Min Post Exercise Research Articles

Effects of the Menstrual Cycle and Acute Aerobic Exercise on Cytokine Levels

Objective: The purposes of this study were: 1) to investigate the effects of menstrual cycle on the basal levels of salivary cytokines (interleukin IL-6 and IL-8) in young healthy women; 2) to examine the influences of prolonged aerobic exercise at ventilatory threshold (VT) on salivary and circulating IL-6 and IL-8 concentrations during menstrual phase. Methods: Eight healthy women participated in three visits (saliva sampling during menstrual, follicular and luteal phases) and two trials (exercise and resting trials during a separate menstrual phase). The exercise trial involved a 60- min cycling at VT and the resting trial involved resting for 90 min.Saliva and blood samples were taken at before, immediately after and 30 min post-exercise and equivalent times during the resting trial. Results: Salivary IL-6 level was higher during the follicular phase than the luteal phase at rest. Salivary IL-8 immediately post-exercise was higher than pre-exercise, and circulating IL-6 was significantly increased from pre-exercise to immediately post-exercise and 30 min post exercise. Conclusion: The results showed that salivary cytokines are influenced by menstrual cycle and prolonged exercise during menstrual phase.However the levels of IL-6 and IL-8 in saliva do not closely reflect those in plasma, and therefore might reflect a local level of inflammation.

The acute effect of exercise and nutrition on respiratory exchange ratio in women

Methods Twenty recreationally active women (Mean ± SD; age 24.6 ± 3.9 yrs; height 164.4 ± 6.6 cm; weight 62.7 ± 6.6 kg; %fat 28.2 ± 4.8 %) participated in this randomized crossover, double-blind study. After preliminary body composition and maximal strength testing, each participant completed six exercise sessions, consisting of three exercise modalities: aerobic endurance exercise (AEE; 30 min, 50% heart rate reserve), high-intensity interval running (HIIT; 10 x 1min on: 1min off, 90% HRR), and high-intensity resistance training (HIRT; 6 exercises: 3 sets, 20 sec rest), and two acute nutritional interventions: 25 grams of CHO (maltodextrin) and PRO (whey protein isolate). Salivary samples were collected before each exercise session to determine estrogen. RER was analyzed via indirect calorimetry (Parvomedics TrueOne 2400) at: baseline, immediately post (IP), 30 minutes (30min) post, and 60 minutes (60min) post-exercise. Subjects were seated and connected to the metabolic cart by a tube for 15 minutes at each time point. A mixed level model [modality (AEE vs. HIIT vs. HIRT) × treatment (CHO vs. PRO) × time (base vs. IP vs. 30min vs. 60min)] covaried for estrogen was used to evaluate RER. Consent to publish the results was obtained from all participants. Results Significant two-way interactions existed between modality and time (p<0.0001) and time and treatment (p<0.0001). Significant modality differences existed between HIIT and AEE (p<0.0001), HIIT and HIRT (p<0.0001), and AEE and HIRT (p=0.0024). RER was significantly higher from HIIT than AEE and HIRT IP exercise (p<0.0001), and significantly lower from HIIT 30min and 60min post exercise (p<0.0001-p=0.0020) than AEE. RER was significantly lower 30min (p=0.0169), but not 60min post (p=0.3603) HIIT vs. HIRT. No significant differences existed between HIRT and AEE IP exercise (p=0.3370); RER was significantly lower for HIRT than AEE 30min and 60min post exercise (p=0.0004-0.0265). For time and treatment, RER was not significantly different between CHO and PRO IP exercise (p=0.1150), but was significantly lower for PRO 30min and 60min post (p<0.0001p=0.0012).

