of heat stress and exercise have been shown to independently increase heat shock protein levels; however, the combination of these two stressors on HSP-72 expression in human skeletal muscle has not been established. The purpose of this study was to determine the effect of a bout of exercise in the heat on HSP-72 expression. METHODS: There were eight recreationally active men (Age = 26.4 +/- 3.1 yr, V(O2)peak = 4.01 +/- 0.25 L min(- 1)) who completed two 30-min bouts of cycle ergometry at 75% of V(O2)peak in a hot (39 degrees C; RH 30%) and cold (9 degrees C; RH 61%) environment. Muscle biopsies were obtained from the vastus lateralis prior to, 6 h post, and 24 h post-exercise to measure HSP-72 protein. Core rectal temperature (Tc), average skin temperature (T(SK)), intramuscular temperature (T(IM)), heart rate (HR), oxygen uptake (V(O2)), sweat rate (SR), and plasma cortisol were measured to determine thermal loads. RESULTS: No significant interactions were present between V(O2) (2.80 +/- 0.2 vs. 2.65 +/- 0.1 L min(-1)) or plasma cortisol (27.1 +/- 2 vs. 19.2 +/- 4 microg dl(-1)) when comparing HT and CD. HR (184 +/- 5 vs. 159 +/- 7 bpm), T(IM) (40.7 +/- 0.2 vs. 40.0 +/- 0.2 degrees C), Tc (38.3 +/- 0.2 vs. 37.9 +/- 0.1 degrees C), T(SK) (36.7 +/- 0.2 vs. 29.6 +/- 0.8 degrees C), and SR (2.0 +/- 0.2 vs. 1.2 +/- 0.2 L h(-1)) were significantly greater when comparing HT and CD. HSP-72 was not altered as a result of either treatment (4.04 +/- 0.87 vs. 2.91 +/- 1.58 ng microg(-1) protein for HT and CD at 6 h post-exercise). DISCUSSION: Exercise in the heat produced a greater thermal load than exercise in the cold; however, no significant increases in HSP-72 were seen when comparing hot and cold conditions.

Novel Form of Curcumin Improves Endothelial Function in Young, Healthy Individuals: A Double-Blind Placebo Controlled Study.

Curcumin, a turmeric extract, may protect against cardiovascular diseases by enhancing endothelial function. In this randomized controlled double-blind parallel prospective study, fifty-nine healthy adults were assigned to placebo, 50 mg (50 mg), or 200 mg (200 mg) curcumin, for 8 weeks. The higher curcumin (200 mg) supplementation produced a dose-mediated improvement in endothelial function measured by flow-mediated dilation (FMD). The outcome was a clinically substantial 3.0% increase (90% CI 0.7 to 5.3%, p = 0.032; benefit : harm odds ratio 546 : 1) with the 200 mg dose, relative to placebo. The 50 mg dose also increased FMD relative to placebo by 1.7% (-0.6 to 4.0%, p = 0.23; 25 : 1), but the outcome was not clinically decisive. In apparently healthy adults, 8 weeks of 200 mg oral curcumin supplementation resulted in a clinically meaningful improvement in endothelial function as measured by FMD. Oral curcumin supplementation may present a simple lifestyle strategy for decreasing the risk of cardiovascular diseases. This trial was registered at ISRCTN registry (ISRCTN90184217).

Ingestion of High Molecular Weight Carbohydrate Enhances Subsequent Repeated Maximal Power: A Randomized Controlled Trial.

Athletes in sports demanding repeat maximal work outputs frequently train concurrently utilizing sequential bouts of intense endurance and resistance training sessions. On a daily basis, maximal work within subsequent bouts may be limited by muscle glycogen availability. Recently, the ingestion of a unique high molecular weight (HMW) carbohydrate was found to increase glycogen re-synthesis rate and enhance work output during subsequent endurance exercise, relative to low molecular weight (LMW) carbohydrate ingestion. The effect of the HMW carbohydrate, however, on the performance of intense resistance exercise following prolonged-intense endurance training is unknown. Sixteen resistance trained men (23±3 years; 176.7±9.8 cm; 88.2±8.6 kg) participated in a double-blind, placebo-controlled, randomized 3-way crossover design comprising a muscle-glycogen depleting cycling exercise followed by ingestion of placebo (PLA), or 1.2 g•kg•bw-1 of LMW or HMW carbohydrate solution (10%) with blood sampling for 2-h post-ingestion. Thereafter, participants performed 5 sets of 10 maximal explosive repetitions of back squat (75% of 1RM). Compared to PLA, ingestion of HMW (4.9%, 90%CI 3.8%, 5.9%) and LMW (1.9%, 90%CI 0.8%, 3.0%) carbohydrate solutions substantially increased power output during resistance exercise, with the 3.1% (90% CI 4.3, 2.0%) almost certain additional gain in power after HMW-LMW ingestion attributed to higher movement velocity after force kinematic analysis (HMW-LMW 2.5%, 90%CI 1.4, 3.7%). Both carbohydrate solutions increased post-exercise plasma glucose, glucoregulatory and gut hormones compared to PLA, but differences between carbohydrates were unclear; thus, the underlying mechanism remains to be elucidated. Ingestion of a HMW carbohydrate following prolonged intense endurance exercise provides superior benefits to movement velocity and power output during subsequent repeated maximal explosive resistance exercise. This study was registered with clinicaltrials.gov (NCT02778373).

