Preferred Speed Research Articles

Trunk variability and local dynamic stability during gait after generalized fatigue induced by incremental exercise test in young women in different phases of the menstrual cycle.

The purpose of this study was to identify how generalized fatigue along with hormonal changes throughout the menstrual cycle affects trunk variability and local dynamic stability during gait. General fatigue was induced by an incremental test on a treadmill, and the menstrual cycle was divided into three phases: follicular, ovulatory, and luteal. Twenty-six healthy, young volunteers (aged 18 to 28 years) who did not use oral contraceptives or other hormonal drugs with a regular menstrual cycle participated in the study. They walked on the treadmill for 4 min at the preferred speed, before the incremental test, followed by four sets of 4 min alternating between walking, also at preferred speed, and resting. From trunk kinematic data, the following were extracted: the mean of the standard deviation along strides, as a measure of variability, and the maximum Lyapunov exponent, as a measure of local dynamic stability (LDS). After the incremental test, variability increased, and LDS decreased. However, they showed a tendency to return to the initial value faster in women compared to previous results for men. In the follicular phase, which has less hormonal release, the volunteers had an almost complete recovery in LDS soon after the first rest interval, suggesting that female hormones can interfere with fatigue recovery. Nevertheless, concerning the LDS, it was significantly lower in the luteal phase than in the follicular phase. Women that are not taking oral contraceptives should be aware that they are susceptible to increased gait instabilities in the pre-menstrual phase after strenuous activities.

Reference Values and Determinants of Spatiotemporal and Kinetic Variables in Recreational Runners.

Identifying atypical lower limb biomechanics may help prevent the occurrence or recurrence of running-related injuries. No reference values for spatiotemporal or kinetic variables in healthy recreational runners are available in the scientific literature to support clinical management. To (1) present speed- and sex-stratified reference values for spatiotemporal and kinetic variables in healthy adult recreational runners; (2) identify the determinants of these biomechanical variables; and (3) develop reference regression equations that can be used as a guide in a clinical context. Descriptive laboratory study. This study involved 860 healthy recreational runners (age, 19-65 years [38.5% women]) tested on an instrumented treadmill at their preferred running speed in randomly allocated, standardized running shoes with either hard or soft cushioning. Twelve common spatiotemporal and kinetic variables-including contact time, flight time, duty factor, vertical oscillation, step cadence, step length, vertical impact peak (VIP), time to VIP, vertical average loading rate, vertical stiffness, peak vertical ground-reaction force (GRF), and peak braking force-were derived from GRF recordings. Reference values for each biomechanical variable were calculated using descriptive statistics and stratified by sex and running speed category (≤7, 8, 9, 10, 11, 12, 13, 14, and ≥15 km/h). Correlations and multiple regression analyses were performed to identify potential determinants independently associated with each biomechanical variable and generate reference equations. The mean running speed was 10.5 ± 1.3 km/h and 9 ± 1.1 km/h in men and women, respectively. While all potential predictors were significantly correlated with many of the 12 biomechanical variables, only running speed showed high correlations (r > 0.7). The adjusted R2 of the multiple regression equations ranged from 0.19 to 0.88. This study provides reference values and equations that may guide clinicians and researchers in interpreting spatiotemporal and kinetic variables in recreational runners. The reference values can be used as targets for clinicians working with recreational runners in cases where there is a clinical suspicion of a causal relationship between atypical biomechanics and running-related injury.

A pelvis-oriented margin of stability is robust against deviations in walking direction

The Margin of Stability (MOS) is often assessed relative to the intended, linear path of walking progression. When an unanticipated or irregular change in direction occurs, such as during a sudden turn or during activities of daily living, distinguishing the lateral from anteroposterior MOS can be challenging. The purpose of this study was to assess an anatomically orientated method of calculating the MOS using the pelvic orientation to define lateral and anteroposterior directions. We hypothesized that when straight walking was disrupted with a curved path, the pelvis-oriented MOS measure would be less variable compared to the global-oriented MOS measure. We recruited 16 unimpaired participants to walk at preferred and fast walking speeds along a straight walking path, as well as a path with an exaggerated, curvilinear deviation. We determined the within-subject mean and standard deviation of the anterior MOS at mid-swing and the posterior and lateral MOS at ipsilateral foot strike. For straight walking and curved walking separately, repeated measures factorial ANOVAs assessed the effects of model (global or pelvis-oriented), limb (left or right), and speed (preferred or fast) on these MOS values. Based on reduced variability during curved walking, the pelvis-oriented MOS was more robust to walking deviations than the globally defined MOS. In straight walking, the pelvis-oriented MOS was characterized by less lateral and more anterior stability with differences exacerbated by faster walking. These results suggest a pelvis-oriented MOS has utility when the path of progression is unknown or unclear.

