Physical activity energy expenditure measured using a portable telemetric device in comparison with a mass spectrometer

Data repeatability for the Cosmed K4 b2 portable metabolic cart during non-steady state exercise

BACKGROUND: Portable metabolic carts are a popular tool to assess aerobic capacity and affirm many cardiorespiratory conditions. They may also measure strength training performance. Given their popularity and increased usage to assess strength training performance; their data accuracy and consistency are important to determine. OBJECTIVE: Measure Cosmed K4 b2 portable metabolic cart data repeatability from consecutive seated calf press workouts. METHODS: Fifteen women and twelve men did two workouts that began with a stationary cycling warm-up followed by calf presses. Gases were measured before the calf press portion of workouts to establish baseline VO2 and VCO2 values, as well as continually throughout and after the calf press protocol. Subjects were detached from the cart once gas values returned to baseline after workouts concluded. In addition to VO2 and VCO2, repeatability was quantified for: breaths per minute, tidal volume, ventilation, O2 uptake relative to body mass, expired O2 and CO2 fractions, percent fat and carbohydrate utilization, METS and total energy cost. Mean and peak values per variable were analyzed. Repeatability was assessed separately for male and female data, as well as with values pooled, by the following: intraclass correlation coefficients, eta squared, limits of agreement, coefficient of variation and smallest real difference percent. RESULTS: Per variable, repeatability values across workouts were low. Female intraclass correlation coefficient mean values were more repeatable for variables related to gas measurements, yet male data were generally more repeatable for those related to substrate usage. CONCLUSIONS: Results for some repeatability indices were influenced by measurement magnitude. Peak values were predictably less repeatable than those for mean values. Most smallest real differences percent scores are so high they were rendered irrelevant or meaningless to determine true differences among paired values. Results suggest low data repeatability that are likely appropriate and realistic for the exercise protocol, hardware and intensity examined.

The COSMED K5 in Breath-by-Breath and Mixing Chamber Mode at Low to High Intensities

PURPOSE

The portable metabolic analyzer COSMED K5 (Rome, Italy) allows for switching between breath-by-breath (BBB) and dynamic micro-mixing chamber (DMC) modes. This study aimed to evaluate the reliability and validity of the K5 in BBB and DMC at low, moderate, and high metabolic rates.

METHODS

Two K5 simultaneously operated in BBB or DMC, whereas (i) a metabolic simulator (MS) produced four different metabolic rates (repeated eight times), and (ii) 12 endurance-trained participants performed bike exercise at 30%, 40%, 50%, and 85% of their individual power output at V˙O2max (repeated three times). K5 data were compared with predicted simulated values and consecutive Douglas bag measurements.

RESULTS

Reliability did not differ significantly between BBB and DMC, whereas the typical error and intraclass correlation coefficients for oxygen uptake (V˙O2), carbon dioxide output (V˙CO2), and minute ventilation (V˙E) ranged from 0.27% to 6.18% and from 0.32 to 1.00 within four metabolic rates, respectively. Validity indicated by mean differences ranged between 0.61% and -2.05% for V˙O2, 2.99% to -11.04% for V˙CO2, and 0.93% to -6.76% for V˙E compared with MS and Douglas bag at low to moderate metabolic rates and was generally similar for MS and bike exercise. At high rates, mean differences for V˙O2 amounted to -4.63% to -7.27% in BBB and -0.38% to -3.81% in DMC, indicating a significantly larger difference of BBB at the highest metabolic rate.

CONCLUSION

The K5 demonstrated accurate to acceptable reliability in BBB and DMC at all metabolic rates. Validity was accurate at low and moderate metabolic rates. At high metabolic rates, BBB underestimated V˙O2, whereas DMC showed superior validity. To test endurance athletes at high workloads, the DMC mode is recommended.