The effects of arm crank ergometry, cycle ergometry and treadmill walking on postural sway in healthy older females

Older adults are increasingly being encouraged to exercise but this may lead to muscle fatigue, which can adversely affect postural stability. Few studies have investigated the effects of upper body exercise on postural sway in groups at risk of falling, such as the elderly. The purpose of this study was to compare the effects arm crank ergometry (ACE), cycle ergometry (CE) and treadmill walking (TM) on postural sway in healthy older females. In addition, this study sought to determine the time necessary to recover postural control after exercise. A total of nine healthy older females participated in this study. Participants stood on a force platform to assess postural sway which was measured by displacement of the centre of pressure before and after six separate exercise trials. Each participant completed three incremental exercise tests to 85% of individual's theoretical maximal heart rate (HRMAX) for ACE, CE and TM. Subsequent tests involved 20-min of ACE, CE and TM exercise at a relative workload corresponding to 50% of each individual's predetermined heart rate reserve (HRE). Post fatigue effects and postural control recovery were measured at different times after exercise (1, 3, 5, 10, 15 and 30-min). None of the participants exhibited impaired postural stability after ACE. In contrast, CE and TM elicited significant post exercise balance impairments, which lasted for ∼10min post exercise. We provide evidence of an exercise mode which does not elicit post exercise balance impairments. Older adults should exercise caution immediately following exercise engaging the lower limbs to avoid fall risk.

Oral adenosine-5'-triphosphate (ATP) administration increases blood flow following exercise in animals and humans.

IntroductionExtracellular adenosine triphosphate (ATP) stimulates vasodilation by binding to endothelial ATP-selective P2Y2 receptors; a phenomenon, which is posited to be accelerated during exercise. Herein, we used a rat model to examine how different dosages of acute oral ATP administration affected the femoral blood flow response prior to, during, and after an exercise bout. In addition, we performed a single dose chronic administration pilot study in resistance trained athletes.MethodsAnimal study: Male Wistar rats were gavage-fed the body surface area, species adjusted human equivalent dose (HED) of either 100 mg (n=4), 400 mg (n=4), 1,000 mg (n=5) or 1,600 mg (n=5) of oral ATP as a disodium salt (Peak ATP®, TSI, Missoula, MT). Rats that were not gavage-fed were used as controls (CTL, n=5). Blood flow was monitored continuously: a) 60 min prior to, b) during and c) 90 min following an electrically-evoked leg-kicking exercise. Human Study: In a pilot study, 12 college-aged resistance-trained subjects were given 400 mg of ATP (Peak ATP®, TSI, Missoula, MT) daily for 12 weeks, and prior to an acute arm exercise bout at weeks 1, 4, 8, and 12. Ultrasonography-determined volumetric blood flow and vessel dilation in the brachial artery was measured at rest, at rest 30 minutes after supplementation, and then at 0, 3, and 6 minutes after the exercise.ResultsAnimal Study: Rats fed 1,000 mg HED demonstrated significantly greater recovery blood flow (p < 0.01) and total blood flow AUC values (p < 0.05) compared to CTL rats. Specifically, blood flow was elevated in rats fed 1,000 mg HED versus CTL rats at 20 to 90 min post exercise when examining 10-min blood flow intervals (p < 0.05). When examining within-group differences relative to baseline values, rats fed the 1,000 mg and 1,600 mg HED exhibited the most robust increases in blood flow during exercise and into the recovery period. Human study: At weeks 1, 8, and 12, ATP supplementation significantly increased blood flow, along with significant elevations in brachial dilation.ConclusionsOral ATP administration can increase post-exercise blood flow, and may be particularly effective during exercise recovery.

Leukocyte subpopulation responses to resistance exercise are different in men and women and affected by protein supplementation (LB800)

Immune cells are integral to the recovery from exercise, but little is known about the effects of supplementation and sex on the immune response. Untrained men (M) (N=88) and women (W) (N=54) performed a squat exercise protocol (6 sets, 10 repetitions, 2 minutes rest between sets at 65% of 1 RM) and randomly received a supplement immediately post exercise of carbohydrate (CHO) (M=27, W=16), whey (WHY) (M=25, W=18) or soy (SOY) (M=27, W=19). Immunophenotypic analysis of leukocytes was performed before (Pre) and 15 and 60 min post exercise (PE). Comparison of sexes disregarding supplementation indicated lower CD4 T cell counts at all time points in women. CD4 T cells continuously declined in men at 15 and 60 min PE while women only decreased below Pre at 60 min PE. Monocytes increased significantly at 15 min PE in women only (M=+11%, W=+17%) but decreased significantly in both sexes at 60 min PE (M=‐21%, W=‐11%). After division by sex and supplement, monocytes were not different from Pre to 60 min PE in women in all groups, but in men monocytes decreased below Pre at 60 min PE in both CHO and SOY. B cells decreased below Pre at 60 min PE in men in all groups, but only decreased below Pre at 60 min PE in women in SOY. Granulocytes continuously increased PE in men in WHY and CHO, and in women in CHO and SOY. Sex and supplementation differentially affect leukocyte compartmentalization with the most apparent effects on monocytes.Grant Funding Source: Supported by the Dairy Research Institute

