Physical Fitness and Health-related Quality of Life in Patients with Colorectal Cancer.

Colorectal cancer is now a frequently treatable illness for most and a chronic disease for many. The number of people living with a diagnosis of colorectal cancer is thus expected to rise. Yet even after successful treatment, colorectal cancer survivors, mostly the elderly, frequently experience health problems and impaired health-related quality of life. We investigated the cross-sectional association between physical fitness, measured with the 6-min walk test, 30-second chair-stand test, and isometric handgrip strength, as well as health-related quality of life, in a cohort of colorectal cancer patients (n=71, mean [SD] age 67±10 years, 63% men; 35, 39 and 25% in stages I, II and III, respectively). Greater performance in the 6-minute walk test and 30-second chair-stand test was associated with higher levels of global health status (p<0.001, p=0.001 respectively), higher functioning (p<0.001) and lower levels of symptomatology (p<0.001; pain and fatigue). Additionally, greater 6-min walk test performance was associated with a better cognitive function (p=0.005). Our results suggest that greater aerobic fitness and lower-extremity muscle strength are cross-sectionally associated with higher levels of global health status, higher functioning and lower levels of symptomatology such as pain and fatigue in colorectal cancer patients.

Cardiorespiratory fitness and adiposity in breast cancer survivors: is meeting current physical activity recommendations really enough?

PURPOSE: Breast cancer (BC) survivors are becoming increasingly predisposed to cardiovascular disease (CVD) mortality. Low cardiorespiratory fitness and physical activity (PA) levels, as well as high values of adiposity indices, contribute to CVD risk. We evaluated adiposity, cardiorespiratory profile, and PA levels in two independent cohorts of BC survivors. METHODS: Data were collected from two groups (99% women) from different areas of Madrid (Spain): group 1, n = 110, age 51.4 ± 9.7 years, median time from diagnosis 365 days (95% confidence interval [CI], 354-401), and group 2, n = 93, age 54.7 ± 8.9 years, 1714 days (95% CI, 1502-1938). We estimated peak oxygen uptake (VO2peak) and measured body mass index (BMI), waist circumference (WC), waist-to-hip index, and accelerometry-determined PA. RESULTS: Both groups had values of BMI in the overweight range (25.3 ± 4.3 and 27.1 ± 5.1 kg/m2, p = 0.003). Estimated VO2peak levels were lower in group 2 than in group 1 (28.1 ± 9.1 and 23.7 ± 8.8 ml/kg/min, p < 0.001), although levels in both groups were low. Yet, the majority of participants in both groups (81 and 88%, p = 0.234) met international PA recommendations (235 ± 196 and 351 ± 173 min/week of moderate-vigorous PA, p < 0.001). Both groups had very low levels of vigorous PA. These results were essentially independent of type of treatment (anthracycline/radiotherapy). CONCLUSIONS: We found a poor cardiorespiratory profile in two independent BC cohorts that differed in median time from diagnosis (as well in socioeconomic status), supporting the notion that implementation of PA (possibly focusing on vigorous PA) and dietary intervention is urgently needed in this patient population.

Physical Activity and Risk of Coronary Heart Disease and Stroke in Older Adults: The Cardiovascular Health Study.

BACKGROUND: Although guidelines suggest that older adults engage in regular physical activity (PA) to reduce cardiovascular disease (CVD), surprisingly few studies have evaluated this relationship, especially in those >75 years. In addition, with advancing age the ability to perform some types of PA might decrease, making light-moderate exercise such as walking especially important to meet recommendations. METHODS AND RESULTS: Prospective cohort analysis among 4207 US men and women of a mean age of 73 years (standard deviation=6) who were free of CVD at baseline in the Cardiovascular Health Study were followed from 1989 to 1999. PA was assessed and cumulatively updated over time to minimize misclassification and assess the long-term effects of habitual activity. Walking (pace, blocks, combined walking score) was updated annually from baseline through 1999. Leisure-time activity and exercise intensity were updated at baseline, 1992, and 1996. Incident CVD (fatal or nonfatal myocardial infarction, coronary death, or stroke) was adjudicated using medical records. During 41,995 person-years of follow-up, 1182 CVD events occurred. After multivariable adjustment, greater PA was inversely associated with coronary heart disease, stroke (especially ischemic stroke), and total CVD, even in those ≥75 years. Walking pace, distance, and overall walking score, leisure-time activity, and exercise intensity were each associated with lower risk. For example, in comparison with a walking pace <2 mph, those that habitually walked at a pace >3 mph had a lower risk of coronary heart disease (0.50; confidence interval, 0.38-0.67), stroke (0.47; confidence interval, 033-0.66), and CVD (0.50; confidence interval, 0.40-0.62). CONCLUSIONS: These data provide empirical evidence supporting PA recommendations, in particular, walking, to reduce the incidence of CVD among older adults.

