Your browser doesn't support javascript.
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 292
Filtrar
1.
Int J Sports Med ; 40(14): 903-908, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31614383

RESUMO

Football players frequently face the occurrence of non-contact injuries. Although there are likely multiple factors that contribute to increased risk of non-contact injury, it remains a challenge to correlate all these factors. However, it is not clear how much of individual training abilities may interfere in these events. As such, the primary aim of the present study was to determine whether the reduction of functional performance of the thigh in the isokinetic knee tests, anthropometric and morbid history can establish risk factors for lower-limb musculoskeletal injuries throughout the season. The incidence of injuries and odds ratios were calculated for suspected risk factors. Hamstring/Quadriceps conventional ratio outside of the safety range (55-64%) may be involved in the occurrence of non-contact muscle injuries and the risk for any musculoskeletal injuries in the lower extremities is 16 times higher when extensor peak of torque exceeds 10% and 12 times higher when flexor peak of torque difference was greater than 10%. This kind of evaluation can result in intervention programs that may decrease the risk of lower-limb musculoskeletal injuries. Based on these results we can establish a specific and individualized exercise program for each athlete and thus protect them during the season.


Assuntos
Extremidade Inferior/lesões , Medição de Risco/métodos , Futebol/lesões , Adolescente , Adulto , Antropometria , Teste de Esforço , Músculos Isquiotibiais/lesões , Músculos Isquiotibiais/fisiologia , Humanos , Joelho/fisiologia , Ligamentos/lesões , Estudos Longitudinais , Extremidade Inferior/fisiologia , Masculino , Condicionamento Físico Humano , Músculo Quadríceps/lesões , Músculo Quadríceps/fisiologia , Fatores de Risco , Futebol/fisiologia , Coxa da Perna/fisiologia , Lesões do Menisco Tibial/fisiopatologia , Adulto Jovem
2.
Int J Sports Med ; 40(12): 779-788, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31487749

RESUMO

Static stretching (SS) can increase joint range of motion (ROM), due to neural, morphological, and physio-psychological factors. Periodized training programs (PD) (e. g., strength, power) are adopted to induce greater adaptations while avoiding overtraining. However, the effectiveness of periodized stretch training adaptations are unknown. Therefore, the objective of this study was to compare the effects of periodized and non-periodized (NP) stretching programs on flexibility, hamstrings stiffness and muscle performance. Sixteen gymnasts were allocated to either periodized or non-periodized SS training and tested pre- and post-8 weeks for countermovement jump height, hip flexors, hip extensors and dorsiflexors ROM, hamstrings stiffness and hamstrings and quadriceps peak torque. Both stretch training groups significantly and similarly increased hip extensor (33.2%), hip flexor (25.2%), and dorsiflexor (23.8%) ROM, hamstrings peak torque (7.9%) and jump height (8.1%) from pre - to post- training. Both groups decreased hamstrings stiffness across the last ten angles (32.1%). PD elicited consistently large magnitude flexibility effect size changes compared to small and moderate magnitude changes for the non-periodized. Therefore, 8-week PD and NP SS programs can decrease young gymnasts' muscle-tendon stiffness and increase muscle performance. However, effect sizes indicate that PD stretch training was more advantageous to increasing flexibility and improving performance.


Assuntos
Desempenho Atlético/fisiologia , Ginástica/fisiologia , Exercícios de Alongamento Muscular/métodos , Músculo Esquelético/fisiologia , Criança , Elasticidade , Teste de Esforço/métodos , Feminino , Músculos Isquiotibiais/fisiologia , Articulação do Quadril/fisiologia , Humanos , Músculo Quadríceps/fisiologia , Amplitude de Movimento Articular/fisiologia , Torque
3.
Int J Sports Med ; 40(11): 717-724, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31426105

RESUMO

The main purpose of the present study was to identify whether and to what extent the individual differences in range of motion and stiffness of the hip joint can account for that in muscle elasticity of the hamstring. Hip extension torque and shear moduli (a measure of elasticity) of the biceps femoris, semitendinosus, and semimembranosus were assessed in 21 young males during unilateral passive hip flexion in the knee-extended position from the anatomical position to the individual's maximal hip flexion angle. Muscle shear modulus was quantified by using ultrasound shear wave elastography. The maximal hip flexion angle correlated negatively with the shear modulus of each muscle (-0.750 ≤ r ≤ -0.612). The joint stiffness correlated positively with the shear modulus of each muscle (0.711 ≤ r ≤ 0.747). These findings suggest that hip flexion ROM and joint stiffness can reflect significantly but only moderately the muscle elasticity of the hamstring.


