Moderate-intensity Cycling Exercise Research Articles

The immediate and sustained effects of acute exercise on planning aspect of executive function

ObjectiveThe purpose of this study was to clarify the immediate and sustained effects of an acute bout of exercise on the planning aspects of executive function. DesignThis study used a 2 × 4 true experimental design. MethodForty participants were randomly assigned to either the exercise or control groups and completed the Tower of London task prior to, immediately following, 30 min after, and 60 min after cessation of a 30 min, moderate intensity cycling exercise. ResultsAcute exercise positively impacted the total move score, which reflects planning efficiency, immediately after the cessation of exercise. Acute exercise also led to longer total initiation times, which were linked to better response inhibition of planning at 30 and 60 min after the cessation of exercise. ConclusionAcute exercise benefits planning, and the types of planning and the time points at which they were assessed modulate the relationship between acute exercise and executive function. Exercise-induced physiological and biological fluctuations have been proposed to explain the effects present immediately after exercise, and the mechanisms of such effects warrant further exploration.

Influence of hormone replacement therapy and aerobic exercise training on oxygen uptake kinetics in postmenopausal women

The purpose of this study was to determine the effects of aerobic exercise training on the adjustment of pulmonary oxygen (O2) uptake (VO2p) kinetics in postmenopausal women in 2 groups: those using hormone replacement therapy (HRT) (HRT group) (n = 7, aged 56 ± 4 years) and those not using HRT (nonHRT group) (n = 8, aged 60 ± 5 years). The influence of training (cycle-ergometer 3 times per week for 6 weeks) on step transitions to both moderate-intensity (80% of the gas exchange threshold) and heavy-intensity (Δ50) cycling exercise was studied. Breath-by-breath VO2p data were collected using a mass spectrometer. There were no differences in baseline characteristics between the HRT and nonHRT groups. Moderate-intensity exercise VO2p kinetics were significantly speeded (p < 0.05) with the τVO2p decreasing from 46 ± 8 s before training to 32 ± 4 s after training. Similarly, during the heavy-intensity exercise, on-transient phase 2 τVO2p was reduced from before training (48 ± 7 s) to after training (38 ± 6 s). The use of HRT did not influence the effect of the endurance exercise training on τVO2p during moderate or heavy exercise in healthy postmenopausal women. To provide insight into the mechanism of adjustment, knee extension exercise was studied, and the VO2p kinetics were significantly speeded (p < 0.05), with the τVO2p of the knee extension exercise decreasing from 62.2 ± 18.3 s before training to 48.0 ± 16.2 s after training. Thus, 6 weeks of exercise training resulted in appreciably faster cycling phase 2 VO2p kinetics during moderate and heavy exercise in older women, independent of HRT use.

VO2p, HR and HHb kinetics in young and older adults during cycling 1 in acute hypoxia

Abstract The adjustment of pulmonary oxygen uptake (VO2p), heart rate (HR), and muscle deoxygenation [HHb] were examined during the transition to moderate-intensity cycling exercise, in eight older adults (70 ± 2 years) and eight young adults (29 ± 4 years) under 2 conditions: normoxia (FIO2=20.9%) and hypoxia (FIO2=15%). The subjects performed repeated step transitions from an active baseline (12 W) to a relative power output (80% VO2 of the first ventilatory threshold) in both conditions. Phase 2 VO2p, HR, and HHb data were fit with an exponential model. For both groups slower phase 2 VO2p kinetics, were found in hypoxia compared to normoxia (34±8 vs 29±6 sec for older adults and 25±4 vs 19±4 sec for young adults). Only the young adult group showed greater HR (33±6 vs 19±4 sec), [HHb] (18±3 vs 15±2 sec) and (24±2 vs 22±2 sec) in hypoxia compared to normoxia, whereas only the older adults group exhibited a greater [HHb]/VO2 (1.13±0.1 vs 1.09±0.1) ratio in hypoxia compared to normoxia. These findings support the idea that, for older adults the main constrain to the VO2p kinetics in hypoxia lies in the microvascular O2 delivery, whereas for young adults factors other than the microvascular O2 delivery (i.e slowed mitochondrial respiration) are responsible for the slowed VO2p kinetics in hypoxia.

