Relationship between shock attenuation and stride length during running at different velocities

The purpose of the study was to investigate the characteristics of shock attenuation during high-speed running. Maximal running speed was identified for each subject [n=8 males, 25 (SD 4.6) years; 80 (8.9) kg; 1.79 (0.06) m] as the highest speed that could be sustained for about 20 s on a treadmill. During testing, light-weight accelerometers were securely mounted to the surface of the distal antero-medial aspect of the leg and frontal aspect of the forehead. Subjects completed running conditions of 50, 60, 70, 80, 90, and 100% of their maximal speeds with each condition lasting about 20 s. Stride length, stride frequency, leg and head peak impact acceleration were recorded from the acceleration profiles. Shock attenuation was analyzed by extracting specific sections of the acceleration profiles and calculating the ratio of head to leg power spectral densities across the 10–20 Hz frequency range. Both stride length and stride frequency increased across speeds (P<0.05) and were correlated with running speed (stride length r=0.92, stride frequency r=0.89). Shock attenuation increased about 20% per m·s^–1 across speeds (P<0.05), which was similar to the 17% increase in stride length per m·s^–1. Additionally, shock attenuation was correlated with stride length (r=0.71) but only moderately correlated with stride frequency (r=0.40) across speeds. It was concluded that shock attenuation increased linearly with running speed and running kinematic changes were characterized primarily by stride length changes. Furthermore, the change in shock attenuation was due to increased leg not head peak impact acceleration across running speeds. Electronic Publication     

Minimum number of days required for a reliable estimate of daily step count and energy expenditure,in people with MS who walk unaided

Background and purposeThe purpose of this study was to examine the minimum number of days needed to reliably estimate daily step count and energy expenditure (EE), in people with multiple sclerosis (MS) who walked unaided.MethodsSeven days of activity monitor data were collected for 26 participants with MS (age = 44.5 ± 11.9 years; time since diagnosis = 6.5 ± 6.2 years; Patient Determined Disease Steps = ≤3). Mean daily step count and mean daily EE (kcal) were calculated for all combinations of days (127 combinations), and compared to the respective 7-day mean daily step count or mean daily EE using intra-class correlations (ICC), the Generalizability Theory and Bland-Altman.ResultsFor step count, ICC values of 0.94–0.98 and a G-coefficient of 0.81 indicate a minimum of any random 2-day combination is required to reliably calculate mean daily step count. For EE, ICC values of 0.96–0.99 and a G-coefficient of 0.83 indicate a minimum of any random 4-day combination is required to reliably calculate mean daily EE. For Bland-Altman analyses all combinations of days, bar single day combinations, resulted in a mean bias within ±10%, when expressed as a percentage of the 7-day mean daily step count or mean daily EE.ConclusionsA minimum of 2 days for step count and 4 days for EE, regardless of day type, is needed to reliably estimate daily step count and daily EE, in people with MS who walk unaided.     

Effect of handling breaks on estimation of heart rate responses to bouts of physical activity among young women: An accelerometer research issue

BackgroundOne of the research interests with regard to accelerometry is the evaluation of physical activity bout under free-living conditions.Research questionThis study aimed to examine the effect of treatment interruption on the estimation of heart rate (HR) response to moderate-to-vigorous intensity physical activity (MVPA) bout.MethodsTwenty-five young women performed at least 30 min of MVPA during 24 h while wearing a uniaxial accelerometer on their waist and a portable HR monitor on their chest simultaneously. Based on the time series data, MVPA bout was defined as physical activity that was maintained at no less than 3 metabolic equivalents (METs) for >10 min without or with interruption, i.e., a 1-, 2-, or 3-min interruption.ResultsThe frequency and duration of MVPA bout significantly increased with interruption (p < 0.01). The HR and estimated MET value for an MVPA bout with interruption were significantly lower than those without interruption (p < 0.01), and the difference gradually increased depending on the duration of the interruptions (p < 0.01).SignificanceThese findings indicate that treatment interruptions could influence the estimation of cardiorespiratory response to MVPA bout under free-living conditions, and interruptions could result in an overestimation of the actual intensity of an MVPA bout.     

Defining a valid day of accelerometer monitoring in adults with mental illness

IntroductionA valid day of accelerometry is commonly defined as an absolute duration of wear time. Data processing inconsistencies can arise when using absolute valid-day criteria for adults with varied waking hours. The aim was to compare the use of absolute and relative valid-day criteria in a sample of adults with mental illness.MethodsData were from 99 non-institutionalised adults with mental illness. Participants were asked to wear an ActiGraph GT3X+ accelerometer continuously for seven days, and to note sleep and non-wear times. Absolute valid-day criteria were defined as a set number of hours/day, and relative criteria as a proportion of waking hours. The mean waking duration, non-wear time, and time spent in physical activity (PA) and sedentary behaviour (SB), were derived from accelerometer data, and compared for a range of absolute and relative criteria. The potential inaccuracy of PA and SB estimates were also estimated.ResultsUse of absolute criteria systematically biased the sample toward those with longer waking hours, and resulted in a median of 86% (IQR = 47%–198%) more non-wear time than relative criteria. The potential inaccuracy of SB was from −2.5% to 0% with relative criteria, and from −2.2% to 10.6% for absolute criteria.ConclusionsFor participant samples with varied waking hours, such as adults with mental illness, a valid-day criterion should be based on the proportion of waking hours, rather than the absolute time. The specific valid-day criterion should be chosen for each study independently, and be accompanied with a measure of the non-wear time.     

Do depression and pain intensity interfere with physical activity in daily life in patients with Chronic Low Back Pain?