Systemic and lower limb hemodynamics following dynamic exercise in type 2 diabetics: effects of exercise intensity and duration (705.12)

For individuals with type 2 diabetes mellitus (T2DM), regular exercise is critical for protecting vascular function and reducing cardiovascular disease risk, but the hemodynamic responses to differing doses of acute exercise in type 2 diabetics (T2D) are unclear. Our aim was to compare postexercise (PE) hemodynamics in T2D in response to four different doses of acute dynamic exercise. Two subjects with well‐controlled T2DM (42‐48 yrs; Hemoglobin A1c: 6.6 ± 0.7%) participated in four study days, during which they exercised on an upright cycle ergometer at four different combinations of exercise duration and intensity: 30 min at 40% VO2 peak (30@40), 30 min at 60% VO2 peak (30@60), 60 min at 40% VO2 peak (60@40), and 60 min at 60% VO2 peak (60@60). Heart rate, arterial pressure, and femoral blood flow (Doppler ultrasound) were measured pre‐exercise and every 15 min through 120 min PE. Femoral vascular conductance (FVC) was calculated as flow/pressure. Compared to pre‐exercise baseline, FVC was higher and mean arterial pressure (MAP) was lower throughout 120 min of recovery in all conditions, except for the 30@40 trial. Expressed as percentage change from pre‐exercise baseline, at 30 min PE, FVC was elevated 7.8 ± 1.3% on the 30@40 day, 32.3 ± 1.9% on the 30@60 day, 40.7 ± 4.6% on the 60@40 day, and 43.9 ± 9.0% on the 60@60 day. Compared to pre‐exercise baseline, at 30 min PE, MAP was reduced 0.53 ± 0.6% on the 30@40 day, 2.1 ± 2.9% on the 30@60 day, 4.2 ± 0.2% on the 60@40 day, and 6.1 ± 0.6% on the 60@60 day. These preliminary results suggest a somewhat dose‐dependent elevation of PE skeletal muscle blood flow and reduction in PE MAP in T2D.Grant Funding Source: Supported by the Salisbury University Faculty Mini‐Grant

The effect of green exercise on blood pressure, heart rate and mood state in primary school children.

The aim of this study was exploratory and sought to examine the effect on blood pressure (BP), heart rate (HR) and mood state responses in primary school children of moderate intensity cycling whilst viewing a green environment compared to exercise alone. Following ethics approval and parental informed consent, 14 children (seven boys, seven girls, Mean age ± SD = 10 ± 1 years) undertook two, 15 min bouts of cycling at a moderate exercise intensity in a counterbalanced order. In one bout they cycled whilst viewing a film of cycling in a forest setting. In the other condition participants cycled with no visual stimulus. Pre-, immediately post-exercise and 15 min post-exercise, BP, HR and Mood state were assessed. Analysis of variance, indicated significant condition X time interaction for SBP (p = 0.04). Bonferroni post-hoc pairwise comparisons indicated that systolic blood pressure (SBP) 15 min post exercise was significantly lower following green exercise compared to the control condition (p = 0.01). There were no significant differences in diastolic blood pressure (DBP) (all p > 0.05). HR immediately post exercise was significantly higher than HR pre exercise irrespective of green exercise or control condition (p = 0.001). Mood scores for fatigue were significantly higher and scores for vigor lower 15 min post exercise irrespective of green exercise or control condition (both p = 0.0001). Gender was not significant in any analyses (p > 0.05). Thus, the present study identifies an augmented post exercise hypotensive effect for children following green exercise compared to exercise alone.

The effect of ‘green exercise’ on post exercise hypotension in children. An exploratory study.

