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1.
Scand J Med Sci Sports ; 34(3): e14597, 2024 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-38445516

RESUMO

We aimed to examine the validity of estimating spatiotemporal and ground reaction force (GRF) parameters during resisted sprinting using a robotic loading device (1080 Sprint). Twelve male athletes (age: 20.9 ± 2.2 years; height: 174.6 ± 4.2 cm; weight: 69.4 ± 6.1 kg; means ± SDs) performed maximal resisted sprinting with three different loads using the device. The step frequency and length and step-averaged velocity, anteroposterior GRF (Fap ), and the ratio of Fap to resultant GRF (RF) were estimated using the velocity and towing force data measured using the device. Simultaneously, the corresponding values were measured using a 50-m force plate system. The proportional and fixed biases of the estimated values against those measured using the force plate system were determined using ordinary least product (OLP) regression analysis. Proportional and fixed biases were observed for most variables. However, the proportional bias was small or negligible except for the step frequency. Conversely, the fixed bias was small for step-averaged velocity (0.11 m/s) and step length (0.04 m), whereas it was large for step frequency (0.54 step/s), Fap (16N), and RF (2.22%). For all variables except step frequency, the prediction intervals in the OLP regression dramatically decreased when the corresponding values were smoothed using a two-step moving average. These results indicate that by using the velocity and force data recorded in the loading device, most of the spatiotemporal and GRF variables during resisted sprinting can be estimated with some correction of the fixed bias and data smoothing using the two-step moving average.


Assuntos
Atletas , Corrida , Suporte de Carga , Adolescente , Humanos , Masculino , Adulto Jovem , Corrida/fisiologia , Robótica
2.
Sensors (Basel) ; 22(9)2022 May 07.
Artigo em Inglês | MEDLINE | ID: mdl-35591264

RESUMO

In order to master the position variation rule of radar false alarm signal under continuous wave (CW) electromagnetic interference and reveal the mechanism of CW on radar, taking a certain type of stepping frequency radar as the research object, theoretical analysis of the imaging mechanism of radar CW electromagnetic interference false alarm signals from the perspective of time-frequency decoupling and receiver signal processing. Secondly, electromagnetic interference injection method is used to test the single-frequency and dual-frequency electromagnetic interference effect of the tested equipment. The results show that under the single frequency CW electromagnetic interference, the sensitive bandwidth of false alarm signal is about ±75 MHz, and the position of false alarm signal irregularity changes. Under the in-band dual-frequency CW electromagnetic interference, the position of non-intermodulation false alarm signal is similar to that of single frequency. However, the distance difference of two non-intermodulation false alarm signals is regular. In addition, the positions of the second-order intermodulation false alarm signals of the tested radar are also regular, and its position changes with the change of the second-order intermodulation frequency difference.

3.
Res Sports Med ; 30(6): 603-615, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-33993825

RESUMO

Sprinting and dribbling a ball are considered essential for success in team sports, such as soccer. The purpose of the present study was to examine straight line (SL) and changes of direction (COD) sprinting and dribbling abilities after a standing and a flying starting position. Twelve amateur U12 male soccer players participated in the study. The participants were tested in four different sprinting conditions. The first consisted of 15 m SL sprinting and dribbling test by standing position; the second consisted of 15 m SL sprinting and dribbling test by flying start. The third condition consisted of 15 m COD sprinting and dribbling test by standing position, and the fourth condition consisted of 15 m COD sprinting and dribbling test by flying start. T-tests analysis indicated significant differences between SL sprinting and dribbling sprinting tests (P < 0.05) and between standing and flying start positions (P < 0.05). Step frequency was higher for sprinting tests (P < 0.05). Moreover, the results showed that step length was longer when players had a standing position (P < 0.05). These findings emphasize the importance for trainers to add parts without ball, focused on the development of certain fitness and running components.