Effect of acetazolamide on respiratory muscle fatigue in humans

Previous studies have demonstrated that carbonic anhydrase inhibition with acetazolamide reduces exercise capacity. The mechanism responsible for this early fatigue is unclear, but may be partly mediated by impaired respiratory muscle function. Inspiratory muscle strength and endurance were assessed in seven healthy men (age 28±5yrs, ±SD) by measuring maximal inspiratory pressure (MIP) and time to task failure during a constant-load breathing test (CLBT), respectively, under control (CON) and acetazolamide (ACZ; 500mg/8h po for 3 days) conditions that were separated by two weeks and randomized between subjects. In addition, MIP was measured before and after moderate-intensity cycling exercise to fatigue while pulmonary gas exchange, plasma pH, and ventilation were measured during exercise. ACZ did not alter pulmonary function (FVC, FEV1, MVV) or MIP measured at rest (CON, −157±47 vs. ACZ, −154±45cmH2O, p>0.05), but decreased time to task failure during the CLBT (CON, 1340±820 vs. ACZ, 698±434s; p=0.01). Exercise duration during cycling exercise was reduced (p=0.003) with ACZ (1090±254s) compared to CON (1944±532s) in the presence of a significantly lower plasma pH and higher ventilation compared to control (p<0.05). Compared to resting values, MIP was reduced (p=0.03) in ACZ but not CON at exhaustion. In conclusion, carbonic anhydrase inhibition with ACZ is associated with impaired respiratory muscle function at rest and following constant load cycling which may contribute to reduced exercise tolerance with carbonic anhydrase inhibition.

Metabolic response to green tea extract during rest and moderate-intensity exercise

BackgroundGreen tea catechins have been hypothesized to increase energy expenditure and fat oxidation by inhibiting catechol-O-methyltransferase (COMT) and thus promoting more sustained adrenergic stimulation. Metabolomics may help to clarify the mechanisms underlying their putative physiological effects. ObjectiveThe study investigated the effects of 7-day ingestion of green tea extract (GTE) on the plasma metabolite profile at rest and during exercise. MethodsIn a placebo-controlled, double-blind, randomized, parallel study, 27 healthy physically active males consumed either GTE (n=13, 1200 mg catechins, 240 mg caffeine/day) or placebo (n=14, PLA) drinks for 7 days. After consuming a final drink (day 8), they rested for 2 h and then completed 60 min of moderate-intensity cycling exercise (56%±4% VO2max). Blood samples were collected before and during exercise. Plasma was analyzed using untargeted four-phase metabolite profiling and targeted profiling of catecholamines. ResultsUsing the metabolomic approach, we observed that GTE did not enhance adrenergic stimulation (adrenaline and noradrenaline) during rest or exercise. At rest, GTE led to changes in metabolite concentrations related to fat metabolism (3-β-hydroxybutyrate), lipolysis (glycerol) and tricarboxylic acid cycle (TCA) cycle intermediates (citrate) when compared to PLA. GTE during exercise caused reductions in 3-β-hydroxybutyrate concentrations as well as increases in pyruvate, lactate and alanine concentrations when compared to PLA. ConclusionsGTE supplementation resulted in marked metabolic differences during rest and exercise. Yet these metabolic differences were not related to the adrenergic system, which questions the in vivo relevance of the COMT inhibition mechanism of action for GTE.

Effect of acute exercise on glycogen synthase in muscle from obese and diabetic subjects.

