The relative importance of total habitual activity and time spent at varying intensities of activ... more The relative importance of total habitual activity and time spent at varying intensities of activity to body fatness is unclear. This study examined the relationship between total activity, minutes spent in moderate-to-vigorous physical activity (MVPA) and vigorous activity with percent body fat in 38 boys (mean age, 9.1 ± 0.7 years) and 38 girls (mean age, 9.0 ± 1.0 years). Percent body fat was estimated using dual-energy X-ray absorptiometry. An RT3 accelerometer was worn for 5.2 ± 0.9 days to assess physical activity. Correlations between activity and percent body fat were significant for total activity (boys: r = -0.42, p = 0.009; girls: r = -0.43, p = 0.008) and ≥vigorous activity (boys: r = -0.46, p = 0.003; girls: r = -0.50, p = 0.002). However, there were no relationships between MVPA and percent body fat. Boys in the lowest sex-specific tertile for vigorous activity (≤ 27 minutes) had higher fat than boys in the higher two tertiles (≥ 27 minutes vigorous activity). Girls in the top sex-specific tertile for MVPA (≥ 127 minutes) had lower fat than girls in the lower tertile (≤ 104.5 minutes). In conclusion, total physical activity and time spent in vigorous activity were more strongly related to body fatness than MVPA in 8-11-year-old boys and girls.
The accurate and reliable assessment of physical activity is necessary for any research study whe... more The accurate and reliable assessment of physical activity is necessary for any research study where physical activity is either an outcome measure or an intervention. The aim of this review is to examine the use of objective measurement techniques for the assessment and interpretation of children's physical activity. Accurate measurement of children's activity is challenging, as the activity is characteristically sporadic and intermittent, consisting of frequent, short bouts. Objective measures of physical activity include heart rate telemetry, pedometry and accelerometry, and each of these methods has strengths and limitations. Heart rate is suited to the measurement of sustained periods of moderate and vigorous activity, pedometry provides a valid measure of total activity, and accelerometry provides a valid measure of total activity as well as the pattern and intensity of activity. As the weaknesses of heart rate and accelerometry for the assessment of activity are not inter-correlated, a combination of the two methods may be more accurate than either method alone. Recent evidence suggests that the Actiheart, an integrated accelerometer and heart rate unit, provides a more accurate prediction of children's energy expenditure than either heart rate or accelerometry alone. However, the cost of the Actiheart is prohibitive for large-scale studies. The pedometer is recommended when only the total amount of physical activity is of interest. When the intensity or the pattern of activity is of interest, accelerometry is the recommended measurement tool.
Exercise-induced muscle damage (EIMD) is characterized by loss of strength, increase in muscle st... more Exercise-induced muscle damage (EIMD) is characterized by loss of strength, increase in muscle stiffness, swelling, and soreness. The aim of this study was to assess the effects of flexibility training of the hamstring muscle group on symptoms of EIMD. Fourteen males (mean ± standard deviation: age = 20.6 ± 0.8 years; mass = 77.3 ± 10.4 kg; height = 1.77 ± 0.05 m) were randomly assigned to a 5-week flexibility (proprioceptive neuromuscular facilitation [PNF]) training or control group. Pre-and post-measures of peak static muscle force at knee joint angles representing decreasing muscle lengths of the hamstrings (25 deg, 30 deg, 40 deg, 80 deg) and flexibility were taken. Flexibility increased significantly following PNF flexibility training (pre-test = 19.4 ± 6.2 cm, post-test = 26.6 ± 6.9 cm), whereas it stayed constant in the control group (pre-test = 16.0 ± 9.3 cm, posttest = 16.7 ± 7.6 cm). Both groups underwent a damaging exercise protocol incorporating six sets of 10 isokinetic eccentric contractions of the hamstrings. Measurements of isometric strength, flexibility, and perceived soreness were recorded prior to and 1, 24, 48 and 72 hours after damage. There was a tendency for the PNF group to recover from strength loss earlier at longer muscle lengths (25 deg, p = 0.06; 30 deg, p = 0.05), but not at shorter muscle lengths. There was no evidence of a protective effect of PNF training on flexibility and soreness. In conclusion, an increase in flexibility of the hamstring muscle group led to some protection from strength loss at long muscle lengths following EIMD.
