Role Of Exercise Intensity Research Articles

Role Of Exercise Intensity in Skeletal Muscle Hypertrophy

Endurance training, a form of physical activity that relies on continuous aerobic exercise and repetitive muscle contractions, is widely acknowledged for its positive effects on overall physical fitness. Aerobic exercise, an essential component of endurance training, has numerous benefits including improved cardiovascular and respiratory health, increased muscle endurance, and enhanced resistance against fatigue. It has also been found to contribute to skeletal muscles, potentially by stimulating the synthesis of proteins involved in muscle fiber formation. Although resistance exercise has been favored for promoting muscle growth, some suggests that aerobic exercise can also produce skeletal muscle hypertrophy comparable to that of resistance exercise if performed correctly. The duration, intensity, and specific type of aerobic exercise play important roles in determining skeletal muscle mass. The mammalian target of rapamycin (mTOR) known as a key regulator of muscle protein synthesis that associated with exercise activity. Several signaling pathways, such as Akt/mTOR and MAPK, are involved in controlling muscle protein synthesis during exercise. This review aimed to understand the impact of aerobic exercise intensity and other training parameters on skeletal muscle, to provide valuable insights for optimizing exercise programs and fostering muscle hypertrophy. In this review, we had systematically searched PubMed and Google Scholar from January 2013 to May 2023. Our result indicated that aerobic exercise can be expected to promote skeletal muscle hypertrophy and improve muscle mass and function. The regulation of skeletal muscle mass is complex, involving various signaling pathways such as mTOR, as well as the influence of hormones and growth factors.

The Impact of Different Intensities of Physical Activity on Serum Urate and Gout: A Mendelian Randomization Study.

Physical activity is a potential protective factor against gout, but the role of exercise intensity in this context remains unclear. To overcome the limitations of observational studies in causal inference, this study employed a two-sample Mendelian randomization approach to explore the impact of different genetically proxied/predicted intensities of physical activity on serum urate concentration and the incidence of gout. Our data related to physical activity, serum urate, and gout were obtained from the UK Biobank, the Global Urate Genetics Consortium (GUGC), and the FinnGen dataset, respectively. Walking was included as representative of typical low-intensity physical activity in the analysis, and the other two types were moderate and vigorous physical activities. The estimation methods we used included the inverse-variance-weighted (IVW) method, MR-Egger regression, weighted-median method, simple-mode method, and weighted-mode method. Sensitivity analyses involved Rucker's framework, Cochran's Q test, funnel plots, MR-PRESSO outlier correction, and leave-one-out analysis. We found suggestive evidence from the inverse-variance-weighted method that moderate physical activity was a potential factor in reducing the incidence of gout (OR = 0.628, p = 0.034), and this association became more substantial in our subsequent sensitivity analysis (OR = 0.555, p = 0.006). However, we observed no distinctive effects of physical activity on serum urate concentration. In conclusion, our study supports some findings from observational studies and emphasizes the preventive role of moderate physical activity against gout. Given the limitations of the existing datasets, we call for future reexamination and expansion of our findings using new GWAS data.

Higher intensity exercise reduces disability more than lower intensity exercise in adults with chronic low back pain: Asystematic review and meta-analysis.

Intensity is an important determinant of physiological adaptations and health benefits of exercise, but the role of exercise intensity on improving outcomes in people with chronic low back pain (CLBP) is unclear. This systematic review aimed to determine the effect of higher versus lower intensity exercise intensity on pain, disability, quality of life and adverse events in people with CLBP. Six databases and four clinical trial registries were searched from inception to 21 December 2022, for randomised controlled trials that compared two or more exercise intensities in adults with CLBP. Data were analysed using random-effects meta-analysis for disability and synthesised narratively for pain, quality of life and adverse events due to limited studies. Risk of bias was assessed using the Cochrane tool and certainty of evidence was evaluated using Grading of Recommendations, Assessment, Development and Evaluations framework. Four trials (n=214 participants, 84% male) reported across five studies were included. Higher intensity exercise reduced disability more than lower intensity exercise at end-treatment (SMD [95% CI]=-0.39 [-0.56 to -0.22]; very low certainty) but not at 6-month follow-up (SMD [95% CI]=-0.20 [-0.53 to 0.13]; very low certainty). Higher intensity exercise did not reliably improve pain and quality of life more than lower intensity exercise. Adverse events did not differ between exercise intensities. All studies were at high risk of bias. Based on very low certainty evidence from a limited number of studies, exercise intensity does not appear to meaningfully influence clinical outcomes in people with CLBP.

