Increasing Exercise Intensity Research Articles

Monitoring Energy Expenditure Using a Multi-Sensor Device-Applications and Limitations of the SenseWear Armband in Athletic Populations.

In order to monitor their energy requirements, athletes may desire to assess energy expenditure (EE) during training and competition. Recent technological advances and increased customer interest have created a market for wearable devices that measure physiological variables and bodily movement over prolonged time periods and convert this information into EE data. This mini-review provides an overview of the applicability of the SenseWear armband (SWA), which combines accelerometry with measurements of heat production and skin conductivity, to measure total daily energy expenditure (TDEE) and its components such as exercise energy expenditure (ExEE) in athletic populations. While the SWA has been shown to provide valid estimates of EE in the general population, validation studies in athletic populations indicate a tendency toward underestimation of ExEE particularly during high-intensity exercise (>10 METs) with an increasing underestimation as exercise intensity increases. Although limited information is available on the accuracy of the SWA during resistance exercise, high-intensity interval exercise, or mixed exercise forms, there seems to be a similar trend of underestimating high levels of ExEE. The SWA, however, is capable of detecting movement patterns and metabolic measurements even at high exercise intensities, suggesting that underestimation may result from limitations in the proprietary algorithms. In addition, the SWA has been used in the assessment of sleep quantity and quality as well as non-exercise activity thermogenesis. Overall, the SWA provides viable information and remains to be used in various clinical and athletic settings, despite the termination of its commercial sale.

The effect of exercise intensity on joint power and dynamics in ergometer double-poling performed by cross-country skiers

The purpose of this study was to examine the effect of increasing exercise intensity on the role of joint powers in ergometer double poling (DP), while taking specific dynamic constraints into account. One main question was whether lower-body power contribution increased or decreased with increasing intensity. Nine male Norwegian national-level cross-country skiers performed ergometer DP at low, moderate, high and maximal intensity. Kinematics, and ground (GRF) and poling (Fpoling) reaction forces were recorded and used in link segment modeling to obtain joint and whole-body dynamics. Joint powers were averaged over the cycle, the poling (PP) and recovery (RP) phases. The contribution of these average powers was their ratios to cycle average poling power. At all intensities, the shoulder (in PP) and hip (mostly in RP) generated most power. Averaged over the cycle, lower-body contribution (sum of ankle, knee and hip power) increased from ∼37% at low to ∼54% at maximal intensity (p < .001), originating mostly from increased hip contribution within PP, not RP. The generation of larger Fpoling at higher intensities demanded a reversal of hip and knee moment. This was necessary to appropriately direct the GRF vector as required to balance the moment about center of mass generated by Fpoling (control of angular momentum). This was reflected in that the hip changed from mostly absorbing to generating power in PP at lower and higher intensities, respectively. Our data indicate that power-transfer rather than stretch-shortening mechanisms may occur in/between the shoulder and elbow during PP. For the lower extremities, stretch-shortening mechanisms may occur in hip, knee and trunk extensors, ensuring energy conservation or force potentiation during the countermovement-like transition from body lowering to heightening. In DP locomotion, increasing intensity and power output is achieved by increased lower-body contribution. This is, at least in ergometer DP, partly due to changes in joint dynamics in how to handle dynamic constraints at different intensities.

Does skeletal muscle carnitine availability influence fuel selection during exercise?