Insulin stimulates glycogen synthase (GS) through dephosphorylation of serine residues, and this effect is impaired in skeletal muscle from insulin-resistant [obese and type 2 diabetic (T2DM)] subjects. Exercise also increases GS activity, yet it is not known whether the ability of exercise to affect GS is impaired in insulin-resistant subjects. The objective of this study was to examine the effect of acute exercise on GS phosphorylation and enzyme kinetic properties in muscle from insulin-resistant individuals. Lean normal glucose-tolerant (NGT), obese NGT, and obese T2DM subjects performed 40 min of moderate-intensity cycle exercise (70% of Vo(2max)). GS kinetic properties and phosphorylation were measured in vastus lateralis muscle before exercise, immediately after exercise, and 3.5 h postexercise. In lean subjects, GS fractional activity increased twofold after 40 min of exercise, and it remained elevated after the 3.5-h rest period. Importantly, exercise also decreased GS K(m) for UDP-glucose from ≈0.5 to ≈0.2 mM. In lean subjects, exercise caused significant dephosphorylation of GS by 50-70% (Ser(641), Ser(645), and Ser(645,649,653,657)), and phosphorylation of these sites remained decreased after 3.5 h; Ser⁷ phosphorylation was not regulated by exercise. In obese NGT and T2DM subjects, exercise increased GS fractional activity, decreased K(m) for UDP-glucose, and decreased GS phosphorylation as effectively as in lean NGT subjects. We conclude that the molecular regulatory process by which exercise promotes glycogen synthesis in muscle is preserved in insulin-resistant subjects.

Intermittent Normobaric Hypoxic Exposures at Rest: Effects on Performance in Normoxia and Hypoxia

It has been speculated that short (-1-h) exposures to intermittent normobaric hypoxia at rest can enhance subsequent exercise performance. Thus, the present study investigated the effect of daily resting intermittent hypoxic exposures (IHE) on peak aerobic capacity and performance under both normoxic and hypoxic conditions. Eighteen subjects were equally assigned to either a control (CON) or IHE group and performed a 4-wk moderate intensity cycling exercise training (1 h x d(-1), 5 d x wk(-1)). The IHE group additionally performed IHE (60 min) prior to exercise training. IHE consisted of seven cycles alternating between breathing a hypoxic gas mixture (5 min; F1O2 = 0.12-0.09) and room air (3 min; F1O2 = 0.21). Normoxic and hypoxic peak aerobic capacity (VO2(peak)) and endurance performance were evaluated before (PRE), during (MID), upon completion (POST), and 10 d after (AFTER) the training period. Similar improvements were observed in normoxic VO2(peak) tests in both groups [IHE: delta(POST-PRE) = +10%; CON: delta(POST-PRE) = + 14%], with no changes in the hypoxic condition. Both groups increased performance time in the normoxic constant power test only [IHE: delta(POST-PRE) = +108%; CON: delta(POST-PRE) = +114%], whereas only the IHE group retained this improvement in the AFTER test. Higher levels of minute ventilation were noted in the IHE compared to the CON group at the POST and AFTER tests. Based on the results of this study, the IHE does not seem to be beneficial for normoxic and hypoxic performance enhancement.

Effect of Textile Hygroscopicity on Stratum Corneum Hydration, Skin Erythema and Skin Temperature During Exercise in the Presence of Wind and No Wind

This crossover designed study examined the influence of textile hygroscopicity on skin temperature responses during 30 minutes of continuous cycling exercise at 60% O 2peak in a thermoneutral environment (20°C and 50% relative humidity) in the convective airflow presence of forced convection (4.5 ± 0.2m · s −2 ) and under minimal convective airflow conditions. Ten well-trained male road cyclists completed two wear trials at random in the forced convection and minimal convective airflow condition wearing a long-sleeved cycling jersey that had a split design with a strongly hygroscopic (SH) fabric (wool) on one half and a weakly hygroscopic (WH) fabric (polyester) on the other half of the garment. The cyclists' mean age was 31±5 years, mean height was 1.81 ± 0.05 m, mean body mass was 83.55 ± 10.89 kg, and mean body surface area was 2.04 ± 0.14 m 2 . The previously reported actions of SH fibers increasing skin temperature through the evolution of sorption heat following moisture absorption, and subsequent elevation in fabric temperature, was assessed. An effect of WH fibers to impact skin temperature through increasing stratum corneum hydration, producing more skin-to-fabric contact and skin erythema, was also investigated. Similar physiological responses in the skin, including temperature, sweating, stratum corneum hydration (inferred from skin resistance) and erythema (indicated by luminous flux), were found for both the SH and WH fabrics under wind and no wind conditions. In conclusion, the textile hygroscopicity of the test garment was not found to significantly influence skin temperature during moderate-intensity cycling exercise for 30 minutes in a thermoneutral environment under minimal wind conditions and in the presence of forced convection.

