Portable Metabolic Measurement System Research Articles

Accelerometer Calibration: The Importance of Considering Functionality.

To compare the accuracy and precision of a hip-worn accelerometer to predict energy cost during structured activities across motor performance and disease conditions. 118 adults self-identifying as healthy (n = 44) and those with arthritis (n = 23), multiple sclerosis (n = 18), Parkinson's disease (n = 17), and stroke (n =18) underwent measures of motor performance and were categorized into groups: Group 1, usual; Group 2, moderate impairment; and Group 3, severe impairment. The participants completed structured activities while wearing an accelerometer and a portable metabolic measurement system. Accelerometer-predicted energy cost (metabolic equivalent of tasks [METs]) were compared with measured METs and evaluated across functional impairment and disease conditions. Statistical significance was assessed using linear mixed effect models and Bayesian information criteria to assess model fit. All activities' accelerometer counts per minute (CPM) were 29.5-72.6% less for those with disease compared with those who were healthy. The predicted MET bias was similar across disease, -0.49 (-0.71, -0.27) for arthritis, -0.38 (-0.53, -0.22) for healthy, -0.44 (-0.68, -0.20) for MS, -0.34 (-0.58, -0.09) for Parkinson's, and -0.30 (-0.54, -0.06) for stroke. For functional impairment, there was a graded reduction in CPM for all activities: Group 1, 1,215 CPM (1,129, 1,301); Group 2, 789 CPM (695, 884); and Group 3, 343 CPM (220, 466). The predicted MET bias revealed similar results across the Group 1, -0.37 METs (-0.52, -0.23); Group 2, -0.44 METs (-0.60, -0.28); and Group 3, -0.33 METs (-0.55, -0.13). The Bayesian information criteria showed a better model fit for functional impairment compared with disease condition. Using functionality to improve accelerometer calibration could decrease variability and warrants further exploration to improve accelerometer prediction of physical activity.

Wrist-worn triaxial accelerometry predicts the energy expenditure of non-vigorous daily physical activities.

Triaxial accelerometry is commonly used to estimate oxygen uptake (VO2) and energy expenditure in health and fitness studies. We tested the correlation of a triaxial accelerometer in terms of a summation of vector magnitudes with gravity subtracted (SVMgs) and measured VO2 for different daily physical activities. Original research, cross-sectional. Twenty volunteers wore a triaxial accelerometer on both wrists while performing 12 assigned daily physical activities for 6min for each activity. The VO2 was determined by indirect calorimetry using a portable metabolic measurement system. The last 3min of each activity was assumed to represent steady-state. The VO2 measured during these periods was averaged and converted into metabolic equivalents (METs). The range of VO2 for all activities was 0.18-3.2L/min (0.8-12.2 METs). Significant differences in SVMgs existed between accelerometer placements on the dominant (120.9±8.7gmin) versus non-dominant hand (99.9±6.8gmin; P=0.016) for the lowest levels of physical activity defined as <1.5 METs. Piecewise linear regression model using 6 METs as the transition point showed similar significant correlations for the non-dominant wrist (r2=0.85; P<0.001) and the dominant wrist (r2=0.86; P<0.001). Using the non-dominant wrist below 6 METs, the slope of the relationship between SVMgs and METs was 105.3±4.3 (95% CI 96.9 to 113.7) indicating an increase in SVMgs of approximately 100 units for every MET increase in oxygen uptake. Wrist-worn triaxial accelerometry reliably predicted energy expenditure during common physical activities <6 METs. More consistent correlations were found when the accelerometer was worn on the non-dominant wrist rather than the dominant wrist.

Is the Veterans Specific Activity Questionnaire Valid to Assess Older Adults Aerobic Fitness?