Cancer Survivor Study (CASUS) on colorectal patients: longitudinal study on physical activity, fitness, nutrition, and its influences on quality of life, disease recurrence, and survival. Rationale and design.

PURPOSE: Evidence suggests that being physically active in combination with a healthy diet contributes to diminish colorectal cancer risk. However, if this is true for colorectal cancer primary prevention, the same is not clear for its recurrence after colorectal cancer treatments. Data on cancer survival are scarce, and there is a need for greater attention on these survivors' lifestyle behavior. This manuscript describes rationale and design of the Cancer Survival Study (CASUS) on colorectal patients, a longitudinal observational study with the aim of investigating how physical activity, physical fitness, and dietary intake are related with their quality of life, disease recurrence, and survival. METHODS: The CASUS on colorectal patients is a longitudinal cohort study on colorectal survivors, aged 18 years or older, recruited 6, 12, and 24 months after surgery. Upon recruitment, patients fill in a battery of questionnaires about physical activity, dietary intake, and quality of life, donate blood samples, do physical fitness tests, and use an accelerometer during 7 days. Repeated analyses will be performed to assess changes over time in physical activity, physical fitness, dietary intake, and other factors in relation to recurrence and survival. CONCLUSIONS: Results will contribute to highlight the role of physical activity, physical fitness, and nutrition in the quality of life of colorectal cancer survivors, recurrence, and survival. This study will provide important information for policymakers on the potential benefits of future physical activity and nutritional interventions, which are inexpensive, as a way to improve general health of colorectal cancer survivors.

Physical activity and heart rate variability in older adults: the Cardiovascular Health Study.

BACKGROUND: Cardiac mortality and electrophysiological dysfunction both increase with age. Heart rate variability (HRV) provides indices of autonomic function and electrophysiology that are associated with cardiac risk. How habitual physical activity among older adults prospectively relates to HRV, including nonlinear indices of erratic sinus patterns, is not established. We hypothesized that increasing the levels of both total leisure-time activity and walking would be prospectively associated with more favorable time-domain, frequency-domain, and nonlinear HRV measures in older adults. METHODS AND RESULTS: We evaluated serial longitudinal measures of both physical activity and 24-hour Holter HRV over 5 years among 985 older US adults in the community-based Cardiovascular Health Study. After multivariable adjustment, greater total leisure-time activity, walking distance, and walking pace were each prospectively associated with specific, more favorable HRV indices, including higher 24-hour standard deviation of all normal-to-normal intervals (Ptrend=0.009, 0.02, 0.06, respectively) and ultralow-frequency power (Ptrend=0.02, 0.008, 0.16, respectively). Greater walking pace was also associated with a higher short-term fractal scaling exponent (Ptrend=0.003) and lower Poincaré ratio (Ptrend=0.02), markers of less erratic sinus patterns. CONCLUSIONS: Greater total leisure-time activity, and walking alone, as well, were prospectively associated with more favorable and specific indices of autonomic function in older adults, including several suggestive of more normal circadian fluctuations and less erratic sinoatrial firing. Our results suggest potential mechanisms that might contribute to lower cardiovascular mortality with habitual physical activity later in life.

Exercise training can induce cardiac autophagy at end-stage chronic conditions: insights from a graft-versus-host-disease mouse model.