Assuntos
Desempenho Atlético , Corrida , Futebol , Atletas , Fenômenos Biomecânicos , Humanos , Masculino
4.
Aging Clin Exp Res ; 33(11): 2989-2994, 2021 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-33778931

RESUMO

BACKGROUND AND AIMS: Gait speed estimation using wearable inertial sensors during daily activities suffers from high complexity and inaccuracies in distance estimation when integrating acceleration signals. The aim of the study was to investigate the agreement between the methods of gait speed estimation using the persons' walk ratio (step-length/step-frequency relation) or step-frequency (number of steps per minute) and a "gold standard". METHODS: For this cross-sectional validation study, 20 healthy community-dwelling older persons (mean age 72.1 years; 70% women) walked at slow, normal, and fast speed over an instrumented walkway (reference measure). Gait speed was calculated using the person's pre-assessed walk ratio. Furthermore, the duration of walking and number of steps were used for calculation. RESULTS: The agreement between gait speed calculation using the walk ratio or step-frequency (adjusted to body height) and reference was r = 0.98 and r = 0.93, respectively. Absolute and relative mean errors of calculated gait speed using pre-assessed walk ratio ranged between 0.03-0.07 m/s and 1.97-4.17%, respectively. DISCUSSION AND CONCLUSIONS: After confirmation in larger cohorts of healthy community-dwelling older adults, the mean gait speed of single walking bouts during activity monitoring can be estimated using the person's pre-assessed walk ratio. Furthermore, the mean gait speed can be calculated using the step-frequency and body height and can be an additional parameter in stand-alone activity monitoring.


Assuntos
Velocidade de Caminhada , Caminhada , Idoso , Idoso de 80 Anos ou mais , Estudos Transversais , Feminino , Marcha , Humanos , Vida Independente , Masculino
5.
J Sports Sci ; 39(9): 1039-1045, 2021 May.
Artigo em Inglês | MEDLINE | ID: mdl-33375895

RESUMO

The natural transition from walking to running occurs in adults at ≅140 steps/min. It is unknown when this transition occurs in children and adolescents. The purpose of this study was to develop a model to predict age- and anthropometry-specific preferred transition cadences in individuals 6-20 years of age. Sixty-nine individuals performed sequentially faster 5-min treadmill walking bouts, starting at 0.22 m/s and increasing by 0.22 m/s until completion of the bout during which they freely chose to run. Steps accumulated during each bout were directly observed and converted to cadence (steps/min). A logistic regression model was developed to predict preferred transition cadences using the best subset of parameters. The resulting model, which included age, sex, height, and BMI z-score, produced preferred transition cadences that accurately classified gait behaviour (k-fold cross-validated prediction accuracy =97.02%). This transition cadence ranged from 136-161 steps/min across the developmental age range studied. The preferred transition cadence represents a simple and practical index to predict and classify gait behaviour from wearable sensors in children, adolescents, and young adults. Moreover, herein we provide an equation and an open access online R Shiny app that researchers, practitioners, or clinicians can use to predict individual-specific preferred transition cadences.


Assuntos
Modelos Logísticos , Corrida/fisiologia , Caminhada/fisiologia , Adolescente , Fatores Etários , Estatura , Índice de Massa Corporal , Peso Corporal , Criança , Teste de Esforço , Feminino , Marcha/fisiologia , Humanos , Masculino , Modelos Teóricos , Fatores Sexuais , Fatores de Tempo , Adulto Jovem
6.
J Sports Sci ; 39(9): 1060-1069, 2021 May.
Artigo em Inglês | MEDLINE | ID: mdl-33258414

RESUMO

This study compared the kinematics (step and joint) and muscle activity of unresisted and active resisted 30 m sprints with different loads (10-40% body mass) in experienced male and female sprinters. Step kinematics were measured using a laser gun and contact mat in 28 male and female participants during unresisted 30 m sprint, and sprints with 10-40% of body mass (BM) active resistance, while peak angular velocities of lower limb was measured, together with muscle activation of nine muscles. Increased resisted loads resulted in slower 30 m times, as a result of lower step velocity mainly caused by shorter step lengths and frequencies, flight times and longer contact times, with a greater effect on women than on men. These step kinematic differences, due to increasing load were accompanied with lower peak joint movements. However, gender differences were only found for peak plantar flexion with unresisted and 10% BM resisted sprints. Furthermore, increasing load decreased calf and hamstring muscles activity, while medial vastus activity increased. Based upon these findings, it was concluded that when introducing active resisted sprints, women should sprint with approximately 10% less active loads than men to have equal step and joint kinematics development over the sprint distance.