Recent adult data has suggested that ‘green exercise’ where exercise is undertaken viewing scenes of nature may enhance health. No studies to date have examined this in children. This study sought to explore the effect of green exercise on the cardiovascular responses in children. Following ethics approval and parental and child consent, 10 prepubertal children (6 boys, 4 girls, Mean age ± SD = 9.4 ± 0.5 years) undertook two bouts of moderate intensity (50% heart rate reserve) cycling for 15 min. In one condition children cycled with no stimulus (Control) whereas in the other children cycled whilst viewing a simulated cycle in a pleasant ‘green’ environment (Green Exercise). Pre exercise, post exercise and 15 min post exercise systolic (SBP) and diastolic (DBP) blood pressure was assessed using automated sphygmomanometry (Bosu Medicus, Bosu, Italy) as was heart rate (Polar Electro, Finland). Repeated measures ANOVA indicated no significant effects for DBP or heart rate (all P > .05). However, there was a significant condition X time interaction for SBP ( F 1,9 = 5.02, P = .05, Pη 2 = .358) whereby SBP was significantly lower 15 min post exercise in the green exercise condition compared to the control condition. This exploratory study suggests that acute aerobic exercise undertaken when viewing scenes of nature may elicit greater postexercise hypotension in prepubertal children compared to exercise alone. The results are limited due to the small sample size but do offer promise as a means to potentially augment the health enhancing effects of aerobic exercise in children.

Acute Post-Exercise Myofibrillar Protein Synthesis Is Not Correlated with Resistance Training-Induced Muscle Hypertrophy in Young Men

Muscle hypertrophy following resistance training (RT) involves activation of myofibrillar protein synthesis (MPS) to expand the myofibrillar protein pool. The degree of hypertrophy following RT is, however, highly variable and thus we sought to determine the relationship between the acute activation of MPS and RT-induced hypertrophy. We measured MPS and signalling protein activation after the first session of resistance exercise (RE) in untrained men (n = 23) and then examined the relation between MPS with magnetic resonance image determined hypertrophy. To measure MPS, young men (24±1 yr; body mass index = 26.4±0.9 kg•m2) underwent a primed constant infusion of L-[ring-13C6] phenylalanine to measure MPS at rest, and acutely following their first bout of RE prior to 16 wk of RT. Rates of MPS were increased 235±38% (P<0.001) above rest 60–180 min post-exercise and 184±28% (P = 0.037) 180–360 min post exercise. Quadriceps volume increased 7.9±1.6% (−1.9–24.7%) (P<0.001) after training. There was no correlation between changes in quadriceps muscle volume and acute rates of MPS measured over 1–3 h (r = 0.02), 3–6 h (r = 0.16) or the aggregate 1–6 h post-exercise period (r = 0.10). Hypertrophy after chronic RT was correlated (r = 0.42, P = 0.05) with phosphorylation of 4E-BP1Thr37/46 at 1 hour post RE. We conclude that acute measures of MPS following an initial exposure to RE in novices are not correlated with muscle hypertrophy following chronic RT.

Exercise is a potent stimulus for enhancing circulating DNase activity

ObjectivesTo elucidate cell free DNA (cfDNA) clearance kinetics following an acute bout of high intensity exercise by measuring circulating DNase activity reduction (AR). Design and methodsSerum cfDNA concentration and DNase-AR were measured prior to and post (immediately post, 7 and 30min post) an acute bout of rowing exercise until exhaustion. ResultsSerum cfDNA concentration was significantly (P≤.001) elevated immediately post (2.5-fold) and 7min post exercise (2.3-fold) with a return close to baseline at 30min post exercise (1.5-fold). The rise in cfDNA was accompanied by a concomitant, significant (P≤.001) decrease in serum DNase-AR from 15.1% prior to exercise to 3.1% AR at cessation of the exercise test and 7min post exercise (3.9% AR). DNase-AR returned close to baseline at 30min post exercise (5.2% AR). ConclusionsA single bout of high intensity exercise is a potent stimulus for enhancing circulating DNase activity in healthy people. Acute exercise may therefore be considered as a non-pharmacological stimulus to trigger DNase activity.This finding may be relevant for pathological conditions associated with increased cfDNA concentrations like cystic fibrosis, where pharmacological recombinant human DNase (rhDNase) treatment has been successfully used to improve patients' health and physical function.