Aerobic fitness in older adults is related to health status, incident disability, nursing home admission, and all-cause mortality. The most accurate quantification of aerobic fitness, expressed as peak oxygen consumption in mL·kg·min, is the cardiorespiratory exercise test; however, it is not feasible in all settings and might offer risk to patients. The Veterans Specific Activity Questionnaire (VSAQ) is a 13-item self-administered symptom questionnaire that estimates aerobic fitness expressed in metabolic equivalents (METs) and has been validated to cardiovascular patients. The purpose of this study was to assess the validity and reliability of the VSAQ in older adults without specific health conditions. A methodological study with a cross-sectional design was conducted with 28 older adults (66-86 years). The VSAQ was administered on 3 occasions by 2 evaluators. Aerobic capacity in METs as measured by the VSAQ was compared with the METs found in an incremental shuttle walk test (ISWT) performed with a portable metabolic measurement system and with accelerometer data. The validity of the VSAQ was found to be moderate-to-good when compared with the METs and distance measured by the ISWT and with the moderate activity per day and steps per day obtained by accelerometry. The Bland-Altman graph analysis showed no values outside the limits of agreement, suggesting good precision between the METs estimated by questionnaire and the METs measured by the ISWT. Also, the intrarater and interrater reliabilities of the instrument were good. The results showed that the VSAQ is a valuable tool to assess the aerobic fitness of older adults.

Validation of Heart Rate Derived from a Physiological Status Monitor-Embedded Compression Shirt Against Criterion ECG

Firefighters are subject to extreme environments and high physical demands when performing duty-related tasks. Recently, physiological status monitors (PSM) have been embedded into a compression shirt to enable firefighters to measure, visualize, log, and transmit vital metrics such as heart rate (HR) to aid in cardiovascular risk identification and mitigation, thereby attempting to improve the health, fitness, and safety of this population. The purpose of this study was to validate HR recorded by the PSM-embedded compression shirt against a criterion standard laboratory ECG-derived HR when worn concurrently with structural firefighting personal protective equipment (PPE) during four simulated firefighting activities. Ten healthy, college-age men (mean ± SD: age: 21 ± 1 yr; body mass: 91 ± 10 kg; body mass index: 26.9 ± 3.1 kg/m2) completed four tasks that are routinely performed during firefighting operations: outdoor fast-paced walking (FW), treadmill walking (TW), searching/crawling (SC), and ascending/descending stairs (AD). They wore the PSM-embedded compression shirt under structural firefighting PPE. HR was recorded concurrently by the PSM-embedded compression shirt and a portable metabolic measurement system accompanied with a standard 12-lead electrocardiograph that was used to provide criterion measures of HR. For all four tasks combined there was very high correlation of PSM and ECG HR (r > 0.99; SEE 0.84 /min) with a mean difference (bias) of −0.02 /min and limits of agreement of −0.07 to 0.02 /min. For individual tasks, the correlations were also high (r-values = 0.99; SEE 0.81–0.89). The mean bias (limits of agreement) was: FW 0.03 (-0.09 to 0.14); TW 0.04 (−0.05 to 0.12); SC −0.01 (−0.12 to 0.10); AD −0.13 (−0.21 to −0.04) /min. These findings demonstrate that the PSM-embedded compression shirt provides a valid measure of HR during simulated firefighting activities when compared with a standard 12-lead ECG.

Energy Expenditure During a 160 km Endurance Race

IntroductionIn endurance racing, horses are required to complete distances of up to 160 km in a single day. To date, the energy expenditure (EE) of such effort has not been quantified. This study aimed to evaluate EE during a 160 km endurance race from heart rate (HR) monitoring.MethodsThree weeks before competing, two endurance horses (H1 and H2) were submitted to a field exercise test to determine their individual VO2‐HR relationship. VO2 and HR were recorded simultaneously at trot (13–14 km/h for 10 min), and at canter (18–19 km/h for 10 min, and 22–23 km/h for 5 min), using the equine K4b2, a portable metabolic measurement system. H1 was then enrolled in Monpazier CEI and H2 in Florac CEI. HR was monitored from 2 minutes before the start to the finishing line of each loop. EE of exercise was calculated from individual VO2‐HR relationship and caloric equivalent of oxygen.ResultsH1 and H2 completed the race at an average speed of 17.02 and 14.46 km/h, respectively. Mean HR was 108 ± 8 and 124 ± 24 and peak HR was 169 and 204 for H1 and H2, respectively. The proportion of time spent at HR≥180 was 0 and 2.7% for H1 and H2 respectively. EE of exercise was evaluated at 177 and 240 MJ for H1 and H2 respectively.ConclusionsA 160‐km endurance race might present a considerable energy cost, at least 5 times the EE of non‐working state.Ethical Animal ResearchThe project was conducted under license from the Department of Health and Animal Care of the French Veterinary Authority (no. A21002) and ethics committee approval n° B0710. Sources of funding: Burgundy Region and AgroSup Dijon. Competing interests: none.

