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1.
Sports Biomech ; 19(1): 120-140, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31456487

RESUMO

Dynamic stability of locomotion plays an important role in running injuries, particularly during trail running where ankle injuries occur frequently. Several studies have investigated dynamic stability of locomotion using wearable accelerometer measurements. However, no study has reviewed how dynamic stability of locomotion is quantified using accelerometry. Therefore, the present review aims to synthetise the methods and findings of studies investigating stability related parameters measured by accelerometry, during locomotion on various surfaces, and among asymptomatic participants. A systematic search of studies associated with locomotion was conducted. Only studies including assessment of dynamic stability parameters based on accelerometry, including at least one group of asymptomatic participants, and conditions that occur during trail running were considered relevant for this review. Consequently, all retrieved studies used a non-obstructive portable accelerometer or an inertial measurement unit. Fifteen studies used a single tri-axial accelerometer placed above the lumbar region allowing outdoor recordings. From trunk accelerations, a combination of index of cycle repeatability and signal dispersion can adequately be used to assess dynamic stability. However, as most studies included indoor conditions, studies addressing the biomechanics of trail running in outdoor conditions are warranted.


Assuntos
Acelerometria/métodos , Corrida/fisiologia , Caminhada/fisiologia , Fenômenos Biomecânicos , Meio Ambiente , Marcha/fisiologia , Humanos , Fatores de Risco , Corrida/lesões , Caminhada/lesões
2.
Med Sci Sports Exerc ; 2019 Oct 23.
Artigo em Inglês | MEDLINE | ID: mdl-31652248

RESUMO

INTRODUCTION: Soft-tissue vibrations can generate discomfort and may necessitate a greater energy demand to preserve an efficient motion in running. Vibration damping is thus of interest from a comfort and performance standpoint. Our purpose was to assess whether changes in midsole material affect the properties of (a) soft-tissue vibrations and (b) myoelectric activity. METHODS: Two midsole conditions were compared. The control condition corresponded to a full ethylene-vinyl-acetate foam midsole. The experimental condition was a bi-material midsole with a material combination of viscous and visco-elastic materials. Twelve participants ran on an indoor track in both conditions while recording the longitudinal acceleration and EMG activity of vastus medialis (VM) and gastrocnemius medialis (GM). Wavelet transforms were performed for EMG and acceleration signals to assess the intensity of the muscle activity at low- and high-frequencies (37-128 Hz and 170-395 Hz, respectively), and to calculate the damping coefficient (D) for soft-tissue vibrations. The soft-tissue vibrations were also characterized by the peak of acceleration (apeak), the frequency of the power peak (fpeak) and the power of the soft-tissue vibrations (PSD[8-55]). RESULTS: The variables apeak and PSD[8-55] decreased for VM and GM in the viscous condition. Prior heel strike, low-frequency EMG activity decreased for VM and high-frequency EMG activity tended to decrease for GM in the viscous condition. The damping D was reduced only for VM, and fpeak was unchanged. CONCLUSION: A more viscous midsole substantially reduced the amplitude of soft-tissue vibrations, but not their frequency. Looking at individual results, it was noted that muscle activity was tuned in response to the acceleration input, and that the damping of soft-tissue vibrations was affected by the intensity of muscle activity.