Patients with chronic pain may have difficulties estimating their own physical activity level in daily life. Pain-related factors such as depression and pain intensity may affect a patients’ ability to estimate their own daily life activity level. This study evaluates whether patients with Chronic Low Back Pain (CLBP) who are more depressed and/or report more pain indeed have a lower objectively assessed daily life activity level or whether they only perceive their activity level as lower. Patients with CLBP were included in a cross-sectional study. During 14 days physical activity in daily life was measured, with both an electronic diary and an accelerometer. Multilevel analyses were performed to evaluate whether a higher level of depression and/or pain intensity was associated with a lower objectively assessed activity level or the discrepancy between the self-reported and objectively assessed daily life activity levels. Results, based on 66 patients with CLBP (mean RDQ score 11.8), showed that the objectively assessed daily life activity level is not associated with depression or pain intensity. There was a moderate association between the self-reported and objectively assessed activity levels (β = 0.39, p < 0.01). The discrepancy between the two was significantly and negatively related to depression (β = −0.19, p = 0.01), indicating that patients who had higher levels of depression judged their own activity level to be relatively low compared to their objectively assessed activity level. Pain intensity was not associated with the perception of a patient’s activity level (β = 0.12, ns).     

Comparison of Self-Report Versus Sensor-Based Methods for Measuring the Amount of Upper Limb Activity Outside the Clinic

Objective

To compare self-reported with sensor-measured upper limb (UL) performance in daily life for individuals with chronic (≥6mo) UL paresis poststroke.

A source of systematic bias in self-reported physical activity: The cutpoint bias hypothesis

ObjectivesEstimates of adults’ moderate-to-vigorous physical activity (MVPA) based on self-report are generally higher than estimates derived from criterion measures. This study examines a possible explanation for part of this discrepancy: the cutpoint bias hypothesis. This hypothesis proposes that inter- and intra-individual variability in energy expenditure, combined with the fact that adults perform a high proportion of daily activities at or just above the traditional 3 MET cutpoint, result in systematic over-estimates of MVPA.DesignCross-sectional.MethodsTime-use recalls (n = 6862) were collected using the Multimedia Activity Recall for Children and Adults from 2210 adults (1215 female, age 16–93 years) from 16 studies conducted in Australia and New Zealand between 2008-2017. Minutes spent in MVPA were estimated using models with varying levels of intra- and inter-individual (total variability) Unadjusted (0% total variability), Low (11.9%), Best Guess (20.7%), and High (30.0%).ResultsIn the Unadjusted model, participants accumulated an average of 129 (standard deviation 127) min/day of MVPA. Estimated MVPA was 98 (110), 99 (107) and 108 (107) min/day in the Low, Best Guess and High variability models, respectively, with intra-class correlation coefficients with the Unadjusted model ranging from 0.78 to 0.83.ConclusionsThese findings support the hypothesis of a cutpoint bias, which probably contributes to the large disparities seen between self-reported and criterion measures of MVPA. Future studies are needed to confirm these findings using other self-report instruments and in other populations.     

Predictors of discordance in self-report versus device-measured physical activity measurement

Purpose

Accurate measurement of free-living physical activity is challenging in population-based research, whether using device-based or reported methods. Our purpose was to identify demographic predictors of discordance between physical activity assessment methods and to determine how these predictors modify the discordance between device-based and reported physical activity measurement methods.

Seasonal variation in physical activity,sedentary behaviour and sleep in a sample of UK adults

Background: Physical activity (PA), sedentary behaviour (SB), sleep and diet have all been associated with increased risk for chronic disease. Seasonality is often overlooked as a determinant of these behaviours in adults. Currently, no study has simultaneously monitored these behaviours in UK adults to assess seasonal variation.

Aim: The present study investigated whether PA, SB, sleep and diet differed over season in UK adults.

Subjects and methods: Forty-six adults (72% female; age?=?41.7?±?14.4 years, BMI?=?24.9?±?4.4?kg/m²) completed four 7-day monitoring periods; one during each season of the year. The ActiGraph GT1M was used to monitor PA and SB. Daily sleep diaries monitored time spent in bed (TIB) and total sleep time (TST). The European Prospective Investigation of Cancer (EPIC) food frequency questionnaire (FFQ) assessed diet. Repeated measures ANOVAs were used to identify seasonal differences in behaviours.

Results: Light-intensity PA was significantly higher in summer and spring (p?p?p?>?0.05).

Conclusions: Findings support the concept that health promotion campaigns need to encourage year-round participation in light intensity PA, whilst limiting SB, particularly during the winter months.     

Children's physical activity and psychological health: the relevance of intensity

Aim: To examine the relevance of physical activity intensity when assessing the relationship between activity and psychological health in 9–10-year-old children.
Methods: Activity was assessed by accelerometry in 57 boys (n = 23) and girls (n = 34). Total activity and time spent in very light (≤1.9 METs) through to vigorous activity (≥6 METs) were recorded. Psychological health inventories to assess anxiety, depression and aspects of self-worth were completed.
Results: Time accumulated in very light activity had positive correlations with anxiety and depression (r > 0.30, p < 0.05) and negative correlations with aspects of physical self-worth (r > −0.29, p < 0.05). Time accumulated in vigorous activity had negative correlations with anxiety and behavioural conduct (r > −0.30, p < 0.05) and positive correlation with aspects of physical self-worth (r > 0.28, p < 0.05). Children spending over 4 h in very light intensity activity had more negative psychological profiles than children spending under 4 h at this intensity.
Conclusion: Aspects of psychological health were negatively correlated with very light intensity activity and positively correlated with vigorous intensity activity. Further research should investigate whether reducing time spent in very light intensity activity and increasing time spent in vigorous intensity activity improves psychological health in children.