Assuntos
Desempenho Atlético/fisiologia , Fenômenos Biomecânicos/fisiologia , Músculo Esquelético/fisiologia , Treinamento Resistido/métodos , Corrida/fisiologia , Adulto , Análise de Variância , Índice de Massa Corporal , Feminino , Marcha/fisiologia , Humanos , Masculino , Fatores Sexuais , Suporte de Carga/fisiologia , Adulto Jovem
7.
Sensors (Basel) ; 19(5)2019 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-30823662

RESUMO

Step Frequency Continuous Wave Ground Penetrating Radar (SFCW-GPR), as a tool for nondestructive testing of shallow soil surface targets, the realization of the function of SFCW-GPR is mainly based on the theory of refraction, reflection and scattering of electromagnetic wave in the discontinuity of dielectric constant. So, the UWB antenna system, an important part of SFCW-GPR, becomes more indispensable. In this paper, an improved modified universal antenna is designed, simulated and fabricated. Based on a typical Bow-tie antenna, it is modified by the methods of lumped loads, cavity-backed loading and structure loading. The simulated and measured results show that the UWB antenna has 1.36 GHz bandwidth from 0.64 to 2.0 GHz with three resonant wavelength peaks, and having been modified and improved, the UWB antenna performances including voltage standing-wave ratio (VSWR), input impedance, the boresight gain and current distribution, are much better than the typical Bow-tie antenna. In addition, the results of verification experiment of Step Frequency Continuous Wave (SFCW) show that the antenna can be applied to the working scenarios of SFCW-GPR.

8.
Scand J Med Sci Sports ; 28(1): 144-151, 2018 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-28345173

RESUMO

Increasing preferred step rate during running is a commonly used strategy in the management of running-related injuries. This study investigated the effect of different step rates on plantar pressures during running. Thirty-two healthy runners ran at a comfortable speed on a treadmill at five step rates (preferred, ±5%, and ±10%). For each step rate, plantar pressure data were collected using the pedar-X in-shoe system. Compared to running with a preferred step rate, a 10% increase in step rate significantly reduced peak pressure (144.5±46.5 vs 129.3±51 kPa; P=.033) and maximum force (382.3±157.6 vs 334.0±159.8 N; P=.021) at the rearfoot, and reduced maximum force (426.4±130.4 vs 400.0±116.6 N; P=.001) at the midfoot. In contrast, a 10% decrease in step rate significantly increased peak pressure (144.5±46.5 vs 161.5±49.3 kPa; P=.011) and maximum force (382.3±157.6 vs 425.4±155.3 N; P=.032) at the rearfoot. Changing step rate by 5% provided no effect on plantar pressures, and no differences in plantar pressures were observed at the medial forefoot, lateral forefoot or hallux between the step rates. This study's findings indicate that increasing preferred step rate by 10% during running will reduce plantar pressures at the rearfoot and midfoot, while decreasing step rate by 10% will increase plantar pressures at the rearfoot. However, changing preferred step rate by 5% will provide no effect on plantar pressures, and forefoot pressures are unaffected by changes in step rate.


Assuntos
Pé/fisiologia , Marcha , Pressão , Corrida/fisiologia , Adulto , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Adulto Jovem
9.
Pediatr Exerc Sci ; 30(1): 115-123, 2018 02 01.
Artigo em Inglês | MEDLINE | ID: mdl-28787247

RESUMO

PURPOSE: We attempted to determine the relationships between the cross-sectional area (CSA) of the trunk and lower limb muscles and sprint performance in male preadolescent sprinters. METHODS: Fifteen sprint-trained preadolescent boys (age 11.6 ± 0.4 y) participated in this study. The CSAs of the participants' trunk and lower limb muscles were measured using magnetic resonance imaging, and these muscles were normalized with free-fat mass. To assess participants' sprint performance, sprint time and variables during the 50-m sprint test were measured. The sprint variables were expressed as their indices by normalizing with body height. RESULTS: The relative CSAs of psoas major, adductors, and quadriceps femoris were significantly correlated with sprint time (r = -.802, -.643, and -.639). Moreover, the relative CSAs of these muscles were significantly correlated with indices of sprint velocity (r = .694, .612, and .630) and step frequency (r = .687, .740, and .590) but not with that of step length. CONCLUSIONS: These findings suggest that greater hip flexor and knee extensor muscularity in male preadolescent sprinters may help achieve superior sprint performance by potentially enhancing their moments, which may be induced by increased step frequency rather than step length during sprinting.