Comparison of Different Kinematic Values of Lower Extremities during Gait between Individuals with Chronic Non-Specific Low Back Pain and Healthy Persons

Objective: The primary purpose of the present study was to compare the differences in lower extremity kinematic parameters in individuals who have chronic non-specific low back pain (CNLBP) with healthy control subjects (CTRL) during subphase of the stance phase. The secondary purpose was to compare the average walking speed of individuals who had CNLBP with CTRL during stance phase. Materials and Methods: The present study was conducted with 26 patients, 13 of 26 were participants with CNLBP and the other 13 were CTRL. To study the subject’s walking characteristics, 3D motion analysis was applied. Each subject was attached to 47 retroreflective markers and asked to walk barefoot on a 10-meter walkway at the preferred walking speed. The independent t-test and Mann Whitney U-test were used to compare joint excursions of each subphase of the stance phase and the average walking speed between two groups. Results: The CNLBP group had significantly lower forefoot motion in the sagittal plane during the initial contact phase than CTRL group, (p=0.017). They exhibited significantly lower hip motion in the sagittal plane (p=0.043), and lower knee motion in the transverse plane (p=0.007) during the forefoot contact phase as well. The CNLBP group exhibited significantly increased rearfoot motion in the frontal plane (p=0.002) during the foot flat phase. Moreover, the CNLBP group had significantly lower hip motion in the sagittal plane during the push-off phase (p=0.033). Conclusion: Individuals with CNLBP might modify their walking characteristics of the lower extremities and walk slower when compared with healthy persons to accommodate the pain they were dealing with. Keywords: Lower Extremity; Kinematics; Chronic Non-specific Low Back Pain; Gait; Gait Speed

"PNP slows down" - linearly-reduced whole body joint velocities and altered gait patterns in polyneuropathy.

Gait disturbances are a common consequence of polyneuropathy (PNP) and a major factor in patients' reduced quality of life. Less is known about the underlying mechanisms of PNP-related altered motor behavior and its distribution across the body. We aimed to capture whole body movements in PNP during a clinically relevant mobility test, i.e., the Timed Up and Go (TUG). We hypothesize that joint velocity profiles across the entire body would enable a deeper understanding of PNP-related movement alterations. This may yield insights into motor control mechanisms responsible for altered gait in PNP. 20 PNP patients (61 ± 14 years) and a matched healthy control group (CG, 60 ± 15 years) performed TUG at (i) preferred and (ii) fast movement speed, and (iii) while counting backward (dual-task). We recorded TUG duration (s) and extracted gait-related parameters [step time (s), step length (cm), and width (cm)] during the walking sequences of TUG and calculated center of mass (COM) velocity [represents gait speed (cm/s)] and joint velocities (cm/s) (ankles, knees, hips, shoulders, elbows, wrists) with respect to body coordinates during walking; we then derived mean joint velocities and ratios between groups. Across all TUG conditions, PNP patients moved significantly slower (TUG time, gait speed) with prolonged step time and shorter steps compared to CG. Velocity profiles depend significantly on group designation, TUG condition, and joint. Correlation analysis revealed that joint velocities and gait speed are closely interrelated in individual subjects, with a 0.87 mean velocity ratio between groups. We confirmed a PNP-related slowed gait pattern. Interestingly, joint velocities in the rest of the body measured in body coordinates were in a linear relationship to each other and to COM velocity in space coordinates, despite PNP. Across the whole body, PNP patients reduce, on average, their joint velocities with a factor of 0.87 compared to CG and thus maintain movement patterns in terms of velocity distributions across joints similarly to healthy individuals. This down-scaling of mean absolute joint velocities may be the main source for the altered motor behavior of PNP patients during gait and is due to the poorer quality of their somatosensory information. https://drks.de/search/de, identifier DRKS00016999.