It is unknown whether relationships detected between physical activity intensity and health diffe... more It is unknown whether relationships detected between physical activity intensity and health differ according to accelerometer thresholds used [sample-specific thresholds (SSTs), published thresholds (PTs) or the individualized activity-related time equivalent (ArteACC)]. SSTs were developed through Acti-Graph calibration in 52 boys, aged 8-10 years. The boys subsequently wore an ActiGraph for seven days. SSTs, PTs and ArteACC for moderate (MPA) and vigorous (VPA) activity were applied. Waist circumference (WC), peak oxygen consumption (VO 2peak ) and blood pressure were assessed. After applying SSTs, 48.9% of boys achieved 60+ minutes of daily MVPA, compared with 8.5% with PTs and 100% with ArteACC. MPA and VPA were correlated with WC and VO 2peak , regardless of whether PTs or SSTs were used (WC: MPA r = -0.37 to -0.43; VO 2peak : r = 0.34 to 0.39, p < 0.05). With ArteACC, only VPA was correlated with WC (r = -0.39, p < 0.01) and VO 2peak (r = 0.35, p < 0.05). Relationships with blood pressure were statistically non-significant. Although estimates of the quantity of activity differed according to thresholds used, relationships detected with health were consistent regardless of whether SSTs or PTs were employed. There was no advantage of using SSTs or individualized thresholds. Researchers are encouraged to use PTs to ensure greater comparability between studies.
This study assessed the nature of the perceived exertion response to treadmill running in 14 heal... more This study assessed the nature of the perceived exertion response to treadmill running in 14 healthy 7-8 year-old children, using the Eston-Parfitt (E-P) Ratings of Perceived Exertion (RPE) scale and a marble dropping task. For the E-P scale and the marble dropping task, the relationships between the RPE and work rate were best described as linear (R2 = .96) and curvilinear (R2 = .94), respectively. This study further suggests that individual respiratory-metabolic cues (oxygen uptake: O2, heart rate: HR, ventilation: VE) may significantly influence the overall RPE to varying degrees in young children. The E-P scale provides an intuitively meaningful and valid means of quantifying the overall perception of exertion in young, healthy children during treadmill running. The marble dropping task is a useful secondary measure of perceived exertion, which provides further insight into the nature of the perceived exertion response to exercise in young children.
Aim: To examine the relevance of physical activity intensity when assessing the relationship betw... more 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.
The international journal of behavioral nutrition and physical activity, Jan 27, 2015
Technological advances have seen a burgeoning industry for accelerometer-based wearable activity ... more Technological advances have seen a burgeoning industry for accelerometer-based wearable activity monitors targeted at the consumer market. The purpose of this study was to determine the convergent validity of a selection of consumer-level accelerometer-based activity monitors. 21 healthy adults wore seven consumer-level activity monitors (Fitbit One, Fitbit Zip, Jawbone UP, Misfit Shine, Nike Fuelband, Striiv Smart Pedometer and Withings Pulse) and two research-grade accelerometers/multi-sensor devices (BodyMedia SenseWear, and ActiGraph GT3X+) for 48-hours. Participants went about their daily life in free-living conditions during data collection. The validity of the consumer-level activity monitors relative to the research devices for step count, moderate to vigorous physical activity (MVPA), sleep and total daily energy expenditure (TDEE) was quantified using Bland-Altman analysis, median absolute difference and Pearson's correlation. All consumer-level activity monitors corre...