3.
Eur J Sport Sci ; : 1-11, 2019 Sep 24.
Artigo em Inglês | MEDLINE | ID: mdl-31549912

RESUMO

We sought to examine the effect of step length manipulation on energy absorption and impact attenuation during graded running. Nineteen runners (10F, 9M) ran on an instrumented treadmill at three step lengths (preferred and ±10% preferred) at each of five grades (0°, ±5°, and ±10°) while 3D motion data were captured. Speed was held constant at 3.33 m/s and step length was manipulated by syncing cadence to a metronome. Manipulating step length altered energy absorption (p ≤ 0.002) and impact attenuation (p < 0.0001) across all grades. Energy absorption at the knee joint was most responsive to step length manipulations [Δ range (±10%SL-PrefSL) = 0.076-0.126 J/kg, p < 0.0001], followed by the ankle (Δ range = 0.026-0.100 J/kg, p = 0.001) and hip (Δ range = 0.008-0.018 J/kg, p < 0.006). Shortening step length reduced knee joint energy absorption at all grades with the smallest effect observed during uphill running (Δ ≥ -0.053 J/kg), while large reductions occurred during level (Δ = -0.096 J/kg) and downhill running (Δ ≥ -0.108 J/kg). Increasing step length resulted in greater knee joint energy absorption (p ≤ 0.037) across all grades of running. Impact attenuation was greatest at long step lengths (Δ = 2.708) and lowest at short step lengths (Δ = -2.061), compared to preferred. Overall, Step length influenced the energy absorption and impact attenuation characteristics of the lower extremity during level and graded running. Adopting a shorter step length may be a useful intervention to reduce knee joint loading, particularly during downhill or level running. Elongating step length placed a greater demand on the lower extremity joints, which may expedite the development of neuromuscular fatigue.

4.
Eur J Sport Sci ; : 1-10, 2019 Aug 08.
Artigo em Inglês | MEDLINE | ID: mdl-31311427

RESUMO

Research has suggested that a high variability in foot strike pattern during downhill running is associated with lower neuromuscular fatigue of the plantar flexors (PF). Given the popularity of trail running, we designed an intervention study to investigate whether a strategy with regular changes in foot strike pattern during downhill running could reduce the extent of fatigue on neuromuscular, energetics and biomechanical parameters as well as increase an uphill time-to-exhaustion trial (TTE) performance. Fourteen experienced trail runners completed two interventional conditions (separated by 15 days) in a pseudo-randomised and counter-balanced order that consisted of 2.5-h of treadmill graded running with (switch condition) or without (control condition) a change between fore- and rear-foot strike pattern every 30 s during the downhill sections. Pre and Post, neuromuscular tests were performed to assess PF central and peripheral fatigue. Energy cost of running was assessed using an indirect calorimetry system and biomechanical gait parameters were acquired with an instrumented treadmill. TTE was performed after both the graded running conditions. There were not significant condition × time interactions (p ≥ .085) for any of the variables considered, and TTE was not different between the two conditions (p = .755). A deliberate strategy to alternate between foot strike patterns did not reduce the extent of fatigue during prolonged graded running. We suggest that it is not the ability to switch between foot strike patterns that minimises fatigue; rather the ability to adapt foot strike pattern to the terrain and therefore a better running technique.

5.
Gait Posture ; 70: 355-360, 2019 05.
Artigo em Inglês | MEDLINE | ID: mdl-30952109

RESUMO

BACKGROUND: Bone fatigue resistance and more generally the ability to dissipate the stress sustained in dynamic tasks are partly affected by tissue properties. Men and women demonstrate substantial differences in body composition. RESEARCH QUESTION: To assess whether gender, as a function of body composition, affects impact-related parameters in running. METHODS: A qualitative study has been conducted. Twelve females and eighteen males performed four 2-min running trials at 2.8 m∙s-1, 3.3 m∙s-1, 3.9 m∙s-1, and 4.4 m∙s-1 while recording axial and transverse tibial acceleration. Peak acceleration and power spectral density within the impact-related frequency range (vibration content) were measured. Bone mineral content, fat mass, lean mass, and muscle mass were assessed using an impedance meter. Two-way (gender × speed) ANOVAs were computed. Multiple linear regressions were then used to assess the magnitude of the effect of body composition indicators on impact-related parameters. RESULTS: Significant gender and speed effects were observed. Females and high running speeds were associated with greater peak acceleration and vibration content at the tibia. Small interactions were observed between muscle mass and axial peak acceleration and vibration content, and between bone mineral content and transverse peak acceleration and vibration content, and axial vibration content. SIGNIFICANCE: Women demonstrated greater mechanical stress than men during running. High mechanical stress was associated with low bone mineral content and muscle mass. These findings may have implications in the prevention and management of bone overuse injuries in runners.


