Effects of expiratory effort on force variability in isometric knee extension / 体力科学

The aim of the present study was to determine the effects of expiratory effort on the magnitude and low-frequency components of force variability during submaximal isometric knee extension (IKE). Eight subjects performed 5-s IKE of the dominant leg at the intensity of 10% of maximal voluntary contraction (10% MVC). During the IKE, the subjects performed one of three forced expirations (FEs) of different effort levels. The three effort levels of FE were 0% effort (normal breathing, FE0), 50% effort (FE50) and 100% effort (FE100). In the expiratory phase of each IKE, the amplitude of the force variability was quantified by the coefficient of variation (FCV), and the low-frequency components of the force variability were evaluated by calculating the peak power values of the filtered force signal (F) and rectified EMG signal with high-pass filtering (rEMGH) of the vastus lateralis muscle. The cross-correlation between F and rEMGH was also calculated. FCV was significantly higher in FE100 than in FE0 and FE50 (p < 0.01). The peak power values of F and rEMGH was significantly higher in FE100 than in FE0 (p < 0.05). Cross-correlation between F and rEMGH with the latter preceding the former was observed in each FE condition. These results suggest that FE with maximal effort (FE100) increased not only the absolute amount of force variation but also low-frequency oscillatory components of force and EMG and that low-frequency oscillations of motor unit firing may be responsible for the increase in force variation induced by FE.

Prevalence And Severity Of Hamstring Tightness Among College Student: A Cross Sectional Study

Introduction: The present study was aimed to study clinic-investigative profile of foot lesions in diabetics in patients presenting in Pravara Rural Hospital, Loni. Materials and Methods: This prospective cross sectional study was under-taken in 50 patients carried out over a period of 2 years. Patients, irrespective of their age and gender, admitted in the inpatient department of surgery with Diabetes mellitus having foot problem and consenting for taking part in the study were included. All patients were evaluated by taking detailed history, clinical examination and necessary inves-tigation done. Results: Most patients present with diabetic foot lesion were in 7th decade of life. females were more commonly affected with male to female ratio 1:1.5. Ulcer was the common lesion seen here which was present in 24(48%) patients while abscess seen in 3 (6%) patients, was the least common lesion. There were many anaemic pa-tients (74%) in current study. Staphylococcus aureus was the commonest grown organism form the pus sample of foot lesions. Of the 50 patients, only 24 (48%) were known diabetics. Also, 18 (36%) patients were known smokers, 12 (24%) were alcoholic. Most patients (35 i.e, 70%) walked bare foot while only 15(30%) patients were using foot-wear. Cardiovascular diseases were common (10 i.e, 20%) associated conditions. Peripheral neuropathy was present in 21 (42%) patients. On staging the patients according to Wagner staging, most of the patients belonged to stage III (23) and IV (14). Doppler study in select patients revealed that 8(16%) patients were detected as impaired blood flow in peripheral vessels, 3(6%) patients showed complete stenosis and 5(10%) patients showed partial stenosis. Conclu-sion: Diabetic foot lesions were common in elderly patients. The most common presentation of foot lesions was ul-cer. The foot lesions were associated with poor blood sugar control, peripheral neuropathy, cardiovascular diseases, anemia, smoking and alcohol addiction. Most patients belonged to Wagner stages III and IV. Staphylococcus aureuswas the commonest grown organism form the pus sample of foot lesions .

Prevalence and Predictors of Patellofemoral Osteoarthritis after Anterior Cruciate Ligament Reconstruction with Hamstring Tendon Autograft