Effect of exercise, heat stress, and hydration on immune cell number and function.

PURPOSE: The purpose of this study was to determine the effect of thermal stress and hydration status on immune function during exercise. METHODS: Ten trained men completed four cycle ergometer rides at 55% VO2peak under the following conditions: EN (euhydrated neutral; 22 degrees C, 30% RH), DN (dehydrated neutral), EH (euhydrated hot; 38 degrees C, 45% RH), and DH (dehydrated hot). During EN and EH, a carbohydrate/electrolyte beverage was consumed at a rate matching sweat loss, and during DN and DH, no fluid was ingested. Blood samples were drawn pre- and postexercise, and at 2 and 24 h of recovery. Cell counts were determined by automated counting and flow cytometry. Neutrophil activity was assessed as superoxide production, lymphocyte function was determined via PHA-stimulated mitogenesis, and natural killer (NK) cell activity was measured with a 51Cr-release assay. Cortisol was assayed via RIA. RESULTS: Lymphocytes proliferation was depressed 2 h after exercise in all conditions (P < 0.05); however, when expressed on a per cell basis, function was greater in the DH and EH conditions. NK activity (max x 10(3) cells) was greater post compared with preexercise in all conditions (EH = 25.5 +/- 16.8, DH = 26.2 +/- 10.5, EN = 19.3 +/- 11.0, and DN = 16.5 +/- 8.7) but was not different between conditions. Leukocyte, neutrophil, lymphocyte, and NK cell counts were also elevated postexercise with the former two remaining elevated 2 h postexercise in the EH and DH conditions. Cortisol was greater postexercise in EH (22.1 +/- 1.3) and DH (27.7 +/- 1.3) compared with EN (17.8 +/- 2.1) and DN (18.9 +/- 1.6 microg x dL(-1). CONCLUSION: Euhydration did not affect cell number or function when compared with a dehydrated state; however, the hot environment caused more severe disturbances in these measures compared with a neutral environment.

Repeated endurance exercise affects leukocyte number but not NK cell activity.

INTRODUCTION/PURPOSE: The purpose of this study was to determine the affects of repeated bouts of exercise in the same day on circulating leukocyte number and NK cell activity (NKCA). METHODS: Ten males (18-25 yr of age) were chosen to complete four trials: two exercise bouts (TB), AM exercise (AM-EX), PM exercise (PM-EX), and control (CN) in a random, counter-balanced order. Exercise consisted of 1-h cycle ergometry, split into three, 20-min segments (5 min at 50% [V0](2peak) and 15 min at 70% [V0](2peak)), and was separated by a 4-h passive recovery. Blood samples were collected from a peripheral arm vein before, immediately, 2 h, and 24 h after the AM bout, and a second series was drawn for the PM bout. Leukocyte subpopulations were measured by manual counting using a hemacytometer and Wright-Giemsa-stained differential slides. NKCA was measured with a whole-blood 51Cr-release assay against K562 target cells. RESULTS Total leukocyte (13.2 +/- 1.2 x 109 L-1, P < 0.035) and neutrophil (7.6 +/- 0.7 x 109 L-1, P < 0.001) counts were significantly higher after two bouts of exercise than a single exercise bout completed in the morning (leukocyte: 7.8 +/- 0.7 x 109 L-1; neutrophil: 5.2 +/- 0.5 x 109 L-1) or afternoon (leukocyte: 9.9 +/- 0.8 x 109 L-1; neutrophil: 5.6 +/- 0.9 x 109 L-1). Lymphocyte counts were significantly greater (P < 0.001) after PM (4.2 +/- 0.5 x 109 L-1) than AM (3.7 +/- 0.4 x 109 L-1) exercise. NKCA was significantly greater (P < 0.001) after exercise in the afternoon (35.3 +/- 8.1%) than morning (27.2 +/- 5.9%). CONCLUSION: PM exercise produced a larger increase in NKCA than AM exercise, possibly indicative of an interaction between exercise and a diurnal effect. These data suggest two bouts of endurance exercise in 1 d produce an "additive effect" for total leukocyte and neutrophil counts. and to a lesser degree lymphocyte counts, but did not appear to impact shifts in NKCA.

Exercise in hot and cold environments: differential effects on leukocyte number and NK cell activity.