Assuntos
Módulo de Elasticidade , Músculos Isquiotibiais/fisiologia , Articulação do Quadril/fisiologia , Amplitude de Movimento Articular , Técnicas de Imagem por Elasticidade , Eletromiografia , Músculos Isquiotibiais/diagnóstico por imagem , Humanos , Masculino , Torque , Ultrassonografia , Adulto Jovem
4.
Gait Posture ; 73: 315-322, 2019 09.
Artigo em Inglês | MEDLINE | ID: mdl-31419759

RESUMO

BACKGROUND: Muscle co-contraction is an accepted clinical measure to quantify the effects of aging on neuromuscular control and movement efficiency. However, evidence of increased muscle co-contraction in old compared to young adults remains inconclusive. RESEARCH QUESTION: Are there differences in lower-limb agonist/antagonist muscle co-contractions in young and old adults, and males and females, during walking and stair use? METHODS: In a retrospective study, we analyzed data from 20 healthy young and 19 healthy old adults during walking, stair ascent, and stair descent at self-selected speeds, including marker trajectories, ground reaction force, and electromyography activity. We calculated muscle co-contraction at the knee (vastus lateralis vs. biceps femoris) and ankle (tibialis anterior vs. medial gastrocnemius) using the ratio of the common area under a muscle pairs' filtered and normalized electromyography curves to the sum of the areas under each muscle in that pair. RESULTS: Old compared to young adults displayed 18%-22% greater knee muscle co-contractions during the entire cycle of stair use activities. We found greater (17%-29%) knee muscle co-contractions in old compared to young adults during the swing phase of walking and stair use. We found no difference in ankle muscle co-contractions between the two age groups during all three activities. We found no difference in muscle co-contraction between males and females at the knee and ankle joints for all three activities. SIGNIFICANCE: Based on our findings, we recommend clinical evaluation to quantify the effects of aging through muscle co-contraction to include the knee joint during dynamic activities like walking and stair use, and independent evaluation of the stance and swing phases.


Assuntos
Articulação do Tornozelo/fisiologia , Marcha/fisiologia , Articulação do Joelho/fisiologia , Contração Muscular/fisiologia , Músculo Esquelético/fisiologia , Subida de Escada/fisiologia , Fatores Etários , Tornozelo/fisiologia , Eletromiografia , Feminino , Músculos Isquiotibiais/fisiologia , Voluntários Saudáveis , Humanos , Joelho , Masculino , Músculo Quadríceps/fisiologia , Estudos Retrospectivos , Adulto Jovem
5.
J Sports Sci ; 37(21): 2452-2458, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31303128

RESUMO

Hamstring strain injury (HSI) rates are higher for males vs. females. This cross-sectional study investigated if inherent differences in biceps femoris long head (BFLH) fascicle length (Lf) exist between recreationally active males and females (i.e., individuals without specific training practice history). Twenty-four young healthy participants (12 males; 12 females) had their BFLH muscle architecture (Lf, pennation angle [θp], and muscle thickness [MT]) measured using B-mode ultrasonography. Eccentric and isometric knee flexion strength were also assessed. BFLH Lf did not differ between sexes when expressed in absolute terms (males, 81.5 ± 14.7 mm; females, 73.6 ± 15.9 mm, P = 0.220, effect size (ES) = 0.52) or relative to femur length (0.140 ≤ P ≤ 0.220, ES = 0.63). Similarly, BFLH θp did not differ between sexes (P = 0.650) but BFLH MT was 18.9% larger for males vs. females (P = 0.024, ES = 0.99). Isometric and eccentric knee flexion strength was greater for males vs. females in absolute terms ([both] P < 0.001, 2.00 ≤ ES ≤ 2.27) and relative to body mass ([both] P < 0.001, 1.93 ≤ ES ≤ 2.13). In conclusion, factors other than BFLH Lf seem likely to be implicated in higher male vs. female HSI rates.


Assuntos
Músculos Isquiotibiais/anatomia & histologia , Estudos Transversais , Feminino , Músculos Isquiotibiais/diagnóstico por imagem , Músculos Isquiotibiais/lesões , Músculos Isquiotibiais/fisiologia , Humanos , Contração Isométrica/fisiologia , Joelho/fisiologia , Masculino , Força Muscular/fisiologia , Fatores de Risco , Fatores Sexuais , Ultrassonografia
6.
Phys Ther Sport ; 39: 69-75, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31277009

RESUMO

OBJECTIVES: To investigate the influence of internal and external foot rotation on medial and lateral hamstring electromyographic (EMG) activity during conventional hamstring exercises in patients following anterior cruciate ligament (ACL) reconstruction. DESIGN: Cross-sectional study. SETTING: EMG activity of medial and lateral hamstrings was recorded during prone leg curl, single-leg bridge and Nordic hamstring exercises with three different foot positions (neutral, internal rotation, external rotation), randomly presented. PARTICIPANTS: Twenty patients 9-15 months after ACL reconstruction with the semitendinosus-gracilis graft. MAIN OUTCOME MEASURES: Concentric and eccentric EMG activity normalized to the EMG activity recorded during a maximal voluntary contraction (MVC). RESULTS: Compared to the neutral position, the EMG activity of the medial hamstring during prone leg curl exercise was significantly increased by internal foot rotation (concentric: +8.7% MVC; eccentric: +5.9% MVC; p < 0.01; d = 0.88-0.99) and decreased by external rotation (concentric: 5.8% MVC; eccentric: 5.2% MVC; p < 0.05; d = 0.67-0.92). Foot position did not significantly affect hamstring EMG activity during single-leg bridge and Nordic hamstring exercises. CONCLUSIONS: Active internal rotation of the foot during prone leg curl exercise can help selectively maximize muscle activity of the medial hamstring portion. This may have implications for post-operative rehabilitation of ACL patients with a semitendinosus-gracilis graft.