Fat and carbohydrate are the major fuel sources utilised for oxidative, mitochondrial ATP resynthesis during human skeletal muscle contraction. The relative contribution of these two substrates to ATP resynthesis and total energy expenditure during exercise can vary substantially, and is predominantly determined by fuel availability and exercise intensity and duration. For example, the increased ATP demand that occurs with an increase in exercise intensity is met by increases in both fat and carbohydrate oxidation up to an intensity of approximately 60-70 % of maximal oxygen consumption. When exercise intensity increases beyond this workload, skeletal muscle carbohydrate utilisation is accelerated, which results in a reduction and inhibition of the relative and absolute contribution of fat oxidation to total energy expenditure. However, the precise mechanisms regulating muscle fuel selection and underpinning the decline in fat oxidation remain unclear. This brief review will primarily address the theory that a carbohydrate flux-mediated reduction in the availability of muscle carnitine to the mitochondrial enzyme carnitine palmitoyltransferase 1, a rate-limiting step in mitochondrial fat translocation, is a key mechanism for the decline in fat oxidation during high-intensity exercise. This is discussed in relation to recent work in this area investigating fuel metabolism at various exercise intensities and taking advantage of the discovery that skeletal muscle carnitine content can be nutritionally increased in vivo in human subjects.

Stair ascending–descending exercise accelerates the decrease in postprandial hyperglycemia more efficiently than bicycle exercise

ObjectiveStair climbing–descending exercise (ST-EX) is a convenient method to increase exercise intensity. We compared the acute effect of ST-EX on lowering postprandial hyperglycemia with that of constant bicycle exercise (BI-EX)...

Underwater Walking Intensity is Modified by a New and Untested Device that Increased the Lower Limb Surface of Movement

Background: This study aimed to compare exercise intensity through measuring oxygen consumption (VO2), heart rate (HR), and rating of perceived effort (RPE) during an underwater walking at a standardized gait velocity (step × min-1) when wearing swimsuit (SS) or aquatic pants (AP) that increased the drag force Methods: 20 young healthy participants (11 M, 9 F) were recruited; each participant was asked to perform two trials in a random order, one with SS, and the other with AP. Each trial consisted in a 20-minute walk on an underwater non-motorized treadmill at 60, 70, 80, and 90 step × min-1. Results: The total number of steps during the two trials and the walked distance was the same when wearing SS or AP at all rhythms. VO2, HR, and RPE were significantly higher with the use of AP at all gait velocities (P < 0.001). Conclusions: Owing to the larger drag force, AP can be considered as an effective device to increase exercise intensity since the cardiorespiratory response was greater when wearing AP rather than SS.

Absence of compensatory vasodilation with perfusion pressure challenge in exercise: evidence for and implications of the noncompensator phenotype

Compromising oxygen delivery (O2D) during exercise requires compensatory vasodilatory and/or pressor responses to protect O2D:demand matching. The purpose of the study was to determine whether compensatory vasodilation is absent in some healthy young individuals in the face of a sudden reduction in exercising forearm perfusion pressure and whether this affects the exercise pressor response. Twenty-one healthy young men (21.6 ± 2.0 yr) completed rhythmic forearm exercise at a work rate equivalent to 70% of their own maximal exercise vasodilation. During steady-state exercise, the exercising arm was rapidly adjusted from below to above heart level, resulting in a reduction in forearm perfusion pressure of -30.7 ± 0.9 mmHg. Forearm blood flow (ml/min; brachial artery Doppler and echo ultrasound), mean arterial blood pressure (mmHg; finger photoplethysmography), and exercising forearm venous effluent (antecubital vein catheter) measurements revealed distinct compensatory vasodilatory differences. Thirteen individuals responded with compensatory vasodilation (509 ± 128 vs. 632 ± 136 ml·min-1·100 mmHg-1; P < 0.001), while eight individuals did not (663 ± 165 vs. 667 ± 167 ml·min-1·100 mmHg-1; P = 0.6). Compensatory pressor responses between groups were not different (5.5 ± 5.5 and 9.7 ± 9.5 mmHg; P = 0.2). Forearm blood flow, O2D, and oxygen consumption were all protected in compensators (all P > 0.05) but not in noncompensators, who therefore suffered compromises to exercise performance (6 ± 14 vs. -36 ± 29 N; P = 0.004). Phenotypic differences were not explained by potassium or nitric oxide bioavailability. In conclusion, both compensator and noncompensator vasodilator phenotype responses to a sudden compromise to exercising muscle blood flow are evident. Interindividual differences in the mechanisms governing O2D:demand matching should be considered as factors influencing exercise tolerance. NEW & NOTEWORTHY In healthy young individuals, compromising submaximally exercising muscle perfusion appears to evoke compensatory vasodilation to defend oxygen delivery. Here we report the absence of compensatory vasodilation in 8 of 21 such individuals, despite their vasodilatory capacity and increases in perfusion with increasing exercise intensity being indistinguishable from compensators. The absence of compensation impaired exercise tolerance. These findings suggest that interindividual differences in oxygen delivery:demand matching efficacy affect exercise tolerance and depend on the nature of a delivery:demand matching challenge.