INTRODUCTION: Exercise and environmental temperature have been reported to affect the immune system, but few studies have examined the combined effects of very hot or cold temperatures during exercise in the same group of subjects. Therefore, the purpose was to examine the immune responses following exercise combined with exposure to hot and cold environments. METHODS: There were 10 men who completed 2 60-min cycle ergometry (60% VO2peak) trials: hot (HT: 38 degrees C, 45% RH) and cold (CD: 8 degrees C, 50% RH). Rectal core temperatures (Tc), average skin temperatures (Tsk), and HR were recorded every 15 min of exercise. Venous blood was collected before (PRE), immediately after (POST), 2 h after (2 h), and 24 h after exercise (24 h). Physiologic strain index (PSI) was calculated. Total and differential leukocytes were determined by manual counting (adjusted for plasma volume shifts). Natural killer cell activity (NKCA) was determined by a whole blood 51Cr-release assay. RESULTS: Tsk, Tc, and PSI were significantly lower in the CD than HT trial (p < 0.05). Total leukocyte count was greater POST (40%) and 2 h (74%) than PRE and 24 h in both conditions (p < 0.05). Neutrophil count was greater POST (49%) and 2 h (132%) than PRE and 24 h in both conditions (p < 0.05). Lymphocyte count was greater POST (24%) in HT than CD (p < 0.05). NKCA was greater POST (38%) than PRE, 2 h, and 24 h in both conditions (p < 0.05). HT caused significant increases for Tc and Tsk above those observed for CD (p < 0.05). PSI was greater in HT (9.92 +/- 0.93) than CD (4.24 +/- 0.56) (p < 0.05). DISCUSSION: Exercise in HT produced more physiological stress than CD; however, this difference was not manifested in the immune system response. Heat and cold stress in combination with exercise produce similar disturbances in immunity during recovery from exercise.

Resistance training reduces subclinical inflammation in obese, postmenopausal women.

PURPOSE: Aerobic exercise is frequently prescribed to reduce inflammatory-related disease (cardiovascular disease and diabetes) risk. Resistance training (RT), however, may be key to maximizing anti-inflammatory benefits of consistent exercise. We examined the influence of RT on inflammatory biomarkers in obese, postmenopausal women. METHODS: Twenty-three women (65.6 ± 2.6 yr; body mass index, 33 kg·m) underwent 12 wk of RT (3 sets, 10 exercises, 3× per week, 8-12 repetition maximum (RM), resistance exercise (EX), N = 11) or social interaction intervention (SI, stretching, knitting, health lectures, 2× per week, control group (CON), N = 12). Both before (BT) and after (AT) RT or SI, blood was collected before (PR), immediately (PO), 2 h (2H), and 24 h (24H) after a single resistance exercise bout (RE) in EX and at the same time points in nonexercise, resting CON. For all time points, blood was analyzed for IL-6, leptin, and lipopolysaccharide (LPS)-stimulated tumor necrosis factor-α (TNF-α) (LPS-TNF) and IL-10 (LPS-IL10). PR samples were also examined for C-reactive protein, TNF-α, and adiponectin, and mRNA expression of toll-like receptor 4 (TLR4) and MC1R. Subcutaneous adipose tissue was extracted BT and AT and analyzed for mRNA expression of monocyte chemotactic protein-1, leptin, CD68, and TLR4. RESULTS: RT improved strength (44%) and reduced circulating C-reactive protein (-33%), leptin (-18%) and TNF-α (-29%) with no change in body composition. IL-6 decreased after SI in CON (-17%). LPS-TNF increased after SI or RT (CON +26%, EX +67%, respectively), whereas LPS-IL10 decreased in CON (-28%) but increased in EX (+20%). RT did not influence inflammatory biomarker gene expression in whole blood or subcutaneous adipose tissue. A single RE bout augmented LPS-TNF and LPS-IL10 at 24H in EX, particularly AT. CONCLUSION: RT reduced markers of subclinical inflammation in circulation in obese, postmenopausal women in the absence of changes in body composition. Chronic RT also enhanced response to endotoxin challenge both at rest (PR) and 24 h after an acute RE bout (24H).

Effect of prior exercise on postprandial triglycerides in overweight young women after ingesting a high-carbohydrate meal.

To examine the effect of prior exercise on the postprandial lipid response to a high-carbohydrate meal in normal-weight (NW=BMI <25) and overweight (OW=BMI >or= 25) women (age 18-25), 10 NW and 10 OW participants completed 2 conditions separated by 1 month. In the morning, the day after control (CT=no exercise) or exercise conditions (EX=60 min cycling at 60% VO(2peak)), participants consumed a high-carbohydrate meal (80% CHO, 15% protein, 5% fat; 75 kJ/kg BM) followed by 6 hr of hourly blood sampling. Blood was analyzed for triglycerides (TG), blood glucose (BG), and insulin (IN). TG levels over the 6-hr period were lower in NW than OW (p= .021) and lower in EX than in CT (p= .006). Area under the curve (AUC) for TG was lower in NW than OW (p= .016) and EX than CT (p= .003). There were nonsignificant tendencies for reduced BG over time (p= .053) and AUC (p= .083), and IN AUC was lower in EX than in CT (p= .040) for both groups and lower in NW than in OW (p= .039). Prior exercise improved TG levels after a high-carbohydrate meal in both groups, and OW women demonstrated a greater postprandial lipemic response than NW regardless of condition. There were tendencies for improved glucose removal with prior exercise in NW vs. OW. Acute exercise can improve postprandial TG responses and might also improve postprandial BG and IN after a large meal in NW and OW young women.