Muscle damage slows oxygen uptake kinetics during moderate-intensity exercise performed at high pedal rate

This study aimed to investigate the dependence of oxygen uptake (VO₂) kinetics on pedal cadence during moderate-intensity exercise following exercise-induced muscle damage (EIMD). Twenty untrained males were randomly assigned to a 50 revolution per minute (rpm) (age, 23.3 ± 1.8 years; VO₂(max), 38.9 ± 2.8 mL·kg⁻¹·min⁻¹) or 100 rpm group (age, 24.4 ± 3.5 years, VO₂(max), 42.9 ± 4.3 mL·kg⁻¹·min⁻¹). Participants completed "step" tests to moderate-intensity exercise from an unloaded baseline on a cycle ergometer before (baseline) and at 24 and 48 h after muscle-damaging exercise (10 sets of 10 eccentric contractions performed on an isokinetic dynamometer with a 2-min rest between each set). Pedal cadence was kept constant throughout each cycling trial (50 or 100 rpm). There were no changes in phase II pulmonary VO₂ kinetics following EIMD for the 50 rpm group (baseline = 35 ± 4 s; 24 h = 35 ± 7 s; and 48 h = 36 ± 9 s). However, the phase II VO₂ was significantly greater at 24 h (59 ± 27 s) compared with baseline (39 ± 6 s) and 48 h (40 ± 9 s) for the 100 rpm group. It is concluded that the effects of EIMD on phase II VO₂ kinetics during moderate-intensity cycling exercise is dependent on pedal cadence. The slower VO₂ kinetics after muscle damage suggests that type II fibers are involved during transition to moderate-intensity exercise at high pedal cadence.

Acute moderate-intensity cycling exercise is associated with reduced fatigue in persons with multiple sclerosis

Background Fatigue is a prominent, disabling symptom of MS. The prevalence and impact of fatigue highlights the need to identify approaches for its management. Purpose To examine changes in fatigue associated with an acute bout of moderate-intensity exercise in persons with multiple sclerosis (MS). Methods Females ( N = 25) with MS completed an incremental exercise test on a cycle ergometer to measure peak oxygen consumption (VO 2peak) and on a separate day completed the abbreviated Profile of Mood States (POMS) before performing 20 min of cycle ergometry at 60% VO 2peak. Participants again completed the POMS at 5, 20, and 60 min after exercise. Results There were small-to-moderate reductions in fatigue subscale scores on the POMS 20 ( d = .39) and 60 ( d = .45) min after the acute bout of exercise. Conclusion We conclude that moderate-intensity cycling exercise was associated with reductions in fatigue and might represent an appropriate stimulus for the chronic management of fatigue in persons with MS.

NF-κB activity in muscle from obese and type 2 diabetic subjects under basal and exercise-stimulated conditions

NF-κB is a transcription factor that controls the gene expression of several proinflammatory proteins. Cell culture and animal studies have implicated increased NF-κB activity in the pathogenesis of insulin resistance and muscle atrophy. However, it is unclear whether insulin-resistant human subjects have abnormal NF-κB activity in muscle. The effect that exercise has on NF-κB activity/signaling also is not clear. We measured NF-κB DNA-binding activity and the mRNA level of putative NF-κB-regulated myokines interleukin (IL)-6 and monocyte chemotactic protein-1 (MCP-1) in muscle samples from T2DM, obese, and lean subjects immediately before, during (40 min), and after (210 min) a bout of moderate-intensity cycle exercise. At baseline, NF-κB activity was elevated 2.1- and 2.7-fold in obese nondiabetic and T2DM subjects, respectively. NF-κB activity was increased significantly at 210 min following exercise in lean (1.9-fold) and obese (2.6-fold) subjects, but NF-κB activity did not change in T2DM. Exercise increased MCP-1 mRNA levels significantly in the three groups, whereas IL-6 gene expression increased significantly only in lean and obese subjects. MCP-1 and IL-6 gene expression peaked at the 40-min exercise time point. We conclude that insulin-resistant subjects have increased basal NF-κB activity in muscle. Acute exercise stimulates NF-κB in muscle from nondiabetic subjects. In T2DM subjects, exercise had no effect on NF-κB activity, which could be explained by the already elevated NF-κB activity at baseline. Exercise-induced MCP-1 and IL-6 gene expression precedes increases in NF-κB activity, suggesting that other factors promote gene expression of these cytokines during exercise.

