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Purpose: Wetsuits have been shown to change swim biomechanics and, thus, increase performance, but not all athletes are comfortable with their use because of possible modifications in motor coordination. The aim of this study was to evaluate the effects of wetsuit use on biomechanical, physiological, and perceptual variables. Methods: Eleven national- and international-level triathletes, familiar with wetsuit use, performed 7 × 200-m front crawl at constant preset speed twice, with and without a full wetsuit. The trunk incline (TI) and index of coordination (IdC) were measured stroke by stroke using video analysis. Stroke, breaths, and kick count, and timing (as breathing/kick action per arm-stroke cycle); stroke length (SL); and underwater length were analyzed using inertial-measurement-unit sensors. Heart rate (HR), rating of perceived exertion (RPE), and swimming comfort were monitored during the task. Results: A lower TI; IdC; number of strokes, kicks, and breaths; HR; and RPE for each 200 m were found in wetsuit compared with swimsuit condition. Higher values of SL and underwater length were found in wetsuit, whereas no differences were found in swimming comfort and timing of kicks and breaths. An increase for swimsuit condition in number of strokes and breaths, HR, and RPE was found during the task compared with the first 200 m. Conclusion: Wetsuit use reduces TI and, thus, drag; increases propelling proficiency; and shows lower fatigability, without modifying motor coordination, compared with swimsuit use at the same speed. The use of a wetsuit during training sessions is recommended to increase comfort and the positive effects on performance.

Purpose We investigated the role of elastic strain energy on the “apparent” efficiency of locomotion (AE), a parameter that is known to increase as a function of running speed (up to 0.5–0.7) well above the values of “pure” muscle efficiency (about 0.25–0.30). Methods In vivo ultrasound measurements of the gastrocnemius medialis (GM) muscle–tendon unit (MTU) were combined with kinematic, kinetic and metabolic measurements to investigate the possible influence of the Achilles tendon mechanical behaviour on the mechanics (total mechanical work, WTOT) and energetics (net energy cost, Cnet) of running at different speeds (10, 13 and 16 km h−1); AE was calculated as WTOT/Cnet. Results GM fascicles shortened during the entire stance phase, the more so the higher the speed, but the majority of the MTU displacement was accommodated by the Achilles tendon. Tendon strain and recoil increased as a function of running speed (P P −1 m−1). Significant negative correlations (P P Conclusion These results support the notion that the dynamic function of tendons is integral in reducing energy expenditure and increasing the “apparent” efficiency of running.

Achilles tendon (AT) mechanical properties can be estimated using an inverse dynamic approach, taking into account the tendon internal moment arm (IMA) and its kinematic behavior. Although AT presents a curvilinear line of action, a straight-line function to estimate IMA and AT length is often utilized in the literature. In this study, we combined kinetic, kinematic and ultrasound data to understand the impact of two different approaches (straight-line vs. curvilinear) in determining AT mechanical properties in vivo (during walking and running at the self-selected speed). AT force and power were calculated based on data of AT IMA and AT length derived by both respective methods. All investigated parameters were significantly affected by the method utilized (paired t-test; p 0.05): when using the curvilinear method IMA was about 5% lower and AT length about 1.2% higher, whereas peak and mean values of AT force and power were 5% higher when compared to the straight-line method (both in walking and running). Statistic-parametric mapping (SMP) analysis revealed significant differences in IMA during the early and the late stance phase of walking and during the late stance phase of running (p 0.01); SPM revealed significant differences also in AT length during the entire stance phase in both locomotion modes (p 0.01). These results confirm and extend previous findings to human locomotion: neglecting the AT curvature might be a source of error, resulting in underestimates not only of internal moment arm and tendon length, but also of tendon force and power.

This study combines metabolic and kinematic measurements at the whole-body level, with EMG and ultrasound measurements to investigate the influence of muscle-tendon mechanical behavior on the energy cost (C

Biomechanics (and energetics) of human locomotion are generally studied at constant, linear, speed whereas less is known about running mechanics when velocity changes (because of accelerations, decelerations or changes of direction). The aim of this study was to calculate mechanical work and power and to estimate mechanical efficiency in shuttle runs (as an example of non-steady locomotion) executed at different speeds and over different distances. A motion capture system was utilised to record the movements of the body segments while 20 athletes performed shuttle runs (with a 180° change of direction) at three paces (slow, moderate and maximal) and over four distances (5, 10, 15 and 20 m). Based on these data the internal, external and total work of shuttle running were calculated as well as mechanical power; mechanical efficiency was then estimated based on values of energy cost reported in the literature. Total mechanical work was larger the faster the velocity and the shorter the distance covered (range: 2.3–3.7 J m−1 kg−1) whereas mechanical efficiency showed an opposite trend (range: 0.20–0.50). At maximal speed, over all distances, braking/negative power (about 21 W kg−1) was twice the positive power. Present results highlight that running humans can exert a larger negative than positive power, in agreement with the fundamental proprieties of skeletal muscles in vivo. A greater relative importance of the constant speed phase, associated to a better exploitation of the elastic energy saving mechanism, is likely responsible of the higher efficiency at the longer shuttle distances.