Assuntos
Composição Corporal/fisiologia , Pé/fisiologia , Corrida/fisiologia , Tíbia/fisiologia , Aceleração , Adulto , Transtornos Traumáticos Cumulativos/prevenção & controle , Feminino , Humanos , Masculino , Corrida/lesões , Fatores Sexuais
6.
Front Physiol ; 9: 1627, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-30555337

RESUMO

Introduction: The aim of this study was to examine, from a crossover experimental design, whether wearing high-pressure compression garments (CGs) during downhill treadmill running affects soft-tissue vibrations, acute and delayed responses in running economy (RE), neuromuscular function, countermovement jump, and perceived muscle soreness. Methods: Thirteen male trail runners habituated to regular eccentric training performed two separate 40-min downhill running (DHR, -8.5°) sessions while wearing either CGs (15-20 mmHg for quadriceps and calves) or control garments (CON) at a velocity associated with ∼55% of VO2max , with a set of measurements before (Pre-), after (Post-DHR), and 1 day after (Post-1D). No CGs was used within the recovery phase. Perceived muscle soreness, countermovement jump, and neuromuscular function (central and peripheral components) of knee extensors (KE) and plantar flexors (PF) were assessed. Cardiorespiratory responses (e.g., heart rate, ventilation) and RE, as well as soft-tissue vibrations (root mean square of the resultant acceleration, RMS Ar ) for vastus lateralis and gastrocnemius medialis were evaluated during DHR and in Post-1D. Results: During DHR, mean values in RMS Ar significantly increased over time for the vastus lateralis only for the CON condition (+11.6%). RE and cardiorespiratory responses significantly increased (i.e., alteration) over time in both conditions. Post, small to very large central and peripheral alterations were found for KE and PF in both conditions. However, the deficit in voluntary activation (VA) was significantly lower for KE following CGs (-2.4%), compared to CON (-7.9%) conditions. No significant differences in perceived muscle soreness and countermovement jump were observed between conditions whatever the time period. Additionally, in Post-1D, the CGs condition showed reductions in neuromuscular peripheral alterations only for KE (from -4.4 to -7.7%) and perceived muscle soreness scores (-8.3%). No significant differences in cardiorespiratory and RE responses as well as countermovement jump were identified between conditions in Post-1D. Discussion: Wearing high-pressure CGs (notably on KE) during DHR was associated with beneficial effects on soft-tissue vibrations, acute and delayed neuromuscular function, and perceived muscle soreness. The use of CGs during DHR might contribute to the enhanced muscle recovery by exerting an exercise-induced "mechanical protective effect."

7.
Sports Med ; 47(4): 615-629, 2017 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-27501719

RESUMO

Most running studies have considered level running (LR), yet the regulation of locomotor behaviour during uphill (UR) and downhill (DR) running is fundamental to increase our understanding of human locomotion. The purpose of this article was to review the existing literature regarding biomechanical, neuromuscular and physiological adaptations during graded running. Relative to LR, UR is characterized by a higher step frequency, increased internal mechanical work, shorter swing/aerial phase duration, and greater duty factor, while DR is characterized by increased aerial time, reduced step frequency and decreased duty factor. Grade also modifies foot strike patterns, with a progressive adoption of a mid- to fore-foot strike pattern during UR, and rear-foot strike patterns during DR. In UR, lower limb muscles perform a higher net mechanical work compared to LR and DR to increase the body's potential energy. In DR, energy dissipation is generally prevalent compared to energy generation. The increased demands for work as running incline increases are met by an increase in power output at all joints, particularly the hip. This implies that UR requires greater muscular activity compared to LR and DR. Energy cost of running (C r) linearly increases with positive slope but C r of DR decreases until a minimum slope is reached at -20 %, after which C r increases again. The effects of slope on biomechanics, muscle contraction patterns and physiological responses have important implications for injury prevention and success of athletes engaged in graded running competitions.


