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1.
J Sports Sci ; 38(2): 187-191, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31783721

RESUMO

The popularity of pre-workout supplements is rising amongst professional athletes and fitness enthusiasts. Despite increased usage, the safety profile of pre-workout supplements is likely to be not well understood. Additionally, many different brands use various undisclosed proprietary blends of active ingredients creating safety regulation difficulties. This lack of oversight could prove unsafe for certain patients. This patient MK is a 33-year-old healthy housewife who presented with central chest tightness, pre-syncope and mild dyspnoea to the emergency department via ambulance. The presentation was in the context of recent strenuous exercise and ingestion of a pre-workout supplement (Alpha Lean-7). Most striking in her presentation was a troponin rise of 50 ng/L, while not very high it is unusual given her lack of cardiac risk factors. She had a 3-day uneventful admission with a downtrending troponin prior to discharge. This case highlights the possible dangers of pharmacologically active ingredients in pre-workout supplements.


Assuntos
Suplementos Nutricionais/efeitos adversos , Isquemia Miocárdica/etiologia , Corrida/fisiologia , Adulto , Cafeína/efeitos adversos , Estimulantes do Sistema Nervoso Central/efeitos adversos , Dispneia/etiologia , Serviço Hospitalar de Emergência , Feminino , Produtos de Degradação da Fibrina e do Fibrinogênio/metabolismo , Humanos , Isquemia Miocárdica/sangue , Síncope/etiologia , Troponina/sangue
2.
Sports Health ; 12(1): 74-79, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-31642726

RESUMO

BACKGROUND: Lower extremity overuse injuries are common among runners, especially first-time marathoners. Hip abductor and quadriceps strengthening is often recommended to reduce running-related injuries. HYPOTHESIS: A 12-week strength training program would decrease the rate of overuse injuries resulting in marathon noncompletion and improve race finishing time. STUDY DESIGN: Randomized trial. LEVEL OF EVIDENCE: Level 2. METHODS: Twelve weeks before the New York City Marathon, first-time marathon runners age 18 years and older were randomized into a strength training group or an observation group. The strength training group was instructed to perform a 10-minute program 3 times weekly using written and video instruction. This program targeted the quadriceps, hip abductor, and core muscle groups. Injuries were self-reported through biweekly surveys, with major injuries being those that resulted in marathon noncompletion and minor injuries being those that impaired training or race performance. RESULTS: A total of 720 runners were enrolled (mean age, 35.9 ± 9.4 years; 69.4% female), of whom 583 runners started the marathon and 579 completed it. The incidence of major injury was 8.9% and minor injury was 48.5%. Fifty two of 64 major injuries were overuse, of which 20 were bone stress injuries. The incidence of overuse injury resulting in marathon noncompletion was 7.1% in the strength training group and 7.3% in the observation group (risk ratio, 0.97; 95% CI, 0.57-1.63; P = 0.90). The mean finishing time was 5 hours 1 ± 60 minutes in the strength training group and 4 hours 58 ± 55 minutes in the observation group (P = 0.35). CONCLUSION: There is a high prevalence of injury among first-time marathon runners, but this self-directed strength training program did not decrease overuse injury incidence resulting in marathon noncompletion. CLINICAL RELEVANCE: Prevention strategies such as strength training need to be developed and evaluated through clinical trials to reduce the high prevalence of overuse injuries in runners, especially for high-risk populations such as first-time marathon runners.


Assuntos
Transtornos Traumáticos Cumulativos/prevenção & controle , Extremidade Inferior/lesões , Força Muscular/fisiologia , Resistência Física/fisiologia , Treinamento de Resistência , Corrida/lesões , Adulto , Transtornos Traumáticos Cumulativos/epidemiologia , Transtornos Traumáticos Cumulativos/fisiopatologia , Humanos , Cidade de Nova Iorque/epidemiologia , Fatores de Risco , Corrida/fisiologia
3.
J Sports Sci ; 38(1): 6-12, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31603027

RESUMO

This study aimed to examine the characteristics of electromyography (EMG) and kinematics of the supporting leg affecting energy cost while running at incline, level, and decline slopes. Twelve male Japanese middle- and long-distance runners volunteered for this study. The subjects were asked to run at 13.5 km·h-1 on a treadmill under three slope conditions. Sagittal plane kinematics and the EMG of the lower limb muscles, respiratory gases were recorded. Energy cost differed significantly between slopes, being the lowest in decline slope and the greatest in incline slope. Integrated EMG (iEMG) of leg extensor muscles was greater in the incline slope than in the decline slope, and iEMG of the gastrocnemius and soleus muscles correlated positively with energy cost. The knee and ankle joint kinematics were associated with energy cost during running. In incline slope, the knee and ankle joints were more extended (plantarflexed) to lift the body. These movements may disturb the coordination between the ankle and knee joints. The gastrocnemius muscle would do greater mechanical work to plantarflex the ankle joint rather than transfer mechanical energy as well as greater mechanical work of mono-articular muscles. These muscular activities would increase energy cost.