Consecutive ultra-short-term heart rate variability to track dynamic changes in autonomic nervous system during and after exercise

Objective: Quantitative measurement of the dynamic changes in autonomic nervous system (ANS) during and after exercise has great significance in clinical, sports training and other fields. A consecutive ultra-short-term (30 s, UST) heart rate variability (HRV) method was proposed to track the exercise-induced autonomic control of heart rate (HR). Approach: Twenty-three healthy young men participated in the study. The first four stages of the Modified Bruce Protocol (S0–S3) were performed. Six HRV indices, i.e. HF (power of high frequency ranged from 0.15 to 0.4 Hz), LF (power of low frequency ranged from 0.04 to 0.15 Hz), LF/HF, SD1 and SD2 of Poincaré plot, and SD2/SD1, over 30 s were calculated every 5 s over 3 min RR time series during, as well as after, exercise. Main results: The results showed that during exercise, SD1, SD2, HF and LF dropped down quickly and tended to stabilize. Particularly, SD1 and HF showed a slight upward trend in the lower three stages while the declining time of SD2 in S3 lasted longer than the other stages. SD2/SD1 increased rapidly first and then decreased slowly. The values of SD2/SD1 in S3 remained higher than those in the other stages. After exercise, SD1, SD2, HF and LF kept increasing first and then declined slowly or fluctuated with decaying amplitudes. SD2/SD1 increased initially, then decreased and fluctuated slightly. Significance: Compared with the indices in frequency domain, the Poincaré indices were more sensitive and accurate in UST measurement of ANS during exercise. The results demonstrated that the UST method could characterize the dynamic changing tendency of ANS during and after exercise and quantify the differences of changes in ANS induced by exercise with different intensities. In particular, the vagal branch functioned dominantly in controlling HR in S0 but the effect of the sympathetic branch on HR enhanced with the increase of exercise intensity. In addition, the transient changes of ANS related with the sudden onset of exercise could also be reflected, despite perhaps being limited by the computation window width to some extent. Thus, the consecutive UST Poincaré indices could provide a feasible and simple method to measure quantitatively the exercise-induced dynamic changes in ANS.

Systematic review: exercise‐induced gastrointestinal syndrome—implications for health and intestinal disease

"Exercise-induced gastrointestinal syndrome" refers to disturbances of gastrointestinal integrity and function that are common features of strenuous exercise. To systematically review the literature to establish the impact of acute exercise on markers of gastrointestinal integrity and function in healthy populations and those with chronic gastrointestinal conditions. Search literature using five databases (PubMed, EBSCO, Web of Science, SPORTSdiscus, and Ovid Medline) to review publications that focused on the impact of acute exercise on markers of gastrointestinal injury, permeability, endotoxaemia, motility and malabsorption in healthy populations and populations with gastrointestinal diseases/disorders. As exercise intensity and duration increases, there is considerable evidence for increases in indices of intestinal injury, permeability and endotoxaemia, together with impairment of gastric emptying, slowing of small intestinal transit and malabsorption. The addition of heat stress and running mode appears to exacerbate these markers of gastrointestinal disturbance. Exercise stress of ≥2hours at 60% VO2max appears to be the threshold whereby significant gastrointestinal perturbations manifest, irrespective of fitness status. Gastrointestinal symptoms, referable to upper- and lower-gastrointestinal tract, are common and a limiting factor in prolonged strenuous exercise. While there is evidence for health benefits of moderate exercise in patients with inflammatory bowel disease or functional gastrointestinal disorders, the safety of more strenuous exercise has not been established. Strenuous exercise has a major reversible impact on gastrointestinal integrity and function of healthy populations. The safety and health implications of prolonged strenuous exercise in patients with chronic gastrointestinal diseases/disorders, while hypothetically worrying, has not been elucidated and requires further investigation.