Assuntos
Reconstrução do Ligamento Cruzado Anterior/reabilitação , Terapia por Exercício , Pé/fisiologia , Músculos Isquiotibiais/fisiologia , Rotação , Adulto , Estudos Transversais , Eletromiografia , Feminino , Humanos , Masculino , Tendões/transplante
7.
J Sports Med Phys Fitness ; 59(7): 1119-1125, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31332988

RESUMO

BACKGROUND: Hamstring strain injuries (HSI) are among the most common injuries in field-based team sports with a high-speed running component. The implementation of the Nordic hamstring exercise (NHE) is a well-documented method of improving eccentric hamstring strength to mitigate the risk of HSI occurrence. Sprint training is specific to the injury mechanism and is thought to activate the hamstrings through maximal eccentric contractions. The purpose of this study was to compare the effects of sprint training and the NHE on eccentric hamstring strength and sprint performance. METHODS: Twenty-eight participants (mean±SD age=16.21±1.34 years; height=1.75m±0.10m; body mass=68.5kg±12.1kg) completed an eccentric hamstring strength assessment and 40m sprint to assess acceleration and maximum speed. Participants were randomly allocated to either a NHE training or sprint training group. Two sessions per week for four-weeks of training was performed with baseline testing procedures repeated in the week following the intervention. Perceptions of soreness were recorded following the warm-up in each training session. RESULTS: Both the NHE (effect size=0.39, P<0.05) and sprint training (effect size=0.29, P<0.05) groups displayed significant gains in eccentric hamstring strength. The NHE group reported trivial improvements in sprint performance, whilst the sprint training group experienced a moderate improvement, specifically in maximum speed (ES=0.83 Moderate). Sprint training also produced greater perceptions of soreness than the NHE following a four-week training intervention, specifically before the start of the last session (P<0.05). CONCLUSIONS: These findings indicate that sprint training had a beneficial effect for both eccentric hamstring strength and sprint performance, whilst also producing greater soreness than the NHE following the final training session. It was concluded that a four-week block of maximum speed training may have both an injury prevention and performance enhancement benefit.


Assuntos
Músculos Isquiotibiais/fisiologia , Força Muscular/fisiologia , Corrida/fisiologia , Adolescente , Exercício/fisiologia , Teste de Esforço/métodos , Feminino , Humanos , Masculino , Fatores de Risco , Lesões dos Tecidos Moles/etiologia , Lesões dos Tecidos Moles/prevenção & controle
8.
J Strength Cond Res ; 33(10): 2595-2601, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31356511

RESUMO

Delgado, J, Drinkwater, EJ, Banyard, HG, Haff, GG, and Nosaka, K. Comparison between back squat, Romanian deadlift, and barbell hip thrust for leg and hip muscle activities during hip extension. J Strength Cond Res 33(10): 2595-2601, 2019-This study compared muscle activities of vastus lateralis (VL), biceps femoris (BF), and gluteus maximus (GM) during the back squat (SQ), Romanian deadlift (RDL), and barbell hip thrust (BHT) exercises performed with the same load (60 kg) and at one repetition maximum (1RM). Eight men with a minimum of 1 year's lower-body strength training experience performed the exercises in randomized order. Before each exercise, surface electromyography (EMG) was recorded during a maximal voluntary isometric contraction (MVIC) and then used to normalize to each muscle's EMG during each trial. Barbell hip thrust showed higher GM activity than the SQ (effect size [ES] = 1.39, p = 0.038) but was not significantly different from RDL (ES = 0.49, p = 0.285) at 1RM. Vastus lateralis activity at 1RM during the SQ was significantly greater than RDL (ES = 1.36, p = 0.002) and BHT (ES = 2.27, p = 0.009). Gluteus maximus activity was higher during MVIC when compared with the 60 kg load for the SQ (ES = 1.29, p = 0.002) and RDL (ES = 1.16, p = 0.006) but was similar for the BHT (ES = 0.22, p = 0.523). There were no significant differences in GM (ES = 0.35, p = 0.215) and BF activities (ES = 0.16, p = 0.791) between 1RM and MVIC for the SQ. These findings show that the RDL was equally as effective as the BHT for isolating the hip extensors, while the SQ simultaneously activated the hip and knee extensors.