Evaluation of a Wearable Physiological Status Monitor During Simulated Fire Fighting Activities

A physiological status monitor (PSM) has been embedded in a fire-resistant shirt. The purpose of this research study was to examine the ability of the PSM-shirt to accurately detect heart rate (HR) and respiratory rate (RR) when worn under structural fire fighting personal protective equipment (PPE) during the performance of various activities relevant to fire fighting. Eleven healthy, college-aged men completed three activities (walking, searching/crawling, and ascending/descending stairs) that are routinely performed during fire fighting operations while wearing the PSM-shirt under structural fire fighting PPE. Heart rate and RR recorded by the PSM-shirt were compared to criterion values measured concurrently with an ECG and portable metabolic measurement system, respectively. For all activities combined (overall) and for each activity, small differences were found between the PSM-shirt and ECG (mean difference [95%CI]: overall: −0.4 beats/min [−0.8, −0.1]; treadmill: −0.4 beats/min [−0.7, −0.1]; search: −1.7 beats/min [−3.1, −.04]; stairs: 0.4 beats/min [0.04, 0.7]). Standard error of the estimate was 3.5 beats/min for all tasks combined and 1.9, 5.9, and 1.9 beats/min for the treadmill walk, search, and stair ascent/descent, respectively. Correlations between the PSM-shirt and criterion heart rates were high (r = 0.95 to r = 0.99). The mean difference between RR recorded by the PSM-shirt and criterion overall was 1.1 breaths/min (95%CI: −1.9 to −0.4). The standard error of the estimate for RR ranged from 4.2 breaths/min (treadmill) to 8.2 breaths/min (search), with an overall value of 6.2 breaths/min. These findings suggest that the PSM-shirt provides valid measures of HR and useful approximations of RR when worn during fire fighting duties.

Test–Retest Reliability of Portable Metabolic Monitoring After Disabling Stroke

Purpose. Impaired economy of gait, prevalent in chronic stroke secondary to residual gait deficits, is associated with intolerance for performing activities of daily living. Gait economy/efficiency is traditionally assessed by determining the rate of oxygen consumption during submaximal treadmill walking. However, the mechanics and energetics of treadmill versus overground walking are very different in stroke survivors with ambulatory deficits. Clearly, overground cardiopulmonary measures are needed to accurately profile movement economy after stroke. An obstacle to obtaining such measures after stroke has been the absence of reliable portable metabolic monitoring equipment. The purpose of this study was to establish the test–retest reliability of a portable metabolic monitoring device during overground walking in hemiparetic stroke survivors. Methods. Twenty-three chronic hemiparetic stroke survivors underwent two 6-minute walk tests while wearing a COSMED K4b2 portable metabolic measurement system. Intraclass correlations coefficients (ICC) were calculated for both cardiopulmonary parameters and distance covered to determine test–retest reliability. An ICC of ≥0.85 was considered reliable. Results. ICCs for relative Vo2 (0.90), absolute Vo2 (0.93), Vco2 (0.93), and minute ventilation (0.95) demonstrated high reliability, but not for heart rate (0.76) or respiratory exchange ratio (0.64). There was no significant difference in the distance each participant walked between the first and second tests, eliminating distance as a potential confounder of our analyses (ICC = 0.99). Conclusions. Our results strongly support the reliability of the K4b2 for quantifying overground gait efficiency after stroke. Use of this device may enable researchers to study how varying poststroke rehabilitation interventions affect this central measure of health and function.

Validation of the Actical Activity Monitor in Middle-Aged and Older Adults

This study was designed to validate the Actical activity monitor in middle-aged and older adults of varying body composition to develop accelerometer thresholds to distinguish between light and moderate intensity physical activity (PA). Nonobese 45 to 64 yr (N = 29), obese 45 to 64 yr (N = 21), and ≥65 yr (N = 23; varying body composition) participants completed laboratory-based sitting, household, and locomotive activities while wearing an Actical monitor and a portable metabolic measurement system. Nonlinear regression analysis was used to identify activity count (AC) cut-points to differentiate between light intensity (<3 METs) and moderate intensity (≥3METs) PA. Using group-specific algorithms, AC cut points for 3 METs were 1634, 1107, and 431 for the obese 45 to 64 yr group, nonobese 45 to 64 yr group, and ≥65 yr group, respectively. However, sensitivity and specificity analysis revealed that an AC cut-point of 1065 yielded similar accuracy for detecting an activity as less than or greater than 3 METs, regardless of age and body composition. For the Actical activity monitor, an AC cut-point of 1065 can be used to determine light and moderate intensity PA in people ≥45 years of age.