Assuntos
Metabolismo Energético/fisiologia , Extremidade Inferior/fisiologia , Corrida/fisiologia , Articulação do Tornozelo/fisiologia , Fenômenos Biomecânicos , Eletromiografia , Teste de Esforço/métodos , Articulação do Quadril/fisiologia , Humanos , Articulação do Joelho/fisiologia , Masculino , Movimento/fisiologia , Músculo Esquelético/fisiologia , Troca Gasosa Pulmonar/fisiologia , Adulto Jovem
4.
J Sports Sci ; 38(1): 53-61, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31623521

RESUMO

This study aimed 1) to examine the validity of inertial measurement unit (IMU)-based hip flexion strength test, and 2) to investigate the hip flexion strength test as an indicator of sprint performance. Eight males performed five repeated hip flexion-extension, while leg motion was recorded using an IMU and a motion capture system (Mocap). As the second experiment, 24 male athletes performed the IMU-based hip flexion strength test and sprinted 50 m, during which step-to-step ground reaction force (GRF) was recorded. The strength test variables were calculated using IMU and Mocap data including angular impulse, mean moment, and positive and negative work and power. Using GRF data, step-to-step spatiotemporal variables were obtained. The results showed high intra-class correlation coefficient and correlation coefficient (both >0.909) between IMU and Mocap for angular impulse, mean moment, positive work and power. The hip flexion mean moment showed significant correlation with running speed from the 5th-8th step section onwards. The angular impulse, mean moment, positive work and power are recommended to be used for the IMU-based hip flexion strength test variables in terms of accuracy and validity. Moreover, the proposed IMU-based hip flexion strength test can be an indicator for better sprinting performance.


Assuntos
Desempenho Atlético/fisiologia , Teste de Esforço/métodos , Quadril/fisiologia , Força Muscular/fisiologia , Corrida/fisiologia , Aceleração , Adulto , Fenômenos Biomecânicos , Humanos , Masculino , Reprodutibilidade dos Testes , Estudos de Tempo e Movimento , Adulto Jovem
5.
J Sports Sci ; 38(1): 29-37, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31631783

RESUMO

This study investigated the role of reactive and eccentric strength in stiffness regulation during maximum velocity sprinting (Vmax) in team sport athletes compared with highly trained sprinters. Thirteen team sport athletes and eleven highly trained sprinters were recruited. Vmax was measured using radar, and stiffness regulation was inferred from modelled vertical and leg spring stiffness. Reactive strength (RSI) was determined from a 0.50 m drop jump, and an eccentric back squat was used to assess maximum isoinertial eccentric force. Trained sprinters attained a higher Vmax than team sport athletes, partly due to a briefer contact time and higher vertical stiffness. Trained sprinters exhibited a moderately higher RSI via the attainment of a briefer and more forceful ground contact phase, while RSI also demonstrated large to very large associations with vertical stiffness and Vmax, respectively. Isoinertial eccentric force was largely correlated with Vmax, but only moderately correlated with vertical stiffness. Reactive and eccentric strength contribute to the ability to regulate leg spring stiffness at Vmax, and subsequently, the attainment of faster sprinting speeds in highly trained sprinters versus team sport athletes. However, stiffness regulation appears to be a task-specific neuromuscular skill, reinforcing the importance of specificity in the development of sprint performance.