INTRODUCTION: Chronic graft-versus-host disease (cGVHD) is a frequent cause of morbimortality after allogeneic hematopoietic stem cell transplantation (allo-HSCT), and severely compromises patients' physical capacity. Despite the aggressive nature of the disease, aerobic exercise training can positively impact survival as well as clinical and functional parameters. We analyzed potential mechanisms underlying the recently reported cardiac function improvement in an exercise-trained cGVHD murine model receiving lethal total body irradiation and immunosuppressant treatment (Fiuza-Luces et al., 2013. Med Sci Sports Exerc 45, 1703-1711). We hypothesized that a cellular quality-control mechanism that is receiving growing attention in biomedicine, autophagy, was involved in such improvement. METHODS: BALB/C female mice (aged 8wk) with cGVHD were randomly assigned to a control/exercise group (n=12/11); the exercise group underwent moderate-intensity treadmill training during 11wk after allo-HSCT. In the hearts of those few mice surviving the entire 11wk period (n=2/5), we studied molecular markers of: macroautophagy induction, preservation of contractile/structural proteins, oxidative capacity, oxidative stress, antioxidant defense, and mitochondrial dynamics. RESULTS: Mainly, exercise training increased the myocardial content of the macroautophagy markers LC3BII, Atg12, SQSTM1/p62 and phospho-ULK1 (S555), as well as of α-tubuline, catalase and glutathione reductase (all p<0.05). CONCLUSIONS: Our results suggest that exercise training elicits a positive autophagic adaptation in the myocardium that may help preserve cardiac function even at the end-stage of a devastating disease like cGVHD. These preliminary findings might provide new insights into the cardiac exercise benefits in chronic/debilitating conditions.

Physical activity intensities in youth: the effect of month of assessment.

BACKGROUND: There is clear evidence that environmental factors play an important role regarding physical activity (PA) and sedentary behaviour (SB) in youth. This short report highlights seasonal differences in the amount and intensities of PA and SB, in Portuguese youth. METHODS: Three hundred and eighty-seven participants (aged 14.7 ± 1.9 years), 220 girls, used the Actigraph GT1M accelerometer for 7 days (15-second epochs), between January and June in 2008. PA and SB differences were assessed using an ANCOVA. RESULTS: Boys had significantly higher values of PA, with the exception of Light intensity. Girls were significantly more sedentary. PA intensities and SB changed significantly according to gender and month of assessment. SB (Gender F = 16.32, p < 0.001; Month F = 2.95, p < 0.013), Light PA (Gender F = 9.30, p = 0.002; Month F = 8.37, p < 0.001; Gender*Month F = 2.24, p = 0.050), Moderate PA (Gender F = 40.04, p < 0.001), Vigorous PA (Gender F = 32.89, p < 0.001; Month F = 2.56, p = 0.027). Both genders increased PA from winter to summer months and SB decreased. CONCLUSIONS: Seasonality in PA intensities and SB suggest that interventions to promote PA and decrease SB must be tailored to take into consideration the month of the year they are going to be implemented and also gender characteristics.

A Challenge Called Ogilvie´s Syndrome.

Ogilvie´s syndrome is a colonic dilation without any existing mechanical obstruction. The risk factors that cause it are not completely understood, but if untreated, the distension can result in rupture or ischaemic bowel perforation. Additionally, the existing guidelines do not agree with each other about the next steps if conservative treatment fails. We report the case of a 71-year-old woman in whom Ogilvie´s syndrome was particularly difficult to manage, and with it, we try to add clinical data to a field with scarce evidence.

Metabolic syndrome, physical activity and cardiac autonomic function.

BACKGROUND: Our primary aim was to investigate the associations that components of metabolic syndrome and physical activity have with cardiac autonomic nervous system activity as estimated by heart rate variability (HRV) in young adults free of metabolic abnormalities. We also aimed to identify predictors of 3-year changes in HRV. METHODS: Physical activity was assessed annually in 163 healthy participants over 3 years (2008-2010). Components of metabolic syndrome measured annually were; waist circumference, systolic blood pressure, high-density lipoprotein, triglycerides, glucose, and C-reactive protein. A linear mixed regression model was used to assess associations between HRV, metabolic syndrome components and physical activity. Linear regression was used to identify predictors of changes in HRV. RESULTS: Metabolic syndrome components were negatively associated with HRV indices and higher heart rate, while physical activity was associated with higher HRV and lower heart rate. Physical activity and inflammation were predictors of positive and negative changes in HRV indices, respectively. CONCLUSIONS: In participants without significant metabolic abnormalities, metabolic syndrome components were still associated with less favourable HRV profiles. Physical activity and inflammation were both able to predict changes in HRV, albeit in different directions. It appears that the process of autonomic dysfunction starts at a young age and may be mediated in part by inflammation. Metabolic syndrome prevalence is increasing in younger populations; promoting the metabolic and autonomic benefits of exercise remains imperative.

Influence of body fat and level of physical activity on rate-pressure product at rest in preschool children.

OBJECTIVE: The rate-pressure product (RPP) has strong correlation with the maximal oxygen consumption and is an indicator of myocardium stress being considered as the best indirect method to measure myocardial oxygen consumption. However, to the best of our knowledge, no studies have addressed in preschool children. The aim of this study was to analyze the influence of percentage of body fat (%BF) and physical activity (PA) patterns on RPP at Rest (RPPrest) as a marker of cardiac load in Preschool children. METHODS: The study comprised 593 preschool children aged 3-6 years-old. Heart rate (HR), systolic (SBP), and diastolic (DBP) blood pressure were taken at rest. The RPP was then calculated. The %BF was estimated from four skinfolds thicknesses and PA was assessed during 7 consecutive days by accelerometry. RESULTS: Our data showed that only %BF (P ≤ 0.001) and vigorous PA (P ≤ 0.05) contributed significantly toward RPPrest variation. However, the multivariate analysis showed that only %BF (P ≤ 0.05) had a significant influence on RPPrest variation. CONCLUSION: These findings suggest that on preschoolers there is an association between RPP at rest and %BF.

Reference curves for BMI, waist circumference and waist-to-height ratio for Azorean adolescents (Portugal).

OBJECTIVE: There are no percentile curves for BMI, waist circumference (WC) or waist-to-height ratio (WHtR) available for Portuguese children and adolescents. The purpose of the present study was to develop age- and sex-specific BMI, WC and WHtR percentile curves for a representative sample of adolescents living in the Portuguese islands of Azores, one of the poorest regions of Europe, and to compare them with those from other countries. DESIGN: Cross-sectional school-based study. Weight, height and WC were objectively measured according to standard procedures. Smoothed percentile curves were estimated using Cole's LMS method. SETTING: Azores, Portugal. SUBJECTS: Proportionate stratified random sample of 1500 adolescents, aged 15-18 years. RESULTS: Results showed some sex differences in the shape of the BMI curves: in girls, the upper percentile values tend to decrease by the age of 16 and 17 years; whereas in boys, the upper percentiles tend to be flat between 15 and 16 years and then increase until the age of 18 years. In both sexes, the upper percentile values of both WC and WHtR decreased slightly by the age of 16 years and then increased steeply. In both sexes, the Azorean values for the 50th and 90th WC percentiles were higher than those reported for adolescents from the majority of other countries. CONCLUSIONS: The reference curves presented herein provide baseline data for the long-term surveillance of Azorean adolescents, as well as for national and international comparisons.

Metabolic risk factors, physical activity and physical fitness in Azorean adolescents: a cross-sectional study.

BACKGROUND: The prevalence of metabolic syndrome has increased over the last few decades in adolescents and has become an important health challenge worldwide. This study analyzed the relationships between metabolic risk factors (MRF) and physical activity (PA) and physical fitness (PF) in a sample of Azorean adolescents. METHODS: A cross-sectional school-based study was conducted on 417 adolescents (243 girls) aged 15-18 from the Azorean Islands, Portugal. Height, weight, waist circumference, fasting glucose, HDL-cholesterol, triglycerides, and blood pressure were measured. A sum of MRF was computed, and adolescents were classified into three groups: no MRF, one MRF and two or more MRF. PA was assessed by a sealed pedometer. PF was assessed using five tests from the Fitnessgram Test Battery. Dietary intake was obtained using a semi-quantitative food frequency questionnaire. RESULTS: Mean daily steps for girls and boys were 7427 ± 2725 and 7916 ± 3936, respectively. Fifty-nine percent of the adolescents showed at least one MRF and 57.6% were under the healthy zone in the 20 m Shuttle Run Test. Ordinal logistic regression analysis showed that after adjusting for sex, body mass index, socio-economic status and adherence to a Mediterranean diet, adolescents who were in the highest quartile of the pedometer step/counts (≥9423 steps/day) and those who achieved the healthy zone in five tests were less likely to have one or more MRF (OR = 0.56;95%CI:0.33-0.95; OR = 0.55;95%CI:0.31-0.98, respectively). CONCLUSIONS: Daily step counts and PF levels were negatively associated with having one or more MRF among Azorean adolescents. Our findings emphasize the importance of promoting and increasing regular PA and PF to reduce the public health burden of chronic diseases associated with a sedentary lifestyle.

The importance of physical education classes in pre-school children.