Assuntos
Articulações/fisiologia , Músculo Esquelético/fisiologia , Corrida/fisiologia , Fenômenos Biomecânicos , , Humanos , Contração Muscular
8.
Eur J Appl Physiol ; 116(10): 1859-73, 2016 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-27456477

RESUMO

Scientific experiments on running mainly consider level running. However, the magnitude and etiology of fatigue depend on the exercise under consideration, particularly the predominant type of contraction, which differs between level, uphill, and downhill running. The purpose of this review is to comprehensively summarize the neurophysiological and biomechanical changes due to fatigue in graded running. When comparing prolonged hilly running (i.e., a combination of uphill and downhill running) to level running, it is found that (1) the general shape of the neuromuscular fatigue-exercise duration curve as well as the etiology of fatigue in knee extensor and plantar flexor muscles are similar and (2) the biomechanical consequences are also relatively comparable, suggesting that duration rather than elevation changes affects neuromuscular function and running patterns. However, 'pure' uphill or downhill running has several fatigue-related intrinsic features compared with the level running. Downhill running induces severe lower limb tissue damage, indirectly evidenced by massive increases in plasma creatine kinase/myoglobin concentration or inflammatory markers. In addition, low-frequency fatigue (i.e., excitation-contraction coupling failure) is systematically observed after downhill running, although it has also been found in high-intensity uphill running for different reasons. Indeed, low-frequency fatigue in downhill running is attributed to mechanical stress at the interface sarcoplasmic reticulum/T-tubule, while the inorganic phosphate accumulation probably plays a central role in intense uphill running. Other fatigue-related specificities of graded running such as strategies to minimize the deleterious effects of downhill running on muscle function, the difference of energy cost versus heat storage or muscle activity changes in downhill, level, and uphill running are also discussed.


Assuntos
Contração Muscular/fisiologia , Fadiga Muscular/fisiologia , Músculo Esquelético/fisiologia , Resistência Física/fisiologia , Esforço Físico/fisiologia , Corrida/fisiologia , Humanos , Análise e Desempenho de Tarefas
9.
PLoS One ; 11(3): e0151687, 2016.
Artigo em Inglês | MEDLINE | ID: mdl-27031830

RESUMO

Ultramarathon runners are exposed to a high number of impact shocks and to severe neuromuscular fatigue. Runners may manage mechanical stress and muscle fatigue by changing their running kinematics. Our purposes were to study (i) the effects of a 110-km mountain ultramarathon (MUM) on tibial shock acceleration and lower limb kinematics, and (ii) whether kinematic changes are modulated according to the severity of neuromuscular fatigue. Twenty-three runners participated in the study. Pre- and post-MUM, neuromuscular tests were performed to assess knee extensor (KE) and plantar flexor (PF) central and peripheral fatigue, and a treadmill running bouts was completed during which step frequency, peak acceleration, median frequency and impact frequency content were measured from tibial acceleration, as well as foot-to-treadmill, tibia-to-treadmill, and ankle flexion angles at initial contact, and ankle range of motion using video analysis. Large neuromuscular fatigue, including peripheral changes and deficits in voluntary activation, was observed in KE and PF. MVC decrements of ~35% for KE and of ~28% for PF were noted. Among biomechanical variables, step frequency increased by ~2.7% and the ankle range of motion decreased by ~4.1% post-MUM. Runners adopting a non rearfoot strike pre-MUM adopted a less plantarflexed foot strike pattern post-MUM while those adopting a rearfoot strike pre-MUM tended to adopt a less dorsiflexed foot strike pattern post-MUM. Positive correlations were observed between percent changes in peripheral PF fatigue and the ankle range of motion. Peripheral PF fatigue was also significantly correlated to both percent changes in step frequency and the ankle angle at contact. This study suggests that in a fatigued state, ultratrail runners use compensatory/protective adjustments leading to a flatter foot landing and this is done in a fatigue dose-dependent manner. This strategy may aim at minimizing the overall load applied to the musculoskeletal system, including impact shock and muscle stretch.