Physiological and metabolic responses as function of the mechanical load in resistance exercise

The present study aimed to investigate the relationship between the mechanical load during resistance exercise and the elicited physiological responses. Ten resistance-trained healthy male subjects performed 1 set of resistance exercise each at 55%, 70%, and 85% of 1 repetition maximum for as many repetitions as possible and in 4 training modes: 4-1-4-1 (4 s concentric, 1 s isometric, 4 s eccentric, and 1 s isometric successive actions), 2-1-2-1, 1-1-1-1, and explosive (maximum velocity concentric). Mean concentric power and total concentric work were determined. Oxygen uptake (V̇O2) was measured during exercise and for 30 min post exercise. Total volume of consumed oxygen (O2 consumed) and excess post-exercise oxygen consumption (EPOC) were calculated. Maximum blood lactate concentration (LAmax) was also determined. V̇O2 exhibited a linear dependency on mean concentric power. Mean concentric power did not have a detectable effect on EPOC and LAmax. An augmentation of total concentric work resulted in significant linear increase of O2 consumed and EPOC. Total concentric work caused a significant increase in LAmax. In general, a higher mechanical load induced a larger physiological response. An increase in mean concentric power elicited higher aerobic energy turnover rates. However, a higher extent of total concentric work augments total energy cost covered by oxidative and (or) glycolytic pathways.

240 : Characterization of leukocyte glucocorticoid receptor translocation in response to physical stress

Physical stress provides an easily manipulated experimental model that allows for the study of interactions between the neuroendocrine and immune systems. Severe exercise elicits marked alterations in circulating stress hormones, causing shifts in leukocyte mobilization and function both during and after exercise. Circulating levels of glucocorticoids and their receptors are known to be altered by acute and chronic exercise. Cortisol binds to the cytosolic glucocorticoid receptors (GCRs) in leukocytes resulting in GC-mediated immunosuppression. Long-term GCRs dysfunction in leukocytes can enhance susceptibility to autoimmune and inflammatory diseases. This study examined physiological cortisol release with strenuous exercise, and measured GCR translocations in peripheral blood T lymphocytes and total leukocytes before and after intense exercise using multispectral imaging flow cytometry. Blood samples were collected before and after intense exercise from 8 healthy participants. The cytosolic levels of FITC-GCRs, GC-GCR complex nuclear (Vybrant Dye) and mitochondria (MitoTrackerRed) translocations were determined for total leukocytes (Leu) and CD3 + lymphocytes. The image-based measurement showed that there was a biphasic response in GCR translocation to the nucleus on the CD3 + GCR Dim lymphocytes before (88%), immediately after (36%) and 30-min (90%) after exercise. There was no change in the CD3 + GCR Bright lymphocytes. The GCR nuclear translocation on GCR Dim Leu expressed a biphasic trend, pre (74%), immediately post (25%) and 30-min (80%) post exercise. The GCR Bright Leu had shown a decreased in GCR translocation over time. It was observed that a portion of the GCR Dim lymphocytes and GCR Dim Leu translocated to the mitochondria after exercise stress. Our data provide insights into the pathophysiological role and mechanisms of cortisol and GCRs on immune cells under subclinical physical stress. This method is particularly important in understanding the GC-induced apoptosis via mitochondria translocation and GC-mediated immunosuppression through nuclear translocation in inflammatory diseases.

The effects of acute exercise on oxidative stress in the skeletal muscle and blood of yearling and mature horses

s / Journal of Equine Veterinary Science 33 (2013) 321-399 324 molasses to encourage consumption. Analysis of urine for ergot alkaloids confirmed levels high enough to elicit toxicosis. Horses were exercised 5 d/wk and subjected to four SET (1/horse/wk), in the third and fourth wk of each period. Each SET consisted of a 10 min warm up in an indoor arena followed byan outdoor trail ride covering 4,875m at the jog (2.1 m/s) and extended trot (3.9 m/s) that required 30-31 min to complete. Variables measured before, during and after the SET included rectal temperature (RT), heart rate (HR), respiration rate (RR), packed cell volume (PCV), blood lactate (BL), percent weight carried (%C), sweat production (SP) and skin temperature (ST) at the poll (STP), exterior forearm (STF) and inner gaskin (STG). One and five min post exercise measurements were taken outdoors with remainingmeasurements recorded indoors at 10, 20, 30, 60, 90,120 min. A composite of ambient air temperature, humidity and solar radiation (WBGT), was recorded during the SET and recovery. A horse effect (p<.05) was observed for HR during the SETand recovery, and for RR and RTexcept near the end of recovery.Regression analysis showed no effect of speed at the jog or extended trot on HR during the SET. Therewas no effect of %C on HR during the SET, however %C had an effect on RR at 90 min and STP at 60 min post SET (p<.02). Horses on TRT had lower HR (p<.05) at 8 of 12 observation points during the SET. Treatment did not affect SP during the SETor HR at 1, 5 and 10 min post exercise. Ergot alkaloids consumption did not affect RR at any time point. Values for RT and ST at 90 min of recovery did not differ from resting values. During the SET, WBGT had no effect on HR, however it did effect resting RT (p<.01) and RR at 10, 30 and 60 min post SET (p<.02). Results of the current study indicate that ergot alkaloids may affect the horse’s ability to perform during outdoor exercise and recover during hot humid