AIM: The purpose of this study was to analyse differences between total physical activity (TPA) and moderate-to-vigorous PA (MVPA) of pre-school children during daily school hours when they attended the physical education class (PED) and school days without PE class (NPED) and to assess the contribution of PE classes to TPA in school hours. METHODS: The sample was composed of 193 pre-school healthy children (96 girls) aged from three to five years old and was conducted between February and December of 2008. Children wore accelerometers for at least four consecutive days during school hours. Data were analysed with specific software, age-specific counts-per-minute cut-off points and a 5 s epoch were used. Independent and general linear model repeated measures were used to assess differences between gender and differences between different days within each gender, respectively. RESULTS: Boys engaged more MVPA than girls (P < 0.05). During PED, pre-school children engaged significantly more in TPA and MVPA than during NPED (P < 0.05). PE class contributed, on average, 27.7% for the TPA and 32.8% of daily MVPA during PED in both gender. CONCLUSION: The results of this study suggest that structured PA such as a PE class increased the daily TPA and MVPA level of pre-school children.

Central fat influences cardiac autonomic function in obese and overweight girls.

It has been suggested that upper-body fat compared with lower-body fat is more closely associated with cardiovascular abnormalities. Our objective was to analyze the relationship between central fat (CF) and cardiac autonomic (cANS) function in obese and overweight girls. Children were classified in two groups based on CF: those above (CFa(50)) and those below the 50th percentile (CFb(50)) of the entire sample. This study included 16 female children who were diagnosed as being overweight or obese (age: 14.3 ± 2.8 years; weight: 75.0 ± 15.8 kg; height: 157.1 ± 8.9 cm; body mass index: 30.1 ± 5.4; and total body fat: 40.5 ± 5.0%; Tanner stage: 4). cANS function was assessed through heart rate variability (HRV) and CF parameters by dual-energy X-ray absorptiometry. Female children with higher CF exhibited significantly higher sympathetic and lower parasympathetic modulation than those with lower CF, independently of total body fat. The data of the present study indicate that CF is associated with less favorable indexes of HRV. In addition, our findings suggest that CF might be an important measure to assess the effect of obesity on cANS function in female children.

Benefits of achieving vigorous as well as moderate physical activity recommendations: evidence from heart rate complexity and cardiac vagal modulation.

The aim of this study was to examine differences in traditional heart rate variability measurements and heart rate complexity (sample entropy) in young adults grouped by objectively measured achievement of either moderate or both moderate and vigorous physical activity recommendations. Of 168 young adults tested (86 females, 82 males; age 20.5 ± 1.2 years), 119 achieved only recommendations for moderate physical activity (moderate group) and 49 achieved recommendations for both moderate and vigorous physical activity (vigorous group). Analysis of covariance controlling for sex, weekly minutes of moderate physical activity, and percentage of body fat was used to assess between-group differences in heart rate variability and heart rate complexity. Logistic regression analysis was used to determine the group characteristics that best predicted high heart rate complexity and vagal indices of heart rate variability. The majority of the autonomic measures were higher (P < 0.05) in the vigorous group, and regression analysis showed that vigorous physical activity was the only multivariate predictor of higher heart rate complexity and higher heart rate variability. Young adults engaged in regular vigorous physical activity were more than twice as likely to have high heart rate complexity than those involved in predominantly moderate exercise. These findings suggest that vigorous physical activity is more closely associated with high heart rate complexity than moderate physical activity in young adults.

Associations Between Depressive Symptoms and Physical Activity Intensity in an Older Adult Population During COVID-19 Lockdown.

INTRODUCTION: The COVID-19 pandemic led to the implementation of physical-social distancing measures-including self-isolation, home confinement, and quarantine around the world, with psychological consequences such as depression. Older adults are especially likely to develop depressive symptomatology. This study aims to investigate the association between physical activity intensities and sedentary behavior with depression levels among previously active older adults during the COVID-19 lockdown. METHODS: A total of 1,123 physically active older Brazilian adults (67.68 ± 5.91 years, 91.00% female) were interviewed by telephone in regard to sociodemographic, general health status, depression (GDS-15), and physical activity (IPAQ-SV) after being home-confined for 11.59 ± 2.42 weeks. Participants were also asked to self-report changes in their physical activity levels and time spent sitting. Descriptive statistics (mean, frequencies), between-groups comparisons (t-tests and chi-square), and hierarchical regression analysis were used. RESULTS: About 83.80% of older adults self-reported a decrease in daily physical activity levels and 73.90% increased sitting time. Overall, depressive symptoms were observed in 30.40, and 20.80% met physical activity recommendations. Daily moderate (ß = -0.174; 95% CI = -0.026; -0.012) and moderate-to-vigorous (ß = -0.183; 95% CI = -0.023; 0.011) physical activity intensities were negatively associated with depression score explaining 2.6 and 2.9% of depression variability, respectively, after adjusting for age, gender, education level, body mass index, and polypharmacy. Daily walking and sitting time were not associated with the depression score (p > 0.05). CONCLUSION: The results provide empiric suggestion supporting moderate to vigorous physical activity as a way to reduce depressive levels among older adults during COVID-19 confinement. Supervised home-based exercise programs, specifically designed for older adults, might be an important strategy to maintain and improve older adults' mental health.