Physiological Responses and Energetics of Competitive Group Exercise in Female Aerobic Gymnasts with Different Levels of Performance

This study investigated the aerobic fitness and physiologic and energetic responses during competitive exercise in aerobic gymnasts. The gymnasts performed a graded treadmill test and competitive group exercises. Energetic response was calculated from oxygen uptake and blood lactate changes. Peak oxygen uptake was similar in International ( M = 45.4m · kg−1 · min.−1, SD = 3.9) and National ( M = 44.7ml · kg−1 · min.−1, SD = 3.6) level groups. During their competitive routines, total energy and the fractions of aerobic, anaerobic alactic, and anaerobic lactic energy were 1,847.7 ( SD = 293.9) and 1,747.3 ( SD = 196.7) J · kg−1, 53.5% ( SD = 3.1) and 60.3% ( SD = 6.1), 25.4% ( SD = 5.9) and 21.4% ( SD = 5.2), and 21.1% ( SD = 5.8) and 18.3% ( SD = 4.5) in international and national level athletes, respectively ( p > .05). The contribution of anaerobic energy was higher in the international level group ( p = .03). It is concluded that the aerobic fitness and absolute energetic and physiological responses of athletes during competitive activities were not different between the aerobic gymnasts groups with different levels of performance, but a higher relative contribution of anaerobic energy was observed in the group with a higher performance level.

Effects of two field continuous incremental tests on cardiorespiratory responses in Standardbred trotters

In humans, cardiorespiratory responses are widely evaluated from field incremental exercise tests. On the contrary, equine exercise physiology faces a huge lack of oxygen consumption measurements (VO2) in field conditions due to technical concerns. The aim of this study was to test the effects of two incremental continuous field tests on cardiorespiratory responses in Standardbred trotters. The two protocols were realized at trot and ended when horses galloped. The tests started at 4.2 m/s (T1) and 6.4 m/s (T2), with speed increments of 1.4 m/s every 3 min for T1 and 0.8 m/s every 2 min for T2. Velocity (v), heart rate (HR) and gas exchanges were recorded continuously, and blood lactate concentration [La(-)] was measured before and after tests. Values recorded at the end of the tests were considered as peak values. The vpeak values were 10.6 ± 0.3 and 10.7 ± 0.7 m/s for T1 and T2 respectively. Horses reached higher VO2peak (T1: 116.6 ± 11.5 ml/min/kg; T2: 88.9 ± 10.2 ml/min/kg; p < 0.05) and HRpeak (T1: 217 ± 5 bpm; T2: 209 ± 3 bpm; p < 0.05) during T1 compared with T2. T1 was significantly longer than T2 (17.5 ± 1.9 vs. 12.9 ± 1.6 min respectively, p < 0.01), and the number of steps entirely ran tended to be different (T1: 5.6 ± 0.6; T2: 6.2 ± 0.8, p = 0.07). Compared to T2, the design of T1 appeared easier to implement and allowed higher cardiorespiratory responses. The relationship between HR-VO2 obtained through T1 gave a better correlation between the two variables than T2. These findings suggest that T1 might be better than T2 for evaluating cardiorespiratory adaptations to exercise and for estimating aerobic energy expenditure in exercising trotters.

A randomized controlled trial comparing the effects of yoga with an active control on ambulatory blood pressure in individuals with prehypertension and stage 1 hypertension

The purpose of this study was to compare the effects of yoga with an active control (nonaerobic exercise) in individuals with prehypertension and stage 1 hypertension. A randomized clinical trial was performed using two arms: (1) yoga and (2) active control. Primary outcomes were 24-hour day and night ambulatory systolic and diastolic blood pressures. Within-group and between-group analyses were performed using paired t tests and repeated-measures analysis of variance (time × group), respectively. Eighty-four participants enrolled, with 68 participants completing the trial. Within-group analyses found 24-hour diastolic, night diastolic, and mean arterial pressure all significantly reduced in the yoga group (-3.93, -4.7, -4.23 mm Hg, respectively) but no significant within-group changes in the active control group. Direct comparisons of the yoga intervention with the control group found a single blood pressure variable (diastolic night) to be significantly different (P=.038). This study has demonstrated that a yoga intervention can lower blood pressure in patients with mild hypertension. Although this study was not adequately powered to show between-group differences, the size of the yoga-induced blood pressure reduction appears to justify performing a definitive trial of this intervention to test whether it can provide meaningful therapeutic value for the management of hypertension.

Evaluation of immediate impact of cane use on energy expenditure during gait in patients with knee osteoarthritis

PURPOSE

The aim of the present study was to assess the immediate impact of cane use on energy expenditure during gait in patients with knee OA analyzing VO(2).