BACKGROUND: The present study aimed to evaluate the prevalence of patellofemoral osteoarthritis (PFOA) and identify the factors that affect PFOA development after single-bundle anterior cruciate ligament (ACL) reconstruction with hamstring autograft. We hypothesized that detecting these factors could be helpful in establishment of a rehabilitation strategy to focus on the modifiable factors. METHODS: Of the 324 patients who underwent primary ACL reconstruction between January 2010 and June 2013, 92 patients who were available for follow-up for a minimum of 36 months after the surgery and underwent second-look arthroscopy were enrolled. Subjective assessments and clinical outcome evaluation were conducted. Arthroscopic cartilage evaluation was done using the Outerbridge classification. Univariable and multivariable logistic regression analyses were used. RESULTS: Ninety-two patients were evaluated at an average of 38.9 ± 5.4 months of follow-up. PFOA above grade 2 was observed in 19 patients (20.7%) at the second-look arthroscopy. Of them, three patients with pre-existing PFOA (3.3%) showed progression of the Outerbridge grade, and 16 (17.4%) had newly developed PFOA. According to the multivariable logistic regression analysis, isokinetic extensor deficit at 60°/sec at the last follow-up (odds ratio [OR], 2.193; 95% confidence interval [CI], 1.081 to 12.439; p = 0.031), age at primary surgery (OR, 1.118; 95% CI, 1.019 to 1.227; p = 0.018), and concurrent meniscectomy at primary surgery (OR, 0.091; 95% CI, 1.012 to 1.177; p = 0.023) were the significant predictors of PFOA development. CONCLUSIONS: Significant predictors of PFOA after ACL reconstruction with hamstring autograft were decreased quadriceps strength at last follow-up, increased age, and concurrent meniscectomy at primary surgery. Quadriceps weakness as a modifiable factor should be considered in the establishment of a rehabilitation strategy to prevent PFOA after ACL reconstruction, especially in older age.

Fadiga muscular entre séries de exercícios isocinéticos em mulheres jovens / Muscle fatigue between isokinetic exercises sets in young women

OBJETIVO: Avaliar o efeito de dois Intervalos de Recuperação (IR) no pico de torque (PT) e no trabalho total (TT) isocinético em mulheres jovens. MÉTODOS: 17 mulheres, destreinadas, (27,2 ± 4,1 anos; 56,8 ± 6,9 kg; 162,6 ± 7,0 cm) realizaram três séries de 10 extensões isocinéticas do joelho a 60° e 180°/s, com um e dois minutos de IR. A análise estatística foi a ANOVA dois x três [IR (um e dois minutos) x série (1ª, 2ª e 3ª)] com α < 0.05. RESULTADOS: Um minuto de IR não foi suficiente para manter o PT e o TT ao longo das séries (p<0,05) a 60º (redução de 15,7% no PT e 19,8% no TT) e 180º/s (redução de 3,6% no PT e de 5,6% no TT). Dois minutos foram suficientes apenas a 180º/s. Contudo, a 60°/s, dois minutos de IR possibilitou um maior PT na segunda e na terceira série em relação a um minuto (p<0,05). CONCLUSÃO: Dois minutos são suficientes para manutenção do PT em um protocolo de treinamento isocinético a 180º/s, mas não a 60º/s em mulheres jovens.

OBJECTIVE: To examine the effect of two rest interval (RI) on isokinetic Peak Torque (PT) and total work (TW) produced by young women. METHODS: 17 untrained women (27.2 ± 4.1 yrs; 56.8 ± 6.9 kg; 162.6 ± 7.0 cm) performed three sets of 10 unilateral isokinetic knee extension repetitions at 60° and 180°/s with one and two minutes of RI. Statistical evaluation was performed using a two x three ANOVA [RI (one and two minutes) x set (1st, 2nd, 3rd)] with α < 0.05. RESULTS: One minute was not enough to keep PT and TW between sets (p<0.05) at 60º (reduction of 15.7% in PT and 19.8% in TW) and 180º/s (reduction of 3.6% in PT and 5.6% in TT). Two minutes was enough only at 180º/s. However, two minutes of RI was greater (p<0.05) than one minutes at 60°/s for PT during the 2nd and 3rd sets. CONCLUSION: Two minutes is sufficient to keep PT within typical isokinetic resistance training protocols at 180º/s, but not at 60º/s in young women.

