Polar Activity Watch 200: a new device to accurately assess energy expenditure.

OBJECTIVES: Energy expenditure (EE) based on movement detection is calculated by a new device, the Activity Watch 200 (AW200). The aim of this study was to validate EE measured by this device against indirect calorimetry (IC) and to assess the reproducibility of AW200 measurements. DESIGN: EE was assessed during a 9.7 km hike. 10 men and 10 women in the age range 35-45 years, and 5 men and 6 women in the age range 50-55 years were tested. One in five participants of each age- and sex-matched group was equipped with a portable metabograph (Oxycon Mobil) for IC measurements. Data were collected every 30 min during the hike, and IC was extrapolated for the remaining four other participants of the group. RESULTS: During the total hike, there was a high correlation between EE obtained from the AW200 and the IC calculation (r = 0.987, p<0.001). Identical values of EE were calculated by both methods during the first 90 min of the hike. However, EE calculated by the AW200 at 120 min and at the end of the hike was lower (p<0.05). Bland-Altman analysis showed limits of agreements between 105 and 279 kJ after 30 and 120 min, respectively. EE measured by the AW200 was well correlated with IC measurements, and limits of agreement between devices were below 10% of the measured values for hike durations longer than 60 min. CONCLUSION: The AW200 appears to be a very useful and accurate device for measuring EE during exercise in recreational hikers and provides a useful tool for keeping track of personal EE.

Use of heart rate to predict energy expenditure from low to high activity levels.

This study evaluated the ability to use the relationship between heart rate (HR) and oxygen uptake (VO2 ) to estimate energy expenditure (EE) from low to high physical activity with different HR-based prediction equations. General prediction equations were established based on the individual relations between HR and EE. Possibilities to improve the EE estimation with using alternatives for respective HR were also assessed. The alternatives were % of HR reserve: 100 x [(activity HR - resting HR)/(maximal HR - resting HR)], (HRR), and the difference between activity HR and resting HR (activity HR - resting HR), (HRnet). Forty-two men (age mean 36.5 [sd 7.6] y, BMI 24.5 [2.4] kg x m(-2), VO2 max 45.2 [6.5]) kg x ml x min(-1) and 47 women (mean age 37.5 [9.5], BMI 23.3 [3.4], VO2 max 36.3 [5.4]) performed an exercise test consisting of physically low-activity tasks and a maximal treadmill uphill walking test. Respiratory gases were obtained from indirect calorimetry. HR was registered by electrocardiography and EE was calculated from (VO2 ) and carbon dioxide (VCO2 ) production. Generalised linear models with random effects were used for the prediction of EE. EE values of the tests (one value at each intensity level) were predicted in separate models by the respective HR, HRR or HRnet values. The other predictors used in all models were body weight, sex and the intensity of exercise. The standard error of estimate (SEE) was 1.41 kcal x min(-1) (5.89 kJ) in the model with HR variable as a predictor, 1.01 kcal x min(-1) (4.22 kJ) with HRR variable, and 1.08 (4.51 kJ) with HRnet variable. The results show that the prediction of EE is more accurate if HRR or HRnet are used in prediction equation instead of HR.

Heart rate during aerobics classes in women with different previous experience of aerobics.

This study measured heart rate during floor and step aerobic classes at three intensity levels. A group of 20 female occasional exercisers [mean age 33 (SD 8) years, mean body mass index 21 (SD 2) kg.m-2 volunteered to participate in six aerobic classes (three floor classes, three step classes) and in a laboratory test as members of one of two groups according to their prestudy regular participation in aerobics classes. Subjects in group A had participated four or more times a week and those of group B less than twice a week. The characteristics of the groups were as follows: group A, n = 10, mean maximal oxygen uptake (VO2max) 38.7 (SD 3.6) ml.kg-1.min-1, mean maximal heart rate (HRmax) 183 (SD 8) beats.min-1; group B, n = 10, VO2max 36.1 (SD 3.6) ml.kg-1.min-1, HRmax 178 (SD 7) beats.min-1. Each class consisted of a warm-up, a 20 min period of structured aerobic exercise (cardiophase) and a cool-down. The cardiophase was planned and guided as light, (rate of perceived exertion, RPE 11-12), moderate (RPE 13-14) or heavy (RPE 15-17) by an experienced instructor. The mean heart rates during the light classes were 72 (step) and 74 (floor) %HRmax in group A and 75 (step) and 79 (floor) %HRmax in group B; during the moderate classes, 84 (step) and 80 (floor) %HRmax in group A and 82 (step) and 83 (floor) %HRmax in group B, and during the heavy classes 89 (step and floor) %HRmax in group A and 88 (step) and 92 (floor) %HRmax in group B. Differences in heart rate and %HRmax were not statistically significant between the groups. However, differences in heart rate and %HRmax between the intensities (light vs moderate, moderate vs heavy and light vs heavy) were significant within both groups (all, P < 0.01). Based on the results, we conclude that intensity management during the aerobics classes was generally successful regardless of the participants' prior participation in aerobics. However, some individuals who were older and/or had less prior participation tended to exceed the targeted heart rate.