The criterion validity of the 2008 Physical Activity and Sedentary Behavior Assessment Questionna... more The criterion validity of the 2008 Physical Activity and Sedentary Behavior Assessment Questionnaire (PASBAQ) was examined in a nationally representative sample of 2,175 persons aged ≥16 years in England using accelerometry. Using accelerometer minutes/day greater than or equal to 200 counts as a criterion, Spearman's correlation coefficient (ρ) for PASBAQ-assessed total activity was 0.30 (95% confidence interval (CI): 0.25, 0.35) in women and 0.20 (95% CI: 0.15, 0.26) in men. Correlations between accelerometer counts/minute of wear time and questionnaire-assessed relative energy expenditure (metabolic equivalent-minutes/day) were higher in women (ρ = 0.41, 95% CI: 0.36, 0.46) than in men (ρ = 0.32, 95% CI: 0.26, 0.38). Similar correlations were observed for minutes/day spent in vigorous activity (women: ρ = 0.39, 95% CI: 0.33, 0.46; men: ρ = 0.31, 95% CI: 0.26, 0.36) and moderate-to-vigorous activity (women: ρ = 0.42, 95% CI: 0.36, 0.48; men: ρ = 0.38, 95% CI: 0.32, 0.45). Corr...
To determine the feasibility and potential role of combining radiostereometric analysis (RSA), ga... more To determine the feasibility and potential role of combining radiostereometric analysis (RSA), gait analysis and activity monitoring in the follow-up of fracture patients. Two patients with similar 41B3 tibial plateau fractures were treated by open reduction internal fixation augmented with impaction bone grafting and were instructed to partial weight bear to 10 kg for the first six postoperative weeks. Fracture reduction and fixation were assessed by postoperative computer tomographic (CT) scanning. Both patients had tantalum markers inserted intra-operatively to monitor their fracture stability during healing using RSA and differentially loaded RSA (DLRSA) at 6 and 12 wk postoperatively. Gait analyses were performed at 1, 2, 6, and 12 wk postoperatively. Activity monitors were worn for 4 wk between the 2 and 6 wk appointments. In addition to gait analysis, knee function was assessed using the patient reported Lysholm scores, and doctor reported knee range of motion and stability, ...
Prior experience of fatiguing tasks is considered essential to establishing an optimal pacing str... more Prior experience of fatiguing tasks is considered essential to establishing an optimal pacing strategy. This study examined the pacing behavior of inexperienced children during self-paced, 800 m running, both individually and within a competitive environment. Thirteen children (aged 9-11 y) completed a graded-exercise test to volitional exhaustion on a treadmill (laboratory trial), followed by three self-paced, individual 800 m time-trials (Trials 1-3) and one self-paced, competitive 800 m time-trial (Trial 4) on an outdoor athletics track. Ratings of perceived exertion (RPE) and heart rate (HR) were measured throughout all trials. Overall performance time improved from Trial 1-3 (250.1 ± 50.4 s & 242.4 ± 51.5 s, respectively, p < .017). The difference in overall performance time between Trials 3 and 4 (260.5 ± 54.2 s) was approaching significance (p = .06). The pacing strategy employed from the outset was consistent across all trials. These findings dispute the notion that an op...
Journal of applied physiology (Bethesda, Md. : 1985), 1999
The relationships between children's activity, aerobic fitness, and fatness are unclear. Indi... more The relationships between children's activity, aerobic fitness, and fatness are unclear. Indirect estimates of activity, e.g., heart rate (HR) and recall, may mask any associations. The purpose of this study was to assess these relationships by using the Tritrac-R3D, a pedometer, and heart rate. Thirty-four children, ages 8-10 yr, participated in the study. The Tritrac and pedometer were worn for up to 6 days. HR was measured for 1 day. Activity measured by Tritrac or pedometer correlated positively to fitness in the whole group (Tritrac, r = 0.66; pedometer, r = 0.59; P < 0.01) and in boys and girls separately (P < 0.05) and correlated negatively to fatness in the whole group (r = -0.42, P < 0.05). In contrast, HR did not correlate significantly to fitness, and HR of >139 beats/min correlated positively to fatness in girls (r = 0.64, P < 0.05). This suggests that HR is misleading as a measure of activity. This study supports a positive relationship between activi...