What is the most effective protocol to induce fatiguein knee joint muscles? a systematic review

The aim of this study was to review the literature to see how the protocols are designed to induce kneejoint muscles fatigue using an isokinetic dynamometer. Materials and Methods: This study consisted of asystematic review and the search for the theoretical composition was performed in the PubMed databaseusing as descriptors the words muscle fatigue, knee, and isokinetic, and as filters the words Abstract available,Humans, Randomized Controlled Trial, and English language. It was not set limits for year of publications.Results: twenty nine studies were found, from which, seventeen were excluded due to exclusion criteria.Conclusion: It became evident in the present review that the greatest reduction in the peak torque occurs inprotocols that use series of trials without determining the number of repetitions, requiring that the movementbe executed until attaining exhaustion. However, if there is a need to determine a number of repetitionsto decrease the the knee joint torque to the levels close to the one attained in the exhaustion protocol, theprotocol that most reduced the knee joint flexor and extensor torque was the one that used five series of 30repetitions with interval of one minute between series, independent of the angular speed and the type ofcontraction, concentric or excentric.

An age-related change in dynamic balance ability and the relationship between dynamic balance ability and isometric knee extension strength-Females from 20 to 85 years old who regularly practiced at gymnastics club- / 体力科学

This study examined age-related changes in dynamic balance (DB) ability, and the relationship between DB ability and isometric knee extension strength (IKES). Subjects were 100 females who regularly performed some light gymnastic exercises at a gymnastics club once or twice a week. Subject ages ranged from 20 to 85 years old. The measured items were height, body weight (BW), IKES, and DB ability. Results were as follows: 1. The average DB ability tended to gradually decrease as the subjects got older. There were some significant differences in the average DB ability between the 20 to 29 and 60 to 69 age groups, and between the 20 to 29 and over 70 age groups. 2. It was shown that there was a significant negative correlation between age and DB ability (r=0.471, p<0.001). 3. There was a significant negative correlation between age and IKES/BW (r=0.579, p<0.001). 4. It was shown that there was a significant positive correlation between IKES/BW and DB ability (r=0.368, p<0.001). 5. There was a significant negative correlation between BMI and DB ability (r=0.370, p<0.001). This study showed that DB ability rapidly decreased over 60 years old, and also the value tended to be higher in persons with a higher knee extension strength and lower BMI. Therefore, it was suggested that it is important to increase the knee extension strength and maintain an appropriate BMI in order to maintain DB ability.

Efeitos de diferentes intervalos de recuperação no volume completado e na percepção subjetiva de esforço em homens treinados / Effects of different rest intervals in volume completed and perceived exertion in trained men

O objetivo do estudo foi comparar o efeito de dois intervalos de recuperação (IR) na cadeira extensora unilateral sobre o volume completado em três séries, no volume total de treino e na percepção subjetiva de esforço (PSE). Doze homens jovens, todos com pelo menos um ano de experiência no treinamento resistido. Os indivíduos realizaram 4 sessões de testes com intervalos de 48hs entre elas. Nas sessões 1 e 2 foram realizados teste e re-teste de 10RM. Nas sessões 3 e 4 realizaram três séries de 10RM. O IR entre as séries foram de 90 e 120s, contrabalanceados entre os dias de teste. A análise estatística foi a ANOVA de medidas repetidas. O teste T-Student para variáveis dependentes foi utilizado para comparar o somatório do volume total de treino nos dois intervalos distintos. Tanto 120 como 90s não conseguiram manter o volume ao longo das três séries, no entanto, com a utilização do IR de 120s foi possível realizar um maior volume total de treino. Em relação a PSE foram encontradas diferenças significativas intraseqüências apenas no IR90s na 3ª série quando comparada com 1ª e 2ª série de 90s, e inter sequências foram encontradas diferenças apenas com a 1ª série de 120s comparada com a 3ª série de 90s. O estudo indicou que o IR de 120s é superior ao de 90s no volume total de treino, entretanto, para manutenção do volume entre ás séries um IR superior deve ser realizado. E a utilização da PSE para identificar intensidade de esforço realizado, parece ser um bom método, visto que o IR de 90s acarretou diferenças entre as séries, o mesmo não aconteceu quando o IR de 120s foi utilizado.