The role of exercise intensity on fatty liver in rats.

Nonalcoholic fatty liver disease (NAFLD) is the most common chronic liver disease and is often caused by obesity. Currently, moderate-intensity continuous training (MICT) and high-intensity interval training (HIIT) are two effective treatments for reducing fat mass in patients with obesity and NAFLD. However, the comparative fat-reducing effects and underlying molecular mechanisms of MICT and HIIT remain unclear. This comprehensive study was performed on male Wistar rats treated with standard diet, high-fat diet, MICT, and HIIT to explore their comparative fat-reducing effects and corresponding molecular mechanisms. HIIT had a greater effect on hepatic vacuolation density and lipid content reduction than MICT, and triglyceride and total cholesterol levels in the serum and the liver demonstrated different sensitivities to different exercise training programs. At the molecular level, both MICT and HIIT altered the processes of fatty acid synthesis, fatty acid transport, fatty acid β-oxidation, and cholesterol synthesis, wherein the transcriptional and translational levels of signaling molecules peroxisome proliferator-activated receptors (PPARs) regulating fatty acid and cholesterol synthesis were strongly changed. Moreover, the metabolic pathways of amino acids, bile acids, and carbohydrates were also affected according to transcriptome analysis, and the changes in the above-mentioned processes in the HIIT group were greater than those in the MICT group. In combination with the search tool for the retrieval of interacting genes/proteins (STRING) analysis and the role of PPARs in lipid metabolism, as well as the expression pattern of PPARs in the MICT and HIIT groups, the MICT-and HIIT-induced fat loss was mediated by the PPAR pathway, causing feedback responses in fatty acid, steroid, amino acid, bile acid, and carbohydrate metabolism, and HIIT had a better fat-reducing effect, which may be initiated by PPAR-α. This study provides a theoretical basis for targeted therapy of patients with obesity and NAFLD.

Role of Exercise Intensity on Th1/Th2 Immune Modulations During the COVID-19 Pandemic.

The COVID-19 pandemic has led to several pioneering scientific discoveries resulting in no effective solutions with the exception of vaccination. Moderate exercise is a significant non-pharmacological strategy, to reduce the infection-related burden of COVID-19, especially in patients who are obese, elderly, and with additional comorbidities. The imbalance of T helper type 1 (Th1) or T helper type 2 (Th2) cells has been well documented among populations who have suffered as a result of the COVID-19 pandemic, and who are at maximum risk of infection and mortality. Moderate and low intensity exercise can benefit persons at risk from the disease and survivors by favorable modulation in Th1/Th2 ratios. Moreover, in COVID-19 patients, mild to moderate intensity aerobic exercise also increases immune system function but high intensity aerobic exercise may have adverse effects on immune responses. In addition, sustained hypoxia in COVID-19 patients has been reported to cause organ failure and cell death. Hypoxic conditions have also been highlighted to be triggered in COVID-19-susceptible individuals and COVID-19 survivors. This suggests that hypoxia inducible factor (HIF 1α) might be an important focus for researchers investigating effective strategies to minimize the effects of the pandemic. Intermittent hypoxic preconditioning (IHP) is a method of exposing subjects to short bouts of moderate hypoxia interspersed with brief periods of normal oxygen concentrations (recovery). This methodology inhibits the production of pro-inflammatory factors, activates HIF-1α to activate target genes, and subsequently leads to a higher production of red blood cells and hemoglobin. This increases angiogenesis and increases oxygen transport capacity. These factors can help alleviate virus induced cardiopulmonary hemodynamic disorders and endothelial dysfunction. Therefore, during the COVID-19 pandemic we propose that populations should engage in low to moderate exercise individually designed, prescribed and specific, that utilizes IHP including pranayama (yoga), swimming and high-altitude hiking exercise. This would be beneficial in affecting HIF-1α to combat the disease and its severity. Therefore, the promotion of certain exercises should be considered by all sections of the population. However, exercise recommendations and prescription for COVID-19 patients should be structured to match individual levels of capability and adaptability.