Assuntos
Músculos Isquiotibiais/fisiologia , Músculo Esquelético , Músculo Quadríceps/fisiologia , Treinamento de Resistência/métodos , Levantamento de Peso/fisiologia , Adolescente , Adulto , Nádegas , Eletromiografia , Exercício/fisiologia , Quadril , Humanos , Contração Isométrica , Masculino , Distribuição Aleatória , Adulto Jovem
9.
Medicina (Kaunas) ; 55(8)2019 Jul 26.
Artigo em Inglês | MEDLINE | ID: mdl-31357518

RESUMO

Background and Objectives: This study considered the use of a generalized additive multilevel model to describe the joint-angle-specific functional hamstring to quadriceps ratio (H:Q ratio) in the knee, using all of the available truly isokinetic data within the range. Materials and Methods: Thirty healthy male basketball players aged 15.0 (1.4) years (average stature = 180.0 cm, SD = 11.1 cm; average body mass = 71.2, SD = 14.9 kg) years were considered. All players considered had no history of lower extremity musculoskeletal injury at the time of testing or during the 6 months before testing, and had been engaged in formal basketball training and competition for 5.9 (2.4) years. Moments of force of the reciprocal concentric and eccentric muscular actions for the knee extensors and flexors assessed by isokinetic dynamometry at 60°âˆ™s-1 were used. Results: Maximum moments of force were attained at different angle positions for knee extension. For knee flexion, it was apparent that there was an ability to maintain high levels of moment of force between 30° and 60° in the concentric muscular action, corresponding to the concentric action of the hamstrings. However, for the eccentric knee flexion, corresponding to the quadriceps action, there was a marked peak of moment of force at about 55°. The functional H:Q ratio for the knee extension was non-linear, remaining higher than 1.0 (i.e., point of equality) from the beginning of the extension until approximately 40° of the knee extension, leveling off below the point of equality thereafter. On average, the functional H:Q ratio for the knee flexion did not attain 1.0 across the range of motion. The functional H:Q ratio for the knee in the present sample peaked at 20° and 80°, declining between these angle positions to below 0.50 at about 0.54. Conclusions: Estimating the form of the non-linear relationship on-the-fly using a generalized additive multilevel model provides joint-angle-specific curves and joint-angle-specific functional H:Q ratio patterns, allowing the identification and monitoring of strength development, with potential implications for injury and performance.


Assuntos
Atletas/estatística & dados numéricos , Músculos Isquiotibiais/fisiologia , Músculo Quadríceps/fisiologia , Amplitude de Movimento Articular/fisiologia , Adolescente , Análise de Variância , Basquetebol/estatística & dados numéricos , Brasil , Humanos , Joelho/fisiologia , Masculino , Força Muscular/fisiologia
10.
J Sports Sci Med ; 18(2): 198-206, 2019 06.
Artigo em Inglês | MEDLINE | ID: mdl-31191088

RESUMO

The present systematic review aimed to analyze the activation of the muscles involved in the barbell hip thrust (BHT) and its transfer to sports activities that include horizontal displacement. A search of the current literature was performed using the PubMed, SPORTDiscuss, Scopus and Google Scholar databases. The inclusion criteria were: (a) descriptive studies, (b) physically trained participants, (c) analyzed muscle activation using normalized EMG signals or as a percentage of maximal voluntary isometric contraction (MVIC) and (d) acute or chronic transfer of the BHT to horizontal displacement activity. Twelve articles met the inclusion criteria and the following results were found: 1) neuromuscular activation: hip extensor muscles (gluteus maximus and biceps femoris) demonstrated greater activation in the BHT compared to the squat. The straight bar deadlift exercise demonstrated greater biceps femoris activation than BHT; 2) Regardless of the BHT variation and intensity used, the muscle excitation sequence is gluteus maximus, erector spinae, biceps femoris, semitendinosus, vastus lateralis, gluteus medius, vastus medialis and rectus femoris; 3) acute transfer: four studies demonstrated a significant improvement in sprinting activities after BHT exercise; 4) as for the chronic transfer: two studies demonstrated improvement of the sprint time, while other two studies failed to present such effect. We concluded that: a) the mechanics of BHT favors greater activation of the hip extensor muscles compared to more conventional exercises; b) regardless of the variation of BHT used, the muscle excitation sequence is gluteus maximus, erector spinae, hamstrings, and quadriceps femoris; c) the acute transfer of the post-activation potentiation of the BHT is significant, improving the sprinting time; and d) despite training with BHT submaximal loads can improve sprint times, further investigations are needed.