Assuntos
Desempenho Atlético/fisiologia , Músculo Quadríceps/fisiologia , Corrida/fisiologia , Composição Corporal , Criança , Quadril , Humanos , Joelho , Imageamento por Ressonância Magnética , Masculino , Músculo Quadríceps/anatomia & histologia , Tronco
10.
J Sports Sci ; 36(5): 499-505, 2018 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-28481686

RESUMO

Our purpose was to compare joint loads between habitual rearfoot (hRF) and habitual mid/forefoot strikers (hFF), rearfoot (RFS) and mid/forefoot strike (FFS) patterns, and shorter stride lengths (SLs). Thirty-eight hRF and hFF ran at their normal SL, 5% and 10% shorter, as well as with the opposite foot strike. Three-dimensional ankle, knee, patellofemoral (PF) and hip contact forces were calculated. Nearly all contact forces decreased with a shorter SL (1.2-14.9% relative to preferred SL). In general, hRF had higher PF (hRF-RFS: 10.8 ± 1.4, hFF-FFS: 9.9 ± 2.0 BWs) and hip loads (axial hRF-RFS: -9.9 ± 0.9, hFF-FFS: -9.6 ± 1.0 BWs) than hFF. Many loads were similar between foot strike styles for the two groups, including axial and lateral hip, PF, posterior knee and shear ankle contact forces. Lateral knee and posterior hip contact forces were greater for RFS, and axial ankle and knee contact forces were greater for FFS. The tibia may be under greater loading with a FFS because of these greater axial forces. Summarising, a particular foot strike style does not universally decrease joint contact forces. However, shortening one's SL 10% decreased nearly all lower extremity contact forces, so it may hold potential to decrease overuse injuries associated with excessive joint loads.


Assuntos
Pé/fisiologia , Antepé Humano/fisiologia , Marcha/fisiologia , Extremidade Inferior/fisiologia , Corrida/fisiologia , Articulação do Tornozelo/fisiologia , Fenômenos Biomecânicos , Articulação do Quadril/fisiologia , Humanos , Articulação do Joelho/fisiologia , Articulação Patelofemoral/fisiologia , Inquéritos e Questionários , Estudos de Tempo e Movimento , Adulto Jovem
11.
J Sports Sci ; 36(12): 1392-1401, 2018 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-28988513

RESUMO

We aimed to investigate the step-to-step spatiotemporal variables and ground reaction forces during the acceleration phase for characterising intra-individual fastest sprinting within a single session. Step-to-step spatiotemporal variables and ground reaction forces produced by 15 male athletes were measured over a 50-m distance during repeated (three to five) 60-m sprints using a long force platform system. Differences in measured variables between the fastest and slowest trials were examined at each step until the 22nd step using a magnitude-based inferences approach. There were possibly-most likely higher running speed and step frequency (2nd to 22nd steps) and shorter support time (all steps) in the fastest trial than in the slowest trial. Moreover, for the fastest trial there were likely-very likely greater mean propulsive force during the initial four steps and possibly-very likely larger mean net anterior-posterior force until the 17th step. The current results demonstrate that better sprinting performance within a single session is probably achieved by 1) a high step frequency (except the initial step) with short support time at all steps, 2) exerting a greater mean propulsive force during initial acceleration, and 3) producing a greater mean net anterior-posterior force during initial and middle acceleration.


Assuntos
Desempenho Atlético , Corrida/fisiologia , Aceleração , Atletas , Fenômenos Biomecânicos , Humanos , Masculino , Análise Espaço-Temporal , Adulto Jovem
12.
J Sports Sci ; 35(4): 339-345, 2017 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-27028346

RESUMO

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 skill and gender (P < 0.001). Our results indicate that RS is optimised at SFs and that, while kvert follows the changes in SF, kleg is lowest at SFs.


Assuntos
Desempenho Atlético , Marcha , Corrida , Adolescente , Adulto , Fenômenos Biomecânicos , Elasticidade , Feminino , Identidade de Gênero , Humanos , Perna (Membro) , Masculino , Educação Física e Treinamento , Fatores Sexuais , Adulto Jovem
13.
J Sports Sci Med ; 15(2): 239-46, 2016 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-27274660