Intensity of Walking Training Impacts Cognition Among Assisted Living Residents With Frailty

Exercise has many proven cognitive benefits but the precise intensity to modify cognition is unclear. This pilot study investigated the role of exercise intensity on cognitive outcomes among assisted living residents. We enrolled n=33 frail or pre-frail residents who completed an 8 week, twice-weekly walking intervention. Participants were 66% female, and on average were 88 years old with a MMSE score=25.6, and low cognitive scores (Category Fluency Animals=10.45, Category Fluency Vegetables=7.67, Trail Making Test A=60.82 seconds, Trail Making Test B=155.18 seconds). Walking sessions used 5-minute intervals focused on maximizing steps, fast speeds, and multi-directions for 45 minutes per session. Participants in the high intensity group walked at >70% heart rate maximum or RPE 15-17 and those randomized to the casual intensity group walked at <60% heart rate maximum or RPE <13. Results showed the casual-intensity group improved more on Category Fluency tests (increase of 0.88 animals and 1.06 vegetables) compared to the high-intensity group (increase of 0.12 animals and increase of 0.35 vegetables). On Trail Making Test A, high-intensity participants had a 7.47 second decrease in time to complete compared to the casual-intensity group (2.00 seconds increase). On Trail Making Test B, high-intensity participants decreased time to complete by 27.13 seconds compared to a 26.19 decrease in the casual-intensity group. Results show promising trends in the role of exercise intensity in impacting different elements of cognition among assisted living residents.

Exercise intensity and markers of inflammation during and after (neo-) adjuvant cancer treatment.

Exercise training has been hypothesized to lower the inflammatory burden for patients with cancer, but the role of exercise intensity is unknown. To this end, we compared the effects of high-intensity (HI) and low-to-moderate intensity (LMI) exercise on markers of inflammation in patients with curable breast, prostate and colorectal cancer undergoing primary adjuvant cancer treatment in a secondary analysis of the Phys-Can randomized trial (NCT02473003). Sub-group analyses focused on patients with breast cancer undergoing chemotherapy. Patients performed 6 months of combined aerobic and resistance exercise on either HI or LMI during and after primary adjuvant cancer treatment. Plasma taken at baseline, immediately post-treatment and post-intervention was analyzed for levels of interleukin 1 beta (IL1B), IL6, IL8, IL10, tumor-necrosis factor alpha (TNFA) and C-reactive protein (CRP). Intention-to-treat analyses of 394 participants revealed no significant between-group differences. Regardless of exercise intensity, significant increases of IL6, IL8, IL10 and TNFA post-treatment followed by significant declines, except for IL8, until post-intervention were observed with no difference for CRP or IL1B. Subgroup analyses of 154 patients with breast cancer undergoing chemotherapy revealed that CRP (estimated mean difference (95% CI): 0.59 (0.33; 1.06); P = 0.101) and TNFA (EMD (95% CI): 0.88 (0.77; 1); P = 0.053) increased less with HI exercise post-treatment compared to LMI. Exploratory cytokine co-regulation analysis revealed no difference between the groups. In patients with breast cancer undergoing chemotherapy, HI exercise resulted in a lesser increase of CRP and TNFA immediately post-treatment compared to LMI, potentially protecting against chemotherapy-related inflammation.

The Role Of Exercise Intensity In Cell Signaling: Is There A Repeated-bout Effect?

PURPOSE: Acute exercise elicits a temporary change in redox balance resulting in activation of antioxidant related gene expression and enzymes. We have previously shown in men that the type of acute exercise stimulus, constant workload (CW) vs. high intensity interval protocol (HIIP) results in different redox responses despite no differences in mean VO2. The present study tested whether these results translate to women. In addition, we asked whether the responses are amplified through a repeated bout effect, by comparing the responses after 1 bout to those after 3 bouts. It was hypothesized that HIIP would render greater cell signaling response compared to CW and that differences would be amplified after 3 sessions. METHODS: Healthy women ages 30-45y participated in this study in a randomized, cross-over design (n=12, projected) with a 2-week washout period between trials. Each participant completed a VO2max on a cycle ergometer to establish the workload for the exercise trials. Subjects were randomized to complete either CW or HIIP sessions first. Each trial occurred every other day for 5 days. A second VO2max was performed prior to the second trial to ascertain that VO2 max had not changed from baseline. CW consisted of 30-min of cycling at 70% VO2max. HIIP consisted of a 9-min ramp-up, 7 intervals of 1-min “all out” intervals at 90-100% VO2max followed by 2-min recovery for a total of 30-min of cycling. Blood draws were taken pre-, and 10- 30-, and 60-min post exercise during the first and third exercise session of each trial. Cell signaling was measured by nuclear localization of Nrf2 as well as protein abundance of GCLC and GSR in PBMCs. GR enzyme activity was measured in erythrocyte lysate. RESULTS: To date, 5 women have enrolled in the study and testing is still underway. The average intensity of the CW trial is 70.3% and the average intensity of the HIIP intervals is 91.7% VO2max. The early data show a trend for increased nuclear Nrf2 and GSR protein abundance HIIP compared to CW, and an amplification of the response after 3 sessions. CONCLUSION: These preliminary data suggest that delivering an exercise stimulus in short “pulses” of high intensity such as the HIIP elicits a greater protective signaling response as compared to a block of moderate CW exercise, and furthermore that these effects are amplified by a repeated bout effect.