Journal of applied physiology (Bethesda, Md. : 1985), 1998
Heart rate telemetry is frequently used to estimate daily activity in children and to validate ot... more Heart rate telemetry is frequently used to estimate daily activity in children and to validate other methods. This study compared the accuracy of heart rate monitoring, pedometry, triaxial accelerometry, and uniaxial accelerometry for estimating oxygen consumption during typical children's activities. Thirty Welsh children (mean age 9.2 +/- 0.8 yr) walked (4 and 6 km/h) and ran (8 and 10 km/h) on a treadmill, played catch, played hopscotch, and sat and crayoned. Heart rate, body accelerations in three axes, pedometry counts, and oxygen uptake were measured continuously during each 4-min activity. Oxygen uptake was expressed as a ratio of body mass raised to the power of 0.75 [scaled oxygen uptake (sVO2)]. All measures correlated significantly (P < 0.001) with sVO2. A multiple-regression equation that included triaxial accelerometry counts and heart rate predicted sVO2 better than any measure alone (R2 = 0.85, standard error of the estimate = 9.7 ml.kg-0.75.min-1). The best of...
Comparisons of isonitrogenous supplements (1.2 g N) of essential amino acids and five keto acid a... more Comparisons of isonitrogenous supplements (1.2 g N) of essential amino acids and five keto acid analogues with four essential amino acids were made in seven patients with stable chronic renal failure (creatinine clearance, 4.6 to 16 ml/min) on moderately protein-restricted diets (4.60 to 7.8 g N per day). Full nitrogen balance data on the four patients who have already completed studies lasting 24 weeks are presented. No benefits of keto acid over amino acid supplements were observed. Two transient episodes of hypercalcemia occurred during keto acid treatment. There was no improvement of renal function with keto acids. Also, no carry-over effects were seen after keto acid treatment. It is concluded that any beneficial effects of keto acids in patients with chronic renal failure are only likely to occur in those taking a diet of less than 30 g protein daily.
The relative importance of total habitual activity and time spent at varying intensities of activ... more The relative importance of total habitual activity and time spent at varying intensities of activity to body fatness is unclear. This study examined the relationship between total activity, minutes spent in moderate-to-vigorous physical activity (MVPA) and vigorous activity with percent body fat in 38 boys (mean age, 9.1 ± 0.7 years) and 38 girls (mean age, 9.0 ± 1.0 years). Percent body fat was estimated using dual-energy X-ray absorptiometry. An RT3 accelerometer was worn for 5.2 ± 0.9 days to assess physical activity. Correlations between activity and percent body fat were significant for total activity (boys: r = -0.42, p = 0.009; girls: r = -0.43, p = 0.008) and ≥vigorous activity (boys: r = -0.46, p = 0.003; girls: r = -0.50, p = 0.002). However, there were no relationships between MVPA and percent body fat. Boys in the lowest sex-specific tertile for vigorous activity (≤ 27 minutes) had higher fat than boys in the higher two tertiles (≥ 27 minutes vigorous activity). Girls in the top sex-specific tertile for MVPA (≥ 127 minutes) had lower fat than girls in the lower tertile (≤ 104.5 minutes). In conclusion, total physical activity and time spent in vigorous activity were more strongly related to body fatness than MVPA in 8-11-year-old boys and girls.
The accurate and reliable assessment of physical activity is necessary for any research study whe... more The accurate and reliable assessment of physical activity is necessary for any research study where physical activity is either an outcome measure or an intervention. The aim of this review is to examine the use of objective measurement techniques for the assessment and interpretation of children's physical activity. Accurate measurement of children's activity is challenging, as the activity is characteristically sporadic and intermittent, consisting of frequent, short bouts. Objective measures of physical activity include heart rate telemetry, pedometry and accelerometry, and each of these methods has strengths and limitations. Heart rate is suited to the measurement of sustained periods of moderate and vigorous activity, pedometry provides a valid measure of total activity, and accelerometry provides a valid measure of total activity as well as the pattern and intensity of activity. As the weaknesses of heart rate and accelerometry for the assessment of activity are not inter-correlated, a combination of the two methods may be more accurate than either method alone. Recent evidence suggests that the Actiheart, an integrated accelerometer and heart rate unit, provides a more accurate prediction of children's energy expenditure than either heart rate or accelerometry alone. However, the cost of the Actiheart is prohibitive for large-scale studies. The pedometer is recommended when only the total amount of physical activity is of interest. When the intensity or the pattern of activity is of interest, accelerometry is the recommended measurement tool.