Comparison of acute supplementation with whey, soy or carbohydrate on lymphocyte responses to resistance exercise

Little is known about the effects of acute supplementation with soy (Soy), whey (WHEY) or carbohydrate (CHO) on lymphocyte subset responses to resistance exercise. We randomized untrained men and women (23.0 ± 3.2 yrs, 72.8 ± 13.0 kg, 26.3 ± 10.6 %fat) to supplement with WHEY (n = 19), Soy (n = 14) or CHO (n = 18) immediately after performing a squat exercise protocol (6 sets, 10 repetitions, 65% of 1RM, 2 min rest between sets). Changes in circulating lymphocyte (LY) counts prior to (Pre) and 15 and 60 min post exercise (PE) were assessed. Most lymphocyte subsets, except NK cells, showed a decrease below Pre at 60 min PE in all supplement groups. NK cells in the Soy group were elevated above Pre at 15 min PE. Soy demonstrated a smaller decrease below baseline for total CD3 T cells at 60 min PE, most likely the result of a smaller decrease in CD8 T cells at 60 PE in comparison to CHO. CD4 T cells although not different from Pre were more elevated in Soy than CHO at 15 min PE. These differences in the magnitude and temporal response patterns between supplement groups indicate that Soy may contain a component that attenuates the post‐exercise lymphopenia. Funded by the Dairy Research Institute.

Myocardial IL‐6R expression and IL‐6 signaling following exercise

Interleukin‐6 (IL‐6) is produced in and released from skeletal muscle during contraction. IL‐6 activity is regulated by a signaling complex with the IL‐6 receptor (IL‐6R). Basal expression of IL‐6R is minimal, but increases with exercise in skeletal muscle. The purpose of this study was to determine if exercise increases myocardial IL‐6R expression, and increases phosphorylation of signal transducer and activator of transcription (STAT3) in the heart. Wild type (WT, n=18) and IL‐6 knock‐out (KO, n=12) mice were grouped as sedentary or exercised. Mice were habituated to treadmill exercise for 4 days increasing from 10–40 min bouts. After 1 d rest, mice performed 3 d exercise for 60 min at 18 m/min. Sedentary animals had equal treadmill time at 0 m/min. Mice were sacrificed pre‐, 0, 30 and 60 min post exercise. Heart, gastroc and plasma were collected, snap frozen and stored at −80°C. Samples were normalized for protein concentration and probed for IL‐6R and P‐STAT3. IL‐6R increased post‐exercise in gastroc (~140%), heart (~250%) and plasma (~300%) in WT only. P‐STAT3 in gastroc increased (~18%) in both WT and KO. Minor increase in P‐STAT3 in heart (~10%) was only in WT. Further study is needed to confirm present findings. It appears exercise causes IL‐6/IL‐6R mediated STAT3 activation in the heart. Findings suggest that alternative cytokines may compensate for lack of IL‐6 in the KO mice. [JCQ Level 3 IGP 2011]