Reliability of the VmaxST Portable Metabolic Measurement System

The purpose of this study was to evaluate the reliability of the VmaxST portable metabolic measurement system. Forty-five healthy adults (age = 25.7 +/- 5.9 yr; height = 171.8 +/- 9.1 cm; weight = 69.6 +/- 12.8 kg; VO2peak) = 40.7 ml/kg/min; percent fat = 21.7 +/- 11.0) performed two separate and identical exercise routines on different days consisting of treadmill walking at 2.0 mph (53.6 m/min), 3.0 mph (80.5 m/min), and 4.0 mph (107.3 m/min) and running at 6.0 mph (160.9 m/min). VE and gas exchange were measured continuously breath-to-breath. A random effects model on log-transformed data yielded coefficients of variation (CV) and intraclass correlation coefficients (ICC) for VO2 and VE of 5.2 - 7.6 %, and 0.77 - 0.92, respectively, for all walking and running trials. For VCO2, CVs were higher (10 - 12 %) and ICCs lower (0.70 - 0.81). Ordinary least squares regression between the individual difference scores and the individual mean scores for VE, VO2 and VCO2, respectively, indicated no systematic bias (all p > 0.05). Bland-Altman analysis also illustrated no systematic bias between repeated measurements. The VmaxST provides reliable measurements of VO2 and VE during walking and running eliciting VE and VO2 at least up to approximately 56 and 2.2 l/min, respectively. The system appears to be less reliable for measuring VCO2.

Validation of an Accelerometer Estimate of Activity Energy Expenditure

Several studies have evaluated the validity of accelerometers in estimating activity energy expenditure (AEE) using linear regression modeling. A new approach has been proposed for the omnidirectional accelerometers where either a single (1R) or double (2R) regression is used to predict AEE depending on whether activity is performed using lower (locomotion) (1R) or upper (activities of daily living, ADLs) (2R) body movement (Heil, 2006). PURPOSE: We evaluated the validity of the 1R and 2R models in predicting AEE for locomotion and ADLs. METHODS: One hundred and two subjects (64 female and 37 male; age = 34.9 ± 12.4 y) completed 6 treadmill (TM) activities at 1.34, 1.56 and 2.23 m·sec−1 at 0 and 3% grades. ADLs consisted of vacuuming, dusting, mopping, sweeping, gardening and other household activities. All activities were performed for 7 minutes with subjects wearing a portable metabolic measurement system. Resting Metabolic Rate (RMR) was measured prior to completion of the activity protocol. A repeated measures analysis of variance was used to examine the difference between measured activity energy expenditure (AEEmeas) and monitor estimated AEE (AEEest). Least squares means (standard error) are reported. RESULTS: For all activities, there was a significant difference between AEEmeas and AEEest, with AEE underestimated by 0.012 (± 0.001) kcal·kg·min−1 and 0.011 (± 0.001) kcal·kg·min−1 for the 1R and 2R, respectively. The AEEest obtained from both the 1R and 2R methods was accurate for TM activities, while each method significantly underestimated AEE R1, 0.024 (± 0.002 kcal·kg·min−1); R2, 0.023 (± 0.002 kcal·kg·min−1) for the ADLs. CONCLUSIONS: Although both the 1R and 2R provided accurate estimates of AEE for TM activities, neither model was accurate for all activities or for the ADLs. The use of this monitor in a free-living environment, where individuals perform a variety of activities, may result in a significant underestimation of activity energy expenditure.