Predictors of Lower Depression Levels in Older Adults During COVID-19 Lockdown.

BACKGROUND: Social distancing during the COVID-19 pandemic may lead to adverse mental health consequences, such as depression, among older adults. This study aimed to investigate the predictors of lower depression scores in older adults living under lockdown. METHODS: 1,123 older Brazilian adults were cross-sectionally assessed for depression, physical activity (PA), pet ownership (dogs, cats, and birds), ability to make video calls, leaving home during lockdown, and not living alone. The statistical procedures included linear regression and analysis of covariance (ANCOVA). RESULTS: After adjusting for age, sex, and race, moderate to vigorous PA (ß = -0.014, p < .001), it was found that PA (ß = -0.905, p < .001) and dog ownership (ß = -0.545, p = .004) were associated with lower depression. No association was observed between depression and other conditions. CONCLUSIONS: With the likelihood of subsequent COVID-19 waves, remotely delivered PA programs might be a strategy to counteract the negative psychological effects of lockdown on older adults.

Compliance with physical activity guidelines in preschool children.

The aims of this study were (1) to document differences in physical activity (both total and moderate-to-vigorous physical activity) between the sexes on weekdays and weekend days in preschoolers, and (2) to assess compliance with recommendations for total physical activity (National Association for Sport and Physical Education guidelines) and moderate-to-vigorous physical activity on weekdays and weekend days in the same children. The sample comprised 245 preschoolers (105 girls, 140 boys) aged 3.5-6.0 years old. Physical activity was assessed using an Actigraph accelerometer. Data were analysed with specific software and activity was measured as counts per minute. An independent t-test and general linear model with repeated-measures were used to assess differences between the sexes and differences between days (weekdays and weekend days) within each sex, respectively. A chi-square test was used to determine differences between the sexes in the proportion of children complying with physical activity guidelines. In both sexes, sedentary behaviour accounted for the majority of the time on weekdays and weekend days (weekdays: 83%; weekend days: 83.9%). Boys engaged in significantly more (P < 0.05) total physical activity and moderate-to-vigorous physical activity than girls (weekdays: boys 155.4 min vs. girls 128.22 min; weekend days: boys 111.2 min vs. girls 90.5 min). On average, preschool children engaged in significantly more (P < 0.05) total physical activity and moderate-to-vigorous physical activity on weekdays than weekend days. Altogether, 74.3% and 93.5% of the children met the National Association for Sport and Physical Education guidelines and moderate-to-vigorous physical activity recommendations respectively on weekdays, whereas compliance with both recommendations was substantially less in both sexes on weekend days. The results of this study suggest that despite 83% of time during the day being spent in sedentary behaviour, most preschool children met the daily physical activity and moderate-to-vigorous physical activity recommendations on weekdays. Future research should consider the two constructs of physical activity and sedentary behaviour independently, as they might not necessarily counteract each other.

Vigorous physical activity and vagal modulation in young adults.

BACKGROUND: Aerobic exercise leads to reduced sympathetic and increased cardiac vagal modulation, providing an antiarrhythmic effect. The optimal exercise intensity to promote this adaptation remains undefined. The aims of the present investigation were twofold. First, to examine differences in heart rate variability (HRV) measures in participants with different levels of objectively measured physical activity (PA). Second, to identify the characteristic of PA which most influences the cardiac autonomic nervous system (cANS) function in young adults. METHODS: Cross-sectional evaluation of 84 adults examining relationships between PA amount and intensities, measured by accelerometry, cANS function derived from HRV. Groups were created based on tertiles of PA and analysis of covariance was used to assess between-group differences in HRV. Stepwise regression analysis was used to determine the characteristic of PA, which best predicted vagal HRV indices. RESULTS: There were significantly higher levels of vagal HRV indices in the most active group compared with the least active group. Regression analysis revealed that the number of bouts of vigorous PA undertaken was the best predictor of the vagal HRV indices assessed. CONCLUSION: This study suggests that vagal modulation is enhanced with high levels of PA and that it is the number of bouts of vigorous PA that is most closely associated with cANS function.