Dihydrotestosterone is elevated following sprint exercise in healthy young men

Dihydrotestosterone (DHT) exerts both functional and signaling effects extending beyond the effects of testosterone in rodent skeletal muscle. As a primer for investigating the role of DHT in human skeletal muscle function, this study aimed to determine whether circulating DHT is acutely elevated in men following a bout of repeat sprint exercise and to establish the importance of training status and sprint performance to this response. Fourteen healthy active young men (Vo2max 61.0 ± 8.1 ml·kg body mass(-1)·min(-1)) performed a bout of repeat sprint cycle exercise at a target workload based on an incremental work-rate maximum (10 × 30 s at 150% Wmax with 90-s recovery). Venous blood samples were collected preexercise and 5 and 60 min after exercise. Five minutes after exercise, there were significant elevations in total testosterone (TT; P < 0.001), free testosterone (FT; P < 0.001), and DHT (P = 0.004), which returned to baseline after 1 h. Changes in DHT with exercise (5 min postexercise - preexercise) correlated significantly with changes in TT (r = 0.870; P < 0.001) and FT (r = 0.914; P < 0.001). Sprinting cadence correlated with changes in FT (r = 0.697; P = 0.006), DHT (r = 0.625; P = 0.017), and TT (r = 0.603; P = 0.022), and habitual training volume correlated with the change in TT (r = 0.569, P = 0.034). In conclusion, our data demonstrate that DHT is acutely elevated following sprint cycle exercise and that this response is influenced by cycling cadence. The importance of DHT in the context of exercise training and sports performance remains to be determined.

Effects of post-exercise recovery in a cold environment on muscle glycogen, PGC-1α, and downstream transcription factors

PurposeThe purpose of this investigation was to determine the impact of post-exercise environmental cold exposure on muscle glycogen, PGC-1α, and downstream transcription factors. MethodsEight males cycled for 1h and recovered in either 7°C (cold) or 20°C (room temp) environment for 4h. Muscle biopsies were obtained pre, post, and 4h post exercise for the analysis of muscle glycogen and mRNA. During recovery participants consumed 1.8gkg−1 of body weight of an oral dextrose solution immediately following the post biopsy and 2h into recovery. Blood samples were obtained post exercise and at 30, 60, 120, 150, 180, and 240min post exercise for the analysis of serum glucose and insulin AUC. ResultsOxygen uptake was lower during room temp than during cold recovery (0.40±0.05L x min−1 vs. 0.80±0.12 L x min−1; p<0.01). There was no effect of temperature on muscle glycogen recovery or glucose AUC. However, insulin AUC was greater during the room temp trial compared to the cold trial (5139±1412 vs. 4318±1272, respectively; p=0.025). PGC-1α gene expression was higher (p=0.029), but ERRα and NRF2 were lower (p=0.019 and p=0.046, respectively) after recovery in the cold. There were no differences in NRF1 (p=.173) or TFAM (p=0.694). ConclusionsThis investigation shows no effect of a cold recovery environment on glycogen re-synthesis but does demonstrate reduced ERRα and NRF2 mRNA despite elevations in PGC-1α mRNA when recovery post-exercise takes place in a cold environment.

Resting and post exercise arterial–ventricular coupling in endurance-trained men and women

The relationship between effective arterial elastance (EA) and left ventricular end-systolic elastance (ELV) is a determinant of cardiac performance, known as arterial-ventricular coupling (AVC). The purpose of this study was to examine the acute effects of high-intensity interval (HI) and low-intensity steady state (SS) exercise on AVC. Twenty-three (13 men, 10 women) young (26 years), endurance-trained individuals completed a VO2 peak test followed by an acute SS and HI exercise bout on separate visits. Before (Pre) and 30- and 60-min after each bout, measures of aortic end-systolic pressure (ESP), left ventricular end-systolic volume and stroke volume were obtained. Across both conditions (HI and SS) and both sexes, at 30 and 60 min post exercise, ESP and ELV were reduced from Pre 30 and 60-min exercise (ESP: 86±7, 77±8 and 73±8 mm Hg; ELV: 4.93±1.53, 4.19±1.38 and 4.10±1.53 mm Hg ml(-1) m(-2)). EA was only reduced at 60 min post exercise (1.90±0.36, 1.78±0.50 and 1.57±0.36). Both EA and ELV were reduced following acute SS and HI exercise. This is likely because of similar reductions in total peripheral resistance following both exercise bouts. These results suggest that endurance-trained individuals are able to match peripheral vascular changes with changes in left ventricular function following dynamic exercise of different intensities.