Mechanical output at a joint level could be influenced by its leverage characteristics and by its functional behaviour and both could change to accommodate the demands of a given locomotor task. In this study, the mechanical power generated at the knee and ankle joints and their functional indexes (i.e. damper, strut, spring and motor like-function) were calculated by using 3D kinematic and kinetic data during hopping at 2, 2.5, 3 and 3.5 Hz. The effective mechanical advantage (i.e. the ratio between internal and external moment arm) of the knee (EMAK) and ankle (EMAA) and joint stiffness were calculated as well. Joint stiffness increased with frequency whereas positive and negative joint power decreased with it, the ankle power values being always larger (20–50%) than those at the knee. EMAA reached its highest value (0.4) during the propulsive phase at 3 Hz whereas no significant changes in EMAK were observed as a function of frequency in both the absorption and propulsive phases. Knee joint-functional index shifted from a spring to a strut-like function with increasing frequency (from 56 to 8% and from 4 to 51%, respectively) while the ankle operated mainly as a spring (from 90 to 53%), its damper and motor-like indexes being negligible at all frequencies (

New findings What is the topic of this review? This narrative review explores past and recent findings on the mechanical determinants of energy cost during human locomotion, obtained by using a mechanical approach based on Konig's theorem (Fenn's approach). What advances does it highlight? Recent developments in analytical methods and of their applications allow a better understanding of the mechanical-bioenergetic interaction. Advances are: 1) the determination of "frictional" internal work; 2) the association between tendon work and apparent efficiency; 3) a better understanding of the role of energy recovery and internal work in pathological gait (amputees, stroke and obese); 4) a comprehensive analysis of human locomotion in (simulated) low gravity conditions. Abstract During locomotion, muscles use metabolic energy to produce mechanical work (in a more or less efficient way); as a matter of fact, energetics and mechanics can be considered as two sides of the same coin, the latter being investigated to understand the former. A mechanical approach based on Konig's theorem (Fenn's approach) has proved to be a useful tool to elucidate the determinants of the energy cost of locomotion (e. g. the pendulum-like model of walking and the bouncing model of running) and has resulted in many advances in this field. During the last 60 years, this approach has been refined and applied to explore the determinants of energy cost and efficiency in a variety of conditions (e.g. low gravity, un-steady speed). This narrative review aims to summarise current knowledge about the role that mechanical work has played in our understanding of energy cost to date, and to underline how recent developments in analytical methods and their applications in specific locomotion modalities (on a gradient, at low gravity and in un-steady conditions) and in pathological gaits (asymmetric gait pathologies, obese subjects and in the elderly) could continue to push this understanding further. The recent in vivo quantification of new aspects that should be included in the assessment of mechanical work (e.g. frictional internal work and elastic contribution) deserve future research and would improve our knowledge on the mechanical-bioenergetic interaction during human locomotion, as well as in sport science and space exploration. This article is protected by copyright. All rights reserved.

Background: Stroke is a leading cause of disability. Nonetheless, the care pathway for stroke rehabilitation takes partially into account the needs of chronic patients. This is due in part to the lack of evidence about the mechanisms of recovery after stroke, together with the poor knowledge of related and influencing factors. Here we report on the study protocol “Rehabilitation and Biomarkers of Stroke Recovery,” which consists of 7 work-packages and mainly aim to investigate the effects of long-term neurorehabilitation on stroke patients and to define a related profile of (clinical-biological, imaging, neurophysiological, and genetic-molecular) biomarkers of long-term recovery after stroke. The work-package 1 will represent the main part of this protocol and aims to compare the long-term effects of intensive self-rehabilitation vs. usual (rehabilitation) care for stroke.Methods: We planned to include a total of 134 adult subacute stroke patients (no more than 3 months since onset) suffering from multidomain disability as a consequence of first-ever unilateral ischemic stroke. Eligible participants will be randomly assigned to one of the following groups: intensive self-rehabilitation (based on the principles of “Guided Self-Rehabilitation Contract”) vs. usual care (routine practice). Treatment will last 1 year, and patients will be evaluated every 3 months according to their clinical presentation. The following outcomes will be considered in the main work-package: Fugl-Meyer assessment, Cognitive Oxford Screen Barthel Index, structural and functional neuroimaging, cortical excitability, and motor and somatosensory evoked potentials.Discussion: This trial will deal with the effects of an intensive self-management rehabilitation protocol and a related set of biomarkers. It will also investigate the role of training intensity on long-term recovery after stroke. In addition, it will define a set of biomarkers related to post-stroke recovery and neurorehabilitation outcome in order to detect patients with greater potential and define long-term individualized rehabilitation programs.Clinical Trial Registration:www.ClinicalTrials.gov, identifier: NCT04323501.