Assuntos
Desempenho Atlético/fisiologia , Extremidade Inferior/fisiologia , Força Muscular/fisiologia , Músculo Esquelético/fisiologia , Condicionamento Físico Humano , Corrida/fisiologia , Aceleração , Adulto , Fenômenos Biomecânicos , Estudos Transversais , Feminino , Humanos , Masculino , Adulto Jovem
6.
J Sports Sci ; 38(2): 214-230, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31795815

RESUMO

Injuries and lack of motivation are common reasons for discontinuation of running. Real-time feedback from wearables can reduce discontinuation by reducing injury risk and improving performance and motivation. There are however several limitations and challenges with current real-time feedback approaches. We discuss these limitations and challenges and provide a framework to optimise real-time feedback for reducing injury risk and improving performance and motivation. We first discuss the reasons why individuals run and propose that feedback targeted to these reasons can improve motivation and compliance. Secondly, we review the association of running technique and running workload with injuries and performance and we elaborate how real-time feedback on running technique and workload can be applied to reduce injury risk and improve performance and motivation. We also review different feedback modalities and motor learning feedback strategies and their application to real-time feedback. Briefly, the most effective feedback modality and frequency differ between variables and individuals, but a combination of modalities and mixture of real-time and delayed feedback is most effective. Moreover, feedback promoting perceived competence, autonomy and an external focus can improve motivation, learning and performance. Although the focus is on wearables, the challenges and practical applications are also relevant for laboratory-based gait retraining.


Assuntos
Desempenho Atlético/fisiologia , Desempenho Atlético/psicologia , Retroalimentação , Monitores de Aptidão Física , Motivação , Corrida/fisiologia , Corrida/psicologia , Traumatismos em Atletas/prevenção & controle , Fenômenos Biomecânicos , Marcha/fisiologia , Humanos , Percepção , Corrida/lesões
7.
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
8.
J Int Soc Sports Nutr ; 16(1): 50, 2019 Nov 07.
Artigo em Inglês | MEDLINE | ID: mdl-31699159

RESUMO

Background In this Position Statement, the International Society of Sports Nutrition (ISSN) provides an objective and critical review of the literature pertinent to nutritional considerations for training and racing in single-stage ultra-marathon. Recommendations for Training. i) Ultra-marathon runners should aim to meet the caloric demands of training by following an individualized and periodized strategy, comprising a varied, food-first approach; ii) Athletes should plan and implement their nutrition strategy with sufficient time to permit adaptations that enhance fat oxidative capacity; iii) The evidence overwhelmingly supports the inclusion of a moderate-to-high carbohydrate diet (i.e., ~ 60% of energy intake, 5-8 g·kg- 1·d- 1) to mitigate the negative effects of chronic, training-induced glycogen depletion; iv) Limiting carbohydrate intake before selected low-intensity sessions, and/or moderating daily carbohydrate intake, may enhance mitochondrial function and fat oxidative capacity. Nevertheless, this approach may compromise performance during high-intensity efforts; v) Protein intakes of ~ 1.6 g·kg- 1·d- 1 are necessary to maintain lean mass and support recovery from training, but amounts up to 2.5 g.kg- 1·d- 1 may be warranted during demanding training when calorie requirements are greater; Recommendations for Racing. vi) To attenuate caloric deficits, runners should aim to consume 150-400 Kcal·h- 1 (carbohydrate, 30-50 g·h- 1; protein, 5-10 g·h- 1) from a variety of calorie-dense foods. Consideration must be given to food palatability, individual tolerance, and the increased preference for savory foods in longer races; vii) Fluid volumes of 450-750 mL·h- 1 (~ 150-250 mL every 20 min) are recommended during racing. To minimize the likelihood of hyponatraemia, electrolytes (mainly sodium) may be needed in concentrations greater than that provided by most commercial products (i.e., > 575 mg·L- 1 sodium). Fluid and electrolyte requirements will be elevated when running in hot and/or humid conditions; viii) Evidence supports progressive gut-training and/or low-FODMAP diets (fermentable oligosaccharide, disaccharide, monosaccharide and polyol) to alleviate symptoms of gastrointestinal distress during racing; ix) The evidence in support of ketogenic diets and/or ketone esters to improve ultra-marathon performance is lacking, with further research warranted; x) Evidence supports the strategic use of caffeine to sustain performance in the latter stages of racing, particularly when sleep deprivation may compromise athlete safety.


