The impact of ActiGraph's low-frequency extension filter on measurement of children's physical activity.

This study examines differences in accelerometer-based measurements of children's movement with and without applying ActiGraph's low-frequency extension (LFE) filter. Thirty children wore ActiGraph GT9X devices during structured physical activity (PA) periods. Raw accelerometry data for each activity period were processed with and without the LFE filter applied. For each activity period, paired t-tests were used to compare vector magnitude counts and minutes spent in moderate-to-vigorous physical activity (MVPA) with and without the LFE filter applied. Repeated measures MANOVA models were used for compositional data analysis of the percentage of time spent in sedentary behaviour and light, moderate, and vigorous PA with and without the LFE filter applied. Applying the LFE filter significantly increased vector magnitude counts and estimated minutes spent in MVPA for all activity periods when compared to the normal filter. For brisk walking, the LFE filter had a significant impact on the composition of time spent in sedentary behaviour and PA intensities. Children's activity data processed with the LFE filter may not be compatible with cut-points for activity levels developed with the normal filter, and caution should be taken when comparing children's activity levels or movement data between studies that do and do not use the LFE filter.

Physical Activity and Enjoyment in Parent-Child Dyads During Shared Physical Activity.

Purpose: The purpose of this study was to compare objectively-measured physical activity (PA) and enjoyment of five shared PAs in parent-child dyads. Method: Thirty-one parent-child dyads (mean±SD; age, parents: 38.0 ± 6.6 years, children: 5.9 ± 1.7 years) completed separate PA sessions, which included five standardized PAs (brisk walking, jumping games, dancing, body-weight exercises, and tag games) in random order for each dyad. Parent and child moderate-to-vigorous PA (MVPA) and accelerometer counts per minute (CPM) were measured using Actigraph GT9X activity monitors. The Visual Analog Scale was used to assess enjoyment of children and parents. Repeated measures ANOVAs and paired t-tests determined differences in PA within and between children and parents for the activities, respectively. Friedman Tests with post hoc Wilcoxon signed-rank tests determined significant differences in enjoyment across the activities for children and parents and Wilcoxon signed-rank tests compared enjoyment between children and parents for each PA. Results: Jumping games resulted in the highest proportion of time spent in MVPA and highest overall CPM for children and parents (p < .05). Compared to parents, children spent proportionally more time in MVPA during jumping games, body-weight exercises, and tag games (all, p < .05). Tag games were the most enjoyable PA for children and parents (p < .05). Children enjoyed body-weight exercises more than parents (p < .05). Conclusions: Future indoor PA programs and research interventions that include parent-child dyads should consider implementing jumping games, body-weight exercises, and tag games during shared PA, which resulted in higher MVPA and enjoyment by both children and parents when compared to walking and dancing.

Validity and reliability of a Chinese rating of perceived exertion scale in young Mandarin speaking adults.

Background: The validity and reliability of the Borg 6-20 rating of perceived exertion (RPE) scale has not been tested among Chinese people from Mainland China. The purpose of this study was to test: 1) The validity of Leung Chinese version and Wang Chinese version of the Borg 6-20 RPE scale; 2) The reliability of Wang Chinese version RPE scale; and 3) The agreement of these two Chinese versions of the RPE scale among young healthy adults from Mainland China. Methods: A total of 26 subjects (11 males, 15 females; age 22.7 ±â€¯3.0 yrs) volunteered to participate. They performed one (n = 3), two (n = 14), or three trials (n = 9) of the Bruce treadmill protocol test within 9.0 ±â€¯5.1 days (validation trials), and 30.4 ±â€¯27.9 days (reliability trials). Power output, heart rate, oxygen consumption, and RPE were recorded. Results: RPE was significantly correlated with power output (Leung version rs ≥ 0.75, Wang version rs ≥ 0.73), heart rate (HR) (Leung version rs ≥ 0.84, Wang version rs  ≥ 0.87), and oxygen consumption (VO2) (Leung version rs  ≥ 0.80, Wang version rs ≥ 0.81) (all p < 0.01). The overall test-retest interclass correlation was 0.94 (p < 0.01). No significant differences in correlations (RPE against power output, HR and VO2) between trials existed for the reliability tests of Wang version scale. No significant differences in correlations (RPE against power output, HR and VO2) between the two Chinese versions of RPE scale existed. Conclusion: Both Chinese RPE scales are valid among young healthy Chinese mandarin speaking adults. The Wang scale is reliable, and the Leung and Wang scales show superior agreement with each other.

The Effects of Varying Structured Physical Activity Duration on Young Children's and Parents' Activity Levels.

Purpose: The purpose of this study was to examine whether structured physical activity (PA) in a family-based community exercise program affects PA of young children and parents. Method: Twenty-two children (mean ± SD; age, 4.9 ± 2.1 years) and their parents (age, 34.3 ± 7.6 years) participated in unstructured PA sessions followed by either short- or long-duration structured PA sessions, while wearing an ActiGraph GT9X activity monitor on their right hip to estimate PA. Independent t-tests compared children's and parents' PA during short- and long-structured PA sessions. Paired t-tests compared short- versus long-structured PA sessions. A mixed model ANOVA compared PA during unstructured versus structured sessions and between children and parents. Results: Children spent proportionately more time in moderate-to-vigorous PA (MVPA) and had higher accelerometer counts/min than parents during short-structured PA (children:60.9 ± 18.8% vs. parents:17.7 ± 6.8%, children:3870 ± 742 vs. parents:1836 ± 556 counts/min, p < .05) and long-structured PA (children:61.1 ± 20.1% vs. parents:12.6 ± 4.9%, children:3415 ± 758 vs. parents:1604 ± 633 counts/min, p < .05). No statistical differences were found between short- and long-structured PA sessions for proportion of time spent in MVPA or counts/min for children or parents (all, p > .05). Children spent proportionally more time in MVPA and had higher counts/min during unstructured PA compared to structured PA (unstructured MVPA:54.4 ± 3.9% vs. structured MVPA:38.2 ± 4.2%, unstructured counts/min:3830 ± 222 vs. structured counts/min:2768 ± 239 counts/min; p < .05). Conclusions: Children were more active than parents during both the unstructured and structured PA sessions. However, unstructured PA sessions resulted in 63-77% and 10-11% of PA recommendations for children and adults, respectively. Family-based exercise programming can provide an opportunity for children and their parents to attain MVPA during the week.

Perceived exertion during resistance exercise by children.

This pilot study examined the validity of a new scale of perceived exertion during acute bouts of resistance exercise in young children. The researchers developed an 11-point numerical scale with five pictures representing youths at various levels of exertion while lifting weights. 26 children (M age 10.1 +/- 1.2 yr.) performed one set of 10 repetitions at 35%, 55%, and 75% of their one-repetition maximum on the chest press and leg press exercises using child-size weight training machines. Scaling procedures for the perceptual anchors on the perceived exertion scale were based on one repetition maximum testing. Children could use this scale to translate into numbers their perceptions of physical exertion during upper and lower body resistance exercise. Perceived exertion distributed as a positive linear function of the percent of one repetition maximum on the chest press and leg press exercises (rs = .70 to .77), and perceived exertion increased significantly across all three exercise intensities on both exercises. These preliminary findings provide partial evidence for validation when this scale was used during resistance exercise with children. Additional validation regarding perceived exertion during resistance exercise with children is warranted.

Maximal strength testing in healthy children.

Strength training has become an accepted method of conditioning in children. However, there is concern among some observers that maximal strength testing may be inappropriate or potentially injurious to children. The purpose of this study was to evaluate the safety and efficacy of 1 repetition maximum (1RM) strength testing in healthy children. Thirty-two girls and 64 boys between 6.2 and 12.3 years of age (mean age 9.3 +/- 1.6 years) volunteered to participate in this study. All subjects were screened for medical conditions that could worsen during maximal strength testing. Under close supervision by qualified professionals, each subject performed a 1RM test on 1 upper-body (standing chest press or seated chest press) and 1 lower-body (leg press or leg extension) exercise using child-size weight training machines. No injuries occurred during the study period, and the testing protocol was well tolerated by the subjects. No gender differences were found for any upper- or lower-body strength test. These findings demonstrate that healthy children can safely perform 1RM strength tests, provided that appropriate procedures are followed.

Comparison of 1 and 2 days per week of strength training in children.

The purpose of this study was to compare the effects of 1 and 2 days per week of strength training on upper body strength, lower body strength, and motor performance ability in children. Twenty-one girls and 34 boys between the ages of 7.1 and 12.3 years volunteered to participate in this study. Participants strength trained either once per week (n = 22) or twice per week (n = 20) for 8 weeks at a community-based youth fitness center. Each training session consisted of a single set of 10-15 repetitions on 12 exercises using child-size weight machines. Thirteen children who did not strength train served as age-matched controls. One repetition maximum (1RM) strength on the chest press and leg press, handgrip strength, long jump, vertical jump, and flexibility were assessed at baseline and posttraining. Only participants who strength trained twice per week made significantly greater gains in 1RM chest press strength, compared to the control group (11.5 and 4.4% respectively, p < .05). Participants who trained once and twice per week made gains in 1RM leg press strength (14.2 and 24.7%, respectively) that were significantly greater than control group gains (2.4%). On average, participants who strength trained once per week achieved 67% of the 1RM strength gains. No significant differences between groups were observed on other outcome measures. These findings support the concept that muscular strength can be improved during the childhood years and favor a training frequency of twice per week for children participating in an introductory strength training program.