Assuntos
Músculos Isquiotibiais/fisiologia , Músculos Paraespinais/fisiologia , Músculo Quadríceps/fisiologia , Levantamento de Peso/fisiologia , Fenômenos Biomecânicos , Nádegas , Quadril , Humanos , Contração Isométrica , Postura , Coxa da Perna
11.
Sports Health ; 11(4): 316-323, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31194624

RESUMO

BACKGROUND: Individuals who experience a subsequent ipsilateral anterior cruci (cruciate)ate ligament (ACL) reinjury may use hazardous muscle activation strategies after primary ACL reconstruction (ACLR). The purpose of this study was to compare electromyograms (EMGs) of the quadriceps, hamstrings, and gastrocnemius muscles during a dynamic hopping task among individuals with a single ACL injury (ACLx1), individuals who went on to have secondary ipsilateral ACL injury (ACLx2), and individuals who have never sustained an ACL injury (ACLx0). HYPOTHESIS: We expected that individuals who went on to experience a secondary ACL injury would use less quadriceps muscle activity as compared with individuals who experienced a single ACL injury. STUDY DESIGN: Cross-sectional study. LEVEL OF EVIDENCE: Level 3. METHODS: Fourteen individuals that were returned to play post-ACLR and 7 non-ACL-injured individuals participated. Individuals who had undergone an ACLR were placed into groups depending on whether they had experienced a secondary ipsilateral ACL reinjury postprimary ACLR. EMG data of the vastus lateralis, biceps femoris, and lateral gastrocnemius were measured during 2 phases of a single-leg dynamic hopping task: preactivity (100 ms prior to ground contact) and reactivity (250 ms post-ground contact). Processed EMG data were compared across groups using 1-way analyses of variance, with post hoc independent t tests where appropriate (P ≤ 0.05). RESULTS: At preactivity, ACLx1 (0.48% ± 0.2%max) was found to use significantly more hamstring activity than ACLx2 (0.20% ± 0.1%max, P = 0.018), but not than ACLx0 (0.38% ± 0.1%max, P > 0.05). At reactivity, both ACL groups were found to use less quadriceps activity than ACLx0 (ACLx1: 0.38% ± 0.1%max, P = 0.016; ACLx2: 0.40% ± 0.1%max, P = 0.033; ACLx0: 0.58% ± 0.1%max), but not than each other (P > 0.05). CONCLUSION: Quadriceps muscle activity during landing was diminished in all ACL participants as compared with participants who had never sustained an ACL injury. Individuals who did not experience a secondary ipsilateral ACL reinjury (ACLx1) used greater levels of hamstring activity prior to landing. CLINICAL RELEVANCE: The higher hamstring activity in patients who did not experience a secondary injury may be interpreted as a protective mechanism that is used to dynamically stabilize the reconstructed limb.


Assuntos
Lesões do Ligamento Cruzado Anterior/fisiopatologia , Lesões do Ligamento Cruzado Anterior/cirurgia , Reconstrução do Ligamento Cruzado Anterior , Traumatismos em Atletas/fisiopatologia , Traumatismos em Atletas/cirurgia , Músculos Isquiotibiais/fisiologia , Músculo Esquelético/fisiologia , Músculo Quadríceps/fisiologia , Adolescente , Adulto , Estudos Transversais , Eletromiografia , Teste de Esforço , Feminino , Humanos , Masculino , Força Muscular , Recidiva , Volta ao Esporte , Adulto Jovem
12.
Sports Health ; 11(4): 324-331, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31173697

RESUMO

BACKGROUND: The impact of maturation on lower extremity strength and function after anterior cruciate ligament reconstruction (ACLR) may help guide future studies of age-specific rehabilitation. HYPOTHESIS: Pediatric ACLR patients would demonstrate higher thigh strength symmetry and knee-related function at return to sport (RTS) compared with adolescent and young adult participants who underwent traditional ACLR. STUDY DESIGN: Prospective cohort study. LEVEL OF EVIDENCE: Level 2. METHODS: A total of 144 young athletes at the time of RTS clearance post-ACLR were classified into 3 maturational groups (pediatric, n = 16 with physeal-sparing ACLR [mean age = 12.3 years; range = 9.2-14.6 years]; adolescent, n = 113 [mean age = 16.5 years; range = 14.1-19.8 years]; young adult, n = 15 [mean age = 22.0 years; range = 20.5-24.9 years]). Quadriceps and hamstring strength were measured using an electromechanical dynamometer. Knee-related function was measured using the International Knee Documentation Committee (IKDC) subjective form and single-leg hop tests. The Limb symmetry Index (LSI) was used in calculations for hop and strength tests. Group differences were compared with Kruskal-Wallis tests and Mann-Whitney U post hoc tests. Proportions of participants meeting literature-recommended RTS criterion cutoffs were compared among the groups using chi-square tests. RESULTS: The pediatric group demonstrated higher quadriceps LSI (P = 0.01), IKDC scores (P < 0.01), single-hop LSI (P < 0.01), and crossover-hop LSI (P = 0.02) compared with the young adult group. In addition, the pediatric group demonstrated higher IKDC scores (P < 0.01) and single-hop LSI (P = 0.02) compared with the adolescent group. The adolescent group demonstrated higher IKDC scores (P < 0.01), single-hop LSI (P = 0.02), and crossover-hop LSI (P = 0.03) compared with the young adult group. The proportions of participants meeting all RTS criterion cutoffs were highest in the pediatric group and lowest in the young adult group (P = 0.03). CONCLUSION: Young athletes at RTS clearance after pediatric ACLR demonstrated higher quadriceps strength symmetry and knee-related function than adolescents and young adults after traditional ACLR. CLINICAL RELEVANCE: These findings demonstrate the need for further study regarding the impact of these group differences on longitudinal outcomes after ACLR, including successful RTS and risk of second ACL injury.