Assuntos
Carboidratos da Dieta/administração & dosagem , Ingestão de Energia , Necessidades Nutricionais , Corrida/fisiologia , Fenômenos Fisiológicos da Nutrição Esportiva , Atletas , Desempenho Atlético , Comportamento Competitivo , Proteínas na Dieta/administração & dosagem , Humanos , Resistência Física , Corrida/classificação , Sociedades
9.
J Sports Med Phys Fitness ; 59(10): 1601-1607, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31694361

RESUMO

BACKGROUND: Outdoor exercise often proceeds in rainy conditions. However, there are very few studies reporting the physiological effects of cold with rain or wet-cold exposure on humans during exercise. The purpose of this study was to investigate the effects of rain on physiological responses during running exercise at 80% V̇Omax in the cold. METHODS: Twelve healthy men (age: 21.7±3.3 years; height: 1.760±0.085 m; body weight: 68.8±7.1 kg; maximal oxygen consumption: 67.3±5.00 mL/kg/min) exercised on a treadmill at 80% V̇Omax intensity for 60 minutes with rain (RAIN) or not (CON) at 5 °C. RESULTS: Rectal temperature was significantly lower in RAIN than in CON at 10, 40, 50, and 60 minutes (P<0.05). Mean weighted skin temperature was significantly lower in RAIN than in CON during exercise (P<0.05). Oxygen consumption and rating of perceived exertion were significantly higher in RAIN than in CON at 50 and 60 minutes (P<0.05). Plasma lactate was significantly higher in RAIN than in CON at 10 minutes and from 40 to 60 minutes (P<0.05). Plasma norepinephrine levels were significantly higher in RAIN than in CON at 10 minutes and from 40 to 60 minutes (P<0.05). CONCLUSIONS: These results suggest that rain increased heat loss during the early phase of exercise in the cold, then heat production increased and transiently suppressed cold stress. However, with time, body heat loss intensified due to increasing wet area, and then energy expenditure and plasma lactate increased due to cold stress. Therefore, rain may decrease exercise performance and affect sport safety.


Assuntos
Temperatura Baixa/efeitos adversos , Metabolismo Energético/fisiologia , Chuva , Corrida/fisiologia , Adolescente , Adulto , Regulação da Temperatura Corporal/fisiologia , Estudos de Casos e Controles , Teste de Esforço/métodos , Humanos , Ácido Láctico/sangue , Masculino , Consumo de Oxigênio/fisiologia , Temperatura Cutânea , Adulto Jovem
10.
J Sports Med Phys Fitness ; 59(10): 1709-1715, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31694363

RESUMO

BACKGROUND: The purpose of this study was to investigate the effects of an Ironman-distance triathlon on bone metabolism. METHODS: Nine recreational male triathletes (39.7±8.2 years old) were voluntarily recruited before a 226-km Ironman triathlon race. Baseline blood samples were collected >1 hour before race. Serial post-race blood sampling time points included immediately (0hr), 1 hour (1hr), 1 day (d), 3 d, and 5 d after the Ironman race. RESULTS: Serum muscle damage markers, serum myoglobin, creatine kinase (CK) and lactate dehydrogenase (LDH) revealed significant post-race peak values immediately, 1hr and 1d after the race, respectively. Except for the marginally higher serum CK and myoglobin at 5d (P=0.01~0.05), all post-race serum levels of muscle damage markers were significantly higher than baseline levels (P<0.01). Serum phosphorus values were significantly higher immediately (0hr) after the Ironman race. Serum osteocalcin, an index specific to bone formation, showed a significant decrease at time points 0hr and 1hr, but a significant increase 1 day after (P<0.01) and a marginal increase 3 and 5 days after (P=0.01~0.05) the race. No difference was shown in type I collagen C-telopeptide (CTX-1), a bone resorption marker. Pearson's correlation between serum osteocalcin and CTX-1 was done at each time point, and significant correlation was shown on the 5th d after the race (r=0.591, P<0.05). CONCLUSIONS: An Ironman-distance contest induces a bone-formative-favoring turnover during the post-race period for amateur male triathletes.


Assuntos
Desempenho Atlético , Osso e Ossos/metabolismo , Adulto , Atletas , Ciclismo/fisiologia , Biomarcadores/análise , Creatina Quinase/sangue , Humanos , L-Lactato Desidrogenase/sangue , Masculino , Pessoa de Meia-Idade , Mioglobina/sangue , Resistência Física/fisiologia , Corrida/fisiologia , Natação/fisiologia
11.
J Strength Cond Res ; 33(11): 3114-3122, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31644517