Combination of Sago and Soy-Protein Supplementation During Endurance Cycling Exercise and Subsequent High-Intensity Endurance Capacity

The purpose of the study was to investigate whether a combination of sago and soy protein ingested during moderate-intensity cycling exercise can improve subsequent high-intensity endurance capacity compared with a carbohydrate in the form of sago and with a placebo. The participants were 8 male recreational cyclists with age, weight, and VO2max of 21.5 +/- 1.1 yr, 63.3 +/- 2.4 kg, and 39.9 +/- 1.1 ml . kg(-1) . min(-1), respectively. The design of the study was a randomized, double-blind placebo-controlled crossover comprising 60 min of exercise on a cycle ergometer at 60% VO2max followed by a time-to-exhaustion ride at 90% VO2max. The sago feeding provided 60 g of carbohydrate, and the sago-soy combination provided 52.5 g of carbohydrate and 15 g of protein, both at 20-min intervals during exercise. Times to exhaustion for the placebo, sago, and sago-soy supplementations were 4.09 +/- 1.28, 5.49 +/- 1.20, and 7.53 +/- 2.02 min, respectively. Sago-soy supplementation increased endurance by 84% (44-140%; p < .001) and by 37% (15-63%; p < .05) relative to placebo and sago, respectively. The plasma insulin response was elevated above that with placebo during sago and sago-soy supplementations. The authors conclude that a combination of sago and soy protein can delay fatigue during high-intensity cycling.

Human Cerebral Blood Flow Increases After Acute Exercise: Arterial Spin Labeling MRI

There is interest in functional magnetic resonance imaging (fMRI) to measure brain activation after exercise. The blood oxygen level dependent (BOLD) fMRI signal varies with cerebral blood flow (CBF), however, it is not known if CBF changes after acute exercise. Previous methods used during exercise (Xe clearance, transcranial doppler) do not provide good spatial localization of CBF. We report the first use of arterial spin labeling (ASL) to detect changes in CBF after exercise. PURPOSE: The aims of this study were to examine: 1) the optimal inversion time to detect changes in CBF in the motor cortex from before to after acute exercise; and 2) if acute exercise alters CBF in the motor cortex at rest or during a finger tapping task. METHODS: Subjects (n = 6) performed 30 minutes of moderate intensity exercise on an electronically braked cycle ergometer (RPE 'somewhat hard'). Before and 10 minutes after exercise relative CBF was measured over four superior contiguous, 6-mm slices (1mm gap) on a 3T GE Signa scanner (8-channel coil) using multiple inversion time (TI) pulsed arterial spin labeling (PASL): FOV=24 cm2, 3.75 mm2 in-plane resolution, FA=90deg, TE=3.2 ms, TR=2000 ms, tag width=600 ms, tag thickness=10 cm, with a 1 cm gap between the tagging band and proximal slice. Two multiple TI runs were obtained at rest and during 4Hz finger-tapping. Four inversion times (675, 975, 1275, 1575 ms) were acquired per run, with 20 interleaved pairs of tag and control images per inversion time (run time 320 s). Heart rate, blood pressure and O2 content, pCO2, and respiration were recorded throughout. RESULTS: Resting CBF increased up to 20% following exercise, with significant differences obtained at an inversion time of 1575 ms (p <.05). Finger tapping-induced CBF in the motor cortex significantly increased from before to after exercise at TI = 1575 ms (p <.01). CONCLUSION: These findings suggest changes in human cerebral blood flow can be detected up to 30 minutes after moderate intensity cycling exercise using pulsed arterial spin labeling at 3T with an inversion time of 1575 ms. This study has important implications for using fMRI after exercise. Prior exercise may introduce variance into the fMRI BOLD signal that reflects increased CBF, not neural activation. Future fMRI studies should take into consideration exercise-induced changes in CBF.

