Inter-individual variability in load carriage economy and comparisons between different load conditions.

Equivocal findings exist for the economy associated with load carried close to the body's centre of mass. Individual variation could explain some of the equivocal findings. This research aimed to examine the extent of individual variation in loaded walking economy. Eighteen females carried load on the back, head and split between the front and back. Individual variation in relative load carriage economy (ELI) was primarily assessed using standard deviation, coefficients of variation (CV) and intraclass correlation coefficients (ICC). There was large inter-individual variation in ELI values with highest mean CV's of 16%, 12% and 10% for head-, back- and combined front and back-loading. Mean ELI values were not significantly different between methods. The large amount of individual variation found here suggests future load carriage research should account for individual variation, particularly when considering sample size and when making inferences on the economy associated with different types of load carriage using group mean data

Repeatability of measurements of oxygen consumption, heart rate and Borg's scale in men during ergometer cycling.

The coefficient of repeatability (COR), expressed as 2-SD of differences, was calculated between two measurements of oxygen consumption (V O2), heart rate (HR) and rating of perceived exertion (RPE) during ergometer cycling by men. The two sets of measurements were performed 5 to 6 weeks apart. Nineteen healthy men performed an incremental maximal exercise test on an ergometer cycle. The load started at 50 W and increased by 5 W 20 s-1 until exhaustion was reached. At 40% of the individual maximum load of the pretest, the load was kept constant for 4 min in order to reach steady state. Gas measurements were recorded continuously by computerized instrumentation. The HR was monitored with electrocardiography (ECG) and the perceived exertion was evaluated using Borg's scale. The COR of V O2 at sub-maximal load was 14% and at maximum load 11%. The values in absolute figures were 209 and 332 ml min-1. The corresponding COR of the HR was 16% at sub-maximum load and 6% at maximum load, and an evaluation of the perceived exertion yielded CORs in absolute values of 4.8 and 1.3, respectively. The COR for V O2, HR and ratings of perceived exertion when cycling on an ergometer cycle thus indicate a better agreement between the measurements at maximum load. The COR of the heart at sub-maximal loads must be kept in mind when using HR for estimation of V O2max. The reported findings should be considered when using tests on an ergometer cycle for evaluating exercise capacity

Day-to-day variation in oxygen consumption at submaximal loads during ergometer cycling by adolescents

The day-to-day variation in oxygen consumption ((V) over dot O-2) during ergometer cycling by 20 healthy adolescents, 10 females and 10 males, was measured using indirect calorimetry. The two sets of measurements were performed on two consecutive days. Great care was taken to minimize possible disturbing factors. Cycling started at 50 and 100 W for female and male adolescents, respectively. The load was increased at a rate of 5 W 30 s(-1). In order to reach steady state, the load was kept constant for 3.5 min twice during the cycling session, at 100 and 130 W for the females and at 130 and 160 W for the males. Cycling continued until exhaustion. The maximal loads were 196 W (mean) and 271 W (mean) for females and males, respectively. At the maximal loads the day-to-day variation (+/-2 SD) in oxygen consumption ((V) over dot O-2) was +/-330 ml min(-1) for females and 390 ml min(-1) for males. At the submaximal loads the day-to-day variation in heart rate (HR) was 9.3 beats min(-1) (+/-2 SD) (coefficient of variation, CV = 3.4% at 130 W) for both sexes. The day-today variation in oxygen consumption ((V) over dot O-2) was +/-199 ml min(-1) (+/-2 SD) at the different submaximal loads and did not differ between female and male adolescents (CV = 5.7% at 130 W). This natural day-to-day variation must be taken into consideration when using a submaximal ergometer cycling test for the evaluation of physical capacity in the two sexes

Comparison of two commonly used reference materials for exercise bicycle tests with a Swedish clinical database of patients with normal outcome

Background: Reference values for working capacity, blood pressure, heart rate, perceived exertion, etc. during bicycle exercise tests have been sought after for many years. This is because earlier commonly used reference values for physical work capacity have been either too low or too high when compared to the clinical experience of several Swedish departments of clinical physiology. The aim of the study was to compare two commonly used reference materials with normal outcomes from a clinical database. Methods: Data from a clinical database of standardized exercise tests in Kalmar, Sweden, between 2004 and 2012, and having been judged as normal, were divided into 5-year categories of 5-10 to 75-80 years of age covering people from 7 to 80 years of age. Results: Maximal working capacity (W-max), maximal heart rate, maximal systolic blood pressure and maximal perceived exertion are presented for each of the 15 age categories. Regression equations are also presented for each sex with age and height as independent predictors. Quantitative comparisons of W-max are calculated for the three materials and possible explanations discussed. Conclusions: Values of W-max lie between the two reference materials most commonly used in Sweden. In addition, the present material covers subjects aged 7-19 years