RESUMO

McMahon, GE and Kennedy, RA. Changes in player activity profiles after the 2015 FIH rule changes in elite women's hockey. J Strength Cond Res 33(11): 3114-3122, 2019-The aim of this study was to compare the player activity profiles of elite international women's hockey players before (2014) and after (2015) the 2015 the International Hockey Federation (FIH) match rule changes at team and positional levels. The match activity profiles (n = 400) of 19 female hockey players (age 23 ± 4 years, mass 63.6 ± 5.5 kg, VO2max 57 ± 6 ml·kg·min in 2014, 58 ± 6 ml·kg·min in 2015) were recorded during competitive international matches in 2014 (match n = 12) and 2015 (match n = 13) using 10-Hz global positioning system units. The practical utility of an effect was only classified as substantial when there was a >75% likelihood that the ±90% confidence interval of the effect size (ES) was equal to or greater than the small (ES ± 0.2) reference value. Mean match time decreased by over 2 minutes from 71.72 ± 1.38 to 69.40 ± 4.72 minutes. There were increases at the team level in relative substitutions (SUB), relative distance (RD), high-speed running (HSR: 3.08-5.27 m·s), and surges (S), with a fall in low-speed running (LSR: 0-3.05 m·s) between 2014 and 2015. There were no changes in the between-position differences observed from 2014 to 2015. Within positions, there were relative increases in RD for all positions, HSR and S for midfield, and in SUB and S in forwards. The 2015 FIH rule changes seem to have increased the general intensity of international women's hockey. However, the different facets of physical performance did not change uniformly across team positions. Therefore, specific modifications to conditioning practices for each position may be warranted to more accurately reflect match demands.


Assuntos
Hóquei/legislação & jurisprudência , Hóquei/fisiologia , Corrida/fisiologia , Adolescente , Adulto , Desempenho Atlético/fisiologia , Feminino , Sistemas de Informação Geográfica , Hóquei/tendências , Humanos , Corrida/tendências , Adulto Jovem
12.
J Sports Sci ; 37(23): 2702-2710, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31608832

RESUMO

The intrinsic foot musculature (IFM) supports the arches of the foot and controls metatarsophalangeal joint (MTPJ) motion. Stronger IFM can increase the effective foot length, potentially altering lower-extremity gearing similar to that of using carbon-fibre-plated footwear. The purpose of this study was to investigate if strengthening of the IFM can alter gait mechanics and improve running economy. Eleven participants were randomly assigned into an experimental group and nine into a control group. The experimental group performed IFM strengthening exercises for ten weeks. Toe-flexor strength, gait mechanics, and running economy were assessed at baseline, five weeks, and ten weeks; using a custom strength testing apparatus, motion capture and force-instrumented treadmill, and indirect calorimetry. Toe-flexor strength increased in the experimental group (p = .006); however, MTPJ and ankle mechanics and running economy did not change. The dearth of changes in mechanics may be due to a lack of mechanical advantage of the IFM, runners staying within their preferred movement path, a need for MTPJ dorsiflexion to facilitate the windlass mechanism, or the primary function of the IFM being to support the longitudinal arch of the foot as opposed to modulating MTPJ mechanics.


Assuntos
Tornozelo/fisiologia , Marcha/fisiologia , Articulação Metatarsofalângica/fisiologia , Força Muscular/fisiologia , Músculo Esquelético/fisiologia , Corrida/fisiologia , Dedos do Pé/fisiologia , Adulto , Fenômenos Biomecânicos , Feminino , Humanos , Masculino , Adulto Jovem
13.
Gait Posture ; 74: 242-249, 2019 10.
Artigo em Inglês | MEDLINE | ID: mdl-31574408

RESUMO

BACKGROUND: Excessive foot pronation during running in individuals with foot varus alignment may be reduced by medially wedged insoles. RESEARCH QUESTION: This study investigated the effects of a medially wedged insole at the forefoot and at the rearfoot on the lower limbs angles and internal moments of runners with excessive foot pronation and foot varus alignment. METHODS: Kinematic and kinetic data of 19 runners (11 females and 8 males) were collected while they ran wearing flat (control condition) and medially wedged insoles (insole condition). Both insoles had arch support. We used principal component analysis for data reduction and dependent t-test to compare differences between conditions. RESULTS: The insole condition reduced ankle eversion (p = 0.003; effect size = 0.63); reduced knee range of motion in the transverse plane (p = 0.012; effect size = 0.55); increased knee range of motion in the frontal plane in early stance and had earlier knee adduction peak (p = 0.018; effect size = 0.52); reduced hip range of motion in the transverse plane (p = 0.031; effect size = 0.48); reduced hip adduction (p = 0.024; effect size = 0.50); reduced ankle inversion moment (p = 0.012; effect size = 0.55); and increased the difference between the knee internal rotation moment in early stance and midstance (p = 0.012; effect size = 0.55). SIGNIFICANCE: Insoles with 7˚ medial wedges at the forefoot and rearfoot are able to modify motion and moments patterns that are related to lower limb injuries in runners with increased foot pronation and foot varus alignment with some non-desired effects on the knee motion in the frontal plane.