Assuntos
Fadiga , Perna (Membro)/fisiologia , Músculo Esquelético/fisiologia , Corrida/fisiologia , Tíbia/fisiologia , Aceleração , Adulto , Fenômenos Biomecânicos , Feminino , Pé/fisiologia , Humanos , Masculino , Pessoa de Meia-Idade
10.
J Biomech ; 49(9): 1765-1771, 2016 06 14.
Artigo em Inglês | MEDLINE | ID: mdl-27087676

RESUMO

Trail runners are exposed to a high number of shocks, including high-intensity shocks on downhill sections leading to greater risk of osseous overuse injury. The type of foot strike pattern (FSP) is known to influence impact severity and lower-limb kinematics. Our purpose was to investigate the influence of FSP on axial and transverse components of shock acceleration and attenuation during an intense downhill trail run (DTR). Twenty-three trail runners performed a 6.5-km DTR (1264m of negative elevation change) as fast as possible. Four tri-axial accelerometers were attached to the heel, metatarsals, tibia and sacrum. Accelerations were continuously recorded at 1344Hz and analyzed over six sections (~400 steps per subject). Heel and metatarsal accelerations were used to identify the FSP. Axial, transverse and resultant peak accelerations, median frequencies and shock attenuation within the impact-related frequency range (12-20Hz) were assessed between tibia and sacrum. Multiple linear regressions showed that anterior (i.e. forefoot) FSPs were associated with higher peak axial acceleration and median frequency at the tibia, lower transverse median frequencies at the tibia and sacrum, and lower transverse peak acceleration at the sacrum. For resultant acceleration, higher tibial median frequency but lower sacral peak acceleration were reported with forefoot striking. FSP therefore differently affects the components of impact shock acceleration. Although a forefoot strike reduces impact severity and impact frequency content along the transverse axis, a rearfoot strike decreases them in the axial direction. Globally, the attenuation of axial and resultant impact-related vibrations was improved using anterior FSPs.


Assuntos
Pé/fisiologia , Corrida/fisiologia , Aceleração , Adulto , Fenômenos Biomecânicos , Humanos , Masculino , Ossos do Metatarso/fisiologia , Pessoa de Meia-Idade , Sacro/fisiologia , Tíbia/fisiologia , Vibração
11.
J Biomech ; 47(7): 1588-93, 2014 May 07.
Artigo em Inglês | MEDLINE | ID: mdl-24679708

RESUMO

Identifying foot strike patterns in running is an important issue for sport clinicians, coaches and footwear industrials. Current methods allow the monitoring of either many steps in laboratory conditions or only a few steps in the field. Because measuring running biomechanics during actual practice is critical, our purpose is to validate a method aiming at identifying foot strike patterns during continuous field measurements. Based on heel and metatarsal accelerations, this method requires two uniaxial accelerometers. The time between heel and metatarsal acceleration peaks (THM) was compared to the foot strike angle in the sagittal plane (αfoot) obtained by 2D video analysis for various conditions of speed, slope, footwear, foot strike and state of fatigue. Acceleration and kinematic measurements were performed at 1000Hz and 120Hz, respectively, during 2-min treadmill running bouts. Significant correlations were observed between THM and αfoot for 14 out of 15 conditions. The overall correlation coefficient was r=0.916 (P<0.0001, n=288). The THM method is thus highly reliable for a wide range of speeds and slopes, and for all types of foot strike except for extreme forefoot strike during which the heel rarely or never strikes the ground, and for different footwears and states of fatigue. We proposed a classification based on THM: FFS<-5.49ms

Assuntos
Pé/fisiologia , Corrida/fisiologia , Aceleração , Adolescente , Adulto , Fenômenos Biomecânicos , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Adulto Jovem
12.
Eur J Appl Physiol ; 113(8): 2077-90, 2013 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-23584279