The aim of this study was to compare the effect of two intervals of recovery (IR) in the unilateral knee extension on the volume completed in three series, the total volume of training and perceived exertion (RPE). Twelve young men, all with at least one year of experience in resistance training. The subjects performed 4 test sessions at intervals of 48 hours between them. In sessions 1 and 2 were tested and re-test of 10RM. In sections 3 and 4 had three sets of 10RM. The IR series were between 90 and 120s, counterbalanced between test days. Statistical analysis was ANOVA with repeated measures. The T-Student test for dependent variables was used to compare the sum of the total volume of training in two distinct ranges. Both 120 and 90s failed to maintain the volume along the three series, however, using the IR 120s could carry a greater volume of training. For RPE significant differences were found only in intrasequence IR90s in 3rd grade when compared with 1st and 2nd series of 90s and between sequences differences were found only with the 1st series of 120 compared with the 3rd set of 90s. The study indicated that the IR of 120 is higher than the 90s in the total volume of training, however, to keep volume between sets an IR system must be done. And the use of the RPE to identify intensity of effort appears to be a good method, since the IR 90s caused differences between the series, it did not happen when the IR of 120 was used.

Efeito do intervalo de recuperação entre séries de extensões isocinéticas de joelho em homens jovens destreinados / Effect of recovery interval between sets of isokinetic knee extensions among untrained young men

OBJETIVO: Avaliar o efeito de dois diferentes Intervalos de Recuperação (IR) entre séries de extensões isocinéticas de joelho no Pico de Torque (PT) e no Trabalho Total (TT) em jovens destreinados. MÉTODOS: Dezoito homens (24,22±2,58 anos; 80,42±11,41 kg) realizaram três séries de 10 extensões isocinéticas com o joelho direito a 60° e 180°/s. O IR entre as séries foram de 1 e 2 minutos, contrabalanceados entre os dois dias de teste, separados por, no mínimo, 48 horas. A taxa de trabalho-recuperação foi de 1:3 e 1:6 para 60°/s e 1:6 e 1:12 para 180°/s. Os voluntários não participavam de programas de treinamento resistido há pelo menos 6 meses. A análise estatística foi a ANOVA de medidas repetidas 2 x 3 [IR (1 e 2 minutos) x série (1ª, 2ª e 3ª)]. O nível de significância foi a<0,05. RESULTADOS: Tanto 1 como 2 minutos não conseguiram manter o PT e o TT ao longo das três séries (p<0,05). Porém, a 60°/s, 2 minutos de IR possibilitaram um melhor PT e TT na segunda e na terceira série que 1 minuto (p<0,05). Já a 180°/s, 2 minutos só foi superior (p<0,05) a 1 minuto na terceira série para o TT. CONCLUSÃO: O estudo indicou que durante um protocolo de treinamento isocinético, homens jovens necessitam mais de 2 minutos para recuperar totalmente o PT a 60°/s, e totalmente o TT a 60° e 180°/s. Entretanto, uma melhor recuperação do PT pode ser alcançada com uma taxa de trabalho-recuperação de 1:12 a 180°/s.

OBJECTIVE: To assess the effect of two recovery intervals (RIs) between sets of isokinetic knee extension exercises on peak torque (PT) and total work (TW), among untrained young men. METHODS: Eighteen men (24.22±2.58 years; 80.42±11.41 kg) performed three sets of ten isokinetic extensions of the right knee, at 60° and 180°/s. The RIs between the sets were one and two minutes long, spread over two test days separated by a minimum of 48 hours. The work-to-recovery ratio was 1:3 and 1:6 for 60°/s, and 1:6 and 1:12 for 180°/s. The subjects had not participated in any resistance training programs within the last six months. The statistical analysis consisted of 2 x 3 repeated-measures ANOVA [RI (one or two minutes) x set (1st, 2nd or 3rd)]. The significance level was a<0.05. RESULTS: Neither one minute nor two minutes RIs maintained the PT and TW throughout the three sets (p<0.05). However, at 60°/s, two minutes RIs enabled better PT and TW in the second and third sets than one minute RIs (p<0.05). At 180°/s, two minutes RIs were only better (p<0.05) than one minute RIs for TW in the third set. CONCLUSION: This study indicated that, during an isokinetic training protocol, young men require more than two minutes of RI for full PT recovery at 60°/s and full TW recovery at 60°/s and 180°/s. However, better PT recovery can be attained with a 1:12 work-to-recovery ratio at 180°/s.