Assuntos
Órtoses do Pé , Pé/fisiologia , Extremidade Inferior/fisiologia , Pronação/fisiologia , Corrida/fisiologia , Sapatos , Adulto , Articulação do Tornozelo/fisiologia , Fenômenos Biomecânicos , Feminino , Articulação do Quadril/fisiologia , Humanos , Cinética , Articulação do Joelho/fisiologia , Masculino , Pessoa de Meia-Idade , Análise de Componente Principal , Amplitude de Movimento Articular
14.
J Appl Biomech ; 35(5): 336-343, 2019 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-31541065

RESUMO

Foot structure and kinematics have long been considered as risk factors for foot and lower-limb running injuries. The authors aimed at investigating foot joint kinetics to unravel their receptive and propulsive characteristics while running barefoot, both with rearfoot and with midfoot striking strategies. Power absorption and generation occurring at different joints of the foot in 6 asymptomatic adults were calculated using both a 3-segment and a 4-segment kinetic model. An inverse dynamic approach was used to quantify mechanical power. Major power absorption and generation characteristics were observed at the ankle joint complex as well as at the Chopart joint in both the rearfoot and the midfoot striking strategies. The power at the Lisfranc joint, quantified by the 4-segment kinetic model, was predominantly generated in both strategies, and at the toes, it was absorbed. The overall results show a large variability in the receptive and propulsive characteristics among the analyzed joints in both striking strategies. The present study may provide novel insight for clinical decision making to address foot and lower-limb injuries and to guide athletes in the adoption of different striking strategies during running.


Assuntos
Articulações do Pé/fisiologia , Marcha , Corrida/fisiologia , Adulto , Articulação do Tornozelo , Fenômenos Biomecânicos , Feminino , Humanos , Masculino , Adulto Jovem
15.
Int J Sports Med ; 40(13): 856-862, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31505701

RESUMO

Several studies report neurological complications such as brain injury induced by ischemia or edema following exhaustive endurance sport. We aimed to detect the frequency of acute brain lesions after a marathon race. In the prospective observational Berlin Beat of Running study, 110 experienced endurance athletes underwent 3-Tesla brain MRI exams 2-3 days prior and within 2 days after a marathon run. MRI results were compared to an age- and sex-matched control group of 68 non-athletes, including the "Age-Related White Matter Changes" (ARWMC) scale to assess white matter lesions (WML) in the brain. 108 athletes (median age 48 years, 24% female, 8% with hypertension; 0% with diabetes) completed the race. No athlete reported neurological deficits, but a single acute ischemic lesion was detected in diffusion-weighted MRI after the race in one athlete. No other acute brain lesions compared to prior MRI were found. An ARWMC score ≥4 was found in 15% of athletes and 12% of non-athletic controls (p=0.7). Chronic ischemic lesions were not found in athletes but in four controls (6%) (p=0.02). In conclusion, acute ischemic brain lesions may be found in endurance runners. Every seventh endurance athlete and every ninth control showed evidence for substantial white matter lesions.


Assuntos
Comportamento Competitivo/fisiologia , Resistência Física/fisiologia , Corrida/fisiologia , Substância Branca/diagnóstico por imagem , Adulto , Arritmias Cardíacas/epidemiologia , Berlim/epidemiologia , Isquemia Encefálica/epidemiologia , Imagem de Difusão por Ressonância Magnética , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Estudos Prospectivos
16.
J Sports Sci ; 37(23): 2735-2743, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31506014