The Effects of Training and Detraining on Metabolic Hormones in Rats

PURPOSE: We conclude that exercise training-induced effects in metabolic hormones continue for a prolonged period of detraining, but they are not associated with exercise intensity or detraining-induced increases in body weight.The purpose of this study was to exam ine the effect of diverse exercise training intensities, training periods and detraining periods on metabolic hormones. METHODS: Eighty-four male Sprague-Dawley rats (aged 6 weeks, 173-200 g) were divided into 12 different groups by training, detraining, and control conditions. Exercise training consisted of low-intensity training and high-intensity training programs performed in the laboratory on a motor-driven rodent treadmill once per day, 5 days per week for 12 weeks. RESULTS: Body weight significantly increased in all the conditions after the 12-week training period, with significant interaction among the conditions (p<.01). Body weights in the low-intensity trained detrained (LTD) and high-intensity trained detrained (HTD) groups were similar to those in the control groups after 6 weeks and 12 weeks of detraining (p<.05). There were significant differences in the hormones (leptin, insulin, and cortisol) between the control and trained detrained condition after 12 weeks of training, and 6 weeks and 12 weeks of detraining (p<.01), with no significant interaction between the trained detrained conditions (p<.05).

Blood Flow Regulation and Oxygen Uptake during High Intensity Forearm Exercise

The vascular strain is very high during heavy handgrip exercise, but the intensity and kinetics to reach peak blood flow, and peak oxygen uptake, are uncertain. PURPOSE: We included 9 young (25±2yr) healthy males to evaluate blood flow and oxygen uptake responses during continuous dynamic handgrip exercise with increasing intensity. METHODS: Blood flow was measured using Doppler-ultrasound and venous blood was drawn from a deep forearm vein to determine arteriovenous oxygen difference (a-vO2diff) during 6-minutes bouts of 60, 80 and 100% of maximal work rate (WRmax), respectively. RESULTS: Blood flow and oxygen uptake increased (p<0.05) from 60%WRmax (557±177(SD) mL[BULLET OPERATOR]min-1; 56.0±21.6 mL[BULLET OPERATOR]min-1) to 80%WRmax (679±190 mL[BULLET OPERATOR]min-1; 70.6±24.8 mL[BULLET OPERATOR]min-1), but no change was seen from 80%WRmax to 100%WRmax. Blood velocity (49.5±11.5 cm[BULLET OPERATOR]sec-1 to 58.1±11.6 cm[BULLET OPERATOR]sec-1) and brachial diameter (0.49±0.05cm to 0.50±0.06 cm) showed concomitant increases (p<0.05) with blood flow from 60% to 80%WRmax, while no differences were observed in a-vO2diff. Shear rate also increased (p<0.05) from 60% (822±196 s-1) to 80% (951±234 s-1) of WRmax. The mean response time (MRT) was slower (p<0.05) for blood flow (60%WRmax:50±22s; 80%WRmax:51±20s; 100%WRmax:51±23s) than a-vO2diff (60%WRmax:29±9s; 80%WRmax:28±5s; 100%WRmax:20±5s), but not different from oxygen uptake (60%WRmax:44±25s; 80%WRmax:43±14s; 100%WRmax:41±32s). No differences were observed in MRT for blood flow or oxygen uptake with increased exercise intensity. CONCLUSION: When approaching maximal intensity, oxygen uptake appeared to reach a critical level at ~80% of WRmax and be regulated by blood flow. This implies that high, but not maximal, exercise intensity may be an optimal stimulus for shear stress-induced small muscle mass training adaptations.