Exercise-induced muscle damage (EIMD) is characterized by loss of strength, increase in muscle st... more Exercise-induced muscle damage (EIMD) is characterized by loss of strength, increase in muscle stiffness, swelling, and soreness. The aim of this study was to assess the effects of flexibility training of the hamstring muscle group on symptoms of EIMD. Fourteen males (mean ± standard deviation: age = 20.6 ± 0.8 years; mass = 77.3 ± 10.4 kg; height = 1.77 ± 0.05 m) were randomly assigned to a 5-week flexibility (proprioceptive neuromuscular facilitation [PNF]) training or control group. Pre-and post-measures of peak static muscle force at knee joint angles representing decreasing muscle lengths of the hamstrings (25 deg, 30 deg, 40 deg, 80 deg) and flexibility were taken. Flexibility increased significantly following PNF flexibility training (pre-test = 19.4 ± 6.2 cm, post-test = 26.6 ± 6.9 cm), whereas it stayed constant in the control group (pre-test = 16.0 ± 9.3 cm, posttest = 16.7 ± 7.6 cm). Both groups underwent a damaging exercise protocol incorporating six sets of 10 isokinetic eccentric contractions of the hamstrings. Measurements of isometric strength, flexibility, and perceived soreness were recorded prior to and 1, 24, 48 and 72 hours after damage. There was a tendency for the PNF group to recover from strength loss earlier at longer muscle lengths (25 deg, p = 0.06; 30 deg, p = 0.05), but not at shorter muscle lengths. There was no evidence of a protective effect of PNF training on flexibility and soreness. In conclusion, an increase in flexibility of the hamstring muscle group led to some protection from strength loss at long muscle lengths following EIMD.
It is unknown whether relationships detected between physical activity intensity and health diffe... more It is unknown whether relationships detected between physical activity intensity and health differ according to accelerometer thresholds used [sample-specific thresholds (SSTs), published thresholds (PTs) or the individualized activity-related time equivalent (ArteACC)]. SSTs were developed through Acti-Graph calibration in 52 boys, aged 8-10 years. The boys subsequently wore an ActiGraph for seven days. SSTs, PTs and ArteACC for moderate (MPA) and vigorous (VPA) activity were applied. Waist circumference (WC), peak oxygen consumption (VO 2peak ) and blood pressure were assessed. After applying SSTs, 48.9% of boys achieved 60+ minutes of daily MVPA, compared with 8.5% with PTs and 100% with ArteACC. MPA and VPA were correlated with WC and VO 2peak , regardless of whether PTs or SSTs were used (WC: MPA r = -0.37 to -0.43; VO 2peak : r = 0.34 to 0.39, p < 0.05). With ArteACC, only VPA was correlated with WC (r = -0.39, p < 0.01) and VO 2peak (r = 0.35, p < 0.05). Relationships with blood pressure were statistically non-significant. Although estimates of the quantity of activity differed according to thresholds used, relationships detected with health were consistent regardless of whether SSTs or PTs were employed. There was no advantage of using SSTs or individualized thresholds. Researchers are encouraged to use PTs to ensure greater comparability between studies.