Assuntos
Lesões do Ligamento Cruzado Anterior/cirurgia , Reconstrução do Ligamento Cruzado Anterior , Traumatismos em Atletas/cirurgia , Extremidade Inferior/fisiologia , Força Muscular , Volta ao Esporte , Maturidade Sexual , Adolescente , Fatores Etários , Lesões do Ligamento Cruzado Anterior/fisiopatologia , Traumatismos em Atletas/fisiopatologia , Criança , Teste de Esforço/métodos , Feminino , Músculos Isquiotibiais/fisiologia , Humanos , Joelho/fisiologia , Masculino , Dinamômetro de Força Muscular , Músculo Quadríceps/fisiologia , Coxa da Perna/fisiologia , Adulto Jovem
13.
Eur J Appl Physiol ; 119(9): 1943-1949, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31236670

RESUMO

PURPOSE: Prolonged static stretching (SS) in isolation (no dynamic warm-up) can impair muscle performance. There are conflicting reports whether impairments are present in antagonist and contralateral muscles. The objective of this study was to assess the effect of unilateral hamstrings SS on ipsilateral stretched and contralateral limbs' strength and jump power. METHODS: The SS (four repetitions of 30-s) and control sessions involved unilateral testing of the stretched leg and contralateral leg for knee extension (KE) maximum voluntary isometric contraction (MVIC) force and electromyography (EMG), drop jump (DJ) height and contact time at 1-min post-stretching. RESULTS: There were significant KE MVIC force impairments for both the SS (p = 0.006, d = 0.3, - 8.1%) and contralateral (p = 0.02, d = 0.20, - 4.2%) leg. With normalized data, there was a near-significant (p = 0.1), small magnitude (d = 0.29), greater force impairment with the ipsilateral (93.0 ± 12.8% of pre-test) versus the contralateral (96.2 ± 9.1% of pre-test) KE MVIC force. DJ height significantly improved for the stretched leg (p = 0.03, d = 0.18, + 9.2%) with near-significant, improvements for the contralateral leg (p = 0.06, d = 0.22, + 12.1%). For the stretched leg, DJ contact time was significantly (p = 0.04, d = 0.18, + 3.4%) prolonged, but there was no significant change with the contralateral leg. CONCLUSIONS: Unilateral hamstrings SS induced strength deficits in the ipsilateral and contralateral knee extension MVIC and a prolongation of the stretched leg DJ contact period. In anticipation of maximal force outputs, prolonged SS in isolation (no dynamic warm-up included) can have negative consequences on antagonist and contralateral muscle performance.


Assuntos
Músculos Isquiotibiais/fisiologia , Joelho/fisiologia , Força Muscular/fisiologia , Adulto , Feminino , Humanos , Contração Isométrica/fisiologia , Articulação do Joelho/fisiologia , Perna (Membro)/fisiologia , Masculino , Pessoa de Meia-Idade , Exercícios de Alongamento Muscular/métodos , Exercício de Aquecimento/fisiologia , Adulto Jovem
14.
Eur J Appl Physiol ; 119(9): 1933-1942, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31230110

RESUMO

PURPOSE: The purpose of this study was to compare the effects of squat training with different depths on lower limb muscle volumes. METHODS: Seventeen males were randomly assigned to a full squat training group (FST, n = 8) or half squat training group (HST, n = 9). They completed 10 weeks (2 days per week) of squat training. The muscle volumes (by magnetic resonance imaging) of the knee extensor, hamstring, adductor, and gluteus maximus muscles and the one repetition maximum (1RM) of full and half squats were measured before and after training. RESULTS: The relative increase in 1RM of full squat was significantly greater in FST (31.8 ± 14.9%) than in HST (11.3 ± 8.6%) (p = 0.003), whereas there was no difference in the relative increase in 1RM of half squat between FST (24.2 ± 7.1%) and HST (32.0 ± 12.1%) (p = 0.132). The volumes of knee extensor muscles significantly increased by 4.9 ± 2.6% in FST (p < 0.001) and 4.6 ± 3.1% in HST (p = 0.003), whereas that of rectus femoris and hamstring muscles did not change in either group. The volumes of adductor and gluteus maximus muscles significantly increased in FST (6.2 ± 2.6% and 6.7 ± 3.5%) and HST (2.7 ± 3.1% and 2.2 ± 2.6%). In addition, relative increases in adductor (p = 0.026) and gluteus maximus (p = 0.008) muscle volumes were significantly greater in FST than in HST. CONCLUSION: The results suggest that full squat training is more effective for developing the lower limb muscles excluding the rectus femoris and hamstring muscles.