Changes In Cortical Neural Arousal As A Result Of Increasing Exercise Intensity

Changes In Cortical Neural Arousal As A Result Of Increasing Exercise Intensity

Competitive and cooperative arm rehabilitation games played by a patient and unimpaired person: effects on motivation and exercise intensity

BackgroundPeople with chronic arm impairment should exercise intensely to regain their abilities, but frequently lack motivation, leading to poor rehabilitation outcome. One promising way to increase motivation is through interpersonal rehabilitation games, which allow patients to compete or cooperate together with other people. However, such games have mainly been evaluated with unimpaired subjects, and little is known about how they affect motivation and exercise intensity in people with chronic arm impairment.MethodsWe designed four different arm rehabilitation games that are played by a person with arm impairment and their unimpaired friend, relative or occupational therapist. One is a competitive game (both people compete against each other), two are cooperative games (both people work together against the computer) and one is a single-player game (played only by the impaired person against the computer). The games were played by 29 participants with chronic arm impairment, of which 19 were accompanied by their friend or relative and 10 were accompanied by their occupational therapist. Each participant played all four games within a single session. Participants’ subjective experience was quantified using the Intrinsic Motivation Inventory questionnaire after each game, as well as a final questionnaire about game preferences. Their exercise intensity was quantified using wearable inertial sensors that measured hand velocity in each game.ResultsOf the 29 impaired participants, 12 chose the competitive game as their favorite, 12 chose a cooperative game, and 5 preferred to exercise alone. Participants who chose the competitive game as their favorite showed increased motivation and exercise intensity in that game compared to other games. Participants who chose a cooperative game as their favorite also showed increased motivation in cooperative games, but not increased exercise intensity.ConclusionsSince both motivation and intensity are positively correlated with rehabilitation outcome, competitive games have high potential to lead to functional improvement and increased quality of life for patients compared to conventional rehabilitation exercises. Cooperative games do not increase exercise intensity, but could still increase motivation of patients who do not enjoy competition. However, such games need to be tested in longer, multisession studies to determine whether the observed increases in motivation and exercise intensity persist over a longer period of time and whether they positively affect rehabilitation outcome.Trial registrationThe study is not a clinical trial. While human subjects are involved, they participate in a single-session evaluation of a rehabilitation game rather than a full rehabilitation intervention, and no health outcomes are examined.

Effects of Different Exercise Strategies and Intensities on Memory Performance and Neurogenesis.

It is well established that physical exercise affects both hippocampal neurogenesis and memory functions. Until now, distinctive effects of controlled and voluntary training (VT) on behavior and neurogenesis as well as interactions between exercise intensity, neurogenesis and memory performance are still elusive. The present study tested the impact of moderate controlled and VT on memory formation and hippocampal neurogenesis and evaluated interactions between exercise performance, learning efficiency and proliferation of progenitor cells in the hippocampus. Our data show that both controlled and VT augmented spatial learning and promoted hippocampal neurogenesis. Regression analysis revealed a significant linear increase of the amount of new hippocampal neurons with increased exercise intensity. Regression analysis of exercise performance on retention memory performance revealed a quadratic, inverted u-shaped relationship between exercise performance and retention of spatial memory. No association was found between the amount of newborn neurons and memory performance. Our results demonstrate that controlled training (CT), if performed with an appropriate combination of speed and duration, improves memory performance and neurogenesis. Voluntary exercise elevates neurogenesis dose dependently to high levels. Best cognitive improvement was achieved with moderate exercise performance.

