Comparison of Actical and activPAL measures of sedentary behaviour in preschool children

ObjectivesThe purpose of this study was to examine the convergent validity of the Actical and activPAL to measure sedentary behaviour (SB) and non-SB in preschoolers in a free-living environment.DesignA convenience sample of 49 preschoolers (22 boys; 4.0 ± 0.5 years) from six early childhood centres in Auckland, New Zealand were included in data analysis.MethodsParticipants wore a hip-mounted Actical and a thigh-mounted activPAL accelerometer simultaneously during centre attendance for one day and data were collected in 15 s epochs. Bland–Altman tests were used to assess differences in group mean minutes and percentage of time in (non-)SB between both monitors. Agreement between binary coded (SB vs. non-SB) 15 s-by-15 s Actical and activPAL data was evaluated by calculating percentage agreement and κ statistic.ResultsThe monitors were worn on average for 294.8 ± 46.3 min resulting in a total of 57,780 15 s epochs. Bland–Altman tests suggested a small group mean difference in (non-)SB (1.3 min; 0.1%) and a wide prediction interval (121.3 min; 39.2%). No obvious systematic bias was observed in the Bland–Altman plot. Percentage agreement between the 15 s-by-15 s Actical and activPAL data of all participants was 73.0% (inter-child range: 36.8–93.8%). The κ statistic showed moderate agreement with a value of 0.46 (95% CI: 0.45–0.47).ConclusionsAlthough the group mean estimate of (non-)SB was similar between the Actical and activPAL, the output of both monitors cannot be considered convergent as meaningful random disagreement was found between both monitors.     

Validation of a pouch-mounted activPAL3 accelerometer

The activPAL accelerometer is a commonly used device for the assessment of physical activity in cross-sectional and intervention research. These devices are usually attached directly to the skin; however, recent studies report problems such as skin irritation associated with this attachment method and therefore adequate alternate methods are needed. The aim of this study was to validate the use of an elasticised pouch to secure an activPAL3c (PAL Technologies, Glasgow, UK) accelerometer for the assessment of sedentary and physical activity behaviours during laboratory and free-living conditions. Twenty-eight healthy adults wore two activPAL3c accelerometers, one secured in an elasticised pouch, and one directly attached to the skin, on the anterior surface of the right thigh during laboratory-based walking at a self-selected pace, treadmill walking at 0.89 m s⁻¹, 1.56 m s⁻¹ and running at 2.2 m s⁻¹, and during free-living conditions. Paired samples t-tests and intraclass correlation coefficients were used to investigate the difference and agreement between accelerometer outputs. No statistically significant difference in step count between pouch-mounted and skin-mounted activPAL3c accelerometers was evident during walking at any speed under laboratory conditions. No statistically significant difference in step count, upright time, sitting time or postural transitions was found between pouch-mounted and skin-mounted activPAL3c accelerometers during free-living conditions. Intraclass correlation coefficients showed a high to very high level of agreement between pouch-mounted and skin-mounted activPAL3c accelerometers for each outcome variable. The use of an elasticised pouch to secure the activPAL3c accelerometer appears to be a valid method of attachment and may offer advantages over direct skin mounting.     

Validation of a pouch-mounted activPAL3 accelerometer

The activPAL accelerometer is a commonly used device for the assessment of physical activity in cross-sectional and intervention research. These devices are usually attached directly to the skin; however, recent studies report problems such as skin irritation associated with this attachment method and therefore adequate alternate methods are needed. The aim of this study was to validate the use of an elasticised pouch to secure an activPAL3c (PAL Technologies, Glasgow, UK) accelerometer for the assessment of sedentary and physical activity behaviours during laboratory and free-living conditions. Twenty-eight healthy adults wore two activPAL3c accelerometers, one secured in an elasticised pouch, and one directly attached to the skin, on the anterior surface of the right thigh during laboratory-based walking at a self-selected pace, treadmill walking at 0.89 m s⁻¹, 1.56 m s⁻¹ and running at 2.2 m s⁻¹, and during free-living conditions. Paired samples t-tests and intraclass correlation coefficients were used to investigate the difference and agreement between accelerometer outputs. No statistically significant difference in step count between pouch-mounted and skin-mounted activPAL3c accelerometers was evident during walking at any speed under laboratory conditions. No statistically significant difference in step count, upright time, sitting time or postural transitions was found between pouch-mounted and skin-mounted activPAL3c accelerometers during free-living conditions. Intraclass correlation coefficients showed a high to very high level of agreement between pouch-mounted and skin-mounted activPAL3c accelerometers for each outcome variable. The use of an elasticised pouch to secure the activPAL3c accelerometer appears to be a valid method of attachment and may offer advantages over direct skin mounting.     