Validity of the VmaxST portable metabolic measurement system

The aim of this study was to assess and compare the validity of the portable VmaxST telemetry metabolic measurement device with that of a standard measurement system (Vmax29). Thirty asymptomatic, moderately active males provided written, informed consent and completed two maximal graded treadmill exercise tests (Bruce) using the VmaxST and the Vmax29 metabolic measurement systems. Tests were performed in random order on separate days to obtain peak values for time to exhaustion, heart rate, systolic and diastolic blood pressure, oxygen consumption ([Vdot]O2), carbon dioxide production ([Vdot]CO2), ventilation ([Vdot] E), and respiratory exchange ratio (RER). Multivariate analysis of variance revealed no significant main effect (P = 0.88) between the two systems across any variable, suggesting similar measurement capabilities between the two systems. Linear regression analyses revealed moderate to high coefficients of determination for [Vdot]O2 (r 2 = 0.99), [Vdot]CO2 (r 2 = 0.99), [Vdot] E (r 2 = 0.99), and RER (r 2 = 0.89). Furthermore, Bland-Altman analyses demonstrated that the VmaxST yielded similar values to the Vmax29, suggesting good agreement between the two systems. Agreement was confirmed when the differences between the methods resulted in a small range as identified by the 95% limits of agreement. Findings from the current study confirm that the VmaxST is a valid device for measuring metabolic and physiological variables during exercise within a controlled laboratory setting.

Validity of a Low-Flow Pneumotach and Portable Metabolic Measurement System

The purpose of this study was to investigate the validity of the MedGraphics VO2000 portable metabolic measurement system coupled with a low-flow pneumotach for the determination of oxygen consumption (VO2), carbon dioxide production (VCO2), and minute ventilation (VE) at rest. Twenty-four (12 male/12 female) young (23±5 y), healthy participants volunteered for this study. Mean height and weight were 173.9 cm (±10.5) and 74.3 kg (±11), respectively. Participants reported to the laboratory between the hours of 0700 and 1000 following a 12-h fast. A MedGraphics VO2000 portable metabolic measurement system equipped with a low-flow pneumotach was arranged in series to a Pre- Vent � pneumotach for the MedGraphics CPX/D metabolic system. Participants rested in a supine position for a 20-min period of acclimation. Inspired and expired gases were collected for 60-min, after the acclimation period, for the analysis of VO2, VCO2, and VE. There were no significant difference (P<0.05) between the systems for VO2 (P=0.12), VCO2 (P=0.45), or VE (P=0.10). There were significant (P<0.05) correlation coefficients between the systems for VO2 (r=0.79), VCO2 (r=0.62), or VE (r=0.68). Bland-Altman plots indicated a good agreement between the two systems for VO2, VCO2 and VE. Results of this study indicated the MedGraphics VO2000 fitted with a low-flow pneumotach provides a valid metabolic measurement system for the measurement of resting metabolic rate.

최대, 최대하 운동시 휴대용 무선 가스분석기의 정확성에 관한 연구

다양한 형태의 필드활동이나 운동 중 산소 섭취량과 에너지 소비량을 측정하기 위해 휴대용 무선 가스분석기가 많이 이용되고 있다. 하지만 휴대용 무선 가스분석기의 정확성에 관한 연구는 부족한 실정이다. 목적: 따라서 본 연구는 최근 가장 널리 사용되고 있는 Cosmed K4b2 (K4b2) 휴대용 무선 가스분석기의 정확성을 Parvo Medics TrueMax 2400 (MC) 가스분석기에 근거하여 비교, 측정하였다. 연구방법: 본 실험을 위해 남녀 8명 (연령＝27.75±6.43, 신장＝169.84±10.14 cm, 체중＝73.90±20.94kg)의 피검자가 트레드밀 운동을 실시하였으며, 각기 다른 운동 강도 (최대 산소 섭취량의 100%, 65%, 45%)에서의 K4b2 정확성을 평가하기 위해 O2(mL·kg-1·min-1 and L·min-1), CO2(L·min-1), FeO2(%), FeCO2(%), respiratory exchange ratio(RER), minute ventilation(VE, L·min-1), and energy expenditure(EE, kcal·min-1)가 측정되었다. K4b2의 측정변인에 대한 통계적 유의성 검사를 위해 2×3(가스분석기×운동강도) 반복측정 변량분석(ANOVA with repeated measures)을 실시하였으며, 통계적 유의성이 있을시는 Sidak adjustments가 실행되었다. 모든 통계적 유의수준은 p≤0.05로 설정되었다. 결과: MC와 비교해볼때 K4b2에서 측정된 RER (p≤0.001)과 VE (p≤0.05) 값은 통계적으로 유의하게 나타났으나 그 외의 다른 모든 측정변인들은 운동강도와 상관없이 두 가스분석기 간에 매우 유사한 것으로 나타났다. 또한 Bland-Altman분석에 의하면, K4b2에서 측정된 VO2 (mL·kg-1·min-1 and L·min-1), VCO2 (L·min-1), TV (L), and EE (kcal·min-1) 수치는 MC에서 측정된 값과 매우 밀접한 관계를 보였다. 결론: MC 가스분석기와 비교해볼 때 휴대용 무선 가스분석기 K4b2에 의해 측정된 RER과 VE 수치가 높게 나타났지만 이를 제외한 다른 모든 변인들은 두 가스 분석기 간에 매우 밀접한 결과를 보였다. 따라서 본 연구 결과는 휴대용 무선 가스분석기 K4b2는 다양한 운동강도에서 산소섭취량 및 에너지 소비량을 측정하는 데 적합함을 입증하였다.

