Physical activity spectrum discriminant analysis-A method to compare detailed patterns between groups

Associations of accelerometer-estimated free-living daily activity impact intensities with 10-year probability of osteoporotic fractures in adults

PURPOSE

Accelerometers are used to objectively measure physical activity; however, the relationship between accelerometer-based activity parameters and bone health is not well understood. This study examines the association between accelerometer-estimated daily activity impact intensities and future risk estimates of major osteoporotic fractures in a large population-based cohort.

METHODS

Participants were 3165 adults 46 years of age from the Northern Finland Birth Cohort 1966 who agreed to wear a hip-worn accelerometer during all waking hours for 14 consecutive days. Raw accelerometer data were converted to resultant acceleration. Impact magnitude peaks were extracted and divided into 32 intensity bands, and the osteogenic index (OI) was calculated to assess the osteogenic effectiveness of various activities. Additionally, the impact peaks were categorized into three separate impact intensity categories (low, medium, and high). The 10-year probabilities of hip and all major osteoporotic fractures were estimated with FRAX-tool using clinical and questionnaire data in combination with body mass index collected at the age of 46 years. The associations of daily activity impact intensities with 10-year fracture probabilities were examined using three statistical approaches: multiple linear regression, partial correlation, and partial least squares (PLS) regression.

RESULTS

On average, participants' various levels of impact were 8331 (SD = 3478) low; 2032 (1248) medium; and 1295 (1468) high impacts per day. All three statistical approaches found a significant positive association between the daily number of low-intensity impacts and 10-year probability of hip and all major osteoporotic fractures. In contrast, increased number of moderate to very high daily activity impacts was associated with a lower probability of future osteoporotic fractures. A higher OI was also associated with a lower probability of future major osteoporotic fractures.

CONCLUSION

Low-intensity impacts might not be sufficient for reducing fracture risk in middle-aged adults, while high-intensity impacts could be beneficial for preventing major osteoporotic fractures.

Accelerometer-measured absolute versus relative physical activity intensity: cross-sectional associations with cardiometabolic health in midlife

BACKGROUND

Observational studies investigating the association between accelerometer-measured physical activity and health all use absolute measures of physical activity intensity. However, intervention studies suggest that the physical activity intensity required to improve health is relative to individual fitness. The aim of this study was to investigate the associations between accelerometer-measured absolute and relative physical activity intensity and cardiometabolic health, and what implications these associations may have on the interpretation of health-associated physical activity.

METHODS

A sample of the cross-sectional Swedish CArdioPulmonary bioImage Study (SCAPIS) consisting of 4,234 men and women aged 55-64 years was studied. Physical activity intensity was measured by accelerometry and expressed as absolute (e.g., metabolic equivalents of task) or relative (percentage of maximal oxygen consumption). Fitness was estimated by the submaximal Ekblom-Bak test. A composite ('metabolic syndrome') score combined measures of waist circumference, systolic blood pressure, high-density lipoprotein, triglycerides, and glycated hemoglobin. Associations of absolute and relative physical activity intensity with the health indicators (i.e., fitness and metabolic syndrome score) were studied by partial least squares regression. Analyses were stratified by fitness level.

RESULTS

Both absolute and relative physical activity intensity associated with the health indicators. However, the strongest associations for absolute intensity varied depending on fitness levels, whereas the associations for relative intensity were more synchronized across fitness groups. The dose-response relationship between moderate-to-vigorous intensity and the health indicators was stronger for relative than for absolute intensity. The absolute and relative moderate-to-vigorous intensity cut-offs intersected at the 5th fitness percentile, indicating that the absolute intensity cut-off is too low for 95% of individuals in this sample. While 99% of individuals fulfilled the general physical activity recommendations based on absolute intensity measures, only 21% fulfilled the recommendations based on relative intensity measures. In relation to a "sufficient" fitness level, 9% fulfilled the recommendations.

CONCLUSIONS

Accelerometer-measured relative physical activity intensity represents the intensity related to health benefits regardless of fitness level. Traditional absolute moderate intensity accelerometer cut-offs are too low for most individuals and should be adapted to the fitness level in the sample studied. Absolute and relative physical activity intensity cannot be used interchangeably.

Dose-response associations of Monitor-Independent Movement Summary with health-related fitness in youth

The purpose of this study was to determine the dose-response associations between Monitor-Independent Movement Summary (MIMS) units and health-related fitness in youth. The sample comprised US children and adolescents who participated in the 2012 National Youth Fitness Survey (NNYFS; N = 1158, 48.9% female). Health-related fitness domains were assessed using tests of cardiorespiratory endurance (timed maximal and graded treadmill tests), muscular strength (modified pull-up and grip tests), and muscular endurance (plank test). Movement data were collected using wrist-worn ActiGraph accelerometers with raw data processed using MIMS and the calculated metrics of average MIMS/day, Peak 60-min MIMS, and Peak 30-min MIMS. Weighted regression models examined linear associations between MIMS metrics and fitness test scores. Nonlinear associations were examined using weighted spline models with knots placed at the 10th, 50th, and 90th percentiles. Models were adjusted for covariates and fit was examined using the coefficient of determination (R2 ). The strongest adjusted linear relationships included a positive association between MIMS/day (per every 1000 units) and maximal endurance times (b = 5.5 s, p < 0.001) and between Peak 60-min MIMS (per every 10 units) and estimated aerobic capacity (b = 1.7 mL/kg/min, p < 0.001), modified pull-ups (b = 0.7 reps, p < 0.001), and plank test scores (b = 5.0 s, p < 0.001). Linear spline models had slightly higher R2 values (R2 range = 16.9%-74.8%) compared to linear models (R2 range = 15.0%-74.5%). The relationship between MIMS metrics and fitness test scores was best modeled as piecewise linear functions. Although all MIMS metrics associated with cardiorespiratory endurance, Peak 60-min MIMS showed stronger associations with tests of muscular strength and endurance.