O.4.1-6 Multidimensional physical activity profiles and changes in physical function and self-reported walking ability among community-dwelling older adults – a 4-year follow-up

Abstract Purpose Physical activity (PA) is multidimensional but often assessed using single metrics. We studied how data-driven PA profiles predict changes in physical functioning and self-reported walking ability over time among older adults. Methods Participants (n = 318) were community-dwelling 75-, 80- and 85-year-olds who wore a thigh-mounted accelerometer for 3-7 days at baseline. PA intensity, fragmentation, absolute and relative PA minutes, sit-to-stand transitions, and gait bout characteristics were used in PA profiling using k-means cluster analysis. Physical function was assessed at baseline and at follow-up 4 years later. Substantial decline in physical function was operationalized as decline of at least 2 points in the Short Physical Performance Battery (SPPB, range 0-12) and at least 0.2 m/s decline in habitual 10-m walking speed. Change in self-reported walking ability during 2 km walk was assessed using a 5-point scale (decline vs. no change/improvement for all). Data were analyzed using logistic regression analysis. Results Three physical activity profiles were identified, and named as Exercisers, Actives and Inactives. Exercisers and Actives accumulated high PA minutes, but Actives engaged in predominantly light intensity PA that was accumulated in shorter bouts. The largest difference was observed in relative PA minutes (minutes exceeding participants’ preferred walking speed). Inactives accumulated the lowest PA minutes, intensity and highest activity fragmentation. During the follow-up period, 32% of participants experienced a substantial decline in walking speed, 24% in SPPB score and 21% in self-reported walking ability. Among women, Exercisers, but not Actives, had lower risk for a substantial decline in walking speed (OR 0.30, 95% CI 0.10-0.95) and SPPB score (0.33, 0.12-0.88) compared to Inactives after adjusting for age, depressive symptoms, comorbidity and baseline walking speed or SPPB score. Among women, Exercisers also had lower risk for decline in self-reported walking ability, but this was explained by differences in health. For men, the differences were not statistically significant. Conclusions Daily PA that is accumulated in longer bouts and at intensity exceeding one’s preferred walking speed may be especially beneficial for the maintenance of physical function with advancing age. Funding Source Academy of Finland, Finnish Ministry of Education & Culture and European Research Council.

O.1.2-9 Sex-related differences in free-living estimates of physical activity energy expenditure between older men and women

Abstract Purpose Physical activity is often quantified as physical activity energy expenditure (PAEE), which may be affected by individual ability to sustain physical activity intensity. We examined if there is a true difference in physical activity between older women and men when their physical capacity is considered. Methods Out of the population-based sample of 1021 (75-85-year-old) adults (62 % women), 410 wore an accelerometer (100 Hz) and a single-channel ECG monitor (250 Hz) for at least 3 days in free-living. A treadmill walk calibration and previously validated equations were used to estimate PAEE from combined acceleration and heart rate sensing using branched equation modelling. Preferred walking speed in a six-minute walking test, fat free mass (FFM) using bioimpedance and isometric maximal leg extension strength scaled to FFM were measured. Independent t-test, Pearson correlation and hierarchical multiple regression were used for statistical analyses. Results PAEE was 41.4 (14.2) kJ/kg/day for men, which was significantly higher (p < 0.001) than the PAEE 34.8 (10.9) for women. Walking speed (1.2 (0.2) vs. 1.1 (0.2) m/s), FFM (56.9 (6.5) vs. 42.1 (4.8) kg) and maximal strength (7.4 (1.8) vs. 6.7 (1.8) N/kg) were higher in men than in women (all p < 0.001). PAEE was significantly associated with walking speed (r = 0.44, p < 0.001), FFM (r = 0.26, p < 0.001), and maximal strength (r = 0.26, p < 0.001). In the regression analysis, 22 % of the variation in PAEE was explained by walking speed, FFM and maximal strength combined (F = 37.8, p < 0.001), whereas adding sex did not improve the model (F = 28.9, p < 0.001). The strongest predictor of PAEE was preferred walking speed (standardized beta=0.35, p < 0.001). Conclusions The results indicate that the observed difference in physical activity volume between sexes was largely explained by physical characteristics, especially the faster preferred walking speed of men compared to women. Free-living physical activity is largely comprised of habitual walking especially in older people which makes walking speed a significant contributor of daily PAEE. Walking speed could be measured more widely in physical activity counselling and health care settings as a potential underlying factor of low physical activity in older people. Support/Funding Sources European Research Council, Academy of Finland and Yrjö Jahnsson Foundation.

Reactive dynamic balance in the geriatric setting : Possibilities for evaluation and quantification in functionally heterogeneous persons

Most falls in older persons occur during walking and are often due to maladaptation in response to gait perturbations. Therefore, the assessment of reactive dynamic balance is highly relevant for determining the individual risk of falling and could enable an early initiation of interventions. The methods available for perturbation of gait and for evaluating the corresponding reaction patterns are critically discussed in order to approach the assessment of reactive dynamic balance. Adiagnostic protocol for perturbation of gait on atreadmill was developed based on the literature. The application of the protocol to map reactive dynamic balance as comprehensively as possible is presented. After the initial determination of the individually preferred gait speed over ~6 min, the participant's gait is disrupted with 9 different types of perturbations over atime period of ~4:30 min. The evaluation options include spatiotemporal parameters and their variability, the margin of stability and the Lyapunov exponent. Dynamic reactive balance is apromising and specific parameter for quantifying the risk of falling in older persons. The comprehensive evaluation of the documented parameters is currently insufficient because there are no established methods or references. The development of aunified method for the sensitive determination of reactive dynamic balance is essential for its use in assessment of the risk of falling in the clinical context and for measuring the success of training.

Towards the Application of Hearables for Near-Fall Detection

Abstract Introduction: Falls and gait disorders often result in hospitalization and immobilization. Near-falls may be one of the earliest signs of increased fall risk. In the literature, several sensor positions are used for fall detection, but few studies include the head as a sensor position. Hearables and hearing aids are increasingly equipped with inertial measurement units (IMUs) and are therefore of particular interest for measuring the risk of falling in everyday life. Methods: Therefore, we investigate the suitability of the ear as a sensor position for near-fall detection in comparison to the standard sensor positions. The motion data of one study participant (female, 63 years) was exemplary analyzed. The participant walked at her individually preferred gait speed on a perturbation treadmill while nine different perturbations (anterior-posterior, medio-lateral and pitch) were applied with a time interval of 20-30 seconds. We used seven IMUs during the measurement at the positions ear, sternum, lumbar, wrist (left/right), foot (left/right). Results: The absolute acceleration signals at the seven different positions show the periodicity of the normal gait before the perturbation. During and after the perturbation changes in the motion pattern can be seen, whereby the response to the perturbation occurs with a slight time lag. The Pearson correlations show that the sensor positions sternum, lumbar and ear correlate well with each other and thus show similar signal characteristics in the reaction to this perturbation. Conclusion: This provides evidence that the ear sensor position is at least comparable to the preferred sensor positions in the literature on the torso. However, these results were obtained under laboratory conditions. Further research is needed to investigate the sensor position at the ear in everyday life.

Effect of increased running speed and weight carriage on peak and cumulative tibial loading.

Tibial stress injuries are a burdensome injury among military recruits. Military activities include running and the carriage of additional weight, and this may be related to the high risk of bone stress injuries. The aim of this study was to quantify tibial loading when running at two different speeds, with and without additional weight, and to quantify their combined influence. Fourteen male distance runners who ran at least 40 km per week ran barefoot on a force-instrumented treadmill in four conditions representing preferred running speed (mean (SD) 3.1 (0.3) m/s) and 20% increased running speed (3.8 (0.4) m/s), with and without 20% of body weight carried in a weight vest. Kinematics and kinetics were synchronously collected. Bending moments were estimated about the medial-lateral axis of the tibial centroid located 1/3rd of the length from distal to proximal. Static equilibrium was ensured at each 1% of stance. Peak bending moments were obtained in addition to cumulative-weighted loading, where weighted loading accounted for the relative importance of the magnitude of the bending moment and the quantity of loading using a bone-dependent weighting factor. There were no interaction effects for running speed and weight carriage on peak or cumulative tibial loading. Running at a 20% faster speed increased peak and cumulative loading per kilometer by 8.0% (p < 0.001) and 4.8% (p < 0.001), respectively. Carriage of an additional 20% of body weight increased peak and cumulative loading per kilometer by 6.6% (p < 0.001) and 8.5% (p < 0.001), respectively. Increasing the physical demand of running by increasing speed or weight carriage increased peak tibial loading and cumulative tibial loading per kilometer, and this may increase the risk of tibial stress injury. Running speed and weight carriage independently influenced tibial loading.

The Effect of Cognitive Task, Gait Speed, and Age on Cognitive-Motor Interference during Walking.

Dual-tasking can cause cognitive-motor interference (CMI) and affect task performance. This study investigated the effects of age, gait speed, and type of cognitive task on CMI during gait. Ten younger and 10 older adults walked on a pressure-sensitive GAITRite walkway which recorded gait speed and step length. Participants walked at a slow, preferred, or fast speed while simultaneously completing four cognitive tasks: visuomotor reaction time (VMRT), serial subtraction (SS), word list generation (WLG), and visual Stroop (VS). Each combination of task and speed was repeated for two trials. Tasks were also performed while standing. Motor and cognitive costs were calculated with the formula: ((single-dual)/single × 100). Higher costs indicate a larger reduction in performance from single to dual-task. Motor costs were higher for WLG and SS than VMRT and VS and higher in older adults (p < 0.05). Cognitive costs were higher for SS than WLG (p = 0.001). At faster speeds, dual-task costs increased for WLG and SS, although decreased for VMRT. CMI was highest for working memory, language, and problem-solving tasks, which was reduced by slow walking. Aging increased CMI, although both ages were affected similarly by task and speed. Dual-task assessments could include challenging CMI conditions to improve the prediction of motor and cognitive status.

A sensory-motor decoder that transforms neural responses in extrastriate area MT into smooth pursuit eye movements.

Visual motion drives smooth pursuit eye movements through a sensory-motor decoder that uses multiple parallel neural pathways to transform the population response in extrastriate area MT into movement. We evaluated the decoder by challenging pursuit in monkeys with reduced motion reliability created by reducing coherence of motion in patches of dots. Our strategy was to determine how reduced dot coherence changes the population response in MT. We then predicted the properties of a decoder that transforms the MT population response into dot coherence-induced deficits in the initiation of pursuit and steady-state tracking. During pursuit initiation, decreased dot coherence reduces MT population response amplitude without changing the preferred speed at its peak. The successful decoder reproduces the measured eye movements by multiplication of 1) the estimate of target speed from the peak of the population response with 2) visual-motor gain based on the amplitude of the population response. During steady-state tracking, the decoder that worked for pursuit initiation failed to reproduce the paradox that steady-state eye speeds do not accelerate to the target speed despite persistent image motion. It predicted eye acceleration to target speed even when monkeys' eye speeds were steady at well below the target speed. To account for the effect of dot coherence on steady-state eye speed, we postulate that the decoder uses sensory-motor gain to modulate the eye velocity positive feedback that normally sustains perfect steady-state tracking. Then, poor steady-state tracking persists because of balance between eye deceleration caused by low positive feedback gain and acceleration driven by MT.NEW & NOTEWORTHY By challenging a sensory-motor system with degraded sensory stimuli, we reveal how the sensory-motor decoder transforms the population response in extrastriate area MT into commands for the initiation and steady-state behavior of smooth pursuit eye movements. Conclusions are based on measuring population responses in MT for multiple target speeds and different levels of motion reliability and evaluating a decoder with a biologically motivated architecture to determine the decoder properties that create the measured eye movements.

Age-related changes in mobility assessments correlate with repetitive goal-directed arm-movement performance

BackgroundThere is ample evidence that mobility abilities between healthy young and elderly people differ. However, we do not know whether these differences are based on different lower leg motor capacity or instead reveal a general motor condition that could be detected by monitoring upper-limb motor behavior. We therefore captured body movements during a standard mobility task, namely the Timed Up and Go test (TUG) with subjects following different instructions while performing a rapid, repetitive goal-directed arm-movement test (arm-movement test). We hypothesized that we would be able to predict gait-related parameters from arm motor behavior, even regardless of age.MethodsSixty healthy individuals were assigned to three groups (young: mean 26 ± 3 years, middle-aged 48 ± 9, old 68 ± 7). They performed the arm-movement and TUG test under three conditions: preferred (at preferred movement speed), dual-task (while counting backwards), and fast (at fast movement speed). We recorded the number of contacts within 20 s and the TUG duration. We also extracted TUG walking sequences to analyze spatiotemporal gait parameters and evaluated the correlation between arm-movement and TUG results.ResultsThe TUG condition at preferred speed revealed differences in gait speed and step length only between young and old, while dual-task and fast execution increased performance differences significantly among all 3 groups. Our old group’s gait speed decreased the most doing the dual-task, while the young group’s gait speed increased the most during the fast condition. As in our TUG results, arm-movements were significant faster in young than in middle-aged and old. We observed significant correlations between arm movements and the fast TUG condition, and that the number of contacts closely predicts TUG timefast and gait speedfast. This prediction is more accurate when including age.ConclusionWe found that the age-related decline in mobility performance that TUG reveals strongly depends on the test instruction: the dual-task and fast condition clearly strengthened group contrasts. Interestingly, a fast TUG performance was predictable by the performance in a fast repetitive goal-directed arm-movements test, even beyond the age effect. We assume that arm movements and the fast TUG condition reflect similarly reduced motor function.Trial registrationGerman Clinical Trials Register (DRKS) number: DRKS00016999, prospectively registered on March, 26, 2019.

Dynamics and energetics of bottlenose dolphin (Tursiops truncatus) fluke-and-glide gait.

Intermittent locomotion composed of periods of active flapping/stroking followed by inactive gliding has been observed with species that inhabit both aerial and marine environments. However, studies on the energetic benefits of a fluke-and-glide (FG) gait during horizontal locomotion are limited for dolphins. This work presents a physics-based model of FG gait and an analysis of the associated cost of transport for bottlenose dolphins (Tursiops truncatus). New gliding drag coefficients for the model were estimated using measured data from free-swimming bottlenose dolphins. The data-driven approach used kinematic measurement from 84 h of biologging tag data collected from three animals to estimate the coefficients. A set of 532 qualifying gliding events were automatically extracted for estimation of the gliding drag coefficient. Next, data from 783 FG bouts were parameterized and used with the model-based dynamic analysis to investigate the cost benefits of FG gait. Experimental results indicate that FG gait was preferred at speeds of ∼2.2-2.7 m s-1. Observed FG bouts had an average duty factor of 0.45 and a gliding duration of 5 s. The average associated metabolic cost of transport (COT) and mechanical cost of transport (MECOT) of FG gait are 2.53 and 0.35 J m-1 kg-1, respectively, at the preferred speeds. This corresponded to a respective 18.9% and 27.1% reduction in cost when compared with model predictions of continuous fluking gait at the same average bout speed. Average thrust was positively correlated with fluking frequency and amplitude as animals accelerated during the FG bouts, whereas fluking frequency and amplitude were negatively correlated for a given thrust range. These results suggest that FG gait enhances the horizontal swimming efficiency of bottlenose dolphins and provides new insights into the gait dynamics of these animals.

How about running on Mars? Influence of sensorimotor coherence on running and spatial perception in simulated reduced gravity.

Motor control, including locomotion, strongly depends on the gravitational field. Recent developments such as lower-body positive pressure treadmills (LBPPT) have enabled studies on Earth about the effects of reduced body weight (BW) on walking and running, up to 60% BW. The present experiment was set up to further investigate adaptations to a more naturalistic simulated hypogravity, mimicking a Martian environment with additional visual information during running sessions on LBPPT. Twenty-nine participants performed three sessions of four successive five-min runs at preferred speed, alternating Earth- or simulated Mars-like gravity (100% vs. 38% BW). They were displayed visual scenes using a virtual reality headset to assess the effects of coherent visual flow while running. Running performance was characterized by normal ground reaction force and pelvic accelerations. The perceived upright and vection (visually-induced self-motion sensation)in dynamic visual environments were also investigated at the end of the different sessions. We found that BW reduction induced biomechanical adaptations independently of the visual context. Active peak force and stance time decreased, while flight time increased. Strong inter-individual differences in braking and push-off times appeared at 38% BW, which were not systematically observed in our previous studies at 80% and 60% BW. Additionally, the importance given to dynamic visual cues in the perceived upright diminished at 38% BW, suggesting an increased reliance on the egocentric body axis as a reference for verticality when the visual context is fully coherent with the previous locomotor activity. Also, while vection was found to decrease in case of a coherent visuomotor coupling at 100% BW (i.e., post-exposure influence), it remained unaffected by the visual context at 38% BW. Overall, our findings suggested that locomotor and perceptual adaptations were not similarly impacted, depending on the -simulated- gravity condition and visual context.

Relationship between rolling resistance, preferred speed, and manual wheelchair propulsion mechanics in non-disabled adults

Purpose To characterize the relationship among rolling resistance (RR), preferred speed, and propulsion mechanics. Methods N = 11 non-disabled individuals (mean (SD)); Age 24 years (2), BMI 23.8 kg/m2 (4.3) completed a submaximal graded wheelchair exercise test (GXTsubmax, fixed speed, terminated at Rating of Perceived Effort (RPE)=8 (0-10 scale)) and a single-blind, within-subject repeated measures wheelchair propulsion experiment (RME). RR at RPE = 10 (estimated maximum workload, Maxestimated) was estimated from the GXTsubmax RPE-RR relationship. RME consisted of N = 19 1-minute trials (self-selected speed) each followed by 2-minutes rest. The trials included N = 16 unique RR between 25-100% of Maxestimated. Averages of all pushes in N = 16 unique 1-minute trials were computed for average RR (N), speed (m/s), peak force (Fpeak (N)), force rate of rise (Fror (N/s)), push frequency (PF (pushes/min)), and push length (PL (deg)). Results Repeated measures correlation assessed relationships among outcome variables (α = 0.05). RR was associated with decreased speed (r=–0.81, p < 0.001), increased Fpeak (r = 0.92), Fror (r = 0.26), and PL (r = 0.32) (all p > 0.001), and unrelated to PF (r = 0.02, p = 0.848). Increased speed was associated with increased Fror (r = 0.23, p = 0.003) and PF (r = 0.27, p < 0.001) and decreased Fpeak (r=–0.66, p < 0.001) and PL (r=-0.25, p < 0.001). Conclusion Increasing RR increases Fpeak despite reducing self-selected speed. RR and speed were strongly and moderately related to Fpeak, respectively, but weakly related to other propulsion mechanics. These results suggest that reducing user-system RR may confer dual benefits of improved mobility and decreased upper extremity loading. Further testing among wheelchair users is required. Clinical trial registration number: NCT04987177

Effect of local ventilation temperature and speed under garments on the thermal response of humans at different metabolic rates

Ventilation under garments is one of the effective solutions to alleviate heat stress in the human body, but ventilation preferences and cooling effects in different body segments at different metabolic rates are not thoroughly studied. Eighteen participants performed three metabolic intensities of cycling exercise at 30 °C, RH 35%, where five body segments underwent adjustable ventilation. The ventilation preferences, psychological and physiological responses, and energy consumption were analyzed. The preferred ventilation temperature was approximately 24.5 ± 1.9 °C and the preferred ventilation speed was 1.56 ± 0.29–1.68 ± 0.27 m s-1. At low and moderate metabolic intensities, the five body segments preferred similar ventilation temperatures. At high metabolic intensity, the back preferred lower ventilation temperatures and higher ventilation speeds than the lower limbs. Additionally, the lower back and chest are considered optimal ventilation body segments to achieve higher overall thermal comfort. This study contributes to the optimization of personal ventilated cooling garments for different metabolism scenarios.

Indoor running temporal variability for different running speeds, treadmill inclinations, and three different estimation strategies.

Inertial measurement units (IMU) constitute a light and cost-effective alternative to gold-standard measurement systems in the assessment of running temporal variables. IMU data collected on 20 runners running at different speeds (80, 90, 100, 110 and 120% of preferred running speed) and treadmill inclination (±2, ±5, and ±8%) were used here to predict the following temporal variables: stride frequency, duty factor, and two indices of running variability such as the detrended fluctuation analysis alpha (DFA-α) and the Higuchi's D (HG-D). Three different estimation methodologies were compared: 1) a gold-standard optoelectronic device (which provided the reference values), 2) IMU placed on the runner's feet, 3) a single IMU on the runner's thorax used in conjunction with a machine learning algorithm with a short 2-second or a long 120-second window as input. A two-way ANOVA was used to test the presence of significant (p<0.05) differences due to the running condition or to the estimation methodology. The findings of this study suggest that using both IMU configurations for estimating stride frequency can be effective and comparable to the gold-standard. Additionally, the results indicate that the use of a single IMU on the thorax with a machine learning algorithm can lead to more accurate estimates of duty factor than the strategy of the IMU on the feet. However, caution should be exercised when using these techniques to measure running variability indices. Estimating DFA-α from a short 2-second time window was possible only in level running but not in downhill running and it could not accurately estimate HG-D across all running conditions. By taking a long 120-second window a machine learning algorithm could improve the accuracy in the estimation of DFA-α in all running conditions. By taking these factors into account, researchers and practitioners can make informed decisions about the use of IMU technology in measuring running biomechanics.

The impact of lecture playback speeds on concentration and memory

BackgroundThe information required to be learned and retained by medical students has continued to increase over the years. The stress that medical students face has already been highlighted in several studies, however, this in combination with a post-pandemic educational system subsequently generated a shift in medical education towards asynchronous streaming of daily lectures as part of the curriculum with variable playback speed options.MethodsThis paper aims to study the effectiveness of playback speeds, principally that of 1.5x and 2x playback speeds. One objective of this study is to analyze the existing literature regarding how playback speeds may impact learning, and to highlight the need for additional research. It has become apparent that there is not enough literature to support the role that playback speeds have in concentration and/or long-term memory retention in medical students. Due to this lack of information on the topic, this paper additionally highlights a study conducted on second year medical students at one university to assess the associations that may exist between lecture playback speeds of 1.5x and 2x and concentration and long-term retention of memory.ResultsBased on the data collected, it was found that there was no significant difference in student concentration or long-term memory retention with regards to lecture playback speeds.ConclusionsAlthough more studies are needed to better understand the topic, it is the current recommendation of the authorial team that students are free to watch medical school lectures at their preferred speed without worry of changes in learning ability.

Identification of subject-specific responses to footwear during running

Placing a stronger focus on subject-specific responses to footwear may lead to a better functional understanding of footwear’s effect on running and its influence on comfort perception, performance, and pathogenesis of injuries. We investigated subject-specific responses to different footwear conditions within ground reaction force (GRF) data during running using a machine learning-based approach. We conducted our investigation in three steps, guided by the following hypotheses: (I) For each subject x footwear combination, unique GRF patterns can be identified. (II) For each subject, unique GRF characteristics can be identified across footwear conditions. (III) For each footwear condition, unique GRF characteristics can be identified across subjects. Thirty male subjects ran ten times at their preferred (self-selected) speed on a level and approximately 15 m long runway in four footwear conditions (barefoot and three standardised running shoes). We recorded three-dimensional GRFs for one right-foot stance phase per running trial and classified the GRFs using support vector machines. The highest median prediction accuracy of 96.2% was found for the subject x footwear classification (hypothesis I). Across footwear conditions, subjects could be discriminated with a median prediction accuracy of 80.0%. Across subjects, footwear conditions could be discriminated with a median prediction accuracy of 87.8%. Our results suggest that, during running, responses to footwear are unique to each subject and footwear design. As a result, considering subject-specific responses can contribute to a more differentiated functional understanding of footwear effects. Incorporating holistic analyses of biomechanical data is auspicious for the evaluation of (subject-specific) footwear effects, as unique interactions between subjects and footwear manifest in versatile ways. The applied machine learning methods have demonstrated their great potential to fathom subject-specific responses when evaluating and recommending footwear.