Oxygen cost of the CF–DND fire fit test in males and females

The Department of National Defence employs a work-related test circuit comprising 10 various firefighting tasks (FF test) to assess the fitness of incumbent Canadian Forces firefighters. The main purpose of this study was to document the oxygen cost of the FF test over a wide range of performance times. These data were then used to predict the oxygen cost associated with the 8 min completion standard. Finally, we examined the influence of gender on selected physiological responses during the FF test. Thirty male and 23 female subjects practiced the test 3-5 times and then completed, in random order and on separate days, a maximal-effort trial while breathing with either a self-contained breathing apparatus (SCBA) or a portable metabolic measurement system (MMC). The breath-by-breath gas exchange data from the MMC were collapsed into a single value that represented the average oxygen cost for each participant to complete the work simulation. To calculate the average VO2 associated with the 8 min completion time, separate regression lines for test duration and average VO2 were generated for males and females. Analyses of covariance (ANCOVA) revealed that the regression lines for the male and female groups coincided, therefore all data were collapsed. The resulting regression equation predicted that the average VO2 associated with the 8 min standard was 34.1 (+/-4.0) mL.kg(-1).min(-1), and this value appears consistent with other research on the oxygen cost of firefighting. There was no evidence to suggest that the oxygen cost of meeting the 8 min standard was different for males or females.

Validation of a portable equine metabolic measurement system

In equine sports medicine, VO2 has been measured exclusively with stationary systems, in laboratories equipped with a treadmill. Measurement during exercise in field conditions has not previously been reported because of the lack of portable equipment designed for horses. A commercially available portable metabolic measurement system, based on breath-to-breath gas analysis and flow spirometry, was adapted to the horse's physiology and morphology (Cosmed K4b2 and Equimask) and its validity tested by (1) repeatability of the measures and (2) comparing metabolic data to those obtained by a reference method (RM). To test the reproducibility of the measurements, 5 healthy saddle horses were subjected twice at 2 day intervals to a similar submaximal standardised incremental exercise test on a treadmill. The same horses performed twice at one week interval an incremental treadmill test to fatigue: the oxygen consumption and ventilation were measured once with the K4b2 system and once with the RM. The metabolic and ventilatory data obtained with both systems were compared. There was a good reproducibility of the metabolic measurements obtained by the K4b2 system at any workload. The VO2 obtained by both systems at any workload was not significantly different. However, the K4b2 expired fraction in CO2 (FETCO2) and carbon dioxide production (VCO2) were significantly lower at high and at maximal workloads. As a consequence, the values of the respiratory exchange ratio were too low and incompatible with normal physiological values. The good reproducibility of the metabolic and ventilatory measurements and the fact that the VO2 measurements at any workload were similar to the data obtained with the reference method suggested that this system may be used for comparison of repeated VO2 measurements in practical field conditions. The K4b2 system could be used to improve knowledge of the energetic cost in different equine sports disciplines and offer the opportunity to undertake performance tests with genuine track conditions, on ridden or harnessed horses, rather than under laboratory conditions.