Acute Exercise Improves Endothelial Function Despite Increasing Vascular Resistance During Stress in Smokers and Non-smokers

Endothelial dysfunction, measured by flow mediated dilation (FMD), and hyper-reactivity to neurovascular challenges are two potential mechanisms by which cigarette smoking can be harmful to the vasculature. It has been suggested that acute exercise may improve endothelial function and attenuate cardiovascular reactivity to neurovascular stressors, but we could not locate studies of female smokers that examined FMD after neurovascular stress. PURPOSE: To determine the effect of an acute bout of moderate-intensity cycling exercise on FMD and cardiovascular responses during neurovascular stress among sedentary female smokers and non-smokers. METHODS: FMD was determined by brachial arterial diameter, arterial velocity and blood flow measured by Doppler ultrasonography after forearm occlusion. Those measures and beat-to-beat finger blood pressure (BP) and heart rate (HR) were also assessed in response to 2 min of forehead cold and 4 min of the Stroop Color-Word conflict test (CWT). Individuals participated in two counterbalanced conditions: 30 minutes of either passive rest or cycling exercise (∼50% VO2peak). FMD was tested 8 min after stress. RESULTS: Baseline FMD and stress responses were not different between smokers and non-smokers. Compared to passive rest, exercise increased FMD (7 ± 2% vs. 5 ± 2%) and resting HR; arterial velocity; and blood flow, and decreased resting SBP in both groups. During the Stroop CWT, arterial velocity (-9 ± 8 vs. 2 ± 2 cm/s) and blood flow (-53 ± 58 vs. 19 ± 38 ml/min) responses were reduced after exercise compared to passive rest in smokers and non-smokers. Similarly, during forehead cold, reductions in arterial velocity (-19 ± 11 vs. -4.5 ± 4.5 cm/s) and blood flow (-107 ± 74% vs. -25 ± 30 ml/min) responses were augmented after exercise compared to passive rest. CONCLUSIONS: Acute cycling exercise improved endothelial function among female smokers and non-smokers despite increasing vascular resistance and reducing limb blood flow during both dilatory and constrictive neurovascular stress in the presence of post-exercise hypotension.

Influence of Blood Donation on Oxygen Uptake Kinetics During Moderate and Heavy Intensity Cycle Exercise

The purpose of this study was to determine the effects of a reduced whole body blood volume on the kinetic response of VO(2) during moderate and heavy intensity exercise. Six males and four females (age, 21+/-2 yrs; height, 175.2+/-5.1 cm; weight, 66.4+/-2.8 kg; VO(2)max, 53.0+/-4.1 ml x kg (-1) x min(-1)), completed a square-wave cycling ramp test to determine ventilatory threshold (VT) and VO(2max). Kinetics trials were completed 24 h pre and post donation of 450 cm (3) of blood. The kinetics trials were moderate intensity (80%VT) and heavy intensity (Delta50% VT - VO(2max)). Breath-by-breath gas exchange, heart rate, blood pressure, haemoglobin O(2) saturation, and blood [lactate] were measured throughout the trials. Post-donation haemoglobin, haematocrit and erythrocyte count were all significantly reduced (p<or= 0.05). Blood donation caused a significant increase in resting heart rate (P<or= 0.05). There were non-significant differences in the time constants or amplitude of phase II VO(2) kinetics in either moderate or heavy exercise (p>or= 0.05), or in the amplitude of the slow component. The capacity of the cardiovascular system to meet the metabolic demands of skeletal muscle at the onset of exercise does not limit the oxygen uptake.

Rapid Restitution of the Lung Functions Following Short-Term Breath-Holding During Moderate Intensity Cycling Exercise

Short periods of breath-holding (BH) occur frequently during various kinds of sports activities. Increased minute oxygen uptake (VO2), increased minute carbon dioxide output (VCO2) and increased minute ventilation (VE) are some of the typical responses just after breaking the BH and resuming breathing and these parameters return to their steady levels over time. This study examined the properties of the restitution processes of lung functions after BH. Exercise tests were carried out with a bicycle ergometer for seven healthy male athletes and the ventilation activities and expired gases were measured with a breath-by-breath based aeromonitor. The respiratory responses to 25 s BH were tested during continuous cycling at three exercise loads (2 W, 22 W and 102 W). A single exponential decay function with two parameters: initial amplitude (A) and time constant ( ), was fitted to the data of VO2, VCO2, VE, expiratory tidal volume (TVE) and respiratory rate (RR) after cessation of the BH. It was found that, except for RR, A was increased and was decreased with increasing the exercise intensity. The A of VCO2 was smaller and was longer than those of VO2 at all load intensities. The difference in the time courses of VO2 and VCO2 may be explained by the different buffer mechanisms of oxygen and carbon dioxide within the body.

Interaction between muscle temperature and contraction velocity affects mechanical efficiency during moderate-intensity cycling exercise in young and older women

The effect of elevated muscle temperature on mechanical efficiency was investigated during exercise at different pedal frequencies in young and older women. Eight young (24 +/- 3 yr) and eight older (70 +/- 4 yr) women performed 6-min periods of cycling at 75% ventilatory threshold at pedal frequencies of 45, 60, 75, and 90 rpm under control and passively elevated local muscle temperature conditions. Mechanical efficiency was calculated from the ratio of energy turnover (pulmonary O(2) uptake) and mechanical power output. Overall, elevating muscle temperature increased (P < 0.05) mechanical efficiency in young (32.0 +/- 3.1 to 34.0 +/- 5.5%) and decreased (P < 0.05) efficiency in older women (30.2 +/- 5.6 to 27.9 +/- 4.1%). The different effect of elevated muscle temperature in young and older women reflects a shift in the efficiency-velocity relationship of skeletal muscle. These effects may be due to differences in recruitment patterns, as well as sarcopenic and fiber-type changes with age.

Effect of exercise-induced muscle damage on ventilatory and perceived exertion responses to moderate and severe intensity cycle exercise

This study examined the effect of exercise-induced muscle damage (EIMD) on ventilatory and perceived exertion responses to cycle exercise. Ten healthy, physically active men cycled for 6 min at moderate intensity and to exhaustion at severe intensity before and 48 h after eccentric exercise (100 squats with a load corresponding to 70% of body mass). Changes in ventilation and ratings of perceived exertion (RPE) were calculated for each individual and expressed against time (moderate and severe exercise) and as a percentage of time to exhaustion (severe exercise). Ventilation increased during moderate exercise at 48 h V(E); 34.5 +/- 5.0 to 36.3 +/- 3.8 l min(-1), P < 0.05) but increases in RPE were not significant. During severe exercise at 48 h, time to exhaustion (TTE) was reduced and V(E) (87.1 +/- 14.1 to 93.8 +/- 11.7 l min(-1)) and RPE (15.5 +/- 1.3 to 16.1 +/- 1.4) were elevated (P < 0.05). When expressed as a percentage of TTE, the differences in ventilation and RPE values disappeared. Findings indicate that the augmented ventilatory response to cycle exercise following EIMD may be an important cue in informing effort perception during high-intensity exercise but not during moderate-intensity exercise.

Superior Mesenteric And Renal Artery Blood Flow During Low And Moderate Intensity Cycling Exercise In Humans

Superior Mesenteric And Renal Artery Blood Flow During Low And Moderate Intensity Cycling Exercise In Humans

Anxiety and mood changes associated with acute cycling in persons with multiple sclerosis

We examined changes in state anxiety (SA) and Total Mood Disturbance (TMD) associated with acute exercise in persons with multiple sclerosis (MS) and the influence of trait anxiety (TA) on the magnitude of the changes. Females (N=25) with MS were separated into subgroups of higher trait anxiety (HTA, n=8) or lower trait anxiety (LTA, n=17). Participants completed an incremental exercise test to measure , and on a separate day completed the trait and state portions of the State-Trait Anxiety Inventory (STAI; Forms Y1 and Y2) and the Profile of Mood States (POMS) before performing 20 minutes of cycle ergometry at 60% of . Participants completed the state portion of the STAI (Form Y1) and the POMS at 5, 20, and 60 minutes after exercise. There were large reductions in SA 5, 20, and 60 minutes after exercise in the HTA group, and SA scores were relatively unchanged in the LTA group. There were large reductions in TMD 5, 20, and 60 minutes after exercise in the HTA group, and small reductions in TMD 20 and 60 minutes post-exercise in the LTA group. Moderate-intensity cycling exercise was associated with reductions in SA and TMD in persons with MS, and changes were larger in individuals reporting higher TA.