METHODS

An observational, cross-sectional study was carried out on 64 symptomatic patients with a diagnosis of knee OA. The assessment of energy expenditure was performed through an analysis of expired gases using the portable K4 apparatus (Cosmed, Model K4 b2, Italy) during the six-min walk test (6MWT). Two tests were performed with a cane and two without a cane on two different days within a seven-day period.

RESULTS

The patients walked farther on the test without the cane (p<0.001). Oxygen expenditure (VO(2)) and the O(2) cost of walking at the end of the 6MWT increased approximately 50% and 80% during cane-assisted gait when compared to gait without the use of a cane (p<0.001). Pain (Borg scale) decreased approximately 20% at the end of the 6MWT with cane-assisted gait in comparison to gait without a cane (p<0.001).

CONCLUSION

Cane use causes an immediate increase in energy expenditure (VO(2)) during gait and O(2) cost of walking and an immediate decrease of pain during gait. It is necessary to do a more prolonged follow up in order to assess the impact of daily cane use on energy expenditure among these patients and determine whether adaptation occurs. Furthermore, it is necessary to study whether daily cane use has a positive impact on important parameters in these patients, such as pain, function and quality of life.

Measurement of human energy expenditure, with particular reference to field studies: an historical perspective

Over the years, techniques for the study of human movement have ranged in complexity and precision from direct observation of the subject through activity diaries, questionnaires, and recordings of body movement, to the measurement of physiological responses, studies of metabolism and indirect and direct calorimetry. This article reviews developments in each of these domains. Particular reference is made to their impact upon the continuing search for valid field estimates of activity patterns and energy expenditures, as required by the applied physiologist, ergonomist, sports scientist, nutritionist and epidemiologist. Early observers sought to improve productivity in demanding employment. Direct observation and filming of workers were supplemented by monitoring of heart rates, ventilation and oxygen consumption. Such methods still find application in ergonomics and sport, but many investigators are now interested in relationships between habitual physical activity and chronic disease. Even sophisticated questionnaires still do not provide valid information on the absolute energy expenditures associated with good health. Emphasis has thus shifted to use of sophisticated pedometer/accelerometers, sometimes combining their output with GPS and other data. Some modern pedometer/accelerometers perform well in the laboratory, but show substantial systematic errors relative to laboratory reference criteria such as the metabolism of doubly labeled water when assessing the varied activities of daily life. The challenge remains to develop activity monitors that are sufficiently inexpensive for field use, yet meet required accuracy standards. Possibly, measurements of oxygen consumption by portable respirometers may soon satisfy part of this need, although a need for valid longer term monitoring will remain.

Metabolic rate and accelerometer output during walking in people with Down syndrome

People with Down syndrome (DS) have reduced gait stability and aerobic fitness that increase the metabolic rate during walking, potentially altering the relationship between metabolic rate and accelerometer output and lowering predictability of energy expenditure from accelerometry.

PURPOSE

This study examined whether the relationship between metabolic rate and activity count rate differs between individuals with and without DS and whether predictability of metabolic rate is different between groups.

METHODS

Metabolic rate was measured in METs with portable spirometry in 18 subjects with DS (24.7±6.7 yr; 10 women) and 18 subjects without DS (26.3±5.2 yr; 10 women) during five overground walking trials, each lasting 6 min, at 0.5, 0.75, 1.0, 1.25, and 1.5 m·s. A uniaxial accelerometer secured at the right side of the hip allowed for the determination of activity count rate.

RESULTS

The relationship between METs and activity count rate in the two groups was analyzed with multilevel modeling with random intercepts and slopes, demonstrating a significant interaction between group and activity count rate (P<0.001). Separate models for each group showed that the activity count rate and its squared significantly predicted METs (P≤0.001). Actual and predicted METs did not differ in each group. Bland-Altman plots showed greater variability in the difference between actual and predicted METs for participants with DS. Mean absolute error of prediction was 19.92% and 14.55% for participants with and without DS, respectively.

CONCLUSIONS

Individuals with DS show altered METs to activity count rate relationship during overground walking and have lower predictability of metabolic rate from uniaxial accelerometer output than individuals without DS.