Exercise Guidelines to Promote Cardiometabolic Health in Spinal Cord Injured Humans: Time to Raise the Intensity?

Spinal cord injury (SCI) is a life-changing event that, as a result of paralysis, negatively influences habitual levels of physical activity and hence cardiometabolic health. Performing regular structured exercise therefore appears extremely important in persons with SCI. However, exercise options are mainly limited to the upper body, which involves a smaller activated muscle mass compared with the mainly leg-based activities commonly performed by nondisabled individuals. Current exercise guidelines for SCI focus predominantly on relative short durations of moderate-intensity aerobic upper-body exercise, yet contemporary evidence suggests this is not sufficient to induce meaningful improvements in risk factors for the prevention of cardiometabolic disease in this population. As such, these guidelines and their physiological basis require reappraisal. In this special communication, we propose that high-intensity interval training (HIIT) may be a viable alternative exercise strategy to promote vigorous-intensity exercise and prevent cardiometabolic disease in persons with SCI. Supplementing the limited data from SCI cohorts with consistent findings from studies in nondisabled populations, we present strong evidence to suggest that HIIT is superior to moderate-intensity aerobic exercise for improving cardiorespiratory fitness, insulin sensitivity, and vascular function. The potential application and safety of HIIT in this population is also discussed. We conclude that increasing exercise intensity could offer a simple, readily available, time-efficient solution to improve cardiometabolic health in persons with SCI. We call for high-quality randomized controlled trials to examine the efficacy and safety of HIIT in this population.

Assessing kinematics and kinetics of functional electrical stimulation rowing

Hybrid functional electrical stimulation (FES) rowing has positive effects on cardiovascular fitness, producing significantly greater aerobic power than either upper body or FES exercise alone. However, there is minimal information on the kinematics, kinetics, and mechanical efficiency of FES-rowing in the spinal cord injured (SCI) population. This study examined the biomechanics of FES-rowing to determine how motions, forces, and aerobic demand change with increasing intensity. Six individuals with SCI and six able-bodied subjects performed a progressive aerobic capacity rowing test. Differences in kinematics (motion profiles), kinetics (forces produced by the feet and arms), external mechanical work, and mechanical efficiency (work produced/volume of oxygen consumed) were compared in able-bodied rowing vs. SCI FES-rowing at three comparable subpeak workloads. With increasing exercise intensity (measured as wattage), able-bodied rowing increased stroke rate by decreasing recovery time, while FES-rowing maintained a constant stroke rate, with no change in drive or recovery times. While able-bodied rowers increased leg and arm forces with increasing intensity, FES-rowers used only their arms to achieve a higher intensity with a constant and relatively low contribution of the legs. Oxygen consumption increased in both groups, but more so in able-bodied rowers, resulting in able-bodied rowers having twice the mechanical efficiency of FES-rowers. Our results suggest that despite its ability to allow for whole body exercise, the total force output achievable with FES-rowing results in only modest loading of the legs that affects overall rowing performance and that may limit forces applied to bone.

Blood flow regulation and oxygen uptake during high-intensity forearm exercise.