Purpose: Although wearing a wetsuit while swimming, when permitted, is primarily for safety reasons (ie, to protect against hypothermia), changes in buoyancy, biomechanics, and exercise performance have been reported. This narrative review covers the benefits of different wetsuit models on performance in swimming and triathlon. Methods: A computer search of online databases was conducted to locate relevant published research until March 2021. After the screening process, 17 studies were selected for analysis. Results: Most of the selected studies involved pool swimmers or triathletes completing short or middle distances in a pool while using a full or a long sleeveless wetsuit. Swimming with wetsuit elicited significant improvements in performance (maximum 11%), mainly by decreasing drag and energy cost, by increasing buoyancy, and by affecting technique. Different rates of change in each factor were found according to swimming ability and wetsuit model. In addition, wearing a wetsuit was often rated as uncomfortable by athletes. Conclusions: Although improvement in swimming performance by wearing a wetsuit has been reported in the literature, the amplitude of the improvement remains questionable. The enhancement in swimming performance is attributable merely to improvements in propulsion proficiency and buoyancy, as well as a reduction in drag. The extent to which athletes are familiar with the use of a wetsuit, their swimming ability, and the wetsuit model may play important roles in this improvement. More studies simulating competition and comparing elite versus nonelite athletes are needed.

BACKGROUND The aim of this study was to determine the influence of spring mass model characteristics (e.g. stiffness) and Achilles tendon properties in determining the energy cost of running in half marathon runners. METHODS Achilles tendon characteristics (i.e. cross-sectional area -ATCSA- and resting length -ATL-) were measured on 32 males by means of an ultrasound apparatus the day before a half marathon race. After these measurements the energy cost of running (C) was determined while the subjects run on a treadmill at the speed (vT) they were expected to maintain during the race (vR); the vertical (kvert) and leg (kleg) stiffness were calculated based on kinematic data. RESULTS No differences were observed between vT and vR. Higher values of vT were associated with larger values of kleg and kvert. The faster runners (with larger vT) were the ones with the lower C (r=-0.43, P

This study combines in vivo ultrasound measurements of the Vastus Lateralis (VL) and Gastrocnemius Medialis (GM) muscles with electromyographic, kinematic and kinetic measurements during treadmill running at different speeds (10, 13 and 16 km⋅h-1 ) to better understand the role of muscle and tendon behaviour in two functionally different muscle-tendon units. In addition, the Force-Length and Force-Velocity relationships of VL and GM were experimentally assessed by combining dynamometry and EMG data with ultrasound measurements. With increasing running speed, the operating length of the fascicles in the stance phase shifted towards smaller lengths in the GM (P

The energy expended to transport the body over a given distance (C, the energy cost) increases with speed both on land and in water. At any given speed, C is lower on land (e.g., running or cycling) than in water (e.g., swimming or kayaking) and this difference can be easily understood when one considers that energy should be expended (among the others) to overcome resistive forces since these, at any given speed, are far larger in water (hydrodynamic resistance, drag) than on land (aerodynamic resistance). Another reason for the differences in C between water and land locomotion is the lower capability to exert useful forces in water than on land (e.g., a lower propelling efficiency in the former case). These two parameters (drag and efficiency) not only can explain the differences in C between land and water locomotion but can also explain the differences in C within a given form of locomotion (swimming at the surface, which is the topic of this review): e.g., differences between strokes or between swimmers of different age, sex, and technical level. In this review, the determinants of C (drag and efficiency, as well as energy expenditure in its aerobic and anaerobic components) will, thus, be described and discussed. In aquatic locomotion it is difficult to obtain quantitative measures of drag and efficiency and only a comprehensive (biophysical) approach could allow to understand which estimates are "reasonable" and which are not. Examples of these calculations are also reported and discussed.

The aim of this study was to perform a kinematic analysis of the in-run, take-off and early flight phases in water ski jumping and to analyse the differences in linear/angular parameters between males and females. Forty-two elite skiers participated in this study (27 males; 15 females); their jumps were video recorded during competitions: the time course of absolute (trunk, thigh, ski) and relative (hip, knee, ankle) angles was calculated, as well as the (trochanter) resultant speed. Males were able to reach faster in-run speeds than females (25.4 ± 1.9 and 21.8 ± 1.2 m/s, respectively) and jumped further (56.2 ± 8.6 and 40.4 ± 6.3 m). Longer jumps were correlated with faster speeds in all phases (r range: 0.87-0.91