Agreement between activPAL3c accelerometers placed at different thigh positions

ActivPAL3c triaxial accelerometers are increasingly used to assess physical activity and sedentary behaviours. However, little is known how attachment site (left vs. right or upper vs. lower thigh) affects activPAL3c accelerometer outcomes. Twenty-eight adults wore four activPAL3c accelerometers attached 2 cm above and below the midpoint of the left and right thigh during five minutes of laboratory-based walking at a self-selected pace, treadmill walking at 0.89 and 1.56 m/s, and treadmill running at 2.22 m/s, and during approximately seven hours of free-living conditions. One-way ANOVA revealed no statistically significant differences in accelerometer output between ActivPAL3c accelerometers at these locations during both laboratory-based, and free-living conditions. Intraclass correlation coefficients showed a high level of agreement between activPAL3c accelerometers during laboratory and free living activities (ICC(2,1) 0.76–1.00). The attachment sites used in this study do not appear to significantly influence outcomes for step count, sitting or walking time, or number of postural transitions from triaxial activPAL3c accelerometers during laboratory-based walking or free-living conditions. Therefore if necessary, to enhance participant compliance during monitoring periods, these sites could be used interchangeably. Studies of longer duration incorporating additional laboratory and recreational activities are needed to confirm these findings.     

Concurrent validity of the ActiGraph GT3X+ and activPAL for assessing sedentary behaviour in 2–3-year-old children under free-living conditions

ObjectivesActiGraph accelerometer cut-points are commonly used to classify sedentary behaviour (SB) in young children. However, they vary from 5counts/5 s to 301counts/15 s, resulting in different estimates and inconsistent findings. The aim was to examine the concurrent validity of ActiGraph GT3X + cut-points against the activPAL for measuring SB in 2–3-year-olds during free-living conditions.DesignObservational validation-study.MethodsSixty children were fitted with the activPAL and ActiGraph simultaneously for at least 2 h. Nine ActiGraph cut-points ranging from 60 to 1488 counts per minute were used to derive SB. Bland & Altman plots and equivalent tests were performed to assess agreement between methods.ResultsEstimates of SB according to the different ActiGraph cut-points were not within the activPAL ±10% equivalent interval (-4.05; 4.05%). The ActiGraph cut-points that showed the lower bias were 48counts/15 s (equivalence lower limit: p =  0.597; equivalence upper limit: p < 0.001; bias: -4.46%; limits of agreement [LoA]: -21.07 to 30.00%) and 5counts/5s (equivalence lower limit: p < 0.001; equivalence upper limit: p =  0.737; bias: -5.11%; LoA: 30.43 to 20.20%). For the 25counts/15s, 37counts/15s and 48counts/15s ActiGraph cut-points, the upper limits were within the equivalent interval (p < 0.001) but not the lower limits (p > 0.05). When using the 5counts/5s and 181counts/15s ActiGraph cut-points, lower limits were within the equivalent interval (p < 0.001) but not the upper limits (p > 0.05). Confidence intervals of the remaining ActiGraph cut-points lie outside the equivalent interval.ConclusionsAlthough none of the ActiGraph cut-points provided estimates of SB that were equivalent to activPAL; estimates from 48counts/15 s and 5counts/5 s displayed the smallest mean bias (˜5%).     