Número máximo de repetições em exercícios isotônicos: influência da carga, velocidade e intervalo de recuperação entre séries / Maximum number of repetitions in isotonic exercises: influence of load, speed and rest interval between sets

INTRODUÇÃO: Pouco se sabe sobre o efeito da velocidade de execução e do intervalo entre séries sobre o desempenho no exercício contra-resistência. OBJETIVO: Comparar o número máximo de repetições até a fadiga voluntária (REPS) na cadeira extensora com o joelho dominante para diferentes cargas, velocidades e intervalos entre séries. MÉTODOS: Nove voluntários (35,8 ± 10,8 anos; 74,2 ± 16,7kg; 171,0 ± 10,0cm) reportaram ao laboratório para determinação de 1RM e REPS em seis situações, determinadas aleatoriamente e separadas por no mínimo 48h: uma série com 60 por cento 1RM a 80°•s¹ e 25°•s-1; uma série com 80 por cento 1RM a 25°•s¹; três séries com 80 por cento 1RM a 80°•s-1 e intervalos de 3 min, 1 min e naquele que permitisse a estabilização da oxigenação muscular (RMox), medida por espectroscopia no infravermelho próximo. RESULTADOS: O teste t dependente mostrou que REPS foi significativamente (p < 0,05) maior na carga leve que na pesada, nas velocidades lenta (leve = 8,8 ± 1,3; pesada = 5,9 ± 0,9) e rápida (leve = 16,3 ± 3,9; pesada = 9,4 ± 1,9), e significativamente maior na velocidade rápida que na lenta, para ambas as cargas. A ANOVA 3x3 não mostrou diferença entre os intervalos na série 1 (3 min = 9,4 ± 1,9; 1 min = 10,8 ± 3,2; RMox = 10,1 ± 3,0), porém, houve diferenças significativas nas séries 2 e 3 entre 3 min (série 2 = 7,0 ± 1,7; série 3 = 6,4 ± 1,3) e 1 min (série 2 = 5,6 ± 1,1; série 3 = 4,8 ± 1,2), mas não entre RMox (série 2 = 6,4 ± 1,7; série 3 = 6,1 ± 1,5) e os demais intervalos. Nos três intervalos, REPS na série 1 foi significativamente maior que nas demais. CONCLUSÕES: O desempenho no exercício contra-resistência é afetado pela carga, velocidade e intervalo entre séries e é independente da recuperação em oxigenação muscular. A prescrição do exercício e a avaliação do desempenho devem levar...

INTRODUCTION: Very little is known about the effects of movement velocity and rest intervals between sets of resistance exercise. PURPOSE: To compare the maximum number of repetitions to volitional fatigue (REPS) on a knee extension machine with the dominant leg for different loads, velocities and rest intervals between sets. METHODS: Nine volunteers (35.8 ± 10.8 years; 74.2 ± 16.7 kg; 171.0 ± 10.0 cm) reported to the laboratory to determine 1RM and REPS under six conditions, randomly determined and separated by at least 48 h: 1 set with 60 percent 1RM at 80°•s-1 and 25°•s-1; 1 set with 80 percent 1RM at 25°•s-1; 3 sets with 80 percent 1RM at 80°•s-1 and rest intervals of 3 min, 1 min and one that allowed recovery or stabilization of muscle oxygenation (RMox), measured by near infrared spectroscopy (NIRS). RESULTS: Dependent samples t-test showed that REPS was significantly (p < 0.05) larger for the lighter than the heavier load, for slow (light = 8.8 ± 1.3; heavy = 5.9 ± 0.9) and fast velocities (light = 16.3 ± 3.9; heavy = 9.4 ± 1.9), and significantly larger for the fast than the slow velocity, for both loads. The 3x3 ANOVA did not show differences among intervals on set 1 (3 min = 9.4 ± 1.9; 1 min = 10.8 ± 3.2; RMox = 10.1 ± 3.0), however, there were significant differences on sets 2 and 3 between 3 min (set 2 = 7.0 ± 1.7; set 3 = 6.4 ± 1.3) and 1 min (set 2 = 5.6 ± 1.1; set 3 = 4.8 ± 1.2), but not between RMox (set 2 = 6.4 ± 1.7; set 3 = 6.1 ± 1.5) and the other intervals. For all three intervals, REPS on set 1 was significantly larger than on the other sets. CONCLUSIONS: Performance in resistance exercise is affected by load, velocity and rest interval between sets and is independent of muscle oxygenation recovery. Exercise prescription and assessment of performance should take these variables into consideration...