Energy expenditure in chronic stroke patients playing Wii Sports: a pilot study

Background

Stroke is one of the leading causes of long-term disability in modern western countries. Stroke survivors often have functional limitations which might lead to a vicious circle of reduced physical activity, deconditioning and further physical deterioration. Current evidence suggests that routine moderate- or vigorous-intensity physical activity is essential for maintenance and improvement of health among stroke survivors. Nevertheless, long-term participation in physical activities is low among people with disabilities. Active video games, such as Nintendo Wii Sports, might maintain interest and improve long-term participation in physical activities; however, the intensity of physical activity among chronic stroke patients while playing Wii Sports is unknown. We investigated the energy expenditure of chronic stroke patients while playing Wii Sports tennis and boxing.

Methods

Ten chronic (≥ 6 months) stroke patients comprising a convenience sample, who were able to walk independently on level ground, were recruited from a rehabilitation centre. They were instructed to play Wii Sports tennis and boxing in random order for 15 minutes each, with a 10-minute break between games. A portable gas analyzer was used to measure oxygen uptake (VO₂) during sitting and during Wii Sports game play. Energy expenditure was expressed in metabolic equivalents (METs), calculated as VO₂ during Wii Sports divided by VO₂ during sitting. We classified physical activity as moderate (3-6 METs) or vigorous (> 6 METs) according to the American College of Sports Medicine and the American Heart Association Guidelines.

Results

Among the 10 chronic stroke patients, 3 were unable to play tennis because they had problems with timing of hitting the ball, and 2 were excluded from the boxing group because of a technical problem with the portable gas analyzer. The mean (± SD) energy expenditure during Wii Sports game play was 3.7 (± 0.6) METs for tennis and 4.1 (± 0.7) METs for boxing. All 8 participants who played boxing and 6 of the 7 who played tennis attained energy expenditures > 3 METs.

Conclusions

With the exception of one patient in the tennis group, chronic stroke patients played Wii Sports tennis and boxing at moderate-intensity, sufficient for maintaining and improving health in this population.

Real-time estimation of daily physical activity intensity by a triaxial accelerometer and a gravity-removal classification algorithm

We have recently developed a simple algorithm for the classification of household and locomotive activities using the ratio of unfiltered to filtered synthetic acceleration (gravity-removal physical activity classification algorithm, GRPACA) measured by a triaxial accelerometer. The purpose of the present study was to develop a new model for the immediate estimation of daily physical activity intensities using a triaxial accelerometer. A total of sixty-six subjects were randomly assigned into validation (n 44) and cross-validation (n 22) groups. All subjects performed fourteen activities while wearing a triaxial accelerometer in a controlled laboratory setting. During each activity, energy expenditure was measured by indirect calorimetry, and physical activity intensities were expressed as metabolic equivalents (MET). The validation group displayed strong relationships between measured MET and filtered synthetic accelerations for household (r 0·907, P < 0·001) and locomotive (r 0·961, P < 0·001) activities. In the cross-validation group, two GRPACA-based linear regression models provided highly accurate MET estimation for household and locomotive activities. Results were similar when equations were developed by non-linear regression or sex-specific linear or non-linear regressions. Sedentary activities were also accurately estimated by the specific linear regression classified from other activity counts. Therefore, the use of a triaxial accelerometer in combination with a GRPACA permits more accurate and immediate estimation of daily physical activity intensities, compared with previously reported cut-off classification models. This method may be useful for field investigations as well as for self-monitoring by general users.

Validation of a portable equine metabolic measurement system

REASONS FOR PERFORMING STUDY

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.

OBJECTIVES

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).

METHODS

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.

RESULTS

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.

CONCLUSIONS

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.

POTENTIAL RELEVANCE

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.

Calibration of two objective measures of physical activity for children

A calibration study was conducted to determine the threshold counts for two commonly used accelerometers, the ActiGraph and the Actical, to classify activities by intensity in children 5 to 8 years of age. Thirty-three children wore both accelerometers and a COSMED portable metabolic system during 15 min of rest and then performed up to nine different activities for 7 min each, on two separate days in the laboratory. Oxygen consumption was measured on a breath-by-breath basis, and accelerometer data were collected in 15-s epochs. Using receiver operating characteristic curve (ROC) analysis, cutpoints that maximised both sensitivity and specificity were determined for sedentary, moderate and vigorous activities. For both accelerometers, discrimination of sedentary behaviour was almost perfect, with the area under the ROC curve at or exceeding 0.98. For both the ActiGraph and Actical, the discrimination of moderate (0.85 and 0.86, respectively) and vigorous activity (0.83 and 0.86, respectively) was acceptable, but not as precise as for sedentary behaviour. This calibration study, using indirect calorimetry, suggests that the two accelerometers can be used to distinguish differing levels of physical activity intensity as well as inactivity among children 5 to 8 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.