Different attentional foci may modify muscle activation during exercises. Our aim was to determine if it is possible to selectively activate the pectoralis major or triceps brachii muscles according to specific verbal instructions provided during the bench press exercise. 13 resistance-trained males (25.6±5.4 yrs, 182.7±9.1 cm, 86.4±9.7 kg) underwent an electromyographic signals acquisition of the sternocostal head, clavicular head of the pectoralis major, the anterior deltoid, and the long head of the triceps brachii (LT) during bench press exercise. Participants performed one non-instructed set (NIS) of 4 repetitions at 50% 1-repetition maximum (1-RM) and one NIS of 4 repetitions at 80% 1-RM. Four additional sets of 4 repetitions at 50% and 80% 1-RM were randomly performed with verbal instructions to isolate the chest muscles (chest instructed set, CIS) or to isolate the triceps muscles (triceps instructed set, TIS). Participants showed significantly higher LT activation during TIS compared to non-instructed set both at 50% (p=0.0199) and 80% 1-RM (p=0.0061) respectively. TIS elicited a significant (p=0.0250) higher activation of LT compared to CIS. Our results suggest that verbal instructions seem to be effective for increasing activity of the triceps brachii but not the pectoralis major during the bench press.

Open-water swimming (OWS) is an outdoor endurance discipline that takes place in oceans, seas, rivers and lakes. OWS involves physiological issues and environmental challenges not typically seen in other events within aquatic sports. However, performance in OWS is determined/affected by the specific challenges of aquatic locomotion; this chapter will thus be introduced by general principles regarding the bioenergetics and biomechanics of swimming with a specific focus on the physiological and biomechanical determinants of endurance speed. When compared to other endurance disciplines, in conventional OWS races sex differences in performance are rather low. Pacing strategies in OWS depend, among other factors, on the benefits of drafting. OWS is in fact a head-to-head competition where finishing position rather than finishing time is important and where the differences between the winner and the other competitors may be only marginal. A common risk in OWS is hypothermia; according to the American Heart Association hypothermia is defined as a core body temperature below 35°C.

Sprint running is a common feature of many sport activities. The ability of an athlete to cover a distance in the shortest time relies on his/her power production. The aim of this study was to provide an exhaustive description of the mechanical determinants of power output in sprint running acceleration and to check whether a predictive equation for internal power designed for steady locomotion is applicable to sprint running acceleration. Eighteen subjects performed two 20 m sprints in a gym. A 35-camera motion capture system recorded the 3D motion of the body segments and the body center of mass (BCoM) trajectory was computed. The mechanical power to accelerate and rise BCoM (external power, Pext ) and to accelerate the segments with respect to BCoM (internal power, Pint ) was calculated. In a 20 m sprint, the power to accelerate the body forward accounts for 50% of total power; Pint accounts for 41% and the power to rise BCoM accounts for 9% of total power. All the components of total mechanical power increase linearly with mean sprint velocity. A published equation for Pint prediction in steady locomotion has been adapted (the compound factor q accounting for the limbs' inertia decreases as a function of the distance within the sprint, differently from steady locomotion) and is still able to predict experimental Pint in a 20 m sprint with a bias of 0.70 ± 0.93 W kg-1 . This equation can be used to include Pint also in other methods that estimate external horizontal power only.

The aim of this study was to validate the accuracy of a 10 Hz GPS device (STATSports, Ireland) by comparing the instantaneous values of velocity determined with this device with those determined by kinematic (video) analysis (25 Hz). Ten male soccer players were required to perform shuttle runs (with 180° change of direction) at three velocities (slow: 2.2 m·s-1; moderate: 3.2 m·s-1; high: maximal) over four distances: 5, 10, 15 and 20 m. The experiments were video-recorded; the “point by point” values of speed recorded by the GPS device were manually downloaded and analysed in the same way as the “frame by frame” values of horizontal speed as obtained by video analysis. The obtained results indicated that shuttle distance was smaller in GPS than video analysis (p < 0.01). Shuttle velocity (shuttle distance/shuttle time) was thus smaller in GPS than in video analysis (p < 0.001); the percentage difference (bias, %) in shuttle velocity between methods was found to decrease with the distance covered (5 m: 9 ± 6%; 20 m: 3 ± 3%). The instantaneous values of speed were averaged; from these data and from data of shuttle time, the distance covered was recalculated; the error (criterion distance-recalculated distance) was negligible for video data (0.04 ± 0.28 m) whereas GPS data underestimated criterion distance (0.31 ± 0.55 m). In conclusion, the inaccuracy of this GPS unit in determining shuttle speed can be attributed to inaccuracy in determining the shuttle distance.

The purpose of this study was to determine the effectiveness of a 9 weeks aquatic training program on aerobic capacity, muscle strength, flexibility, balance and body composition in 34 healthy young adult women. Five typical water based exercises (WE) of known intensity were utilized during the classes; intensity ranged from “moderate” to “hard” according to ACSM criteria (RPE range 12–14). The group physical activity level and food intake were not significantly different before and after training. A significant decrease for the skin folds sum (−4.6 %) and for %fat mass (−3.8 %) calculated according to skin folds technique was found after training. DXA regional data showed a significant increase in the fat-free mass of arms (2.4 %) and trunk (0.9 %). According to the Astrand step test, the training program led to an increase of estimated maximal oxygen uptake (14.9 %) and a decrease in sub-maximal Heart Rate (−6.9 %). A significant change in the majority of the physical capacities tested was found: abdominal and upper body muscular endurance (21 and 36 %, respectively), leg flexors and extensors maximal strength (12 and 8 %, respectively) as well as balance (34 %) all improved after training (p

Objective: Prehospital spinal motion restriction as a prevention technique for secondary neurological injury is a key principle in emergency medicine. Our aim was to evaluate the effectiveness of different cervical spinal cord motion restriction techniques of awake and cooperative healthy volunteers during extrication. Methods: Twenty-three healthy volunteers were asked to exit a car (unassisted) with a rigid cervical collar (CC condition) or without it (autonomous exit: AE; instructed exit: IE); they were also extricated by two rescuers after setting a rigid cervical collar and by using an extrication device (CC + XT condition). Eight 3 D infrared cameras were calibrated around the vehicle to measure cervical spine angle, angular speed and acceleration in the sagittal plane. Surface wireless EMG electrodes were used to record superior trapezius, erector spinae and rectus abdominis muscle activity. All measures were recorded during two phases: device positioning (maneuver) and vehicle exiting. Results: The lowest range of motion was observed in CC during maneuver and exit (about 17°), the greatest in AE and IE (about 45°); when the extrication device was utilized along with the cervical collar (CC + XT) an increase, rather than a further decrease, in the range of motion was observed (about 25° during maneuver and exit). Larger values of angular speed and acceleration were observed in CC + XT when compared to CC, both during maneuver and exit (p < 0.001). The lowest EMG activity was observed during maneuver in CC and CC + XT; during exit a lower EMG activity was observed in CC + XT compared to CC (p < 0.001). Thus, when an extrication device is utilized (CC + XT), a lower active control of the cervical spine region is associated with faster and more brisk movements of the cervical spine compared to CC alone. Conclusions: Our findings support the idea that spinal motion restriction via rigid cervical collar of awake and cooperative trauma patients is effective in reducing cervical spine motion in the sagittal plane during vehicle extrication.

INTRODUCTION: The first widely-available dry-land training machines for swimmers were introduced about 40 years ago. They were designed so that swimmers could perform resistance exercise whilst more-closely replicating the movements of swimming, than when using other gymnasium-based resistance training machines. These machines were subsequently adapted and used as measurement tools (ergometers) in an array swimming research study. This narrative review categorizes and summarizes what has been shown by the research studies that have utilized this laboratory-based ergometry. EVIDENCE ACQUISITION: A search was conducted in PubMed, Web of Science, ScienceDirect and Scopus (1970-2018) and relevant publications were included. Publications were grouped into 4 main areas of research: 1) physiological responses to exercise; 2) functional evaluation of swimmers; 3) monitoring of training; 4) muscular work output of swimmers. EVIDENCE SYNTHESIS: Significant differences were showed between swim bench exercise and real swimming, especially in regard to the muscles involved. The difficulties of accurate reproduction of the movements and coordinated dynamic actions of swimming have not been overcome. Nevertheless, the literature shows that the use of these devices has provided a valuable contribution to swimming physiology, while overcoming difficulties presented by attempting to make physiological measurements in the water. CONCLUSIONS: In spite of its limitations, laboratory-based ergometry has allowed a valuable contribution to the understanding of the physiology, effects of training and efficiency of swimming.

The purpose of this study was to assess metabolic and kinematic parameters (contact and flight time, step length and frequency) while walking at the preferred speed (1.44 ± 0.22 m · s−1) and while performing an incremental running test (up to exhaustion) on a motorised treadmill (MT) and on a curved non-motorised treadmill (CNMT). Twenty-five volunteers (24.1 ± 3.4 years; 64.7 ± 11.2 kg) participated in the study. Maximal running speed on MT was significantly larger (P < 0.001) than on CNMT (4.31 ± 0.50 vs. 3.75 ± 0.39 m · s−1) but no differences in heart rate or oxygen uptake were observed at this speed. The energy cost of walking (Cw) and running (Cr) were significantly greater (P < 0.001) on CNMT than on MT (37 and 17%, respectively). No major differences in kinematic parameters were observed at paired, submaximal, running speeds (2.22–3.89 m · s−1) but was systematically larger in CNMT (of about 340 ml · min−1 · kg−1). This systematic difference can be expressed in terms of a larger “equivalent speed” on CNMT (of about 0.42 m · s−1) and should be attributed to factors other than the kinematic ones, such as the belt characteristics (e.g. friction, type of surface and curvature).