PECULIARITY OF MUSCLE STRENGTH IN THE LOWER LIMBS OF SOCCER PLAYERS FROM THE PERSPECTIVE OF ISOKINETIC MUSCLE STRENGTH AND MRI FINDINGS IN COMPARISON WITH THOSE OF ARCHERS / 体力科学

This study examined peculiarities in both muscle strength and cross-sectional area (CSA) among soccer players in comparison with those of archers as contrasting athletes. Subjects were 15 male soccer players and 9 male archers at N University. Measurement items were height, body weight (BW), isokinetic muscle strength (knee extension, knee flexion, hip extension, hip flexion) and CSA (psoas muscles). Isokinetic muscle strength (30, 120, 240°/sec.) was measured by Cybex6000 (Lumex Co.), and the psoas muscle CSA was determined using magnetic resonance imaging (Hitachi, Japan). Results were as follows : 1. There was no significant difference in isokinetic knee extension and flexion strength/BW at all angular velocities between soccer players and archers. 2. On isokinetic hip flexion strength/BW, the average values of soccer players were significantly higher at all angular velocities than those of archers. However, there was no significant difference in the average values of isokinetic hip extension strength at all angular velocities between the two groups. 3. The average value for the psoas muscle CSA in soccer players was significantly higher than that of archers. In this study, the biggest difference in muscle strength between soccer players and archers was hip flexion strength, and the CSA of the psoas muscle in soccer players, which is the main component of hip flexion, was significantly larger than that of archers. These findings showed the peculiarity of soccer players due to the constant demands of movements involved in ball kicking and running during practice and competition.

Comparison of Exercise Indexes between Knee Extension-Flexion Exercise and Treadmill Exercise

OBJECTIVE: To obtain clinical usefulness of knee extension- flexion exercise by comparing the exercise indexes between treadmill exercise and knee extension-flexion exercise and to collect reference of exercise indexes using knee extension-flexion exercise. METHOD: Sixty four young healthy subjects participated in two modes of exercise. Subjects performed exercise using isokinetic dynamometer in one leg knee extension-flexion exercise and treadmill running using Bruce protocol in treadmill exercise. We recorded oxygen consumption, heart rate during rest and exercise. RESULTS: When comparing exercise indexes using treadmill exercise, we obtained relative exercise indexes using knee extension-flexion exercise, male 15.96%, female 15.77% in work rate, male 48.46%, female 52.53% in peak oxygen consumption, male 73.57%, female 80.82% in peak heart rate, male 65.97%, female 65.20% in oxygen pulse, male 56.07%, female 62.50% in peak tidal volume, male 82.56%, female 82.53% in peak respiratory rate, male 47.79%, female 49.48% in peak minute ventilation. In dynamic variables, we obtained male 266.82%, female 292.98% in ratio increase in oxygen consumption to increase in work rate. CONCLUSION: Knee extension-flexion exercise showed enough response to evaluate cardiorespiratory function through low work rate. Therefore knee extension-flexion exercise may be used for an exercise tolerance test in patients who cannot perform established exercise tolerance test.

Effect of teeth clenching on muscle strength during repeated isokinetic knee extensions / 体力科学

The purpose of this study was to investigate the effect of teeth clenching on isokinetic knee extension force during repeated voluntary contractions. We assessed isokinetic muscle strength in association with teeth clenching during 100 consecutive knee extensions at 60 degrees per second (deg/s) using a Cybex 6000 isokinetic dynamometer. In this study, 8 healthy male volunteers (28.4 ± 3.89 years) were asked to perform isokinetic contractions in an extended cycle of five contractions without teeth clenching followed by five contractions with the teeth clenching. The peak torque per body weight was statistically analyzed. In our results, the peak torque per body weight with teeth clenching were significantly greater than those without teeth clenching in the first 70 cycles; however, no significant differences were shown at 71-100 cycles. There was a significant negative correlation between the number of knee extensions and the difference in peak torque per body weight derived from with and without teeth clenching (r=-0.475, p<0.0001) . Our findings reveal that the effect of teeth clenching on the isokinetic muscle strength of knee extension is dependent on muscular fatigue, and that the improving effect of teeth clenching on isokinetic muscle strength declines with increasing muscular fatigue.