Bioenergetics and Time-Motion Analysis of Competitive Basketball

Although basketball has been considered highly intensive, objective findings about actual bioenergetic demands of this sport are limited. PURPOSE: To assess bioenergetic traits of collegiate basketball by measuring oxygen consumption (VO2), heart rate (HR), blood lactate concentration (LA), and perceived exertion (RPE), as well as performing a time-motion analysis in team scrimmages. METHODS: Six female and six male collegiate basketball players (20.0 ± 1.2 and 20.8 ± 0.9 years old, respectively) were recruited as subjects. Each subject was monitored for 20 min in a team scrimmage while wearing a portable metabolic measurement system. All scrimmages were conducted in the same way as actual games with the presence of referees, coaches, and spectators. VO2 and HR were measured by the portable system every 20 sec during the scrimmage and LA and RPE were measured in brief breaks every 5 min. Also, the subject's performance was videotaped to conduct time-motion analysis. A treadmill GXT (graded exercise test) was performed on a separate day to measure VOpmmax. RESULTS: The female and male players demonstrated VO2 of 33.4 ± 3.6 and 37.0 ± 2.4 ml/kg/min and LA of3.2±0.8 and 4.1 ± 1.2mmol/L throughout the scrimmages. They spent 34.1 % of play time performing active movements including running and jumping while 56.9 % of time walking and 9.0 % standing. No significant differences were observed between females and males in the variables measured (P>0.05), except that the males expended significantly greater energy through the scrimmages (356.5 ± 60.0 vs. 239.0 ± 29.5 kcal; p <0.05). VO2max (6 females and 4 males) was significantly correlated to VO2 during play (r2 = 0.45; p<0.05) and percent of duration for active movements during play (r2 = 0.88 for females and 0.93 for males; p<0.05). CONCLUSIONS: This study demonstrated a greater oxygen cost playing basketball than the value in a previously developed compendium (28.0 ml/kg/min). The correlation analysis suggests that enhancement of aerobic capacity allows greater activity of play in basketball.Figure

Validation Of An Integrated Heart Rate/Physical Activity Monitor

PURPOSE: To validate a novel physical activity monitor (PAM-III) with the ability to collect inertial sensor and heart rate measurement data simultaneously in a single, discreet, low-profile device. METHODS: 19 healthy males (age 26.9 ± 6.4yr.; ht: 179.7 ± 7.2 cm; wt: 79.5 ± 10.4 kg; % fat: 16.0 ± 7.4) and 25 healthy females (age 24.8 ± 4.8 yr.; ht: 166.1 ± 5.2 cm; wt: 62.2 ± 8.9 kg; % fat: 25.9 ± 11.4) underwent two separate exercise sessions on different days that consisted of treadmill walking on a level grade at 2.0, 3.0, and 4.0 mph, and running at 6.0 mph. Subjects exercised for 5 min at each speed, with 3 min rest periods between each bout. Pulmonary ventilation and gas exchange were measured breath-to-breath with a Sensormedics VmaxST portable metabolic measurement system. Peak aerobic capacity was assessed during an inclined walking treadmill test to volitional fatigue. During each exercise session subjects wore the PAM-III device (waistband; heart rate monitored via surface electrodes) and a Polar heart rate monitor. RESULTS: An n-fold cross-validation technique was used to establish the coefficients of a (fixed-structure) linear predictive model for each individual and then to evaluate model performance on unseen data. In particular, the training dataset for each subject excluded a single 30-sec exercise epoch, which was then used to evaluate the model; this process was repeated for all 30-sec exercise epochs for that subject and results accumulated over all subjects. Model inputs were heart rate, rotational kinetic energy, and acceleration vector magnitude and activity counts; model output was total energy expenditure (kcal/ min). Data from the VmaxST were 30-second averages. This model produced a mean r2across all individuals of 0.94 (range = 0.82 to 0.98) and a pooled r2 of 0.95. The mean RMS error across all subjects was 0.76 kcal/min. The second model was a “generic” linear model synthesized across all subjects using an n-fold cross-validation technique. The model was trained using all exercise data from (N – 1) subjects and then evaluated using the exercise data from the excluded subject; the process was repeated for all subjects. Model inputs included heart rate, rotational kinetic energy, acceleration vector magnitude activity counts, height, and weight; the output was total energy expenditure (kcal/min). This model produced a mean r2 across all individuals of 0.91 (range = 0.76 to 0.98) and a pooled r2 of 0.76. The mean RMS error =1.81 kcal/min. CONCLUSIONS: The PAM-III integrated heart rate/physical activity monitor provides very good estimates of energy expenditure during walking and jogging. Supported by R21 CA112323-01A1 and an NIH grant to the GCRC RR00847

Energy Expenditure During Single Versus Multiple Set Resistance Training Protocols