RESUMO

Mountain endurance running has increased in popularity in recent years. Thus the aim of the present study was to determine if maximal oxygen uptake (VO2max) and energy cost of running (Cr) measured during level and uphill running are associated. Ten high level male endurance mountain runners performed three maximal oxygen uptake tests at three slope conditions (0, 12.5 and 25%). Metabolic data, step frequency (SF) and step length (SL) were recorded. No significant differences were found in VO2max (63.29 (±3.84), 63.97 (±3.54) and 63.70 (±3.58) mlO2/kg(-1)/min(-1)) or associated metabolic data at 0, 12.5 and 25% slope respectively. High intra-individual correlations were found between metabolic data measured in the three conditions. The energy cost of running was significantly different between slopes (0.192 (±0.01), 0.350 (±0.029) and 0.516 (±0.035) mlO2/kg(-1)/min(-1), p < 0.01), 0, 12.5 and 25% respectively. However, Cr0% was not correlated with either Cr25% or Cr12.5% (rs = 0.09 and rs = 0.10), in contrast, Cr25% and Cr12.5% were correlated (rs = 0.78). Step length was positively correlated with speed under the three slope conditions. Step frequency was significantly lower at 25 compared to 12.5 and 0% slope. We found that the maximum aerobic power did not differ between level and graded treadmill tests. However, the increase in Cr on the inclined versus level conditions varied between subjects. None of the measured anthropometric or kinematic variables could explain the higher increase in Cr of some subjects when running uphill. Thus, a short graded (5min at 12.5%) running test should be performed at a submaximal velocity (around 40% of level vVO2max) to enhance understanding of an endurance runner's uphill capability. Key pointsIn elite endurance mountain runners, there is no difference in VO2max values between level and uphill running.In a homogeneous group of mountain runners, uphill Cr is not associated with level Cr.To assess performance potential of endurance mountain runners, a standardized uphill running protocol should be performed.

14.
J Muscle Res Cell Motil ; 36(6): 463-77, 2015 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-26728749

RESUMO

Myosin in muscle transduces ATP free energy into the mechanical work of moving actin. It has a motor domain transducer containing ATP and actin binding sites, and, mechanical elements coupling motor impulse to the myosin filament backbone providing transduction/mechanical-coupling. The mechanical coupler is a lever-arm stabilized by bound essential and regulatory light chains. The lever-arm rotates cyclically to impel bound filamentous actin. Linear actin displacement due to lever-arm rotation is the myosin step-size. A high-throughput quantum dot labeled actin in vitro motility assay (Qdot assay) measures motor step-size in the context of an ensemble of actomyosin interactions. The ensemble context imposes a constant velocity constraint for myosins interacting with one actin filament. In a cardiac myosin producing multiple step-sizes, a "second characterization" is step-frequency that adjusts longer step-size to lower frequency maintaining a linear actin velocity identical to that from a shorter step-size and higher frequency actomyosin cycle. The step-frequency characteristic involves and integrates myosin enzyme kinetics, mechanical strain, and other ensemble affected characteristics. The high-throughput Qdot assay suits a new paradigm calling for wide surveillance of the vast number of disease or aging relevant myosin isoforms that contrasts with the alternative model calling for exhaustive research on a tiny subset myosin forms. The zebrafish embryo assay (Z assay) performs single myosin step-size and step-frequency assaying in vivo combining single myosin mechanical and whole muscle physiological characterizations in one model organism. The Qdot and Z assays cover "bottom-up" and "top-down" assaying of myosin characteristics.


Assuntos
Músculo Esquelético/metabolismo , Músculo Estriado/metabolismo , Cadeias Leves de Miosina/metabolismo , Actinas/metabolismo , Animais , Suínos
15.
bioRxiv ; 2024 Jun 02.
Artigo em Inglês | MEDLINE | ID: mdl-38854143

RESUMO

Older adults and neurological populations tend to walk with slower speeds, more gait variability, and a higher metabolic cost. This higher metabolic cost could be related to their increased gait variability, but this relationship is still unclear. The purpose of this study was to determine how increased step length variability affects the metabolic cost of waking. Eighteen healthy young adults completed a set of 5-minute trials of treadmill walking at 1.20 m/s while we manipulated their step length variability. Illuminated rectangles were projected onto the surface of a treadmill to cue step length variabilities of 0, 5 and 10% (coefficient of variation). Actual step lengths and their variability were tracked with reflective markers on the feet, while metabolic cost was measured using indirect calorimetry. Changes in metabolic cost across habitual walking (no projections) and the three variability conditions were analyzed using a linear mixed effects model. Metabolic power was largest in the 10% condition (4.30 ± 0.23 W/kg) compared to 0% (4.16 ± 0.18 W/kg) and habitual (3.98 ± 0.25 W/kg). The participant's actual step length variability did not match projected conditions for 0% (3.10%) and 10% (7.03%). For every 1% increase in step length variability, there is an 0.7% increase in metabolic cost. Our results demonstrate an association between the metabolic cost of walking and gait step length variability. This suggests that increased gait variability contributes to a portion of the increased cost of walking seen in older adults and neurological populations.