Acute leptin response after high intensity interval and moderate intensity continuous runs

The possible direct role of exercise intensity and duration on leptin concentrations is conflicting. The aim of this study was to evaluate the acute effects of high intensity interval (HIIE) and moderate intensity continuous (MICE) exercise on plasma leptin response. Seven young volunteers underwent three tests: 1) a treadmill graded exercise test to identify running peak velocity (PV); 2) HIIE: 5 × 2 min work bouts at 90% of PV, interspersed by 2 min of passive recovery and; 3) MICE: 30 min at 70 % of PV. Blood samples were drawn for the assays of leptin before and 30 minutes after HIIE and MICE. A 2-way repeated measures ANOVA showed a significant main effect of time [F(1,6) =17,52; p=0,006], no significant effect of condition (type of exercise) (F(1,6) = 0,16; p = 0,68) and no significant interaction (condition × time) (F(1,6)= 0,48, p=0,51). Leptin decreased 30 min after HIIE (t= 2,95, p=0,025) and MICE (t=4,18; p=0,005). There was no difference between the HIIE and MICE conditions immediately after exercise (t=0,90; p=0,40). After HIIE and MICE, leptin decreased in the same magnitude. It appears that both exercise modalities result in physical stress which is sufficient to improve short-term leptin sensibility.

Shear stress and cerebrovascular function during acute isometric exercise: the role of exercise intensity and aging

Introduction: Exercise reduces the risk of developing vascular dysfunction, implicated in the progression of cardiovascular and cerebrovascular diseases. However, our understanding of how exercise can be optimised for improvements in brain health with increasing age, is limited. In the peripheral vasculature, episodic increases in blood flow and shear-stress promote acute and chronic improvements in vascular function. At the brain, evidence is less clear. Increases in cerebral blood flow (CBF) and shear stress are observed with low-intensity exercise, and these responses are dampened in older compared with younger adults. Whether the CBF shear stress response is intensity- and age-dependent is not known. In older adults, attenuations in CBF during exercise may be related to impaired vascular function, or an attenuated response to increases in blood pressure (hysteresis). Our study aims to examine CBF during varying increases in exercise intensity using isometric handgrip exercise. It is hypothesised that higher intensity isometric exercise will be associated with increased blood pressure and CBF, including shear-mediated internal carotid artery (ICA) dilation in young adults, but not in older adults. We also hypothesise CBF will not be associated with changes in blood pressure during exercise in older adults.

Effect of Acute Intermittent Exercise on Cognitive Flexibility: the Role of Exercise Intensity

The benefits of physical exercise on brain function and its metabolism are well documented, and it is established that acute aerobic exercise could enhance executive function. The aim of this study was to report the effect of exercise intensity during acute intermittent exercise (IE) on executive function and heart rate outcomes. Twenty male subjects performed a series of six consecutive 3-min bouts of exercise at either 60 or 95% of peak power output (PPO), interspersed by 3 min of passive recovery on a bicycle ergometer. Reaction time (ms) and accuracy (%) of switching task using a computerized Stroop task were recorded before and after warm-up, after each bout of exercise and every 15 min during a 1-h passive recovery following exercise. A two-way repeated measures ANOVA was performed to quantify the effects of exercise time (bouts) and condition (exercise intensity). The ANOVA revealed a main effect of time and an interaction between intensity and time for the heart rate and heart rate variability, RPE, and perceived difficulty of cognitive tasks (p < 0.05). The session at 95% PPO induced a more important subjective and objective fatigue than at 60%. Also, participants found the switching task more difficult after the third repetition at 95% and throughout the repetition of the task during IE. Compared to baseline, cognitive performance was improved at both intensities (main effect of time; p < 0.05). However, IE at 60% induced lower reaction time (ES = − 1.1) than at 95% (ES = − 0.7). The decrease in reaction time persisted during the recovery period, following IE at 60% but returned to baseline 30 min after the IE at 95%. Our results demonstrate that both moderate and high exercise intensity enhance cognitive performance during and following IE. The greater perceived exertion and lower parasympathetic activity during exercise at 95% PPO could be responsible for the smaller improvement on reaction time, when compared to exercise at 60% PPO.