Prediction of change in maximal aerobic power by the 2-km walk test after walking training in middle-aged adults.

The aim was to study the 2-km walk test's accuracy in predicting maximal aerobic power (VO2max) and its changes during 15-week walking training in 108 healthy middle-aged adults. Training prescription was 65-75% of VO2max 50 min/session, four times weekly. VO2max was measured walking on a treadmill and predicted from the 2-km walk test using gender-specific equations including age, body mass index, performance time and heart rate. The difference in VO2max between the walk test and the maximal exercise test before training was -0.9 ml x min(-1) x kg(-1) (SD 4.4) in men and -2.2 (3.5) in women. The total error was from 4.1 to 4.5 ml x min(-1) x kg(-1). After training the increase in measured VO2max was 2.9 ml x min(-1) x kg(-1) more in the walkers compared to the controls. The difference between the predicted and measured changes in VO2max during training ranged from -1.8 to -1.0 ml x min(-1) x kg(-1) between the study groups except in walking men, for whom the walk test overestimated the difference. The total error was from 3.1 to 4.9 ml x min(-1) x kg(-1). The 2-km walk test can be used as a reasonably accurate field test to predict changes in VO2max due to aerobic training in healthy nonathletic adults.

Heart rate monitors: state of the art.

Heart rate is a useful indicator of physiological adaptation and intensity of effort. Therefore, heart rate monitoring is an important component of cardiovascular fitness assessment and training programmes. The electrocardiogram (ECG) and Holter monitoring devices are accurate, but they are not appropriate for use in field settings due to cost, size and complexity of operation. Lightweight telemetric heart rate monitors equipped with conventional electrodes have been available since 1983 and have been shown to be accurate and valid tools for heart rate monitoring and registering in the field. Polar Electro Oy has been at the forefront of ambulatory heart rate monitor technology for 15 years. This paper reviews the development of Polar heart rate monitors and their measurement accuracy compared to Holter ECG devices at rest and during exercise, both in adults and in children.

Feasibility of a 2-km walking test for fitness assessment in a population study.

A simple 2-km Walking Test has been developed for determining the cardiorespiratory fitness of healthy adults. In the present study the following aspects of the feasibility of this test for population assessment were investigated: participation willingness, the percentage of test qualified subjects, the percentage of acceptable test performances and the resources needed for field test administration. A representative sample was drawn from the 27 to 65-year-old population in a rural municipality in northeastern Finland. Subjects were recruited on the basis of the results of health questionnaires and interviews. One fourth of the volunteers were excluded from the test because of health problems. The 2-km walking tests were administered outdoors in the municipality center. More than 50% of the subjects successfully completed two consecutive walking tests. This study indicated that the 2-km Walking Test is a feasible alternative as a measure of cardiovascular fitness for large population groups and could potentially be used in exercise related health promotion programmes.

Training effects of cross-country skiing and running on maximal aerobic cycle performance and on blood lipids.

Two experiments were carried out to compare the cardiorespiratory and metabolic effects of cross-country skiing and running training during two successive winters. Forty-year-old men were randomly assigned into skiing (n = 15 in study 1, n = 16 in study 2), running (n = 16 in study 1 and n = 16 in study 2) and control (n = 17 in study 1 and n = 16 in study 2) groups. Three subjects dropped out of the programme. The training lasted 9-10 weeks with 40-min exercise sessions three times each week. The training intensity was controlled at 75%-85% of the maximal oxygen consumption (VO2max) using portable heart rate metres and the mean heart rate was 156-157 beats.min-1 in the training groups. In the pooled data of the two studies the mean increase in the VO2max (in ml.min-1.kg-1) on a cycle ergometer was 17% for the skiing group, 13% for the running group and 2% for the control group. The increase in VO2max was highly significant in the combined exercise group compared to the control group but did not differ significantly between the skiing and running groups. The fasting serum concentrations of lipoproteins and insulin did not change significantly in any of the groups. These results suggested that training by cross-country skiing and running of the same duration and intensity at each session for 9-10 weeks improved equally the cardiorespiratory fitness of untrained middle-aged men.