16.
Micromachines (Basel) ; 14(7)2023 Jun 27.
Artigo em Inglês | MEDLINE | ID: mdl-37512631

RESUMO

The existing producing processes of micro spiral swimmers are complex. Here, a microswimmer with a magnetic layer on the surface of the spiral carbon nanotubes is proposed, which has a simple producing process. For the microswimmer, its equations of the velocities and out-step frequency are deduced. Using these equations, the velocities and out-step frequency of the microswimmer and their changes with related parameters are investigated. Results show that its velocities are proportional to the radius and helix angle of the spiral carbon nanotubes, and its out-step frequencies are proportional to magnetic field strength, the helix angle and magnetic layer thicknesses of the spiral carbon nanotubes, and inversely proportional to the fluid viscosity. The out-step frequency of the microswimmer is measured, which is in good agreement with the calculative ones.

17.
Hum Mov Sci ; 89: 103086, 2023 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-37119660

RESUMO

It is commonly thought that at prescribed speeds humans choose gait parameters that minimize the cost of transportation. However, it is unclear whether and how the relationship between step length and step frequency is affected by the additional physiological factors caused by constraints. We performed a series of experiments to understand the selection of gait parameters under different constraints from a probabilistic perspective. First, we show that the effect of constraining step length on step frequency (i.e., monotonically decrease, Experiment I) is different from the effect of constraining step frequency on step length (i.e., inverted-U, Experiment II). Using the results from Experiment I and II, we summarized the marginal distribution of step length and step frequency and built their joint distribution in a probabilistic model. The probabilistic model predicts the selection of gait parameters by achieving the maximum probability of joint distribution of step length and step frequency. In Experiment III, the probabilistic model could well predict gait parameters at prescribed speeds, and it is similar to minimizing the cost of transportation. Finally, we show that the distribution of step length and step frequency were completely different between constrained and non-constrained walking. We argue that constraints in walking are major factors determining how humans choose gait parameters due to their involvement of mediators, i.e., attention or active control. Using the probabilistic model to account for gait parameters has an advantage compared with fixed-parameter models in that it can still include the effect of hidden mechanical, neurophysiological, or psychological variables by grouping them into distribution curves.


Assuntos
Marcha , Caminhada , Humanos , Caminhada/fisiologia , Marcha/fisiologia , Modelos Estatísticos , Fenômenos Biomecânicos
18.
Gait Posture ; 98: 283-288, 2022 10.
Artigo em Inglês | MEDLINE | ID: mdl-36242910

RESUMO

BACKGROUND: The duty factor (reflecting the ratio of stance to flight time) is an important variable related to running performance, economy, and injury risk. According to the dual-axis model, the duty factor and the cadence are sufficient to describe an individual's running style at a certain speed. To test this model, one should be able to modulate both variables independently. While acoustic pacing is an established method for cadence modulation, no such method is available for duty-factor modulation. RESEARCH QUESTIONS: Can people modulate their duty factor based on verbal instructions to change either their stance or flight time without changing their cadence? And, if so, which instruction is most effective? METHODS: Twelve participants ran on an instrumented treadmill and completed four training blocks starting with a baseline trial and ending with a performance trial in which they followed verbal instructions to both increase and decrease their stance and flight time. Acoustic pacing at their preferred cadence was present during the first part of each trial. We calculated the duty factor and cadence for paced and non-paced parts of each trial, assessed the effectiveness of the instructions aimed at changing the duty factor, and examined the effects of instructions and acoustic pacing on cadence using Bayesian statistics. RESULTS: The duty factor changed in intended directions with verbal instructions to increase and decrease the stance and flight time (18.04 ≤ BF10 ≤ 4954.42), without differences between the instructions or during and after acoustic pacing. The instructions and acoustic pacing did not result in a consistent change in cadence (0.40 ≤ BF10 ≤ 2.59). SIGNIFICANCE: Runners can change their duty factor through verbal instructions pertaining to stance or flight time, without clear concomitant effects on cadence. Running styles can thus be altered with verbal instructions to change stance or flight time for duty-factor modulation, optionally combined with acoustic pacing to prescribe cadence.