Accuracy of inclinometer functions of the activPAL and ActiGraph GT3X+: A focus on physical activity

PurposeThe purpose of the study was to examine the accuracy of inclinometer functions of the ActiGraph GT3X+ (AG) (worn on the waist and wrist) and the activPAL (AP) in assessing time spent sitting, standing, and stepping.MethodsA total of 62 adults (age: 18–40 yrs; male:37; female:25) wore three activity monitors (AG waist, and AG wrist, and AP) while completing 15 different types of activities. The 15 activities were classified into 3 different postures (sitting, standing, and stepping) based on the directly observed behaviors. Minutes estimated from the inclinometers of the three monitors were directly compared to those from direct observation (criterion method) using mean absolute percent error (MAPE) values, effect sizes (Cohen’s D), and equivalence testing.ResultsThe AP was more accurate than the both waist- and wrist-worn AG in both sitting and standing activities, but the AG was more accurate than the AP in stepping activity when the stepping activity was determined with 0.7 step/s threshold. Equivalence testing indicated that the time measured by the waist-, wrist-worn AG, and AP showed significant equivalence to the time in the equivalence zone (90% confidence interval: 2.7 to 3.3 min) for 6, 5, and 7 activities, respectively.ConclusionsThe AP was reasonably accurate for detecting sitting, standing, and stepping, and the AG was very accurate for classifying stepping when the stepping activity was determined by the formula created by 0.7 step/s threshold. It is expected that the result of the study would contribute to performing movement pattern analyses and health promotion research for classifying activities.     

Visuomotor adaptation of voluntary step initiation in older adults

It has been suggested that feedforward planning of gait and posture is diminished in older adults. Motor adaptation is one mechanism by which feedforward commands can be updated or fine-tuned. Thus, if feedforward mechanisms are diminished in older adults, motor adaptation is also likely to be limited. The purpose of the study was to compare the ability of healthy older versus young adults in generating a voluntary stepping motor adaptation in response to a novel visual sensory perturbation. We recorded stepping movements from 18 healthy older and 18 young adults during baseline and adaptation stepping blocks. During baseline, the stepping target remained stationary; in adaptation, a visual perturbation was introduced by shifting the target laterally during mid-step. We compared adaptation between groups, measured by improvements in endpoint accuracy and movement duration. Older adults adapted stepping accuracy similarly to young adults (accuracy improvement: 29.7 ± 27.6% vs. 37.3 ± 22.9%, older vs. young group respectively, p = 0.375), but showed significant slowness during movement. Thus older adults were able to achieve accuracy levels nearly equivalent to younger adults, but only at the expense of movement speed, at least during the early adaptation period (movement duration: 1143.7 ± 170.6 ms vs. 956.0 ± 74.6 ms, p < 0.001). With practice, however, they were able to reduce movement times and gain speed and accuracy to levels similar to young adults. These findings suggest older adults may retain the ability for stepping adaptations to environmental changes or novel demands, given sufficient practice.     

Effects of different movement modes on plantar pressure distribution patterns in obese and non-obese Chinese children

Walking, slow running (jogging) and fast running often occur in daily life, Physical Education Class and Physical Fitness Test for children. However, potential impact of jogging and running on plantar pressure of children is not clear. The purpose of this study was to compare the characteristics of plantar pressure distribution patterns in obese and non-obese children during walking, jogging and running, and evaluate biomechanical effects of three movements on obese children. A 2-m footscan plantar pressure plate (RSscan International, Belgium) was used to collect the gait data of 20 obese children (10.69 ± 2.11 years; 1.51 ± 0.11 m; 65.15 ± 14.22 kg) and 20 non-obese children (11.02 ± 1.01 years; 1.48 ± 0.07m; 38.57 ± 6.09 kg) during three movements. Paired t-test and independent sample t-test were performed for statistical comparisons and ANOVA was used for comparisons of gait characteristics among three movements. Significance was defined as p < 0.05. Propulsion phase during jogging for obese children was the longest among three movements (p = 0.02). Peak pressures under metatarsal heads IV, V (M4, M5), midfoot (MF), heel medial (HM) and heel lateral (HL) during jogging for obese children were the highest among three movements (p = 0.005, p = 0.003, p = 0.004, p = 0.03, p = 0.01). Arch index (AI) of left foot during jogging for obese children was the largest (p = 0.04).ConclusionsPlantar pressure distribution during three movements changed differently between two groups. The peak pressures under most plantar regions and AI during jogging for obese children were the largest among three movements, indicating that jogging caused more stress to their lower extremities. Obese children perhaps should not consider jogging as regular exercise.     

Field evaluation of a random forest activity classifier for wrist-worn accelerometer data

Objectives

Wrist-worn accelerometers are convenient to wear and associated with greater wear-time compliance. Previous work has generally relied on choreographed activity trials to train and test classification models. However, validity in free-living contexts is starting to emerge. Study aims were: (1) train and test a random forest activity classifier for wrist accelerometer data; and (2) determine if models trained on laboratory data perform well under free-living conditions.

Week-to-week differences of children's habitual activity and postural allocation as measured by the ActivPAL monitor

BackgroundQuantification of sitting and standing is possible with the ActivPAL accelerometer, using algorithms to classify activity into time spent sitting, standing and stepping. The purpose of this study was to determine children's week-to-week differences in time spent sitting/lying and standing along with other measures as provided by the ActivPAL accelerometer during continuous wearing of the ActivPAL monitor.MethodsFifty-six children (age 10.2 ± 0.9 years, mean ± SD) were recruited from 30 urban schools in Auckland, New Zealand. Children wore the monitor for 24 h per day up to 14 days. Analyses were performed with mixed modeling. Reliability was expressed as change in the mean from week to week, intraclass correlation coefficient (ICC) and standard error of measurement (SEM).ResultsMean week-to-week differences in percent time spent sitting/lying, standing and stepping on week days and weekend days for girls and boys were typically small. Step and sit-to-stand counts differences were small and unclear respectively. ICC values ranged from 0.40 to 0.79 during week days and 0.25–0.60 during weekends. SEM for time spent sitting/lying, standing and stepping were ～3.5%, ～2.5% and ～1.5% respectively.ConclusionThe ActivPAL showed moderate to low week-to-week reliability for habitual activity and postural allocation under free living conditions in boys and girls. Interventions aimed at a moderate reduction in sitting time (～5% of the day) will require modest sample sizes for adequate precision.     

Dorsiflexion deficit during jogging with chronic ankle instability

The purpose of the study was to determine whether individuals with chronic ankle instability (CAI) demonstrate altered dorsiflexion/plantar flexion range of motion (ROM) compared to controls during jogging. The case control study took place in a university motion analysis laboratory. Fourteen volunteers participated in the study, seven suffered from CAI (age 25 ± 4.2 years, height 173 ± 9.4 cm, mass 71 ± 8.1 kg) and seven were healthy, matched controls (age 25 ± 4.5 years, height 168 ± 5.9 cm, mass 67 ± 9.8 kg). All subjects jogged on an instrumented treadmill while a ten-camera motion analysis system collected three-dimensional kinematics of the lower extremities. The main outcome measure was sagittal plane (dorsiflexion/plantar flexion) range of motion of the ankle throughout the gait cycle. CAI subjects had significantly less dorsiflexion compared to the control group from 9% to 25% during jogging (4.83 ± 0.55°). CAI subjects demonstrated limited ankle dorsiflexion ROM during the time of maximal dorsiflexion during jogging. Limited dorsiflexion ROM during gait among individuals with CAI may be a risk factor for recurrent ankle sprains. These deficits should be treated appropriately by rehabilitation clinicians.     

Validity of the activPAL monitor to measure stepping activity and activity intensity: A systematic review

BackgroundAccumulating step counts and engaging in moderate-to-vigorous intensity physical activity is positively associated with numerous health benefits. The activPAL is a thigh-worn monitor that is frequently used to measure physical activity.Research questionCan the activPAL accurately measure stepping activity and identify physical activity intensity?MethodsWe systematically reviewed validation studies examining the accuracy of activPAL physical activity outcomes relative to a criterion measure in adults (>18 years). Citations were not restricted to language or date of publication. Sources were searched up to May 16, 2021 and included Scopus, EMBASE, MEDLINE, CINAHL, and Academic Search Premier. The study was pre-registered in Prospero (ID# CRD42021248240). Study quality was determined using a modified Hagströmer Bowles checklist.ResultsThirty-nine studies (20 laboratory arms, 17 semi-structured arms, 11 uncontrolled protocol arms; 1272 total participants) met the inclusion criteria. Most studies demonstrated a high validity of the activPAL to measure steps across laboratory (12/15 arms), semi-structured (10/13 arms) and uncontrolled conditions (5/7 arms). Studies that demonstrated low validity were generally conducted in unhealthy populations, included slower walking speeds, and/or short walking distances. Few studies indicated that the activPAL accurately measured physical activity intensity across laboratory (0/6 arms), semi-structured (0/5 arms) and uncontrolled conditions (2/5 arms). Using the default settings, the activPAL overestimates light-intensity activity but underestimates moderate-to-vigorous intensity activity. The overall study quality was 11.5 ± 2.0 out of 19.ConclusionDespite heterogeneous methodological and statistical approaches, the included studies generally provide supporting evidence that the activPAL can accurately detect stepping activity but not physical activity intensity. Strategies that use alternative data processing methods have been developed to better characterize physical activity intensity, but all methods still underestimate vigorous-intensity activity.     

Effect of multifocal lens glasses on the stepping patterns of novice wearers

Multifocal lens glasses (MfLs) negatively affect vision, increase falling risk and contribute to gait changes during stepping. Previous studies on the effects of MfLs on gait have focused on experienced wearers. Thus, the initial response of first-time wearers, who may face significant challenges in adapting to these glasses, is not well understood. This study aimed to quantify the effects of MfLs on novice wearers during stepping up and down. Additionally, young adults were compared against a middle-aged adults to determine the validity of convenience sampling in testing novice response to MfLs. Fifteen young adults (18–34 y.o.) and seven middle-aged adults (46–56 y.o.) were recruited to perform stepping trials while wearing progressive MfLs and blank single lens glasses. Participants stepped up and down from a 75 mm and 150 mm step in randomized order. Step placement, minimum toe clearance, lower body kinematics and stepping time were measured during step up. Step placement, minimum heel clearance, vertical forces and stepping time were measured during step down. MfLs significantly increased toe clearance in the lead and trailing legs, hip flexion, knee flexion and stepping time during step up and increased vertical forces and stepping time during step down. Step placement and hip angle explained 17% of the toe clearance variability. Changes during step up suggest a more conservative adaptation while increased forces during step down suggest a reduced level of control. No age group effects were observed, which supports the use of convenience sampling for evaluating the novice response to MfLs.     

Flexible learning spaces reduce sedentary time in adolescents

ObjectivesMany schools internationally are replacing traditional classrooms (TC) with innovative flexible learning spaces (FLS) to improve academic outcomes. Via a stealth approach, there may be additional unintended health benefits if students reduce their total and prolonged sitting. The aim of this study was to compare student sitting patterns between TC and FLS.DesignSchool-based cross-over trial.MethodsStudents at nine secondary schools (n = 191, M age = 13.2 ± 1.0 years) wore activPAL accelerometers in both a traditionally furnished and arranged classroom (TC), and a FLS containing a variety of furniture and layout options, utilizing student-centered pedagogies, for the duration of one double classroom lesson (M = 76 min). The lesson content and teacher were consistent across both conditions. Data were analyzed using multilevel mixed-effects linear regression.ResultsIn FLS, students spent less class time sitting (mean = 18%; 95% CI: −20.8, −15.0), and accumulated more breaks in sitting (2.1; 95% CI: 0.8, 3.5 per 60 min), more bouts of intermittent (≤9 min) sitting (2.2; 95% CI: 0.8, 3.6 per 60 min), and fewer bouts of prolonged (≤30 min) sitting (−0.2; 95% CI: −0.3, −0.1 per 60 min), than in TC. Students also spent more class time standing (15%; 95% CI: 12.7, 18.0) and stepping (3%; 95% CI: 2.0, 3.1) in FLS than TC.ConclusionThe results suggest that, by stealth, elements of FLS including a variety of furniture and resources, and greater use of student-centered pedagogies, facilitate improvements in adolescents’ sedentary profiles during class time. This may translate into beneficial health impacts over a longer period given the health benefits of reducing total and breaking up prolonged sitting.     