What Can One Minute of the Day Tell about Physical Activity?

High cardiorespiratory fitness (CRF) allows individuals to perform daily activities and operate at a higher intensity level. This study investigates the connection between the CRF and peak intensity of physical activity (PA) in absolute and relative terms. A total of 3587 participants (1447 men, 51.9 ± 13.0 years; 2140 women, 50.0 ± 13.0 years) provided substantial accelerometer wear time, and their CRF was estimated via the 6 min walking test. Participants were divided into CRF thirds by age group and sex. Daily one-minute peak intensities were captured in both absolute terms and relative to individual CRF levels. In absolute terms, the highest CRF third had the highest intensity value for men (6.4 ± 1.7 MET; 5.9 ± 1.4 MET; 5.3 ± 1.0 MET) and for women (6.4 ± 1.6 MET; 5.9 ± 1.3 MET; 5.4 ± 1.1 MET). In relative terms, the highest CRF third utilized the least aerobic capacity for men (49 ± 14%; 51 ± 13%; 56 ± 14%) and for women (52 ± 13%; 54 ± 12%; 62 ± 15%). One minute of daily activity offers valuable insights into an individual's CRF and the effort demanded during PA. Fitter individuals can sustain higher PA intensity levels in absolute terms, whereas individuals with lower CRF utilize a greater fraction of their aerobic capacity. Consequently, heightened CRF not only allows for enhanced intensity levels but also safeguards against strenuous PA during daily routines.

Move for Your Heart, Break a Sweat for Your Mind: Providing Precision in Adolescent Health and Physical Activity Behaviour Pattern

PURPOSE

Adolescent health benefits of different physical activity (PA) intensities, especially of lower intensities, are debated due to challenges in accelerometer data processing and analyses. Using a new accelerometer data processing method and multivariate pattern analysis, this study investigated the association of PA intensities with indicators of cardiovascular and mental health.

METHODS

Adolescents (n = 1,235, mean age 13.6 years, 41% males) were examined for cardiovascular health: body mass index (BMI) z-score, waist circumference (WC), resting heart rate and blood pressure, white blood cell count (WBC), pulse wave velocity (PWV), and answered questionnaires assessing stress and psychosomatic symptoms. Sex, age, and socioeconomic status were confounders. Hip-worn accelerometer data were processed with 10 Hz frequency extended method and a spectrum of 22 PA intensity categories was analyzed for association with health using partial least squares regression.

RESULTS

Total explained variances for BMI z-score, WC, resting heart rate, stress, and psychosomatic symptoms were higher (3.3%-8.7%) compared to diastolic blood pressure, WBC, and PWV (0.9%-1.4%). We found positive associations of high-end moderate PA and vigorous PA with cardiovascular and mental health indicators. More sedentary time and lower level of light PA were associated with higher BMI z-score, WC, resting heart rate, diastolic blood pressure, WBC, and PWV, but not with mental health indicators. Very vigorous PA was negatively associated with resting heart rate, stress, and psychosomatic symptoms.

DISCUSSION

In adolescents, PA of varying intensities were generally found to be positively associated with better cardiovascular health, but only higher intensity PA was associated with better mental health.

The interrelationship between physical activity intensity, cardiorespiratory fitness, and executive function in middle-aged adults: An observational study of office workers

Background

Previous evidence supports a beneficial effect of physical activity on executive function across the whole lifespan. Yet, the interrelationships of the intensities of physical activity, cardiorespiratory fitness, and executive function require further investigation in adults.

Aim

Using unfiltered accelerometry data and high-resolution intensity classification, we sought to estimate the associations of physical activity with cardiorespiratory fitness and executive function in adult office workers.

Methods

We included 343 full-time office workers (mean age: 42.41 years, range of age: 36-49 years). Executive function was assessed using Stroop, Trail making tests (part-B), and 2-back tests, and a composite score was produced to reflect the general executive function performance. Physical activity was assessed using the Actigraph GT3X+-monitor, worn by each participant for seven days at the hip. Raw accelerometry data were processed by the 10 Hz frequency extended method and divided into 22 intensity bins and sleep time. Cardiorespiratory fitness was estimated using the submaximal Ekblom-Bak cycle ergometer test. Data were analyzed using partial least squares regressions.

Results

In adults, cardiorespiratory fitness was closely correlated with a wide range of absolute physical activity intensity patterns. A higher level of executive function in adults was associated with both higher absolute physical activity intensities and cardiorespiratory fitness, which was independent of age, sex, and education levels. A very weak association between intensities, fitness, and executive function was observed in high-fit adults. Among low-fit adults, although a positive association started already toward the upper end of moderate intensity, there still appeared to be an association between intensities, cardiorespiratory fitness, and executive function. That is, cardiorespiratory fitness may mediate the association between absolute physical activity intensities and executive function up to a certain level.

Conclusion

The maintenance of executive function in adulthood was related to both physical activity intensities and cardiorespiratory fitness, while their interrelationship was not equal across fitness levels. It is highly recommended to consider the cardiorespiratory fitness level in future studies that focus on executive functions in aging as well when designing individualized physical activity training programs.