PURPOSE Since current efforts promoting physical activity recommend participation in both cardiorespiratory and resistance training programs the quantification of the energy cost of commonly used resistance protocols facilitates more accurate exercise prescriptions. The purpose of this study was to compare energy expenditure of single and multiple set resistance training protocols using indirect calorimetry. METHODS 24 subjects (12 male, 12 female), mean age 21.4 ± 1.3 years, performed both a 1 and 3 set, 5- exercise, upper body protocol at 70% of their 1 repetition maximum for 10 repetitions using a lifting cadence of 15 reps/min. Testing sessions were separated by at least 48 hours. Cardiorespiratory data were recorded over the entire exercise session, including a 5 minute recovery period, using a Cosmed K4b2 (Rome, Italy) portable metabolic measurement system. RESULTS Data (mean ± SD) are presented in the table belowTable 1Gross and net energy cost for the multiple set protocol was significantly greater (p ≤ 0.001). There was no significant difference (p <0.05) in the rate of energy expenditure (Kcalċmin−1) between the two conditions. Significant gender differences (p <0.001) in absolute and relative energy cost (gross kcal, net kcal, kcal·kg lbm−1) were discovered for both conditions. VE/VO2 values were 40.27 ± 7.4 for the 1 set and 44.21 ± 7.5 for the 3 set protocol, respectively. The total workout times were approximately 23 and 47 minutes, while the actual lifting time was 2.5 and 7.5 minutes, respectively. CONCLUSIONS When the volume of work was tripled, the energy cost was approximately doubled (135% increase). Male subjects had significantly higher absolute and relative energy costs than female subjects for both the single and multiple set protocols. The multiple set protocol yielded higher metabolic and cardiorespiratory responses than the single set protocol. These findings have implications with regard to caloric balance, exercise prescription and workout design.

Assessment Of The Kb1-c Portable Metabolic Measurement System During Submaximal Cycle And Treadmill Exercise

PURPOSE The purpose of this study was to evaluate the validity and reliability of the portable KB1-C Metabolic Analysis system during submaximal exercise intensities. METHODS Thirteen apparently health subjects (age: 21.9 ± 0.4 yrs; height: 175.1 ± 2.6 cm; weight: 75.3 ± 4.3 kg; %BF: 15.0 ± 1.8) were recruited. Each subject exercised on a treadmill and a cycle ergometer. The stages for the treadmill protocol included rest and 2.0, 3.0, 4.0, 5.0 and 6.0 miles per hour (mph). The stages for the cycle ergometer protocol included rest and 50, 75, 100, 125, 150 and 175 Watts. Each subject exercised for five minutes at each exercise intensity. Expired air was collected and simultaneously analyzed for oxygen consumption (Vo2), carbon dioxide production (Vco2), minute ventilation (Ve), fraction of expired oxygen (FEO2) and fraction of expired carbon dioxide (FECO2) by the KB1-C and True Max 2400 computerized metabolic systems. Data collected over the last two minutes were averaged and compared. A two-way ANOVA with repeated measures (instrument × stage) was used to identify differences between the two metabolic systems during each stage of the submaximal exercise test. Pearson's correlation coefficient was used to identify relationships between the two instruments. RESULTS Oxygen consumption, Vco2, and Ve increased significantly (p< 0.05) with increased exercise intensity. During the treadmill test, oxygen consumption and Ve were significantly different between the two systems at rest. VCO2 measured by the KB1-Cwas significantly higher at rest, 2.0, and 4.0 mph compared to the True Max system. On the other hand, FEO2 and FECO2 were not significantly different between systems. During the cycle ergometer test, Vo2, and Ve were not significantly different between instruments at 50, 75 and 100 Watts but KB1-C was significantly higher than the True Max at rest and significantly lower than the True Max at 125, 150 and 175 Watts. VCO2 was significantly different at all exercise intensities between instruments. Fraction of expired oxygen assessed by the KB1-C was significantly higher at 125, 150, and 175 Watts compared to the True Max system. On the other hand, FECO2 was not significantly different between instruments. Finally, correlations for Vo2 values between the two systems were r≥0.85. CONCLUSIONS These results indicate that the KB1-C can be used in the assessment of oxygen consumption, especially at low and moderate exercise intensities. However, at higher exercise intensities, especially if a cycle ergometer is used, KB1-C does not present equally valid results. It is possible that the differences between instruments may be even greater at maximal exercise intensities.

Assessment Of The Kb1-c Portable Metabolic Measurement System During Submaximal Cycle And Treadmill Exercise

Assessment Of The Kb1-c Portable Metabolic Measurement System During Submaximal Cycle And Treadmill Exercise