Oxynet: A collective intelligence that detects ventilatory thresholds in cardiopulmonary exercise tests.

The problem of the automatic determination of the first and second ventilatory thresholds (VT1 and VT2) from cardiopulmonary exercise test (CPET) still leads to controversy. The reliability of the gold standard methodology (i.e. expert visual inspection) feeds into the debate and several authors call for more objective automatic methods to be used in the clinical practice. In this study, we present a framework based on a collaborative approach, where a web-application was used to crowd-source a large number (1245) of CPET data of individuals with different aerobic fitness. The resulting database was used to train and test an artificial intelligence (i.e. a convolutional neural network) algorithm. This automatic classifier is currently implemented in another web-application and was used to detect the ventilatory thresholds in the available CPET. A total of 206 CPET were used to evaluate the accuracy of the estimations against the expert opinions. The neural network was able to detect the ventilatory thresholds with an average mean absolute error of 178 (198) mlO2/min (11.1%, r = 0.97) and 144 (149) mlO2/min (6.1%, r = 0.99), for VT1 and VT2 respectively. The performance of the neural network in detecting VT1 deteriorated in case of individuals with poor aerobic fitness. Our results suggest the potential for a collective intelligence system to outperform isolated experts in ventilatory thresholds detection. However, the inclusion of a larger number of VT1 examples certified by a community of experts will be likely needed before the abilities of this collective intelligence can be translated into the clinical use of CPET.

Effects of Nordic walking training on functional parameters in Parkinson's disease: a randomized controlled clinical trial.

We compare the effects of Nordic walking training (NW) and Free walk (FW) on functional parameters (motor symptoms, balance) and functional mobility (Timed Up and Go at Self-selected Speed - TUGSS, and at forced speed, TUGFS; Self-selected Walking Speed, SSW; locomotor rehabilitation index, LRI) of Parkinson's disease (PD) patients. The study included 33 patients with clinical diagnosis of idiopathic PD, and staging between 1 and 4 in the Hoehn and Yahr scale (H&Y) randomized into two groups: NW (N = 16) and FW (N = 17) for 6 weeks. Baseline characteristics were compared trough a one-way ANOVA. Outcomes were analyzed using the Generalized Estimation Equations (GEE) with a Bonferroni post-hoc. Data were analyzed using SPSS v.20.0. Improvements in UPDRS III (P < 0.001), balance scores (P < 0.035), TUGSS distance (P < 0.001), TUGFS distance (P < 0.001), SSW (P < 0.001), and LRI (P < 0.001) were found for both groups. However, the NW group showed significant differences (P < 0.001) when compared to the FW group for the functional mobility. We conclude the NW improves functional parameters and walking mobility demonstrating that NW is as effective as the FW, including benefits for FW on the functional mobility of people with PD.

Adaptations to changing speed, load, and gradient in human walking: cost of transport, optimal speed, and pendulum.

It has been observed that the optimal speed (OPT) of human walking is independent of load on level surfaces because of the unaltered trajectory of the center of mass and consequent conservation of the pendular mechanism. However, the role of the inverted pendulum mechanism that combines speed, load, and gradient during walking remains unknown. In the present study, 10 subjects walked on a treadmill, with and without loading (25% of the body mass), at different speeds and slopes (0%, +7%, and +15%). The three-dimensional motion and VO2 were simultaneously registered. The mechanical external and internal work and the cost of transport (C) changed with the speed and gradient, but the load only affected C. OPT decreased with increasing gradient, and the pendular mechanics (R) was modified mainly as a result of changes in speed and gradient. OPT and R were independent of the load in these gradients. Remarkably, R increased with increasing speed and decreased (to 30%) with an increasing gradient; moreover, R was independent of load. Therefore, the energy-saving strategy by the pendular mechanism persists, although at a diminished level, in loaded walking on gradients and partially explains the OPT in this condition.

The landing-take-off asymmetry of human running is enhanced in old age.

The landing-take-off asymmetry of running was thought to derive from, or at least to be consistent with, the physiological property of muscle to resist stretching (after landing) with a force greater than it can develop during shortening (before take-off). In old age, muscular force is reduced, but the deficit in force is less during stretching than during shortening. The greater loss in concentric versus eccentric strength with aging led us to hypothesize that older versus younger adults would increase the landing-take-off asymmetry in running. To test this hypothesis, we measured the within-step changes in mechanical energy of the centre of mass of the body in old and young subjects. The difference between the peaks in kinetic energy attained during the fall and during the lift of the centre of mass is greater in the old subjects. The difference between the time to lift and accelerate the centre of mass (positive work) and to absorb the same amount of energy during the downward displacement (negative work) is also greater in the old subjects. Both these findings imply a difference in force between stretching and shortening during the bounce, which is greater in the old subjects than in the young subjects. This is qualitatively consistent with the more asymmetric force-velocity relation found in aged muscle and supports, even if does not prove, the hypothesis that the landing-take-off asymmetry in running derives from the different response of muscle to stretching and shortening.

Old men running: mechanical work and elastic bounce.

It is known that muscular force is reduced in old age. We investigate what are the effects of this phenomenon on the mechanics of running. We hypothesized that the deficit in force would result in a lower push, causing reduced amplitude of the vertical oscillation, with smaller elastic energy storage and increased step frequency. To test this hypothesis, we measured the mechanical energy of the centre of mass of the body during running in old and young subjects. The amplitude of the oscillation is indeed reduced in the old subjects, resulting in an approximately 20% smaller elastic recovery and a greater step frequency (3.7 versus 2.8 Hz, p=1.9x10(-5), at 15-17 km h(-1)). Interestingly, the greater step frequency is due to a lower aerial time, and not to a greater natural frequency of the system, which is similar in old and young subjects (3.6 versus 3.4 Hz, p=0.2). Moreover, we find that in the old subjects, the step frequency is always similar to the natural frequency, even at the highest speeds. This is at variance with young subjects who adopt a step frequency lower than the natural frequency at high speeds, to contain the aerobic energy expenditure. Finally, the external work to maintain the motion of the centre of mass is reduced in the old subjects (0.9 versus 1.2 J kg(-1) m(-1), p=5.1x10(-6)) due to the lower work done against gravity, but the higher step frequency involves a greater internal work to reset the limbs at each step. The net result is that the total work increases with speed more steeply in the old subjects than in young subjects.