Effect of Exercise Duration on Subsequent Appetite and Energy Intake in Obese Adolescent Girls.

There is a growing interest regarding the effect of exercise on appetite and energy intake in youth. While the role of exercise intensity has been a primary focus of study, the effect of exercise duration on subsequent food intake has not been fully examined in obese adolescents. On three separate mornings in a randomly assigned order, obese adolescent girls (n = 20) aged 12-15 years old were asked to perform a rest session (control, CON) or two cycling sessions for 20 (EX20) or 40min (EX40) set at their ventilatory threshold. Absolute and relative energy intake were measured from an ad libitum lunch meal 30min after rest or exercise and appetite feelings assessed using visual analogue scales throughout the day. Hunger, satiety, and prospective food consumption were not significantly different between conditions. Absolute energy intake (kcal) did not differ between conditions, while relative energy intake on EX40 (571 ± 381kcal) was significantly lower than during CON (702 ± 320kcal; p < .05) and EX20 (736 ± 457kcal; p < .05). Fat ingestion (in grams) was significantly lower on CON (7.8 ± 3.2g) compared with EX20 (10.3 ± 4.6g; p < .01). Protein intake (in grams) was higher on EX20 (37.0 ± 16.6g) compared with both CON (29.5 ± 11.7g; p < .01) and EX40 (33.1 ± 10.9g; p < .05). However, the percentage of total energy derived from each macronutrient was not different between conditions. Obese adolescent girls do not compensate for an acute bout of exercise set at their ventilatory threshold by increasing energy intake, regardless of the exercise duration.

Is Vigorous Exercise Training Superior to Moderate for CVD Risk after Menopause?

Postmenopausal women have an increased risk for cardiovascular disease through many factors, such as a sedentary lifestyle and reduced heart rate variability (HRV). Endurance training improves coronary risk but the role of exercise intensity is unclear. The purpose of this observational study was to evaluate the effects of moderate versus vigorous exercise on cardiovascular disease risk in postmenopausal women. Thirty-six postmenopausal women who self-reported training at moderate (3–5.9 METS; n=18; age 58.9±4.4yr) or vigorous intensities (>6 METS; n=18; age 59.7±5.2yr) participated. C-reactive protein (CRP), HRV, VO 2 max, and stress (Perceived Stress Survey, Menopause Rating Scale) were measured. Groups were compared using independent samples t- tests, and associations of exercise intensities with CRP and HRV were assessed using multiple regression. CRP, HRV, and VO 2 max were similar ( p >0.05). Vigorous exercise had lower stress subscale scores ( p <0.01) and higher counter-stress subscale scores compared to moderate ( p <0.05). There was a positive association between time spent in vigorous exercise and HRV ( p <0.05).Vigorous exercise may not confer additional benefits in CRP and HRV over moderate, except for stress reduction. However, more time spent in vigorous exercise was associated with higher HRV. Therefore, increased parasympathetic tone may provide cardioprotection after menopause.

Effect of exercise intensity on Nrf2 signalling in young men

Introduction: The transcription factor Nrf2 is the master regulator of antioxidant defence. Recent data indicate a single bout of moderate-intensity stationary cycling at a constant workload upregulates Nrf2 signalling in young, but not older men; however, the role of exercise intensity on Nrf2 activation has not been tested. We hypothesised that a high-intensity interval session would elicit a greater Nrf2 response than moderate aerobic exercise.Methods: Nrf2 signalling in response to two 30-min cycling protocols (high-intensity interval and constant workload) was compared in young men (25 ± 1y, n = 16). Participants completed exercise trials in random order with blood collected pre-, immediately post-, and 30-mins post exercise. Five participants completed a control trial without any physical activity. Nrf2 signalling was determined by measuring protein expression of Nrf2 in whole cell and nuclear fractions. Plasma 8-isoprostanes as well as peripheral mononuclear cell glutathione reductase (GR) and superoxide dismutase activity were measured as markers of oxidative stress.Results: The exercise trials elicited significant increases in nuclear Nrf2 (p < .01), but increases in whole cell Nrf2 did not reach statistical significance. GR activity and plasma 8-isoprostanes increased significantly in response to exercise (p < .05), and GR response was higher in the high-intensity trial (p < .05).Conclusion: Our findings indicate that acute aerobic exercise elicits activation of nuclear Nrf2, regardless of exercise intensity, but that higher-intensity exercise results in greater activity of GR. Future experiments should explore the effect of exercise mode and duration on Nrf2 signalling, and the role of intensity in compromised populations.