Assuntos
Corrida , Humanos , Fenômenos Biomecânicos , Teorema de Bayes , Corrida/lesões , Teste de Esforço , Fatores de Tempo
19.
Front Physiol ; 13: 820666, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-35492612

RESUMO

We tested the hypothesis that restricting either step frequency (SF) or stride length (SL) causes a decrease in ventilatory response with limited breath frequency during sinusoidal walking. In this study, 13 healthy male and female volunteers (mean ± SD; age: 21.5 ± 1.8 years, height: 168 ± 7 cm, weight: 61.5 ± 8.3 kg) participated. The walking speed was sinusoidally changed between 50 and 100 m⋅min-1 with periods from 10 to 1 min. Using a customized sound system, we fixed the SF at 120 steps⋅min-1 with SL variation (0.83-0.41 m) (SF fix ) or fixed the SL at 0.7 m with SF variation (143-71 steps⋅min-1) (SL fix ) during the subjects' sinusoidal walking. Both the subjects' preferred locomotion pattern without a sound system (Free) and the unprompted spontaneous locomotor pattern for each subject (Free) served as the control condition. We measured breath-by-breath ventilation [tidal volume (VT) and breathing frequency (Bf)] and gas exchange [CO2 output ( V . CO2), O2 uptake ( V . O2)]. The amplitude (Amp) and the phase shift (PS) of the fundamental component of the ventilatory and gas exchange variables were calculated. The results revealed that the SF fix condition decreased the Amp of the Bf response compared with SL fix and Free conditions. Notably, the Amp of the Bf response under SF fix was reduced by less than one breath at the periods of 5 and 10 min. In contrast, the SL fix condition resulted in larger Amps of Bf and V . E responses as well as Free. We thus speculate that the steeper slope of the V . E - V . CO2 relationship observed under the SL fix might be attributable to the central feed-forward command or upward information from afferent neural activity by sinusoidal locomotive cadence. The PSs of the V . E , V . O2, and V . CO2 responses were unaffected by any locomotion patterns. Such a sinusoidal wave manipulation of locomotion variables may offer new insights into the dynamics of exercise hyperpnea.

20.
Gait Posture ; 92: 328-332, 2022 02.
Artigo em Inglês | MEDLINE | ID: mdl-34915404

RESUMO

BACKGROUND: Different approaches have been implemented to calculate stepping cadence (steps/min) that vary in the time demominator used. Given the differences in how stepping intensity are calculated, it is unclear if they are more so associated with total step counts. RESEARCH OBJECTIVE: This study compared three methods of calculating stepping cadence and determined their relationship with total step counts. METHODS: 132 participants (74♀; 35 ± 20 years; body mass index: 24.9 ± 4.0 kg•m-2) wore an activPAL monitor 24-hr/day for up to 8-d (total: 869-d). The total steps/day, time spent stepping (0.1 s resolution; to calculate bout stepping rate), time spent stepping in 60 s epochs (step accumulation), and awake time (awake cadence) were determined. Each cadence method (in steps/min) were compared via Spearman's rank correlation. The relationships versus total step count were determined, and the strength of these relationships compared between cadence measures (95% confidence interval of correlation differences). RESULTS: Bout stepping rate (85 ± 14 steps/min) was larger than step accumulation (34 ± 12 steps/min) and awake cadence (10 ± 5 steps/min, both: P < 0.001). Step accumulation was positively strongly related to bout stepping rate (ρ = 0.813; P < 0.001) whereas awake cadence was weakly related to bout stepping rate (ρ = 0.496; P < 0.001). Step accumulation (ρ = 0.634; P < 0.001) and awake cadence (ρ = 0.964; P < 0.001) were more related to step counts than bout stepping rate (ρ = 0.497; P < 0.001; 95% confidence intervals of correlation differences: step accumulation=0.10-0.17, awake cadence: 0.42-0.52). SIGNIFICANCE: Without a precise measure of time spent stepping, stepping cadence is lower using the step accumulation and awake cadence methods. Step accumulation and awake cadence are more related to total step counts than bout stepping rate. Bout stepping rate outcomes reflect continuous stepping rate, does not rely on a preset epoch, and may have less overlap with step counts, which may have implications for determining the unique contributions of step count versus stepping cadence on health outcomes.


Assuntos
Acelerometria , Caminhada , Acelerometria/métodos , Índice de Massa Corporal , Humanos
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