The vascular strain is very high during heavy handgrip exercise, but the intensity and kinetics to reach peak blood flow, and peak oxygen uptake, are uncertain. We included 9 young (25 ± 2 yr) healthy males to evaluate blood flow and oxygen uptake responses during continuous dynamic handgrip exercise with increasing intensity. Blood flow was measured using Doppler-ultrasound, and venous blood was drawn from a deep forearm vein to determine arteriovenous oxygen difference (a-vO2diff) during 6-min bouts of 60, 80, and 100% of maximal work rate (WRmax), respectively. Blood flow and oxygen uptake increased (P < 0.05) from 60%WRmax [557 ± 177(SD) ml/min; 56.0 ± 21.6 ml/min] to 80%WRmax (679 ± 190 ml/min; 70.6 ± 24.8 ml/min), but no change was seen from 80%WRmax to 100%WRmax Blood velocity (49.5 ± 11.5 to 58.1 ± 11.6 cm/s) and brachial diameter (0.49 ± 0.05 to 0.50 ± 0.06 cm) showed concomitant increases (P < 0.05) with blood flow from 60% to 80%WRmax, whereas no differences were observed in a-vO2diff Shear rate also increased (P < 0.05) from 60% (822 ± 196 s-1) to 80% (951 ± 234 s-1) of WRmax The mean response time (MRT) was slower (P < 0.05) for blood flow (60%WRmax 50 ± 22 s; 80%WRmax 51 ± 20 s; 100%WRmax 51 ± 23 s) than a-vO2diff (60%WRmax 29 ± 9 s; 80%WRmax 29 ± 5 s; 100%WRmax 20 ± 5 s), but not different from oxygen uptake (60%WRmax 44 ± 25 s; 80%WRmax 43 ± 14 s; 100%WRmax 41 ± 32 s). No differences were observed in MRT for blood flow or oxygen uptake with increased exercise intensity. In conclusion, when approaching maximal intensity, oxygen uptake appeared to reach a critical level at ~80% of WRmax and be regulated by blood flow. This implies that high, but not maximal, exercise intensity may be an optimal stimulus for shear stress-induced small muscle mass training adaptations.NEW & NOTEWORTHY This study evaluated blood flow regulation and oxygen uptake during small muscle mass forearm exercise with high to maximal intensity. Despite utilizing only a fraction of cardiac output, blood flow reached a plateau at 80% of maximal work rate and regulated peak oxygen uptake. Furthermore, the results revealed that muscle contractions dictated bulk oxygen delivery and yielded three times higher peak blood flow in the relaxation phase compared with mean values.

Turns in Jogging Increase Energy Expenditure: Proposed Home Exercise for Sedentary People

Introduction: We need to reevaluate exercise habits and exercise intensity in order to improve our health. We examined a new exercise pattern termed “slow jogging with turns”, which incorporates turns as an extra load in addition to jogging. This study aim to estimate Mets to create a home-exercise protocol. Subjects and Methods: Ten participants performed slow jogging with turns and treadmill jogging in random order. Slow jogging with turns was performed in six stages at distances of 2.0 to 5.0 m, and treadmill jogging was performed at the same velocities as that for slow jogging with turns. We measured oxygen consumption, heart rate, and rating of perceived exertion. Results: Mets data of slow jogging with turns and treadmill jogging were analyzed using repeated measurement ANOVA with p-value <0.01. Mets during slow jogging with turns were 6.5 ± 0.7 to 10.8 ± 0.9. Mets during slow jogging with turns were significantly higher than those during treadmill jogging at equivalent speeds (p<0.0001). Distance of slow jogging with turns corresponding to Mets was calculated as follows: SJT distance (m) = (target Mets-3.06)/1.5 Conclusion: Slow jogging with turns can increase exercise intensity effectively, and exercise intensity can be adjusted individually by changing jogging distance. This form of exercise can be performed, anytime, anywhere and when done at greater than moderate intensity, helps increase energy expenditure in daily life.

Neuromuscular, metabolic and ventilatory fatigue threshold from an incremental cycling test using 1-min exercise periods