AB Purpose: A bioenergetical analysis of different exercise modes near maximal oxygen consumption (V[spacing dot above]O2max) intensity is scarce, hampering the prescription of training to enhance performance. We assessed the time sustained in swimming, rowing, running, and cycling at an intensity eliciting V[spacing dot above]O2max and determined the specific oxygen uptake (V[spacing dot above]O2) kinetics and total energy expenditure (Etot-tlim). Methods: Four subgroups of 10 swimmers, 10 rowers, 10 runners, and 10 cyclists performed (i) an incremental protocol to assess the velocity (vV[spacing dot above]O2max) or power (wV[spacing dot above]O2max) associated with V[spacing dot above]O2max and (ii) a square wave transition exercise from rest to vV[spacing dot above]O2max/wV[spacing dot above]O2max to assess the time to voluntary exhaustion (Tlim-100%V[spacing dot above]O2max). The V[spacing dot above]O2 was measured using a telemetric portable gas analyzer (K4b2, Cosmed, Rome, Italy) and V[spacing dot above]O2 kinetics analyzed using a double exponential curve fit. Etot-tlim was computed as the sum of its three components: aerobic (Aer), anaerobic lactic (Analac), and anaerobic alactic (Anaalac) contributions. Results: No differences were evident in Tlim-100% V[spacing dot above]O2max between exercise modes (mean +/- SD: swimming, 187 +/- 25; rowing, 199 +/- 52; running, 245 +/- 46; and cycling, 227 +/- 48 s). In contrast, the V[spacing dot above]O2 kinetics profile exhibited a slower response in swimming (21 +/- 3 s) compared with the other three modes of exercise (rowing, 12 +/- 3; running, 10 +/- 3; and cycling, 16 +/- 4 s) (P < 0.001). Etot-tlim was similar between exercise modes even if the Analac contribution was smaller in swimming compared with the other sports (P < 0.001). Conclusion: Although there were different V[spacing dot above]O2 kinetics and ventilatory patterns, the Tlim-100%V[spacing dot above]O2max was similar between exercise modes most likely related to the common central and peripheral level of fitness in our athletes.

Previous research has shown that walkers provided with interactive simulations of footstep sounds on a surface material different from the one they are walking upon, experience pseudo-haptic illusions and adjust their walking kinematic according to the perceived surfaces’ compliance. Since walking on real grounds with different degrees of compliance leads to different metabolic costs, an open question is whether pseudo-haptic illusions created by interactive footstep sounds are able to affect the metabolic parameters. This study investigated whether metabolic cost and movement’s kinematics are affected by such interactive auditory feedback in a constrained condition as walking on a treadmill. Participants were walking on a treadmill under three listening conditions: actual footsteps sounds, interactive simulations of footstep sounds on gravel and snow. The metabolic and kinematic data, as well as the perceived exertion, sense of effort, easiness, and feeling of sinking were recorded. Results showed that interactive footstep sounds provided during treadmill walking did not affect kinematic and metabolic parameters of walking, while they were effective in modulating participants’ perception. These results suggest that in a constrained and non self-selected pattern of locomotion the sound of action, even though correctly perceived, is not strong enough to induce a change in the metabolic and kinematics of the locomotion.

Context:Although the popularity of open-water swimming (OWS) events has significantly increased in the last decades, specific studies regarding performance of elite or age-group athletes in these events are scarce.Purpose:To analyze the existing literature on OWS.Methods:Relevant literature was located via computer-generated citations. During August 2016, online computer searches on PubMed and Scopus databases were conducted to locate published research.Results:The number of participants in ultraendurance swimming events has substantially increased in the last 10 y. In elite athletes there is a higher overall competitive level of women than of men. The body composition of female athletes (different percentage and distribution of fat tissue) shows several advantages (more buoyancy and less drag) in aquatic conditions that determine the small difference between males and females. The main physiological characteristics of open-water swimmers (OW swimmers) are the ability to swim at high percentage of (80–90%) for many hours. Furthermore, to sustain high velocity for many hours, endurance swimmers need a high propelling efficiency and a low energy cost.Conclusion:Open-water races may be characterized by extreme environmental conditions (water temperature, tides, currents, and waves) that have an overall impact on performance, influencing tactics and pacing. Future studies are needed to study OWS in both training and competition.

The purpose of this study was to explore the relationships between mechanical power, thrust power, propelling efficiency and sprint performance in elite swimmers. Mechanical power was measured in 12 elite sprint male swimmers: (1) in the laboratory, by using a whole-body swimming ergometer (W'TOT) and (2) in the pool, by measuring full tethered swimming force (FT) and maximal swimming velocity (Vmax): W'T = FT · Vmax. Propelling efficiency (ηP) was estimated based on the “paddle wheel model” at Vmax. Vmax was 2.17 ± 0.06 m · s−1, ηP was 0.39 ± 0.02, W'T was 374 ± 62 W and W'TOT was 941 ± 92 W. Vmax was better related to W'T (useful power output: R = 0.943, P < 0.001) than to W'TOT (total power output: R = 0.744, P < 0.01) and this confirms the use of the full tethered test as a valid test to assess power propulsion in sprinters and to estimate swimming performance. The ratio W'T/W'TOT (0.40 ± 0.04) represents the fraction of total mechanical power that can be utilised in water (e.g., ηP) and was indeed the same as that estimated based on the “paddle wheel model”; this supports the use of this model to estimate ηP in swimming. © 2017 Informa UK Limited, trading as Taylor & Francis Group.

To explore the interplay between arms-only propelling efficiency (η p), mechanical power output ( $$\dot W_{\text{tot}}$$ ) and swimming speed (V); these three parameters are indeed related through the following equation V 3 = 1/kη p $$\dot W_{\text{tot}}$$ (where k is the speed-specific drag; k = F/V 2); thus, the larger are η p and $$\dot W_{\text{tot}}$$ the larger is V. We furthermore wanted to test the hypothesis that a multiple linear regression between $$\dot W_{\text{tot}}$$ , η p and V would have a stronger correlation coefficient than a linear regression between $$\dot W_{\text{tot}}$$ and V alone. To this aim we recruited 29 master swimmers (21 M/8F) who were asked to perform (1) an incremental protocol at the arm-ergometer (dry-land test) to determine $$\dot W_{\text{tot}}$$ at $$\dot V$$ O2max (e.g. $$\dot V$$ max); (2) a maximal 200 m swim trial (with a pull buoy: arms only) during which V and η p were determined. No relationship was found between $$\dot W_{\text{max}}$$ and η p (not necessarily the swimmers with the largest $$\dot W_{\text{max}}$$ are those with the largest η p and vice versa) whereas significant correlations were found between $$\dot W_{\text{max}}$$ and V (R = 0.419, P = 0.024) and η p and V (R = 0.741, P = 0.001); a multiple linear regression indicates that about 75 % of the variability of V can be explained by the variability of $$\dot W_{\text{max}}$$ and η p (R = 0.865, P

Classical cross-country skiing can be performed using three main techniques: diagonal stride (DS), double poling (DP), and double poling with kick (DK). Similar to other forms of human and animal gait, it is currently unclear whether technique selection occurs to minimize metabolic cost or to keep some mechanical factors below a given threshold. The aim of this study was to find the determinants of technique selection. Ten male athletes roller skied on a treadmill at different slopes (from 0° to 7° at 10km/h) and speeds (from 6 to 18km/h at 2°). The technique preferred by skiers was gathered for every proposed condition. Biomechanical parameters and metabolic cost were then measured for each condition and technique. Skiers preferred DP for skiing on the flat and they transitioned to DK and then to DS with increasing slope steepness, when increasing speed all skiers preferred DP. Data suggested that selections mainly occur to remain below a threshold of poling force. Second, critically low values of leg thrust time may limit the use of leg-based techniques at high speeds. A small role has been identified for the metabolic cost of locomotion, which determined the selection of DP for flat skiing.

The purpose of this study was to investigate the changes in selected biomechanical variables in 80-m maximal sprint runs while imposing changes in step frequency (SF) and to investigate if these adaptations differ based on gender and training level. A total of 40 athletes (10 elite men and 10 women, 10 intermediate men and 10 women) participated in this study; they were requested to perform 5 trials at maximal running speed (RS): at the self-selected frequency (SFs) and at SF ±15% and ±30%SFs. Contact time (CT) and flight time (FT) as well as step length (SL) decreased with increasing SF, while kvert increased with it. At SFs, kleg was the lowest (a 20% decrease at ±30%SFs), while RS was the largest (a 12% decrease at ±30%SFs). Only small changes (1.5%) in maximal vertical force (Fmax) were observed as a function of SF, but maximum leg spring compression (ΔL) was largest at SFs and decreased by about 25% at ±30%SFs. Significant differences in Fmax, Δy, kleg and kvert were observed as a function of...

Purpose:The effects of different loads on kinematic and kinetic variables during sled towing were investigated with the aim to identify the optimal overload for this specific sprint training.Methods:Thirteen male sprinters (100-m personal best: 10.91 ± 0.14 s) performed 5 maximal trials over a 20-m distance in the following conditions: unloaded and with loads from 15% to 40% of the athlete’s body mass (BM). In these calculations the sled mass and friction were taken into account. Contact and flight times, stride length, horizontal hip velocity (vh), and relative angles of hip, knee, and ankle (at touchdown and takeoff) were measured step by step. In addition, the horizontal force (Fh) and power (Ph) and maximal force (Fh0) and power (Ph0) were calculated.Results:vh, flight time, and step length decreased while contact time increased with increasing load (P < .001). These variables changed significantly also as a function of the step number (P < .01), except between the 2 last steps. No differences were observed in Fh among loads, but Fh was larger in sled towing than in unloaded. Ph was unaffected by load up to +20%BM but decreased with larger loads. Fh0 and Ph0 were achieved at 20%BM. Up to 20%BM, no significant effects on joint angles were observed at touchdown and takeoff, while at loads >30%BM joint angles tended to decrease.Conclusion:The 20%BM condition represents the optimal overload for peak power production—at this load sprinters reach their highest power without significant changes in their running technique (eg, joint angles).

Purpose:To analyze the effects of swimming pace on the relative contribution of leg kick to swimming speed and to compare arm-stroke efficiency (ηF) assessed when swimming with the arms only (SAO) and while swimming front crawl (FCS) using individual and fixed adjustments to arm-stroke and leg-kick contribution to forward speed.Methods:Twenty-nine master swimmers (21 men, 8 women) performed SAO and FCS at 6 self-selected speeds from very slow to maximal. The average swimming speed (v), stroke frequency (SF), and stroke length (SL) were assessed in the central 10 m of the swimming pool. Then, a 2nd-order polynomial regression was used to obtain values of v at paired SF. The percentage difference in v between FCS and SAO, for each paired SF, was used to calculate the relative contributions of the arm stroke (AC) and leg kick (LC) to FCS. Then ηF was calculated using the indirect “paddle-wheel” approach in 3 different ways: using general, individual, and no adjustments to AC.Results:The LC increased with SF (and speed) from –1% ± 4% to 11% ± 1% (P < .05). At the lower FCS speeds, ηF calculated using general adjustments was lower than ηF calculated using individual adjustments (P < .05), but differences disappear at the fastest speeds. Finally, ηF calculated using individual adjustments to LC in the FCS condition did not differ with ηF assessed in the SAO condition at all the investigated speeds.Conclusions:The relative contributions of the arm stroke and leg kick should be individually estimated to reduce errors when calculating arm-stroke efficiency at different speeds and in different swimmers.

Acceleration and deceleration phases characterise shuttle running (SR) compared to constant speed running (CR); mechanical work is thus expected to be larger in the former compared to the latter, at the same average speed (v mean). The aim of this study was to measure total mechanical work (W tot + , J kg−1 m−1) during SR as the sum of internal (W int + ) and external (W ext + ) work and to calculate the efficiency of SR. Twenty males were requested to perform shuttle runs over a distance of 5 + 5 m at different speeds (slow, moderate and fast) to record kinematic data. Metabolic data were also recorded (at fast speed only) to calculate energy cost (C, J kg−1 m−1) and mechanical efficiency (eff+ = W tot + C −1) of SR. Work parameters significantly increased with speed (P

Determining the efficiency of a swimming stroke is difficult because different “efficiencies” can be computed based on the partitioning of mechanical power output (Ẇ) into its useful and nonuseful components, as well as because of the difficulties in measuring the forces that a swimmer can exert in water. In this paper, overall efficiency (ηO= ẆTOT/Ė, where ẆTOTis total mechanical power output, and Ė is overall metabolic power input) was calculated in 10 swimmers by means of a laboratory-based whole-body swimming ergometer, whereas propelling efficiency (ηP= ẆD/ẆTOT, where ẆDis the power to overcome drag) was estimated based on these values and on values of drag efficiency (ηD= ẆD/Ė): ηP= ηD/ηO. The values of ηDreported in the literature range from 0.03 to 0.09 (based on data for passive and active drag, respectively). ηOwas 0.28 ± 0.01, and ηPwas estimated to range from ∼0.10 (ηD= 0.03) to 0.35 (ηD= 0.09). Even if there are obvious limitations to exact simulation of the whole swimming stroke within the laboratory, these calculations suggest that the data reported in the literature for ηOare probably underestimated, because not all components of ẆTOTcan be measured accurately in this environment. Similarly, our estimations of ηPsuggest that the data reported in the literature are probably overestimated.

The decrease in swimming performance (v max) that occurs with age is a not only consequence of the physiological decrease in maximal metabolic power ( $${\dot{E}}_{\it max}$$ ) but can also be expected to depend on an increase in the energy cost of swimming (C) $${\nu}_{\rm max} = {\dot {E}}_{\rm max}/C.$$ In turn, for a given speed and stroke C = W d / (ηPηo) where W d is hydrodynamic resistance, ηP is propelling efficiency and ηo is overall efficiency. The aim of this study was to measure C in 47 male masters (31–85 years old) swimming the front crawl at sub-maximal, aerobic, speeds. During the experiments propelling efficiency and projected frontal area (A eff, an index of W d) were also determined by kinematic analysis. “Elder” masters (60–80 years) swam at a significantly slower pace (0.65 vs. 0.91 m s−1), with a lower ηP (0.23 vs. 0.31) and a larger A eff (0.39 vs. 0.23 m2) than “younger” masters (30–60 years). No significant differences in C (1.45 kJ m−1, on the average) were observed as a function of age or speed, but C values were significantly higher than those assessed in young elite swimmers at the very same speeds; the difference increasing with age with a rate of 0.75 % per year. With the due considerations (in this study the observed changes in ηP, A eff and C can be either attributed to changes in speed or age) these data confirm the hypothesis that an increase in C contributes to the decrease in swimming performance that occurs with age.