This study assessed the nature of the perceived exertion response to treadmill running in 14 heal... more This study assessed the nature of the perceived exertion response to treadmill running in 14 healthy 7-8 year-old children, using the Eston-Parfitt (E-P) Ratings of Perceived Exertion (RPE) scale and a marble dropping task. For the E-P scale and the marble dropping task, the relationships between the RPE and work rate were best described as linear (R2 = .96) and curvilinear (R2 = .94), respectively. This study further suggests that individual respiratory-metabolic cues (oxygen uptake: O2, heart rate: HR, ventilation: VE) may significantly influence the overall RPE to varying degrees in young children. The E-P scale provides an intuitively meaningful and valid means of quantifying the overall perception of exertion in young, healthy children during treadmill running. The marble dropping task is a useful secondary measure of perceived exertion, which provides further insight into the nature of the perceived exertion response to exercise in young children.
Aim: To examine the relevance of physical activity intensity when assessing the relationship betw... more 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.
The international journal of behavioral nutrition and physical activity, Jan 27, 2015
Technological advances have seen a burgeoning industry for accelerometer-based wearable activity ... more Technological advances have seen a burgeoning industry for accelerometer-based wearable activity monitors targeted at the consumer market. The purpose of this study was to determine the convergent validity of a selection of consumer-level accelerometer-based activity monitors. 21 healthy adults wore seven consumer-level activity monitors (Fitbit One, Fitbit Zip, Jawbone UP, Misfit Shine, Nike Fuelband, Striiv Smart Pedometer and Withings Pulse) and two research-grade accelerometers/multi-sensor devices (BodyMedia SenseWear, and ActiGraph GT3X+) for 48-hours. Participants went about their daily life in free-living conditions during data collection. The validity of the consumer-level activity monitors relative to the research devices for step count, moderate to vigorous physical activity (MVPA), sleep and total daily energy expenditure (TDEE) was quantified using Bland-Altman analysis, median absolute difference and Pearson's correlation. All consumer-level activity monitors corre...
The criterion validity of the 2008 Physical Activity and Sedentary Behavior Assessment Questionna... more The criterion validity of the 2008 Physical Activity and Sedentary Behavior Assessment Questionnaire (PASBAQ) was examined in a nationally representative sample of 2,175 persons aged ≥16 years in England using accelerometry. Using accelerometer minutes/day greater than or equal to 200 counts as a criterion, Spearman's correlation coefficient (ρ) for PASBAQ-assessed total activity was 0.30 (95% confidence interval (CI): 0.25, 0.35) in women and 0.20 (95% CI: 0.15, 0.26) in men. Correlations between accelerometer counts/minute of wear time and questionnaire-assessed relative energy expenditure (metabolic equivalent-minutes/day) were higher in women (ρ = 0.41, 95% CI: 0.36, 0.46) than in men (ρ = 0.32, 95% CI: 0.26, 0.38). Similar correlations were observed for minutes/day spent in vigorous activity (women: ρ = 0.39, 95% CI: 0.33, 0.46; men: ρ = 0.31, 95% CI: 0.26, 0.36) and moderate-to-vigorous activity (women: ρ = 0.42, 95% CI: 0.36, 0.48; men: ρ = 0.38, 95% CI: 0.32, 0.45). Corr...
To determine the feasibility and potential role of combining radiostereometric analysis (RSA), ga... more To determine the feasibility and potential role of combining radiostereometric analysis (RSA), gait analysis and activity monitoring in the follow-up of fracture patients. Two patients with similar 41B3 tibial plateau fractures were treated by open reduction internal fixation augmented with impaction bone grafting and were instructed to partial weight bear to 10 kg for the first six postoperative weeks. Fracture reduction and fixation were assessed by postoperative computer tomographic (CT) scanning. Both patients had tantalum markers inserted intra-operatively to monitor their fracture stability during healing using RSA and differentially loaded RSA (DLRSA) at 6 and 12 wk postoperatively. Gait analyses were performed at 1, 2, 6, and 12 wk postoperatively. Activity monitors were worn for 4 wk between the 2 and 6 wk appointments. In addition to gait analysis, knee function was assessed using the patient reported Lysholm scores, and doctor reported knee range of motion and stability, ...
Prior experience of fatiguing tasks is considered essential to establishing an optimal pacing str... more Prior experience of fatiguing tasks is considered essential to establishing an optimal pacing strategy. This study examined the pacing behavior of inexperienced children during self-paced, 800 m running, both individually and within a competitive environment. Thirteen children (aged 9-11 y) completed a graded-exercise test to volitional exhaustion on a treadmill (laboratory trial), followed by three self-paced, individual 800 m time-trials (Trials 1-3) and one self-paced, competitive 800 m time-trial (Trial 4) on an outdoor athletics track. Ratings of perceived exertion (RPE) and heart rate (HR) were measured throughout all trials. Overall performance time improved from Trial 1-3 (250.1 ± 50.4 s & 242.4 ± 51.5 s, respectively, p < .017). The difference in overall performance time between Trials 3 and 4 (260.5 ± 54.2 s) was approaching significance (p = .06). The pacing strategy employed from the outset was consistent across all trials. These findings dispute the notion that an op...
Journal of applied physiology (Bethesda, Md. : 1985), 1999
The relationships between children's activity, aerobic fitness, and fatness are unclear. Indi... more The relationships between children's activity, aerobic fitness, and fatness are unclear. Indirect estimates of activity, e.g., heart rate (HR) and recall, may mask any associations. The purpose of this study was to assess these relationships by using the Tritrac-R3D, a pedometer, and heart rate. Thirty-four children, ages 8-10 yr, participated in the study. The Tritrac and pedometer were worn for up to 6 days. HR was measured for 1 day. Activity measured by Tritrac or pedometer correlated positively to fitness in the whole group (Tritrac, r = 0.66; pedometer, r = 0.59; P < 0.01) and in boys and girls separately (P < 0.05) and correlated negatively to fatness in the whole group (r = -0.42, P < 0.05). In contrast, HR did not correlate significantly to fitness, and HR of >139 beats/min correlated positively to fatness in girls (r = 0.64, P < 0.05). This suggests that HR is misleading as a measure of activity. This study supports a positive relationship between activi...
Journal of applied physiology (Bethesda, Md. : 1985), 1998
Heart rate telemetry is frequently used to estimate daily activity in children and to validate ot... more Heart rate telemetry is frequently used to estimate daily activity in children and to validate other methods. This study compared the accuracy of heart rate monitoring, pedometry, triaxial accelerometry, and uniaxial accelerometry for estimating oxygen consumption during typical children's activities. Thirty Welsh children (mean age 9.2 +/- 0.8 yr) walked (4 and 6 km/h) and ran (8 and 10 km/h) on a treadmill, played catch, played hopscotch, and sat and crayoned. Heart rate, body accelerations in three axes, pedometry counts, and oxygen uptake were measured continuously during each 4-min activity. Oxygen uptake was expressed as a ratio of body mass raised to the power of 0.75 [scaled oxygen uptake (sVO2)]. All measures correlated significantly (P < 0.001) with sVO2. A multiple-regression equation that included triaxial accelerometry counts and heart rate predicted sVO2 better than any measure alone (R2 = 0.85, standard error of the estimate = 9.7 ml.kg-0.75.min-1). The best of...
Comparisons of isonitrogenous supplements (1.2 g N) of essential amino acids and five keto acid a... more Comparisons of isonitrogenous supplements (1.2 g N) of essential amino acids and five keto acid analogues with four essential amino acids were made in seven patients with stable chronic renal failure (creatinine clearance, 4.6 to 16 ml/min) on moderately protein-restricted diets (4.60 to 7.8 g N per day). Full nitrogen balance data on the four patients who have already completed studies lasting 24 weeks are presented. No benefits of keto acid over amino acid supplements were observed. Two transient episodes of hypercalcemia occurred during keto acid treatment. There was no improvement of renal function with keto acids. Also, no carry-over effects were seen after keto acid treatment. It is concluded that any beneficial effects of keto acids in patients with chronic renal failure are only likely to occur in those taking a diet of less than 30 g protein daily.
Uploads
Papers by Alex Rowlands