Aim: Extensive research has been directed towards the identification of the threshold that demarcates fatiguing from non-fatiguing exercise during an incremental workout on a cycle ergometer. As the exercise intensity increases, fatigue compromises not only the cardiovascular and respiratory systems, but also the neuromuscular system. The objective of this work was to calculate the neuromuscular fatigue threshold from surface electromyographic amplitude (EMG-FT) and determine possible associations between this threshold and the metabolic (onset of blood lactate accumulation, OBLA) and ventilatory (ventilatory threshold, VT, and respiratory compensation point, RCP) thresholds.  Methods: Sixteen cyclists performed incremental cycle ergometer rides to exhaustion with bipolar surface sEMG signals recorded from the vastus lateralis. The participants were road cyclists engaged in regular training and amateur road races. On average, cyclists trained at least four times a week covering a weekly distance ranging between 400 and 600 km, plus competition or Sunday training. Cyclists had a national competitive experience of 4.3 (1.7) years and had performed an average of 20,000 km riding. Before the incremental exercise test started, cyclists performed 5 min of unloaded cycling. The test was initiated at a workload of 125 W and the load was increased by 25 W every 1 min until the subjects could no longer continue to exercise (Fig. 1a). At this time, the power achieved was referred to as the maximal power. To calculate the EMG-FT, the deVries’ model was employed using 1-min exercise periods. Blood samples were taken every two minutes during the test. OBLA was calculated as the power output corresponding to a blood lactate concentration of 4.0 mmol/L. During the incremental exercise, breath by breath analysis was performed using a turbine flow-meter connected to a face mask and data of oxygen uptake and carbon dioxide production and ventilatory parameters. One-way repeated-measures ANOVA was used to determine whether there were significant differences in average power output among the EMG-FT, OBLA, VT, and RCP. Pearson correlation coefficients were calculated to determine the relationships among EMG-FT, OBLA, VT, and RCP.  Results: The maximal power tolerated was 403.8 ± 36.5 W. The power output at EMG-FT (372 ± 25 W) was comparable (P>0.05) to that of RCP (381 ± 36 W), but significantly higher (P 0.05), but it was positively correlated with those of VT (0.78, P<0.001) and RCP (0.85, P<0.001).  Conclusions: Our results do not support the existence of a relationship between EMG-FT and lactate concentration. A significant correlation was found between the sEMG-based threshold and gas exchange thresholds, although this correlation may not be causative. Second, application of deVries’ model using of 1-min exercise periods could result in overestimation of the fatigue threshold since such short exercise periods could be insufficient to detect EMG signs of neuromuscular fatigue

2016 AHA/ACC Guideline on the Management of Patients With Lower Extremity Peripheral Artery Disease: A Report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines.

2016 AHA/ACC Guideline on the Management of Patients With Lower Extremity Peripheral Artery Disease: A Report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines.

Modulating effects of exercise training regimen on skeletal muscle properties in female polo ponies.

BackgroundThe match play patterns in equestrian polo are unique and require specific training programs to ensure sport performance. The effect of commonly used exercise training regimens on the adaptation of skeletal muscle is unclear. The present study investigated the modulating effects of the classic training regimen, comprised of aerobic exercise training with increasing exercise intensities and varying duration combined with match play, on the properties of muscle in polo ponies. Nine healthy adult female polo ponies were subjected to four consecutive subsets of 1 year classic training regimen including basal activity (B), low intensity (L), low to moderate intensity (LM), and low to moderate intensity training plus match play during polo tournament (LMP), respectively. At the end of each training period, gluteus medius muscle samples were taken for determination of muscle fiber type distribution, muscle metabolic capacity, capillary density, and lipid and glycogen content. The expression profile of metabolic genes including succinate dehydrogenase (SDH), phosphofructokinase (PFK), glycogen phosphorylase (PYG), and glycogen synthase (GYS) were also measured.ResultsAmong all exercise training subsets, only LMP exercise period caused an increase in the number of oxidative fibers (type IIa), along with increases in properties related to oxidative metabolism including high capillary density, intramuscular lipid content, and expression of SDH and PYG genes, with a corresponding decrease in the number of type IIx muscle fibers.ConclusionThe combination of low to moderate and high intensity training in LMP are only sufficient to induce changes in oxidative characteristics. As the first scientific evidence providing such insight about the classic polo training regimen, the data forms a basis for further consideration in training program design.Electronic supplementary materialThe online version of this article (doi:10.1186/s12917-016-0874-6) contains supplementary material, which is available to authorized users.