Metabolic Cost of Overground Gait in Younger Stroke Patients and Healthy Controls

PURPOSE

Locomotor impairment, such as that which may occur following a stroke, results in increased energy expenditure during walking. Previous research quantifying this increased metabolic demand has focused on older people; thus, the aim of this study was to investigate the physiological cost of walking in younger patients following stroke.

METHODS

Thirteen stroke patients (mean age of 40.7+/-10.0 yr) and 13 age- and sex-matched controls participated. Each subject walked for 5 min around an elliptical course (two cones set 9.5 m apart) at their own preferred walking speed (PWS). The percentage of expired oxygen was measured using a portable gas analyzer. Following a 5-min rest, the control subjects repeated the procedure, but at the PWS of the patient to whom they were matched.

RESULTS

The PWS of the stroke patients was significantly lower than that of the controls (P<0.001); however, there was no significant difference in terms of oxygen uptake (P=0.403). When the distance walked was considered, there was a statistically significant difference in oxygen uptake per unit of distance between the two groups (P<0.001) and also between the patients PWS and the controls walking at the PWS of the patients.

CONCLUSION

The high metabolic cost of walking would suggest that, even for younger stroke patients, early rehabilitation should consider aerobic evaluation and training with the aim of optimizing functional independence.

Changes in physiological and stroke parameters during a maximal 400-m free swimming test in elite swimmers

The aim of this study was to analyse the variations of the metabolic and technical parameters during a maximal 400-m freestyle event. Seven trained male swimmers swam a maximal 400-m freestyle as if in competition (255.8 +/- 6.9 s). Intermediate time and stroke rate (SR) were recorded at each length (25 m). To estimate the changes in metabolic parameters during the 400-m event, they swam a 300-, 200-, and 100-m test set from each length of the 400-m event results, resting 90 min between each test. The exact speed at each length was given with a visual light pacer. Oxygen uptake (VO(2)) and blood lactate concentration ( [Lac]) were measured before and immediately after each test. VO(2) and [Lac] were stable during the 100-, 200-, and 300-m test but significantly higher (p < 0.05) during 400-m test. The estimated contribution of anaerobic metabolism (EsCANA ) during the first 100-m and the 400-m represented 45 % and 20 % of total energy output, respectively. Speed decreased significantly (p < 0.05) after the first 100-m and remained stable until the end. SR decreased significantly after the first 100-m, then increased until the end, while stroke length (SL) decreased linearly throughout the 400-m. During the first or the last 100-m, EsCANA was not correlated with the changes in V, SR, or SL between the second and the first 100-m, and between the fourth and the third 100-m, respectively. To conclude, this study showed that the swimmers were not able to maintain stable SL during the 400-m event. Thus, to sustain stable velocity and to compensate for the decrease in SL, swimmers increased SR throughout the last 300-m.

America's obesity epidemic: measuring physical activity to promote an active lifestyle

The incidence of overweight and obesity in the United States and worldwide has reached epidemic proportions. To effectively intervene, dietetics professionals and other health care practitioners need to address both sides of the energy balance equation when counseling clients and patients. Often, the focus on energy intake supersedes the promotion of a physically active lifestyle. Incorporating appropriate and sufficient physical activity into one's life is an essential component of achieving and maintaining a healthful body weight. This review summarizes background knowledge on the benefits of physical activity for health and provides an overview of available tools for measuring physical activity and energy expenditure. The physical and mental health benefits of an active lifestyle, current physical activity recommendations for the US public, the prevalence of inactivity in the United States, and components of energy expenditure are reviewed. Additionally, tools for estimating total energy expenditure, resting metabolic rate, and physical activity are evaluated and suitable approaches for applying these tools are provided.