RESUMO

The capacity of foot-strike running patterns to influence the functional properties of the Achilles tendon is controversial. This study used transmission-mode ultrasound to investigate the influence of habitual running foot-strike pattern on Achilles tendon properties during barefoot walking and running. Fifteen runners with rearfoot (RFS) and 10 with a forefoot (FFS) foot-strike running pattern had ultrasound transmission velocity measured in the right Achilles tendon during barefoot walking (≈1.1 ms-1) and running (≈2.0 ms-1). Temporospatial gait parameters, ankle kinematics and vertical ground reaction force were simultaneously recorded. Statistical comparisons between foot-strike patterns were made using repeated measure ANOVAs. FFS was characterised by a significantly shorter stance duration (-4%), greater ankle dorsiflexion (+2°), and higher peak vertical ground reaction force (+20% bodyweight) than RFS running (P < .05). Both groups adopted a RFS pattern during walking, with only the relative timing of peak dorsiflexion (3%), ground reaction force (1-2%) and peak vertical force loading rates (22-23%) differing between groups (P < .05). Peak ultrasound transmission velocity in the Achilles tendon was significantly higher in FFS during walking (≈100 ms-1) and running (≈130 ms-1) than RFS (P < .05). Functional Achilles tendon properties differ with habitual footfall patterns in recreational runners.


Assuntos
Tendão do Calcâneo/fisiologia , Pé/fisiologia , Marcha/fisiologia , Corrida/fisiologia , Tendão do Calcâneo/diagnóstico por imagem , Adulto , Tornozelo/fisiologia , Fenômenos Biomecânicos , Feminino , Humanos , Masculino , Ultrassonografia , Adulto Jovem
17.
J Sports Sci ; 37(23): 2751-2758, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31506039

RESUMO

This study used the intensity gradient (IG) and average acceleration metrics to describe children's activity profiles and explore associations with body mass index (BMI) z-score. Two hundred and forty-six children (n = 138 girls) aged 9.6 ± 1.4 years wore a wrist-mounted ActiGraph wGT3X-BT accelerometer for 7 days on their non-dominant wrist. Physical activity (PA) metrics captured included: the IG which describes the intensity distribution of accelerations across the 24 h monitoring period; average acceleration which provides a measure of the volume of activity; total moderate-to-vigorous PA (MVPA) and inactive time. Acceleration was averaged over 5s epochs. Finally, BMI z-score was calculated for each participant. Average acceleration was negatively associated with BMI z-score (p < 0.05) independent of age and gender but not IG. The IG was negatively associated with BMI z-score independent of potential correlates and average acceleration. Total MVPA was not associated with BMI-z score. The IG and average acceleration metrics may be used to explore the independent or cumulative effects of the volume and intensity distribution of activity upon measures of health and well-being in children to inform specific activity recommendations.


Assuntos
Índice de Massa Corporal , Exercício/fisiologia , Aceleração , Actigrafia/instrumentação , Criança , Estudos Transversais , Feminino , Monitores de Aptidão Física , Humanos , Masculino , Análise de Regressão , Corrida/fisiologia , Comportamento Sedentário , Velocidade de Caminhada/fisiologia
18.
Gait Posture ; 74: 212-217, 2019 10.
Artigo em Inglês | MEDLINE | ID: mdl-31561119

RESUMO

BACKGROUND: A growing body of literature supports the promising effect of real-time feedback to re-train runners. However, no studies have comprehensively assessed the effects of foots trike and cadence modification using different forms of real-time feedback provided via wearable devices. RESEARCH QUESTION: The purpose of the present study was to determine if a change could be made in foot strike pattern and plantar loads using real-time visual, auditory and combined feedback provided using wearable devices. METHODS: Visual, auditory and combined feedback were provided using wearable devices as fifteen recreational runners ran on a treadmill at self-selected speed and increased cadence. Plantar loads and location of initial contact were measured with a flexible insole system. Repeated measures ANOVAs with Bonferroni adjusted pair-wise comparisons were used to assess statistical significance. RESULTS AND SIGNIFICANCE: A significant effect of condition was noted on location of center of pressure (p < 0.01). Bonferroni-adjusted post-hoc comparisons showed that feedback conditions differed from baseline as well as the new cadence conditions, however did not differ from each other. A significant interaction effect (region x feedback) was found for plantar loads (maximum force P < 0.001). Significant effects of feedback were noted at the heel (P < 0.001), medial midfoot (P < 0.001), lateral midfoot (P < 0.001), medial forefoot (P = 0.003), central forefoot (P = 0.003), and great toe (P = 0.004) but not at the lateral forefoot (P = 0.6) or lateral toes (P = 0.507). SIGNIFICANCE: The unique findings of our study showed that an anterior shift of the center of pressure, particularly when foot strike modification was combined with 10% increased cadence. We found lower heel and midfoot loads along with higher forefoot and great toe loads when foot strike modification using real-time feedback was combined with increased cadence. Our findings also suggest that auditory feedback might be more effective than visual feedback in foot-strike modification.