Age-related changes in gait adaptability in response to unpredictable obstacles and stepping targets

BackgroundA large proportion of falls in older people occur when walking. Limitations in gait adaptability might contribute to tripping; a frequently reported cause of falls in this group.ObjectiveTo evaluate age-related changes in gait adaptability in response to obstacles or stepping targets presented at short notice, i.e.: approximately two steps ahead.MethodsFifty older adults (aged 74 ± 7 years; 34 females) and 21 young adults (aged 26 ± 4 years; 12 females) completed 3 usual gait speed (baseline) trials. They then completed the following randomly presented gait adaptability trials: obstacle avoidance, short stepping target, long stepping target and no target/obstacle (3 trials of each).ResultsCompared with the young, the older adults slowed significantly in no target/obstacle trials compared with the baseline trials. They took more steps and spent more time in double support while approaching the obstacle and stepping targets, demonstrated poorer stepping accuracy and made more stepping errors (failed to hit the stepping targets/avoid the obstacle). The older adults also reduced velocity of the two preceding steps and shortened the previous step in the long stepping target condition and in the obstacle avoidance condition.ConclusionCompared with their younger counterparts, the older adults exhibited a more conservative adaptation strategy characterised by slow, short and multiple steps with longer time in double support. Even so, they demonstrated poorer stepping accuracy and made more stepping errors. This reduced gait adaptability may place older adults at increased risk of falling when negotiating unexpected hazards.     

The influence of age on the thresholds of compensatory stepping and dynamic stability maintenance

The purpose of this study was to investigate the effects of age on compensatory-stepping thresholds and dynamic stability maintenance in response to postural disturbances. It was hypothesized that, with older age, anterior but not posterior stepping thresholds would be reduced. Thirteen young adults (31.1 ± 0.8 years), 11 middle-aged adults (57.6 ± 2.5 years), and 11 older adults (73.8 ± 5.3 years) participated in this study. Surface translations were delivered as subjects stood on a microprocessor-controlled treadmill. Subjects were instructed to “try not to step”. Stepping thresholds were defined as the largest displacement at a given peak treadmill-belt velocity for which a subject could prevent stepping. The margin of stability was calculated to estimate the minimum dynamic stability at the stepping thresholds. Age-related declines in the ability to prevent forward steps were apparent. Anterior stepping thresholds were reduced with age. The minimum margin of stability associated with anterior stepping thresholds was not influenced by age. Therefore, smaller disturbance displacements caused middle-aged and older subjects to become dynamically unstable to the point of stepping. Posterior stepping thresholds were not influenced by age. It is concluded that an age-related decline in anterior, but not posterior, stepping thresholds was due to an impaired ability to maintain dynamic stability after a disturbance.     

Age-related changes in mediolateral dynamic stability control during volitional stepping

The control of mediolateral dynamic stability during stepping can be particularly challenging for older adults and appears to be related to falls and hip fracture. The specific mechanisms or control challenges that lead to mediolateral instability, however, are not fully understood. This work focussed on the restabilisation phase of volitional forward stepping, subsequent to foot contact, which we believe to be a principal determinant of mediolateral dynamic stability. Twenty younger (age 24 ± 5 years; 50% women) and 20 older participants (age 71 ± 5 years; 50% women) performed three different single-step tasks of various speed and step placement, which varied the challenge to dynamic stability. The trajectory of the total body centre of mass (COM) was quantified. Mediolateral COM incongruity, defined as the difference between the peak lateral and final COM position, and trial-to-trial variability of incongruity were calculated as indicators of dynamic stability. Older adults exhibited increased instability compared to young adults, as reflected by larger COM incongruity and trial-to-trial variability. Such increases among older adults occurred despite alterations in COM kinematics during the step initiation and swing phases, which should have led to increased stability. Task related increases in instability were observed as increased incongruity magnitude and trial-to-trial variability during the two rapid stepping conditions, relative to preferred speed stepping. Our findings suggest that increased COM incongruity and trial-to-trial variability among older adults signify a reduction in dynamic stability, which may arise from difficulty in reactive control during the restabilisation phase.     

How many days are enough for measuring weekly activity behaviours with the ActivPAL in adults?

ObjectivesThe purpose of this study was to determine the number of monitoring days needed to reliably measure weekly activity behaviours with the ActivPAL (AP) monitor in adults.DesignCross-sectional study.MethodsParticipants (90 adults (51.1% men); age = 39.1 ± 12.43 years) wore an AP for 7 consecutive days. Mean time spent sitting/lying, standing and stepping per day, and mean number of transitions from sitting to standing per day were calculated for each participant using 7 days of monitoring (reference). Estimates for these activities were also derived from a combination of randomly selected days (from 1 to 6 days), and randomly selected weekdays and weekend days, and compared with the reference using ANOVA, correlation coefficients and Bland-Altman methods Spearman–Brown Prophecy Formula, based on Intraclass correlation of 0.8, was used to predict the minimum number of days needed to represent activity behaviours as measured with the AP.ResultsAt least five days of monitoring were necessary to achieve a reliability of 0.8 for all postures and transitions. Correlation coefficients between estimates derived from any combination of 5 days and the reference were high (rho = 0.96–0.98). When using a combination of weekdays and weekend days, mean biases were comparable with those shown by any combination of days, but 95% limits of agreement were narrower.ConclusionsWhen using the AP for a week, data from a combination of any 5 days provided reliable estimates of all activities and transitions per day, but more precise estimates were achieved if at least 1 weekend day was included.     

Match running performance in elite Australian Rules Football

There is little information describing the match running demands of elite-level Australian Rules Football (AF). The aims of this study were to examine: (1) match running demands; and (2) the influence of periods of increased physical activity on subsequent running performance in the Australian Football League. Time-motion analyses were performed 1–9 times per player from 16 professional AF players from the same club during games in 2005–2007, using portable global positioning systems during 65 matches. Game movements (standing, walking, jogging, running, higher-speed running, and sprinting) and distances (total distance covered [TD]; low-intensity activity [LIA, distance <14.4 km h^?1]; and, high-intensity running distance [HIR, distance > 14.4 km h^?1]) were collected. The influence of the first half physical activities on second half activities, and each quarter on the subsequent quarter were analysed. The mean (±SD) TD and HIR distance covered during the games were 12,939 ± 1145 m and 3880 ± 663 m respectively. There were reductions in TD in the second (?7.3%), third (?5.5%) and fourth (?10.7%) quarters compared to the first quarter (p < 0.01). The HIR was reduced after the first quarter (p < 0.001). Players that covered larger TD or HIR during the first half or quarter decreased distance in the next half and quarter, respectively (p < 0.001). These results show that a reduction in exercise intensity is inevitable during an AF match and that higher intensity activities reduce towards the end of games. High average speed during each half or quarter also affects subsequent running performance in elite-level AF.     

Tibial impact accelerations in gait of primary school children: The effect of age and speed

Tibial stress fractures are associated with increased lower extremity loading at initial foot-ground contact, reflected in high peak positive acceleration (>8 g) of the tibia in adults. There is no reported data on peak positive acceleration of the tibia in children during walking and running. The aim of this study was to establish tibial peak positive acceleration responses in children across a range of age and gait speeds. Twenty-four children aged 8.5 ± 1.4 years with no known gait pathology comprised two age groups; Young (7–9 year, n = 12) and Older (10–12 years, n = 12). Wireless Inertial Measurement Unit comprising a tri-axial accelerometer was securely taped to the anteromedial aspect of the distal tibia to measure peak positive acceleration responses while walking and running on the treadmill at 3 different speeds (20% below baseline, baseline, and 20% above baseline). Results showed significant increase in peak positive acceleration with increased gait speed and greater variability in young children compared to older children. The study suggests that ground impact in walking, but not running, is mature by age 7 years. Future studies should explore strategies using peak positive acceleration responses to monitor ground impact during sport activities and its application in gait retraining.