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In laboratory settings, human locomotion encounters minimal opposition from air resistance. However, moving in nature often requires overcoming airflow. Here, the drag force exerted on the body by different headwind or tailwind speeds (between 0 and 15 m·s−1) was measured during walking at 1.5 m·s−1 and running at 4 m·s−1. To our knowledge, the biomechanical effect of drag in human locomotion has only been evaluated by simulations. Data were collected on eight male subjects using an instrumented treadmill placed in a wind tunnel. From the ground reaction forces, the drag and external work done to overcome wind resistance and to sustain the motion of the center of mass of the body were measured. Drag increased with wind speed: a 15 m·s−1 headwind exerted a drag of ∼60 N in walking and ∼50 N in running. The same tailwind exerted −55 N of drag in both gaits. At this wind speed, the work done to overcome the airflow represented ∼80% of the external work in walking and ∼50% in running. Furthermore, in the presence of fast wind speeds, subjects altered their drag area (CdA) by adapting their posture to limit the increase in air friction. Moving in the wind modified the ratio between positive and negative external work performed. The modifications observed when moving with a head- or tailwind have been compared with moving uphill or downhill. The present findings may have implications for optimizing aerodynamic performance in competitive running, whether in sprints or marathons. NEW & NOTEWORTHY: This is the first study to assess the biomechanical adaptations to a wide range of wind speeds inside a wind tunnel. Humans increase their mechanical work and alter their drag area (CdA) by adapting their posture when walking and running against increasing head and tailwinds. The observed drag force applied to the subject is different between walking and running at similar headwind speeds. [ABSTRACT FROM AUTHOR]

Unsteady locomotion (e. g., sprints and shuttle runs) requires additional metabolic (and mechanical) energy compared to running at constant speed. In addition, sprints or shuttle runs with relevant speed changes (e. g., with large accelerations and/or decelerations) are typically short in duration and, thus, anaerobic energy sources must be taken into account when computing energy expenditure. In sprint running there is an additional problem due to the objective difficulty in separating the acceleration phase from a (necessary and subsequent) deceleration phase. In this review the studies that report data of energy expenditure during sprints and shuttles (estimated or actually calculated) will be summarized and compared. Furthermore, the (mechanical) determinants of metabolic energy expenditure will be discussed, with a focus on the analogies with and differences from the energetics/mechanics of constant-speed linear running. [ABSTRACT FROM AUTHOR]

We compared running mechanics parameters determined from ground reaction force (GRF) measurements with estimated forces obtained from double differentiation of kinematic (K) data from motion analysis in a broad spectrum of running speeds (1.94-5.56 m⋅s-1). Data were collected through a force-instrumented treadmill and compared at different sampling frequencies (900 and 300 Hz for GRF, 300 and 100 Hz for K). Vertical force peak, shape, and impulse were similar between K methods and GRF. Contact time, flight time, and vertical stiffness (kvert) obtained from K showed the same trend as GRF with differences < 5%, whereas leg stiffness (kleg) was not correctly computed by kinematics. The results revealed that the main vertical GRF parameters can be computed by the double differentiation of the body center of mass properly calculated by motion analysis. The present model provides an alternative accessible method for determining temporal and kinetic parameters of running without an instrumented treadmill. [ABSTRACT FROM AUTHOR]

COVID-19 pandemic led many countries to implement lockdown measures. Italy declared lockdown from 9th March to 3rd May 2020, and universities shifted to online classes. Home confinement could prevent students from achieving the physical activity and sleep levels recommended for their psychophysical health, and medicine students are already known to be at risk of inactivity and reduced sleep due to their time-consuming curricula. This study aimed at describing medicine students' behaviours during lockdown and comparing them with pre-lockdown data and current recommendations. A cross-sectional questionnaire survey was conducted among 6th-year Italian medicine students (n = 714; age=25 ± 2 y; female: 62%; male: 38%) in October–November 2019. The same survey was repeated in 6th-year students during lockdown (n = 394; age=25 ± 2 y; female: 73%; male: 27%), and extended to 1st–5th year (total 1st–6th-year sample during lockdown: n = 1471; age=23 ± 2 y; female: 70%; male: 30%). International Physical Activity Questionnaire Short Form (IPAQ) and selected questions from Pittsburgh Sleep Quality Index were administered to evaluate physical activity, sitting and sleep time. Decreased physical activity, and increased sitting and sleep time were observed from pre- to during lockdown in 6th-year students (p<0.01). 1st–6th-year students featured 10 [8–12] hours sitting (median [Q1–Q3]) and an IPAQ score of 1170 [400–2348] MET-min/week. Even participants with higher physical activity featured high sitting time. Sleeping less than recommended (<7 h/night) was associated with more sitting time and less energies to perform daily activities. Strategies fostering compliance with current guidelines for physical activity, sedentary behaviour and sleep should be implemented, especially in case of a repeated or intermittent lockdown. [ABSTRACT FROM AUTHOR]

Purpose: Recently, some studies have suggested that overall training intensity may be more important than training volume for improving swimming performance. However, those studies focused on very young subjects, and/or the difference between high-volume and high-intensity training was blurred. The aim of this study was to investigate in masters swimmers the effects of manipulation of training volume and intensity on performance and physiological variables. Methods: A group of 10 male masters swimmers (age 32.3 ± 5.1 y) performed 2 different 6-wk training periods followed by 1 wk of tapering. The first period was characterized by high training volume performed at low intensity (HvLi), whereas the second period was characterized by low training volume performed at high intensity (LvHi). Peak oxygen consumption (...O2peak) during incremental arm exercise, individual anaerobic threshold (IAT), and 100-m, 400-m, and 2000-m-freestyle time were evaluated before and at the end of both training periods. Results: HvLi training significant increased ...O2peak (11.9% ± 4.9% [mean change ± 90%CL], P = .002) and performance in the 400-m (-2.8% ± 1.8%, P = .002) and 2000-m (-3.4% ± 2.9%, P = .025), with a likely change in IAT (4.9% ± 4.7%, P > .05). After LvHi training, speed at IAT (12.4% ± 5.3%, P = .004) and 100-m performance (-1.2% ± 0.8%, P = .001) also improved, without any significant changes in ...O2peak, 2000-m, and 400-m. Conclusions: These findings indicate that in masters swimmers an increase of training volume may lead to an improvement of ...O2peak and middle- to long-distance performance. However, a subsequent period of LvHi training maintains previous adjustments and positively affects anaerobic threshold and short-distance performance. [ABSTRACT FROM AUTHOR]