Assuntos
Exercício/fisiologia , Músculos Isquiotibiais/fisiologia , Joelho/fisiologia , Força Muscular/fisiologia , Postura/fisiologia , Músculo Quadríceps/fisiologia , Coxa da Perna/fisiologia , Adulto , Eletromiografia/métodos , Humanos , Masculino , Treinamento de Resistência/métodos , Adulto Jovem
15.
Eur J Sport Sci ; 19(10): 1336-1341, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31099729

RESUMO

Match-induced fatigue of knee muscle strength and agonist-antagonist strength-ratios may affect both performance and risk of injury in soccer players. Once explosive tasks are imperative in soccer as well as hamstring strain injuries occur during high-velocity moments, rapid force capacity of this muscle group is especially important. This study evaluated the effect of match-induced fatigue on knee muscle strength and strength-ratio parameters after a single professional soccer match. Male professional soccer players (n = 16; 24.2 ± 3.9 years) were tested before and after a soccer match (56.2 ± 22.6 min of playing) for knee flexors (hamstring) and extensors (quadriceps) isometric peak torque (MVC) and rate of torque development (RTD) - as well as the hamstring-to-quadriceps ratio (H:Q) - at 30° of knee flexion. Knee injuries often occur at this joint angle, which is common in sprinting, pivoting, sidecutting, and jumping. Match-induced fatigue caused a left shift in the knee extensors torque-time curve with no significant change in both early (i.e. 0-50 ms) and late (i.e. 0-200 ms) RTD, and a right shift in the knee flexors torque-time curve with a decrease in early RTD (∼16%, p = .029) and late RTD (∼11%, p = .011). Knee extensors and knee flexors peak torque remained unchanged (p > .05). Early RTD H:Q decreased by∼24% (p = .027), while late RTD H:Q and MVC H:Q remained unchanged (p > .05). In conclusion, match-induced fatigue impaired the ability to rapidly produce force at an angle where injuries are most susceptible to occur. Important information is missed if only the traditional H:Q is considered.


Assuntos
Músculos Isquiotibiais/fisiologia , Contração Isométrica , Fadiga Muscular , Futebol/fisiologia , Adulto , Atletas , Comportamento Competitivo , Humanos , Articulação do Joelho/fisiologia , Masculino , Torque , Adulto Jovem
16.
Knee ; 26(3): 564-577, 2019 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-31097362

RESUMO

BACKGROUND: Braces for medial knee osteoarthritis can reduce medial joint loads through a combination of three mechanisms: application of an external brace abduction moment, alteration of gait dynamics, and reduced activation of antagonistic muscles. Although the effect of knee bracing has been reported independently for each of these parameters, no previous study has quantified their relative contributions to reducing medial knee loads. METHODS: In this study, we used a detailed musculoskeletal model to investigate immediate changes in medial and lateral loads caused by two different knee braces: OA Assist and OA Adjuster 3 (DJO Global). Seventeen osteoarthritis subjects and eighteen healthy controls performed overground gait trials in unbraced and braced conditions. RESULTS: Across all subjects, bracing reduced medial loads by 0.1 to 0.3 times bodyweight (BW), or roughly 10%, and increased lateral loads by 0.03 to 0.2 BW. Changes in gait kinematics due to bracing were subtle, and had little effect on medial and lateral joint loads. The knee adduction moment was unaltered unless the brace moment was included in its computation. Only one muscle, biceps femoris, showed a significant change in EMG with bracing, but this did not contribute to altered peak medial contact loads. CONCLUSIONS: Knee braces reduced medial tibiofemoral loads primarily by applying a direct, and substantial, abduction moment to each subject's knee. To further enhance brace effectiveness, future brace designs should seek to enhance the magnitude of this unloader moment, and possibly exploit additional kinematic or neuromuscular gait modifications.