Assuntos
Pé/fisiologia , Feedback Formativo , Corrida/fisiologia , Dispositivos Eletrônicos Vestíveis , Suporte de Carga/fisiologia , Adulto , Análise de Variância , Teste de Esforço , Feminino , Calcanhar/fisiologia , Humanos , Masculino , Atividade Motora/fisiologia , Sapatos , Dedos do Pé/fisiologia , Adulto Jovem
19.
Gait Posture ; 74: 176-181, 2019 10.
Artigo em Inglês | MEDLINE | ID: mdl-31539798

RESUMO

BACKGROUND: Running is a popular physical activity that benefits health; however, running surface characteristics may influence loading impact and injury risk. Machine learning algorithms could automatically identify running surface from wearable motion sensors to quantify running exposures, and perhaps loading and injury risk for a runner. RESEARCH QUESTION: (1) How accurately can machine learning algorithms identify surface type from three-dimensional accelerometer sensors? (2) Does the sensor count (single or two-sensor setup) affect model accuracy? METHODS: Twenty-nine healthy adults (23.3 ±â€¯3.6 years, 1.8 ±â€¯0.1 m, and 63.6 ±â€¯8.5 kg) participated in this study. Participants ran on three different surfaces (concrete, synthetic, woodchip) while fit with two three-dimensional accelerometers (lower-back and right tibia). Summary features (n = 208) were extracted from the accelerometer signals. Feature-based Gradient Boosting (GB) and signal-based deep learning Convolutional Neural Network (CNN) models were developed. Models were trained on 90% of the data and tested on the remaining 10%. The process was repeated five times, with data randomly shuffled between train-test splits, to quantify model performance variability. RESULTS: All models and configurations achieved greater than 90% average accuracy. The highest performing models were the two-sensor GB and tibia-sensor CNN (average accuracy of 97.0 ±â€¯0.7 and 96.1 ±â€¯2.6%, respectively). SIGNIFICANCE: Machine learning algorithms trained on running data from a single- or dual-sensor accelerometer setup can accurately distinguish between surfaces types. Automatic identification of surfaces encountered during running activities could help runners and coaches better monitor training load, improve performance, and reduce injury rates.


Assuntos
Acelerometria/métodos , Algoritmos , Aprendizado de Máquina , Corrida/fisiologia , Adulto , Exercício , Feminino , Humanos , Masculino , Adulto Jovem
20.
Gait Posture ; 74: 182-186, 2019 10.
Artigo em Inglês | MEDLINE | ID: mdl-31539799

RESUMO

BACKGROUND: Injury rates are high in populations that regularly undertake weight-bearing physical activity, particularly military populations. Military training activities, that often include load carriage, have been associated with lower limb injury occurrence, specifically stress fractures. RESEARCH QUESTION: Recent work identified plantar loading variables as risk factors for lower limb stress fractures in Royal Marines recruits that were assessed during barefoot running. This study aimed to quantify how those plantar loading variables changed in Royal Marines recruits following a prolonged military load carriage activity, to further understand potential mechanisms for lower limb stress fractures. METHODS: Bilateral, synchronised plantar pressure and lower limb kinematic data were recorded during barefoot running at 3.6 m s-1 (±5%) pre- and post- a 12.8-km training activity (∼150 min). The training activity was completed with an average speed typical of walking (1.4 m.s-1), and 35.5 kg of additional load was carried throughout. Data were collected from 32 male Royal Marines recruits who completed the training activity in week-21 of the 32-week training programme. Plantar pressure variables and ankle dorsiflexion were compared between pre- and post-activity. RESULTS: Post-activity there was reduced loading under the forefoot and increased loading under the rearfoot and midfoot. There was no change in dorsiflexion touchdown angle, but an increase in peak dorsiflexion and range of motion post-activity. SIGNIFICANCE: The increased rearfoot loading, reduced forefoot loading and increased ankle dorsiflexion following a prolonged military load carriage activity suggest a reduced transfer of loading from the rearfoot to the forefoot during stance, which may have implications for the development of stress fractures, particularly of the metatarsals.


Assuntos
Pé/fisiologia , Militares , Corrida/fisiologia , Caminhada/fisiologia , Suporte de Carga/fisiologia , Adulto , Fenômenos Biomecânicos , Feminino , Humanos , Masculino , Amplitude de Movimento Articular/fisiologia , Fatores de Risco , Adulto Jovem
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