Persistence of functional sympatholysis post-exercise in human skeletal muscle

Blunting of sympathetic vasoconstriction in exercising muscle is well-established. Whether it persists during the early post-exercise period is unknown. This study tested the hypothesis that it persists in human skeletal muscle during the first 10 min of recovery from exercise. Eight healthy young males (21.4 ± 0.8 yrs, SE) performed 7 min of forearm rhythmic isometric handgrip exercise at 15% below forearm critical force (fCF). In separate trials, a cold pressor test (CPT) of 2 min duration was used to evoke forearm sympathetic vasoconstriction in each of Rest (R), Steady State Exercise (Ex), 2–4 min Post-Exercise (PEearly), and 8–10 min Post-Exercise (PElate). A 7 min control exercise trial with no CPT was also performed. Exercising forearm brachial artery blood flow, arterial blood pressure, cardiac output (CO), heart rate (HR), forearm deep venous catecholamine concentration, and arterialized venous catecholamine concentration were obtained immediately prior to and following the CPT in each trial. CPT resulted in a significant increase in forearm venous plasma norepinephrine concentration in all trials (P = 0.007), but no change in arterialized plasma norepinephrine (P = 0.32). CPT did not change forearm venous plasma epinephrine (P = 0.596) or arterialized plasma epinephrine concentration (P = 0.15). As assessed by the %reduction in forearm vascular conductance (FVC) the CPT evoked a robust vasoconstriction at rest that was severely blunted in exercise (R = −39.9 ± 4.6% vs. Ex = 5.5 ± 7.4%, P < 0.001). This blunting of vasoconstriction persisted at PEearly (-12.3 ± 10.1%, P = 0.02) and PElate (-18.1 ± 8.2%, P = 0.03) post-exercise. In conclusion, functional sympatholysis remains evident in human skeletal muscle as much as 10 min after the end of a bout of forearm exercise. Persistence of functional sympatholysis may have important implications for blood pressure regulation in the face of a challenge to blood pressure following exercise.

Intense Resistance Exercise Induces Early and Transient Increases in Ryanodine Receptor 1 Phosphorylation in Human Skeletal Muscle

BackgroundWhile ryanodine receptor 1 (RyR1) critically contributes to skeletal muscle contraction abilities by mediating Ca2+ion oscillation between sarcoplasmatic and myofibrillar compartments, AMP-activated protein kinase (AMPK) senses contraction-induced energetic stress by phosphorylation at Thr172. Phosphorylation of RyR1 at serine2843 (pRyR1Ser2843) results in leaky RyR1 channels and impaired Ca2+homeostasis. Because acute resistance exercise exerts decreased contraction performance in skeletal muscle, preceded by high rates of Ca2+-oscillation and energetic stress, intense myofiber contractions may induce increased RyR1 and AMPK phosphorylation. However, no data are available regarding the time-course and magnitude of early RyR1 and AMPK phosphorylation in human myofibers in response to acute resistance exercise.PurposeDetermine the effects and early time-course of resistance exercise on pRyR1Ser2843 and pAMPKThr172 in type I and II myofibers.Methods7 male subjects (age 23±2 years, height: 185±7 cm, weight: 82±5 kg) performed 3 sets of 8 repetitions of maximum eccentric knee extensions. Muscle biopsies were taken at rest, 15, 30 and 60 min post exercise. pRyR1Ser2843 and pAMPKThr172 levels were determined by western blot and semi-quantitative immunohistochemistry techniques.ResultsWhile total RyR1 and total AMPK levels remained unchanged, RyR1 was significantly more abundant in type II than type I myofibers. pRyR1Ser2843 increased 15 min and peaked 30 min (p<0.01) post exercise in both myofiber types. Type I fibers showed relatively higher increases in pRyR1Ser2843 levels than type II myofibers and remained elevated up to 60 min post resistance exercise (p<0.05). pAMPKThr172 also increased 15 to 30 min post exercise (p<0.01) in type I and II myofibers and in whole skeletal muscle.ConclusionResistance exercise induces acutely increased pRyR1Ser2843 and concomitantly pAMPKThr172 levels for up to 30 min in resistance exercised myofibers. This provides a time-course by which pRyR1Ser2843 can mechanistically impact Ca2+handling properties and consequently induce reduced myofiber contractility beyond immediate fatiguing mechanisms.