PurposeOur recent study of three accelerometer brands in various ambulatory activities showed that the mean amplitude deviation (MAD) of the resultant acceleration signal performed best in separating different intensity levels and provided excellent agreement between the three devices. The objective of this study was to derive a regression model that estimates oxygen consumption (VO2) from MAD values and validate the MAD-based cut-points for light, moderate and vigorous locomotion against VO2 within a wide range of speeds.Methods29 participants performed a pace-conducted non-stop test on a 200 m long indoor track. The initial speed was 0.6 m/s and it was increased by 0.4 m/s every 2.5 minutes until volitional exhaustion. The participants could freely decide whether they preferred to walk or run. During the test they carried a hip-mounted tri-axial accelerometer and mobile metabolic analyzer. The MAD was calculated from the raw acceleration data and compared to directly measured incident VO2. Cut-point between light and moderate activity was set to 3.0 metabolic equivalent (MET, 1 MET = 3.5 ml · kg-1 · min-1) and between moderate and vigorous activity to 6.0 MET as per standard use.ResultsThe MAD and VO2 showed a very strong association. Within individuals, the range of r values was from 0.927 to 0.991 providing the mean r = 0.969. The optimal MAD cut-point for 3.0 MET was 91 mg (milligravity) and 414 mg for 6.0 MET.ConclusionThe present study showed that the MAD is a valid method in terms of the VO2 within a wide range of ambulatory activities from slow walking to fast running. Being a device-independent trait, the MAD facilitates directly comparable, accurate results on the intensity of physical activity with all accelerometers providing tri-axial raw data.

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The 6MWT performed along a 15-m track is a valid field test for predicting VO max of healthy adults with accuracy of about 1MET.

Walking with poles (Nordic walking, NW) has become popular. We compared training responses of brisk walking (W) or NW on cardiorespiratory and neuromuscular fitness. We randomized 121 non-obese sedentary women (aged 50-60) to an NW or W group (NWG, WG), to train 40 min four times weekly for 13 weeks. Intensity was based on subjective perception of exertion. Cardiorespiratory performance was assessed in four levels corresponding to 50%, 65%, 80% and 100% of peak VO(2). Fifty-four NWG and 53 WG subjects completed the study. The mean intensity was about 50% of heart rate (HR) reserve. The baseline peak VO(2) was 25.8 (SD 3.9) mL/min/kg. Both groups improved peak VO(2) similarly (NWG 2.5 mL/min/kg, 95% confidence interval (CI) 1.9-3.3; WG 2.6, CI 1.9-3.3). In the submaximal stages while walking with or without poles, HR and lactate decreased after training in both groups, but the changes were not statistically significantly different between the groups. Of the neuromuscular tests after training, the only significant difference between the groups was in the leg strength in the one-leg squat, favoring WG. In conclusion, both training modes improved similarly health-enhancing physical fitness, and they were feasible and safe.

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