RESUMO

Impact reduction has become a factor of interest in the prevention of running-related injuries such as stress fractures. Currently, the midfoot strike pattern (MFS) is thought as a potential way to decrease impact. The purpose was to test the effects of two long-term interventions aiming to reduce impact during running via a transition to an MFS: a foot strike retraining versus a low-drop/low-heel height footwear. Thirty rearfoot strikers were randomly assigned to two experimental groups (SHOES and TRAIN). SHOES progressively wore low-drop/low-heel height shoes and TRAIN progressively adopted an MFS, over a 3-month period with three 30-min running sessions per week. Measurement sessions (pre-training, 1, 2 and 3 months) were performed during which subjects were equipped with three accelerometers on the shin, heel and metatarsals, and ran for 15 min on an instrumented treadmill. Synchronized acceleration and vertical ground reaction force signals were recorded. Peak heel acceleration was significantly lower as compared to pre-training for SHOES (-33.5 ± 12.8 % at 2 months and -25.3 ± 18.8 % at 3 months, p < 0.001), and so was shock propagation velocity (-12.1 ± 9.3 %, p < 0.001 at 2 months and -11.3 ± 4.6 %, p < 0.05 at 3 months). No change was observed for TRAIN. Important inter-individual variations were noted in both groups and reported pains were mainly located at the shin and calf. Although it induced reversible pains, low-drop/low-heel height footwear seemed to be more effective than foot strike retraining to attenuate heel impact in the long term.


Assuntos
Órtoses do Pé , Corrida/fisiologia , Adolescente , Traumatismos em Atletas/prevenção & controle , Fenômenos Biomecânicos , Feminino , Humanos , Masculino , Equipamentos de Proteção , Corrida/lesões , Sapatos/classificação , Equipamentos Esportivos , Adulto Jovem
13.
Eur J Appl Physiol ; 113(3): 599-609, 2013 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-22875194

RESUMO

Running-related stress fractures have been associated with the overall impact intensity, which has recently been described through the loading rate (LR). Our purpose was to evaluate the effects of four acute interventions with specific focus on LR: wearing racing shoes (RACE), increasing step frequency by 10 % (FREQ), adopting a midfoot strike pattern (MIDFOOT) and combining these three interventions (COMBI). Nine rearfoot-strike subjects performed five 5-min trials during which running kinetics, kinematics and spring-mass behavior were measured for ten consecutive steps on an instrumented treadmill. Electromyographic activity of gastrocnemius lateralis, tibialis anterior, biceps femoris and vastus lateralis muscles was quantified over different phases of the stride cycle. LR was significantly and similarly reduced in MIDFOOT (37.4 ± 7.20 BW s(-1), -56.9 ± 50.0 %) and COMBI (36.8 ± 7.15 BW s(-1), -55.6 ± 29.2 %) conditions compared to NORM (56.3 ± 11.5 BW s(-1), both P < 0.001). RACE (51.1 ± 9.81 BW s(-1)) and FREQ (52.7 ± 11.0 BW s(-1)) conditions had no significant effects on LR. Running with a midfoot strike pattern resulted in a significant increase in gastrocnemius lateralis pre-activation (208 ± 97.4 %, P < 0.05) and in a significant decrease in tibialis anterior EMG activity (56.2 ± 15.5 %, P < 0.05) averaged over the entire stride cycle. The acute attenuation of foot-ground impact seems to be mostly related to the use of a midfoot strike pattern and to a higher pre-activation of the gastrocnemius lateralis. Further studies are needed to test these results in prolonged running exercises and in the long term.


Assuntos
Traumatismos em Atletas/prevenção & controle , Corrida/fisiologia , Adolescente , Adulto , Fenômenos Biomecânicos , Osso e Ossos/lesões , Eletromiografia , Teste de Esforço , Feminino , Humanos , Articulações/lesões , Articulações/fisiologia , Masculino , Fadiga Muscular/fisiologia , Músculo Esquelético/lesões , Músculo Esquelético/fisiologia , Recreação/fisiologia , Comportamento de Redução do Risco , Resultado do Tratamento , Adulto Jovem
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