Physiological adaptations to interval training and the role of exercise intensity.

Interval exercise typically involves repeated bouts of relatively intense exercise interspersed by short periods of recovery. A common classification scheme subdivides this method into high-intensity interval training (HIIT; 'near maximal' efforts) and sprint interval training (SIT; 'supramaximal' efforts). Both forms of interval training induce the classic physiological adaptations characteristic of moderate-intensity continuous training (MICT) such as increased aerobic capacity (V̇O2 max ) and mitochondrial content. This brief review considers the role of exercise intensity in mediating physiological adaptations to training, with a focus on the capacity for aerobic energy metabolism. With respect to skeletal muscle adaptations, cellular stress and the resultant metabolic signals for mitochondrial biogenesis depend largely on exercise intensity, with limited work suggesting that increases in mitochondrial content are superior after HIIT compared to MICT, at least when matched-work comparisons are made within the same individual. It is well established that SIT increases mitochondrial content to a similar extent to MICT despite a reduced exercise volume. At the whole-body level, V̇O2 max is generally increased more by HIIT than MICT for a given training volume, whereas SIT and MICT similarly improve V̇O2 max despite differences in training volume. There is less evidence available regarding the role of exercise intensity in mediating changes in skeletal muscle capillary density, maximum stroke volume and cardiac output, and blood volume. Furthermore, the interactions between intensity and duration and frequency have not been thoroughly explored. While interval training is clearly a potent stimulus for physiological remodelling in humans, the integrative response to this type of exercise warrants further attention, especially in comparison to traditional endurance training.

Acute Exercise and Motor Memory Consolidation: The Role of Exercise Intensity.

A single bout of high intensity aerobic exercise (~90% VO2peak) was previously demonstrated to amplify off-line gains in skill level during the consolidation phase of procedural memory. High intensity exercise is not always a viable option for many patient groups or in a rehabilitation setting where low to moderate intensities may be more suitable. The aim of this study was to investigate the role of intensity in mediating the effects of acute cardiovascular exercise on motor skill learning. We investigated the effects of different exercise intensities on the retention (performance score) of a visuomotor accuracy tracking task. Thirty six healthy male subjects were randomly assigned to one of three groups that performed either a single bout of aerobic exercise at 20 min post motor skill learning at 45% (EX45), 90% (EX90) maximal power output (Wmax) or rested (CON). Randomization was stratified to ensure that the groups were matched for relative peak oxygen consumption (ml O2/min/kg) and baseline score in the tracking task. Retention tests were carried out at 1 (R1) and 7 days (R7) post motor skill learning. At R1, changes in performance scores were greater for EX90 compared to CON (p<0.001) and EX45 (p = 0.011). The EX45 and EX90 groups demonstrated a greater change in performance score at R7 compared to the CON group (p = 0.003 and p<0.001, respectively). The change in performance score for EX90 at R7 was also greater than EX45 (p = 0.049). We suggest that exercise intensity plays an important role in modulating the effects that a single bout of cardiovascular exercise has on the consolidation phase following motor skill learning. There appears to be a dose-response relationship in favour of higher intensity exercise in order to augment off-line effects and strengthen procedural memory.

Endothelial function following glucose ingestion in adults with prediabetes: Role of exercise intensity.