Assuntos
Braquetes , Articulação do Joelho/fisiopatologia , Osteoartrite do Joelho/terapia , Adulto , Idoso , Fenômenos Biomecânicos/fisiologia , Estudos de Casos e Controles , Eletromiografia , Feminino , Marcha/fisiologia , Músculos Isquiotibiais/fisiologia , Humanos , Masculino , Pessoa de Meia-Idade , Osteoartrite do Joelho/fisiopatologia , Adulto Jovem
18.
J Electromyogr Kinesiol ; 47: 49-56, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31121550

RESUMO

PURPOSE: This study investigated the effect of knee joint angle and age on torque steadiness of knee extensors (KE) at varying submaximal isometric contractions. METHODS: 22 young (24.0 ±â€¯2.6 years; 11 women) and 22 older (69.4 ±â€¯2.4 years; 10 women) healthy men and women participated. Maximal voluntary isometric contraction (MVIC) of the KE and flexors was examined at 90° and 60° of knee flexion (0°â€¯= full extension). At each angle, participants performed KE isometric contractions (20%, 50% and 80% MVIC) to evaluate torque steadiness, whereas surface EMG was concurrently acquired from the vastus lateralis and biceps femoris muscles. RESULTS: Age-related impairment in torque steadiness was observed only at 20% MVIC (p < 0.01). A lower level of steadiness (p < 0.001) with a higher level of agonist and antagonist activations (all p < 0.01) was observed at 90° of knee flexion in comparison with contractions at 60°. Young participants were less steady when performing contractions at 90° compared with contractions at 60° of flexion (p < 0.001), whereas there was no difference for older participants. Furthermore, a significant effect of agonist activation and antagonist co-activation on torque steadiness was observed, but only in young participants (all p < 0.05). CONCLUSIONS: These findings suggest that: (1) knee joint angle affects torque steadiness differently in young and older individuals; (2) an age-related impairment in steadiness was only presented at the lowest considered contraction intensity; and (3) the muscle activation responses were not associated with steadiness in older individuals.


Assuntos
Envelhecimento/fisiologia , Eletromiografia/métodos , Articulação do Joelho/fisiologia , Amplitude de Movimento Articular/fisiologia , Torque , Adulto , Idoso , Feminino , Músculos Isquiotibiais/fisiologia , Humanos , Contração Isométrica/fisiologia , Masculino , Músculo Esquelético/fisiologia , Músculo Quadríceps/fisiologia , Adulto Jovem
19.
Int J Sports Med ; 40(7): 468-476, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31096292

RESUMO

The risk of anterior cruciate ligament injury in female handball players is high. Fatigue of active stabilizers and increases in joint laxity are often mentioned in the literature as causal factors. However, no studies have been carried out on this population. Our objective is to determine the effect of muscle fatigue on active and passive knee stability in female handball players. This prospective study assessed tibiofemoral joint laxity, as well as hamstring and quadriceps strength, before (Tinitial), during and 3 min after (Tfinal) an isokinetic fatigue protocol (25 repetitions of knee flexion / extension at 180°.s-1). Laxity values (slope of the displacement-load curve and anterior tibial translation) were measured using a GNRB-Rotab® arthrometer; torque values were measured at specific joint angles and peak muscle torque using an isokinetic dynamometer. Nineteen women (20.9±2.4 years, 62.0±4.9 kg, 166±5 cm) were included. Normalized peak torque decreased significantly between the first three and last three repetitions of the fatigue protocol (p<0.0001, ES=3.2 and 3.2). Slope of the displacement-load curve and anterior tibial translation, functional and conventional ratios did not change significantly between Tinitial and Tfinal. Active and passive markers of knee stability were not altered by a fatigue protocol in female handball players, suggesting these players have a large capacity for recovery. These results suggest that muscle strengthening to prevent ACL injury in female handball players may be inappropriate.Level of evidence: Level 2b, Prospective Cohort.


Assuntos
Instabilidade Articular/fisiopatologia , Articulação do Joelho/fisiologia , Fadiga Muscular/fisiologia , Esportes/fisiologia , Lesões do Ligamento Cruzado Anterior/fisiopatologia , Feminino , Músculos Isquiotibiais/fisiologia , Humanos , Articulação do Joelho/fisiopatologia , Força Muscular , Estudos Prospectivos , Músculo Quadríceps/fisiologia , Fatores de Risco , Torque , Adulto Jovem
20.
Scand J Med Sci Sports ; 29(8): 1083-1091, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31033024

RESUMO

Hamstring injuries are highly prevalent in many running-based sports, and predominantly affect the long head of biceps femoris. Re-injury rates are also high and together lead to considerable time lost from sport. However, the mechanisms for hamstring injury during high-speed running are still not fully understood. Therefore, the aim of this review was to summarize the current literature describing hamstring musculotendon mechanics and electromyography activity during high-speed running, and how they may relate to injury risk. The large eccentric contraction, characterized by peak musculotendon strain and negative work during late swing phase is widely suggested to be potentially injurious. However, it is also argued that high hamstring loads resulting from large joint torques and ground reaction forces during early stance may cause injury. While direct evidence is still lacking, the majority of the literature suggests that the most likely timing of injury is the late swing phase. Future research should aim to prospectively examine the relationship between hamstring musculotendon dynamics and hamstring injury.


Assuntos
Traumatismos em Atletas/etiologia , Músculos Isquiotibiais/lesões , Corrida/lesões , Fenômenos Biomecânicos , Eletromiografia , Músculos Isquiotibiais/fisiologia , Quadril , Humanos , Joelho , Tendões/fisiologia , Torque
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA