Influence Of Exercise Intensity Research Articles

Left Ventricular Function and Cardiac Biomarker Release -The Influence of Exercise Intensity, Duration and Mode: A Systematic Review and Meta-Analysis

Left Ventricular Function and Cardiac Biomarker Release -The Influence of Exercise Intensity, Duration and Mode: A Systematic Review and Meta-Analysis

Carotid Chemoreflex Regulation of Post‐Exercise Cardiac Autonomic Control in Healthy Humans: Influence of Exercise Intensity

The recovery of cardiac autonomic control from exercise has two phases. The fast phase lasts about 60 s after exercise, and is largely dependent on the cardiac vagal reactivation. The slow phase is 300 s in duration, and is dependent on both the cardiac vagal reactivation and sympathetic withdrawal. Indexes of post‐exercise cardiac autonomic control are widely used in the clinical practice to predict morbidity and mortality. However, the mechanisms that regulate the post‐exercise cardiac autonomic control remain unclear. The carotid chemoreflex regulates cardiac autonomic control at rest, and carotid chemoreceptors are stimulated by humoral and neural signals related to exercise. As the extent of the humoral and neural responses are dependent upon exercise intensity, we hypothesized the carotid chemoreflex could regulate post‐exercise cardiac autonomic control in an exercise‐intensity‐dependent manner.Thirteen healthy humans performed ramp incremental exercise up to either moderate‐intensity (MI; i.e., ventilatory threshold) or high‐intensity exercise (HI; i.e., 90% peak workload). Both MI and HI exercise were followed by 5 min of active recovery (i.e., unloaded cycling) while breathing, in random order, normoxia (21% of O2, control), hyperoxia (100% of O2, carotid chemoreflex inhibition) or hypoxia (12% of O2, carotid chemoreflex stimulation). Gas administration started 10 s before the onset of recovery from exercise. The fast phase of cardiac autonomic control recovery from exercise was assessed by the heart rate (HR) reduction at 60 s post‐exercise (HRR60s). The slow phase was assessed by the time constant of exponential HR decay (HRRτ) over 300 s and the HR reduction at 300 s post‐exercise (HRR300s). Fast and slow phases were assessed by the square root of mean squared differences of successive R‐R intervals of 30‐s data segments (RMSSD30s).As compared to normoxia, hyperoxia did not change HRR60s at either exercise intensities. Hypoxia did not change HRR60s at MI, but decreased HRR60s at HI (normoxia: 29 ± 8 vs hypoxia: 17 ± 9 bpm; P < 0.01). Hyperoxia and hypoxia did not change HRRτ. Hyperoxia did not affect HRR300s, but hypoxia decreased HRR300s similarly at both exercise intensities (MI: normoxia = 32 ± 14 vs hypoxia = 26 ± 17 bpm; HI: normoxia = 55 ± 7 vs hypoxia = 48 ± 11 bpm; post hoc for gas main effect: P = 0.03). Finally, regardless of the time, hyperoxia increased RMSSD30s (MI: normoxia = 15 ± 7 vs hyperoxia = 19 ± 10 ms; HI: normoxia = 5 ± 3 vs hyperoxia = 6 ± 3 ms, post hoc for gas main effect: P < 0.01), whereas hypoxia decreased RMSSD30s (MI: hypoxia = 13 ± 9 ms vs normoxia; HI: hypoxia = 4 ± 2 vs normoxia, post hoc for gas main effect: P < 0.01) at both exercise intensities.In conclusion, the carotid chemoreflex regulates both the fast and slow phases of post‐exercise cardiac autonomic control in healthy humans; however, only the fast phase regulation is dependent on the exercise intensity. These results suggest that sensitization of the carotid chemoreflex with exercise plays an important role for the post‐exercise cardiac vagal reactivation.Support or Funding InformationFAPESP 2015/22198‐2; 2018/03501‐4This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Effects of a Short-Term Cycling Interval Session and Active Recovery on Non-Linear Dynamics of Cardiac Autonomic Activity in Endurance Trained Cyclists.

Measurement of the non-linear dynamics of physiologic variability in a heart rate time series (HRV) provides new opportunities to monitor cardiac autonomic activity during exercise and recovery periods. Using the Detrended Fluctuation Analysis (DFA) technique to assess correlation properties, the present study examines the influence of exercise intensity and recovery on total variability and complexity in the non-linear dynamics of HRV. Sixteen well-trained cyclists performed interval sessions with active recovery periods. During exercise, heart rate (HR) and beat-to-beat (RR)-intervals were recorded continuously. HRV time domain measurements and fractal correlation properties were analyzed using the short-term scaling exponent alpha1 of DFA. Lactate (La) levels and the rate of perceived exertion (RPE) were also recorded at regular time intervals. HR, La, and RPE showed increased values during the interval blocks (p < 0.05). In contrast, meanRR and DFA-alpha1 showed decreased values during the interval blocks (p < 0.05). Also, DFA-alpha1 increased to the level in the warm-up periods during active recovery (p < 0.05) and remained unchanged until the end of active recovery (p = 1.000). The present data verify a decrease in the overall variability, as well as a reduction in the complexity of the RR-interval-fluctuations, owing to increased organismic demands. The acute increase in DFA-alpha1 following intensity-based training stimuli in active recovery may be interpreted as a systematic reorganization of the organism with increased correlation properties in cardiac autonomic activity in endurance trained cyclists.

Exercise intensity and middle cerebral artery dynamics in humans

Despite its necessity for understanding healthy brain aging, the influence of exercise intensity on cerebrovascular kinetics is currently unknown. We, therefore characterized middle cerebral artery blood flow velocity (MCAv) kinetics associated with two exercise intensities: low and moderate. We hypothesized that increasing exercise intensity would increase the MCAv amplitude response (Amp) and that age and estimated fitness (V̇O2max) would be related to Amp. Baseline (BL) values were collected for 90-seconds followed by a 6-minute exercise bout. Heart rate, end-tidal CO2, mean arterial pressure and MCAv were recorded throughout. MCAv kinetics were described by Amp, time delay (TD) and time constant (τ). Sixty-four adults completed the study. Amp was greater during moderate compared to low exercise intensity (p < 0.001) while no difference was observed in either TD (p = 0.65) or τ (p = 0.47). Amp was negatively associated with age (p < 0.01) and positively correlated with estimated V̇O2max (p < 0.01). Although Amp declines with age, maintaining higher V̇O2max may benefit the cerebrovascular response to exercise.

Influence of exercise intensity during hemodialysis on solute removal

Influence of exercise intensity during hemodialysis on solute removal

Examining the Influence of Exercise Intensity and Hydration on Gastrointestinal Temperature in Collegiate Football Players.

DeMartini-Nolan, JK, Martschinske, JL, Casa, DJ, Lopez, RM, Stearns, RL, Ganio, MS, and Coris, E. Examining the influence of exercise intensity and hydration on gastrointestinal temperature in collegiate football players. J Strength Cond Res 32(10): 2888-2896, 2018-Debate exists regarding the influence of intensity and hydration on body temperature during American football. The purpose of this study was to observe body core temperature responses with changes in intensity and hydration. Twenty-nine male football players (age = 21 ± 1 year, height = 187 ± 9 cm, mass = 110.1 ± 23.5 kg, body mass index [BMI] = 31.3 ± 5.0, and body surface area [BSA] = 2.34 ± 0.27 m) participated in 8 days of practice in a warm environment (wet bulb globe temperature: 29.6 ± 1.6° C). Participants were identified as starters (S; n = 12) or nonstarters (n = 17) and linemen (L; n = 14) or nonlinemen (NL; n = 15). Variables of interest included core body temperature (T), hydration status, and physical performance characteristics as measured by a global positioning system. Intensity measures of average heart rate (138 ± 9 bpm), low-velocity movement (4.2 ± 1.7%), high-velocity movement (0.6 ± 0.6%), and average velocity (0.36 ± 0.10 m·s) accounted for 42% of the variability observed in T (38.32 ± 0.34° C, r = 0.65, p = 0.01). Hydration measures (percent body mass loss = -1.56 ± 0.80%, urine specific gravity [Usg] = 1.025 ± 0.006, and urine color [Ucol] = 6 ± 1) did not add to the prediction of T (p = 0.83). Metrics of exercise intensity accounted for 39% of the variability observed in maximum T (38.83 ± 0.42° C, r = 0.62, p = 0.02). Hydration measures did not add to this prediction (p = 0.40). Low-velocity movement, high-velocity movement, average velocity, BMI, and BSA were significantly different (p = 0.002, p < 0.001, p = 0.02, p < 0.001, p < 0.001, respectively) between L vs. NL. Heart rate and T were not different between L and NL (p > 0.05). Exercise intensity primarily accounted for the rise in core body temperature. Although L spent less time at higher velocities, T was similar to NL, suggesting that differences in BMI and BSA added to thermoregulatory strain.

Acute HIIE elicits similar changes in human skeletal muscle mitochondrial H2O2 release, respiration, and cell signaling as endurance exercise even with less work.

It remains unclear whether high-intensity interval exercise (HIIE) elicits distinct molecular responses to traditional endurance exercise relative to the total work performed. We aimed to investigate the influence of exercise intensity on acute perturbations to skeletal muscle mitochondrial function (respiration and reactive oxygen species) and metabolic and redox signaling responses. In a randomized, repeated measures crossover design, eight recreationally active individuals (24 ± 5 yr; V̇o2peak: 48 ± 11 ml·kg-1·min-1) undertook continuous moderate-intensity [CMIE: 30 min, 50% peak power output (PPO)], high-intensity interval (HIIE: 5 × 4 min, 75% PPO, work matched to CMIE), and low-volume sprint interval (SIE: 4 × 30 s) exercise, ≥7 days apart. Each session included muscle biopsies at baseline, immediately, and 3 h postexercise for high-resolution mitochondrial respirometry ( Jo2) and H2O2 emission ( Jh2o2) and gene and protein expression analysis. Immediately postexercise and irrespective of protocol, Jo2 increased during complex I + II leak/state 4 respiration but Jh2o2 decreased ( P < 0.05). AMP-activated protein kinase and acetyl co-A carboxylase phosphorylation increased ~1.5 and 2.5-fold respectively, while thioredoxin-reductase-1 protein abundance was ~35% lower after CMIE vs. SIE ( P < 0.05). At 3 h postexercise, regardless of protocol, Jo2 was lower during both ADP-stimulated state 3 OXPHOS and uncoupled respiration ( P < 0.05) but Jh2o2 trended higher ( P < 0.08) and PPARGC1A mRNA increased ~13-fold, and peroxiredoxin-1 protein decreased ~35%. In conclusion, intermittent exercise performed at high intensities has similar dynamic effects on muscle mitochondrial function compared with endurance exercise, irrespective of whether total workload is matched. This suggests exercise prescription can accommodate individual preferences while generating comparable molecular signals known to promote beneficial metabolic adaptations.

The long and winding road: Effects of exercise intensity and type upon sustained attention

Aerobic exercise enhances the ability to sustain attention (peaking at moderate intensities) by stimulating noradrenergic activity, which affects the fronto-parietal attention network. Prior exercise studies examining attention have focused on the influence of exercise intensity, yet few studies have examined the influence of the type of exercise protocol administered. Here, we propose that sustained attention is greater during (a) moderate compared to low intensity exercise, and (b) moderate intensity exercise administered at a varied-load compared to a constant-load but the same overall intensity. To test this hypothesis, we recorded attentional focus in twelve male cyclists during a sustained attention to response task (SART) in four conditions; at rest, and during exercise at a low constant-, moderate constant- and moderate varied-load intensity. The change in α-amylase (indicative of the noradrenergic response) from saliva samples and activation of the right prefrontal and parietal cortices using near-infrared spectroscopy were recorded. The findings revealed that moderate intensity exercise at a constant-load leads to faster responses and less accuracy in the SART than rest and low intensity exercise. Moderate intensity exercise at a variable-load leads to even faster responses but with no loss of accuracy in the SART. This pattern of results is explained by a larger increase in salivary α-amylase during moderate (constant and varied) intensity cycling and higher activation in the dorso-lateral prefrontal cortex during the varied, but not the constant-load condition. In conclusion, we show that, in addition to exercise intensity, the type of exercise also has important implications upon attentional focus. While moderate intensity exercise generally enhances attentional focus, monotonous exercise at a constant-load may mask such benefits.

Non-linear dynamics of heart rate variability during incremental cycling exercise

ABSTRACTWithin the last years complex models of cardiovascular regulation and exercise fatigue have implemented heart rate variability (HRV) as a measure of autonomic nervous system. Using detrended fluctuation analysis (DFA) to assess heart rate correlation properties, the present study examines the influence of exercise intensity on total variability and complexity in non-linear dynamics of HRV. Sixteen cyclists performed a graded exercise test on a bicycle ergometer. HRV time domain measures and fractal correlation properties were analyzed using short-term scaling exponent alpha1 of DFA. Amplitude and complexity of HRV parameters decreased significantly. DFA-alpha1 increased from rest to low exercise intensity and showed an almost linear decrease from higher intensities until exhaustion. These findings support a qualitative change in self-organized heart rate regulation from a complex autonomic control at rest and low intensities towards a breakdown of the interaction in control mechanisms with non-autonomic heart rate control dominating at high intensities.

Moderate- and High-Intensity Exercise Training Improve “Free-Living” Glycemic Control Independently of Weight Loss

The independent effects of exercise training (without weight loss) on glycemic control are controversial, and the influence of exercise intensity is not well understood. The aim of this study was to determine the effect of 12 weeks (4 sessions/week) of high-intensity interval training (HIIT) or moderate-intensity continuous training (MICT) without weight loss, on “free-living” 24h glycemic control using continuous glucose monitoring (CGM). Eighteen obese adults (33±3 kg·m-2) performed HIIT, involving 10 x 1 min intervals at ∼90% HRmax interspersed with 1 min recovery (n=8), or MICT, involving 45 min at ∼70% HRmax (n=10). CGM was performed under standardized dietary control for 48h before and after training. After training, subjects exercised the day before, but not on Day 1 of CGM measurement. On Day 2 of post-training CGM data collection, participants performed their regular exercise session (HIIT or MICT) before breakfast. This approach allowed us to assess the effects of exercise training on glycemic control on a day with and without exercise. On Day 1 post-training, 24h glucose area under the curve (AUC) was modestly lower than pre-training in both groups (HIIT: 130±11 vs. 126±7 mM·h-1 · 24h; MICT: 138±7 vs. 133±7 mM·h-1 · 24h, p=0.02). There were no differences between HIIT and MICT (p=0.22). The improved 24h glycemic control after training was primarily due to modestly lower postprandial responses to breakfast (p=0.03) and dinner (p=0.002), with no differences between HIIT and MICT. On Day 2 post-training, which included a session of exercise, glycemic control remained better than pre-training in both groups (p=0.006), but interestingly was not improved further by the acute exercise session (p=0.82 for Day 1 vs. Day 2 post-training). In conclusion, exercise training improved 24h “free-living” glycemic responses in the absence of weight loss, and in general, the intensity of exercise training did not impact this improvement in glycemic control. Disclosure M.W. Schleh: None. B.J. Ryan: None. J.B. Gillen: None. A. Ludzki: None. J.F. Horowitz: None.

The Influence of Exercise Intensity on Training Load in Professional Cycling.

The Influence of Exercise Intensity on Training Load in Professional Cycling.

Exercise reduces depression and inflammation but intensity matters

BackgroundExercise may help to mitigate symptoms of depression by reducing inflammation; however, little is known about the influence of exercise intensity on depressed mood. MethodsIn the present study, sixty-one university students were assigned to six weeks of high-intensity interval training (HIT), moderate continuous training (MCT), or no exercise (CON) during their academic term. We measured changes in depression, anxiety and perceived stress along with pro-inflammatory cytokines tumor necrosis factor alpha (TNF-α), interleukin-6 (IL-6), interleukin-1 beta (IL-1β), and C-reactive protein (CRP). ResultsDepression increased for CON, demonstrating how quickly mental health can decline for students during their academic term. In contrast, MCT decreased depression and pro-inflammatory cytokine TNF-α levels. Although HIT decreased depressive symptoms, it also increased perceived stress, TNF-α and IL-6 relative to MCT. This may be due to the higher level of physical stress evoked by the more strenuous exercise protocol. ConclusionsTaken together, the results suggest that moderate-intensity exercise may be an optimal intensity of exercise for the promotion of mental health by decreasing TNF-α. This is critical for informing the use of exercise as medicine for mental health.

Benefits of Acute Aerobic Exercise on Neuroplastic Potential in Depression

Depression affects millions of Americans and is a leading contributor to disability and mortality in the United States. Evidence indicates that neuroplasticity is impaired in those with depression and successful treatment for depression appears to reestablish neuroplastic potential. Aerobic exercise (AE) has well-established antidepressant effects and has been shown to modulate neuroplasticity in non-depressed subjects. To date, the acute influence of exercise intensity on indices of neuroplastic adaptation have yet to be described. PURPOSE: To examine the efficacy of acute AE as a neuro-modulatory intervention in non-depressed control subjects. METHODS: Thirteen non-depressed subjects (8 female; 34.5 ± 8.7 years old) completed three experimental sessions that included assessment of corticospinal excitability (CE), AE (15 minutes) and paired associative stimulation (PAS) to determine neuroplastic potential. CE was assessed via transcranial magnetic stimulation and surface electromyography of the abductor pollicis brevis muscle before and after exercise, and for one hour after PAS. AE was performed on a stationary cycle ergometer at low intensity (LO), 35% heart rate reserve (HRR); high intensity (HI), 70% HRR; or a non-exercise control condition (CON). The primary outcome was change in peak-to-peak motor evoked potential amplitude relative to baseline assessment. RESULTS: Mean post-exercise CE across all time points was increased 26.2% in the LO condition, and 2.9% in the CON condition while the HI condition reduced CE 6.3%. Immediately following exercise, the LO condition produced a rapid 27.1% increase in CE while the HI condition produced a rapid 16.3% decrease in CE. Both the LO and HI conditions demonstrated a homeostatic response immediately post-PAS with a 15.0% reduction and 27.8% increase in CE, respectively. CONCLUSION: Lower exercise intensity appears to have a greater influence on increasing CE. Interestingly, the rapid effects of exercise appeared to be reversed by PAS suggesting the presence of homeostatic metaplasticity during these conditions. Modulation of CE via exercise in depression has yet to be established but may underlie the anti-depressant effects of AE. Work examining the influence of AE on CE in depression is currently in progress.

The Influence of Exercise Intensity on Postexercise Baroreflex Sensitivity

Purpose: The purpose of this study was to investigate the influence of exercise intensity on postexercise supine and tilt baroreflex sensitivity (BRS). Method: Nine healthy, active men performed 2 conditions of interval cycling of 40% maximal work rate (WRmax) and 75% WRmax of matched work done and a control condition of no exercise in a counterbalanced order. BRS outcome measures were determined at preexercise and postexercise up to +24 hr in supine and tilt positions. R-R interval and blood pressure data were collected over consecutive 10-min periods and were analyzed by Fast Fourier transformation analysis. Results: A fully repeated analysis of variance revealed a significant interaction (p < .05) between time and condition in supine for BRSαLF, F(3, 134) = 5.19, p < .05, ES = .39, and BRSTFTG, F(3, 134) = 5.65, p < .05, ES = .41, and in tilt for BRSUpUp, F(3, 134) = 3.54, p < .05, ES = .31, BRSDownDown, F(3, 134) = 5.94, p < .05, ES = .43, BRSαLF, F(4, 134) = 6.23, p < .05, ES = .44, and BRSTFTG, F(4, 134) = 9.22, p < .05, ES = .54. There were significant differences (p < .05) between condition comparisons at +15 min and between control and 75% WRmax and between the 40% WRmax and 75% WRmax conditions at +60 min. At +15 min, BRS was lower in the 75% WRmax condition compared with the 40% WRmax condition and the control condition, and it was lower in the 40% WRmax condition than in the control condition. Conclusion: The findings demonstrate an intensity-dependent relationship in the BRS response following exercise.

What influences acceptability andengagement with a high intensity exercise programme for people with stroke? Aqualitative descriptive study.

Intensity refers to the amount of effort or rate of work undertaken during exercise. People receiving rehabilitation after stroke frequently do not reach the moderate to high intensity exercise recommended to maximise gains. To explore the factors that influence the acceptability of, and engagement with, a high intensity group-based exercise programme for people with stroke. This qualitative descriptive study included 14 people with stroke who had completed a 12-week, high intensity group-based exercise rehabilitation programme. Semi-structured interviews were used to explore the acceptability of high intensity exercise and the barriers and facilitators to engagement. Interviews were recorded, transcribed and analysed using qualitative content analysis. The participants found high intensity exercise rehabilitation acceptable despite describing the exercise intensity as hard and reporting post-exercise fatigue. Participants accepted the fatigue as a normal response to exercise, and it did not appear to negatively influence engagement. The ease with which an individual engaged in high intensity exercise rehabilitation appeared to be mediated by inter-related factors, including: seeing progress, sourcing motivation, working hard, the people involved and the fit with the person and their life. Participants directly related the intensity of their effort to the gains that they made. In this study, people with stroke viewed training at higher intensities as a facilitator, not a barrier, to engagement in exercise rehabilitation. The findings may challenge assumptions about the influence of exercise intensity on engagement.

Short-term interval training at both lower and higher intensities in the severe exercise domain result in improvements in V̇O₂ on-kinetics.

Although high-intensity interval training (HIT) seems to promote greater improvements in aerobic parameters than continuous training, the influence of exercise intensity on [Formula: see text] on-kinetics remains under investigation. After an incremental test, twenty-one recreationally trained cyclists performed several time-to-exhaustion tests to determine critical power (CP), and the highest intensity (I HIGH), and the lowest exercise duration (T LOW) at which [Formula: see text] is attained during constant exercise. Subjects also completed a series of step transitions to moderate- and heavy-intensity work rates to determine pulmonary [Formula: see text] on-kinetics. Surface electromyography (EMG) of vastus lateralis muscle and blood lactate accumulation (∆BLC) was measured during heavy exercise. Subjects were assigned to one of two 4-week work-matched training groups: the lower [105% CP: n=11; 4×5min at 105% CP (218±39W), 1min recovery] or the upper [I HIGH: n=10; 8×100% I HIGH (355±60W), 1:2 work:recovery ratio] intensity of the severe exercise domain. The two interventions were similarly effective in reducing the phase II [Formula: see text] time constant during moderate (105% CP: 34±13 to 25±8s; I HIGH: 31±9 to 23±6s) and heavy exercise (105% CP: 25±7 to 18±5s; I HIGH: 27±7 to 16±5s) and in reducing the amplitude of [Formula: see text] slow component, EMG amplitude, and ∆BLC during heavy exercise. In conclusion, the short-term adjustments in response to step transitions to moderate and heavy exercise were independent of training intensity within the severe exercise domain.

Effect of Different Exercise Intensities on the Myotendinous Junction Plasticity.

Myotendinous junctions (MTJs) are anatomical regions specialized in transmission of contractile strength from muscle to tendon and, for this reason, a common site where acute injuries occur during sport activities. In this work we investigated the influence of exercise intensity on MTJ plasticity, as well as on the expression of insulin-like growth factor 1 (IGF-1) and transforming growth factor beta (TGF-β) and their receptors in muscle and tendon. Three groups of rats were analyzed: control (CTRL), slow-runner (RUN-S) and fast-runner (RUN-F) trained using a treadmill. Ultrastructural and morphometric analyses of distal MTJs from extensor digitorum longus muscles have been performed. Contractile strength and hypertrophy were investigated by using in vivo tension recordings and muscle cross-sectional area (CSA) analysis, respectively. mRNA levels of PGC-1α, vinculin, IGF-1Ea and TGF-β have been quantified in muscle belly, while IGF-1Ea, TGF-β and their receptors in tendon. Morphometry revealed an increased MTJ complexity and interaction surface between tissues in trained rats according to training intensity. CSA analysis excluded hypertrophy among groups, while muscle strength was found significantly enhanced in exercised rats in comparison to controls. In muscle tissue, we highlighted an increased mRNA expression of PGC-1α and vinculin in both trained conditions and of TGF-β in RUN-F. In tendon, we mainly noted an enhancement of TGF-β mRNA expression only in RUN-F group and a raise of Betaglycan tendon receptor mRNA levels proportional to exercise intensity. In conclusion, MTJ plasticity appears to be related to exercise intensity and molecular analysis suggests a major role played by TGF-β.

Influence of Exercise Intensity for Improving Depressed Mood in Depression: A Dose-Response Study

IntroductionExercise effectively improves mood in major depressive disorder (MDD), but the optimal exercise stimulus to improve depressed mood is unknown. PurposeTo determine the dose–response relationship of acute exercise intensity with depressed mood responses to exercise in MDD. We hypothesized that the acute response to exercise would differ between light, moderate, and hard intensity exercise with higher intensities yielding more beneficial responses. MethodsOnce weekly, 24 women (age: 38.6±14.0) diagnosed with MDD underwent a 30-minute session at one of three steady-state exercise intensities (light, moderate, hard; rating of perceived exertion 11, 13 or 15) or quiet rest on a stationary bicycle. Depressed mood was evaluated with the Profile of Mood States before, 10 and 30 minutes post-exercise. ResultsExercise reduced depressed mood 10 and 30 minutes following exercise, but this effect was not influenced by exercise intensity. Participants not currently taking antidepressants (n=10) had higher baseline depression scores, but did not demonstrate a different antidepressant response to exercise compared to those taking antidepressants. ConclusionsTo acutely improve depressed mood, exercise of any intensity significantly improved feelings of depression with no differential effect following light, moderate, or hard exercise. Pharmacological antidepressant usage did not limit the mood-enhancing effect of acute exercise. Acute exercise should be used as a symptom management tool to improve mood in depression, with even light exercise an effective recommendation. These results need to be replicated and extended to other components of exercise prescription (e.g., duration, frequency, mode) to optimize exercise guidelines for improving depression.

Influence of exercise intensity and duration on functional and biochemical perturbations in the human heart.

Strenuous endurance exercise induces transient functional and biochemical cardiac perturbations that persist for 24-48h. The magnitude and time-course of exercise-induced reductions in ventricular function and increases in cardiac injury markers are influenced by the intensity and duration of exercise. In a human experimental model, exercise-induced reductions in ventricular strain and increases in cardiac troponin are greater, and persist for longer, when exercise is performed within the heavy- compared to moderate-intensity exercise domain, despite matching for total mechanical work. The results of the present study help us better understand the dose-response relationship between endurance exercise and acute cardiac stress/injury, a finding that has implications for the prescription of day-to-day endurance exercise regimes. Strenuous endurance exercise induces transient cardiac perturbations with ambiguous health outcomes. The present study investigated the magnitude and time-course of exercise-induced functional and biochemical cardiac perturbations by manipulating the exercise intensity-duration matrix. Echocardiograph-derived left (LV) and right (RV) ventricular global longitudinal strain (GLS), and serum high-sensitivity cardiac troponin (hs-cTnI) concentration, were examined in 10 males (age: 27±4years; V̇O2, peak : 4.0±0.8lmin(-1) ) before, throughout (50%, 75% and 100%), and during recovery (1, 3, 6 and 24h) from two exercise trials. The two exercise trials consisted of 90 and 120min of heavy- and moderate-intensity cycling, respectively, with total mechanical work matched. LVGLS decreased (P<0.01) during the 90min trial only, with reductions peaking at 1h post (pre: -19.9±0.6%; 1h post: -18.5±0.7%) and persisting for >24h into recovery. RVGLS decreased (P<0.05) during both exercise trials with reductions in the 90min trial peaking at 1h post (pre: -27.5±0.7%; 1h post: -25.1±0.8%) and persisting for >24h into recovery. Serum hs-cTnI increased (P<0.01) during both exercise trials, with concentrations peaking at 3h post but only exceeding cardio-healthy reference limits (14ngl(-1) ) in the 90min trial (pre: 4.2±2.4ngl(-1) ; 3h post: 25.1±7.9ngl(-1) ). Exercise-induced reductions in ventricular strain and increases in cardiac injury markers persist for 24h following exercise that is typical of day-to-day endurance exercise training; however, the magnitude and time-course of this response can be altered by manipulating the intensity-duration matrix.

Physical activity intensity and type 2 diabetes risk in overweight youth: a randomized trial

The chronic effects of high-intensity endurance training on metabolic health outcomes in overweight adolescents remains poorly understood. To test the hypothesis that high-intensity endurance training (ET) is superior to moderate-intensity ET for improving risk factors for type 2 diabetes in overweight adolescents. In this randomized trial, 106 overweight and obese adolescents (15.2 years; 76% female; 62% Caucasian) were randomly assigned to high-intensity ET (70-85% of heart rate reserve, n=38), moderate-intensity ET (40-55% heart rate reserve; n=32) or control for 6 months (n=36). The primary and secondary outcome measures were insulin sensitivity assessed using a frequently sampled intravenous glucose tolerance test and hepatic triglyceride content with magnetic resonance spectroscopy. Exploratory outcomes were cardiorespiratory fitness, physical activity and MRI and dual x-ray absorptiometry-derived measures of adiposity. The study had 96% retention and attendance was 61±21% and 55±24% in the high- and moderate-intensity ET arms. Intention-to-treat analyses revealed that, at follow-up, insulin sensitivity was not different between high-intensity (-1.0 mU kg(-1) min(-1); 95% confidence interval (CI): -1.6, +1.4 mU kg(-1) min(-1)) and moderate-intensity (+0.26 mU kg(-1) min(-1); 95% CI: -1.3, +1.8 mU kg(-1) min(-1)) ET arms compared with controls (interaction, P=0.97). Similarly, hepatic triglyceride at follow-up was not different in high-intensity (-1.7% fat/water (F/W); 95% CI: -7.0, +3.6% F/W) and moderate-intensity (-0.40% FW; 95% CI: -6.0, +5.3% F/W) ET compared with controls. Both high intensity (+4.4 ml per kg-FFM (fat-free mass) per minute; 95% CI: 1.7, 7.1 ml kg-FFM(-1) min(-1)) and moderate intensity (+4.4 ml kg-FFM(-1) min(-1); 95% CI: 1.6, 7.3 ml kg-FFM(-1) min(-1)) increased cardiorespiratory fitness, relative to controls (interaction P<0.001). ET improves cardiorespiratory fitness among obese adolescents; however, owing to lack of compliance, the influence of exercise intensity on insulin sensitivity and hepatic triglycerides remains unclear.