To determine whether high intensity exercise (HIE) would improve endothelial function more than an isocaloric bout of moderate intensity exercise (MIE) following glucose ingestion in adults with prediabetes. Twelve subjects with prediabetes completed all three conditions: time-course matched control and isocaloric exercise (∼200 kcal) at moderate (MIE; at lactate threshold) and high intensity (HIE; 75% of difference between lactate threshold and VO2 peak). Brachial artery flow-mediated dilation (FMD) was measured before exercise (baseline), within 30 min postexercise, and 1 and 2 hr following a 75 g oral glucose tolerance test (OGTT). Plasma F2-isoprostanes were also assessed during the protocol (i.e., baseline to 2 hr OGTT) as a biomarker of oxidative stress. MIE reduced postexercise F2-isoprostanesAUC compared with time-course matched control and HIE. Although exercise had no statistical effect on FMD postexercise or during the OGTT, elevations in FMDAUC after MIE and HIE were associated with reduced postexercise F2-isoprostanesAUC . Exercise at either intensity had no effect on FMD immediately postexercise following glucose administration. However, individuals with reduced oxidative stress responses to exercise had greater exercise-induced improvement in FMD. Further work is required to identify the mechanism by which exercise alters oxidative stress to enhance endothelial function.

Role of Exercise Intensity on Intramyocelluar Lipid Level After Exercise in Subjects with Moderate Insulin Resistance

It is known that the increased intramyocellular lipid (IMCL) levels observed in obese subjects are closely associated with insulin resistance (IR) in muscle 1). Interestingly, some reports suggested low intensity exercise (LIE) decreased IMCL and improved IR 2). On the other hand, a few reports showed vigorous intensity exercise (VIE) improved IR, but increased IMCL level 3) 4). This phenomenon is a reminiscent of endurance-trained athletes, who possess a high oxidative capacity and enhanced insulin sensitivity, also have higher IMCL content known as athlete’s paradox (AP) 5) 6). From these findings, we hypothesized exercise intensity is one of the determinants of AP.

Role of exercise intensity on GLUT4 content, aerobic fitness and fasting plasma glucose in type 2 diabetic mice.

Type 2 diabetes mellitus (T2D) results in several metabolic and cardiovascular dysfunctions, clinically characterized by hyperglycaemia due to lower glucose uptake and oxidation. Physical exercise is an effective intervention for glycaemic control. However, the effects of exercising at different intensities have not yet been addressed. The present study analysed the effects of 8 weeks of training performed at different exercise intensities on type 4 glucose transporters (GLUT4) content and glycaemic control of T2D (ob/ob) and non-diabetic mice (ob/OB). The animals were divided into six groups, with four groups being subjected either to low-intensity (ob/obL and ob/OBL: 3% body weight, three times/week/40 min) or high-intensity (ob/obH and ob/OBH: 6% body weight, three times per week per 20 min) swimming training. An incremental swimming test was performed to measure aerobic fitness. After the training intervention period, glycaemia and the content of GLUT4 were quantified. Although both training intensities were beneficial, the high-intensity regimen induced a more significant improvement in GLUT4 levels and glycaemic profile compared with sedentary controls (p < 0.05). Only animals in the high-intensity exercise group improved aerobic fitness. Thus, our study shows that high-intensity training was more effective for increasing GLUT4 content and glycaemia reduction in insulin-resistant mice, perhaps because of a higher metabolic demand imposed by this form of exercise.

Effectiveness of a community football programme on improving physiological markers of health in a hard-to-reach male population: the role of exercise intensity

The present study evaluated the effectiveness of participation in recreational football during a community health programme, on physiological markers of health within a hard to reach population. Nine men (Age: 33 ± 9 years, Mass: 75.4 ± 13.7 kg, Height: 1.74 ± 0.07 m and Body Fat: 19 ± 2%) were recruited to participate in the study in collaboration with an English Premier League Football Club. Participants completed the 12-week football-based programme which included two coached football sessions each week. Physiological tests for blood pressure, resting heart rate, cholesterol and an anthropometrical test for body composition were completed at three time points during the study (Weeks – 1, 6 and 12) in an attempt to evaluate the impact of the intervention on health. During each training session, measurements of intensity (%HRmax, identified from the yoyo intermittent level 1 test), duration and rating of perceived exertion were made. The 12-week programme (mean HRmax throughout programme = 75 ± 4% beats min−1; mean RPE throughout programme = 6 ± 1) elicited few changes in physiological markers of health with the only significant change been a decrease in resting heart rate from weeks 6 to 12 (87 ± 22 beats min−1 at week-6, to 72 ± 17 beats min−1; p < 0.05). These data would suggest that the current community football-related health project was not effective in improving physiological markers of health, but was able to maintain their level of health. A lack of improvement may be due to the low intensity of sessions and a lack of coach education for the promotion of sessions that aim to improve health.