Relationship between the intensity of muscle contraction and muscie oxygenation of the m. rectus femoris during dynamic knee extension / 体力科学

This study investigated the relationship between the intensity of muscle contraction and muscle oxygenation during dynamic knee extension. Six healthy male subjects (age 24.6±1.2 years) performed knee extension (concentric : 1 s/eccentric : 1 s) to exhaustion at 3 different intensities, 30%, 20% and 10% of maximum voluntary contractile strength (MVC) . A near-infrared spectroscopy (NIRS) probe and surface electrodes of the electromyogram were fixed on the m. rectus femoris. The muscle oxygenation and integral electromyogram (IEMG) were recorded both during and after dynamic knee extension.<BR>The summary of the results was as follows.<BR>1) Continuous time of knee extension decreased with increasing intensity of muscle contraction. There were significant differences between 10%MVC and 20%MVC (p<0.001), and 10%MVC and 30%MVC (p<0.001) .<BR>2) The oxy-hemoglobin level during knee extension decreased with increasing intensity of muscle contraction. There were significant differences between 10%MVC and 30%MVC (p<0.001), 20%MVC and 30%MVC (p<0.001), and 10%MVC and 20%MVC (p<0.05) .<BR>3) Recovery time after knee extension increased with increasing intensity of muscle contraction. There were significant differences between 10%MVC and 30%MVC (p<0.01), and 20%MVC and 30%MVC (p<0.01) .<BR>4) The IEMG increased with increasing time of knee extension. The maximum value was observed just before completing the knee extension on the IEMG. The rate of increase in the IEMG increased with decreasing intensity of muscle contraction.<BR>These results suggest that muscle oxygenation during dynamic knee extension decreases with increasing intensity of muscle contraction, and influences continuous time of muscle contraction.

Effect of teeth clenching on force-velocity relationships in isokinetic knee extension / 体力科学

To investigate the effect of teeth clenching on isokinetic knee extension at various velocities, isokinetic muscle strength during knee extension was measured in association with teeth clenching at 30, 60, 150, 300 and 450 degrees per second (deg/s) using the Cybex 6000 isokinetic dynamometer. The volunteer subjects were 9 healthy males (26.2±0.97 years) . The peak torque per body weight and average power per body weight were statistically analyzed. Our results demonstrated that the peak torque per body weight with teeth clenching at 30, 60 and 150 deg/s significantly increased by 7.0%, 7.4% and 4.9%, respectively (p<0.05), but no significant differences were found at 300 and 450 deg/s. While the average power per body weight with teeth clenching at 30, 60 and 150 deg/s significantly increased by 6.5%, 6.1% and 6.9%, respectively (p<0.05), no sig-nificant differences were found at 300 and 450 deg/s. A significant negative correlation was shown between the isokinetic angular velocity and the difference in peak torque per body weight derived from with and without teeth clenching (r=-0.699; p<0.05) . These findings suggested that the effect of teeth clenching on isokinetic muscle strength of knee extension was dependent on the angular velocity, and at lower angular velocities teeth clenching had the effect of increasing the isokinetic muscle strength during knee extension.

Evaluation of torque-velocity curve and maximal power output of knee extensor under isokinetic contraction / 体力科学

In recent years, the knee extensor forces of athletes have usually been evaluated by measuring isokinetic output torque. The purpose of this study was to confirm the usefulness of normalizing the torque (force) -velocity curve and calculating the maximal power of knee extensor under isokinetic contraction.<BR>Seventy two (46 elite, 26 non-elite) Japanese male sprinters were chosen as the subjects in this study. The peak torque of the dominant side of knee extensor was measured by using the isokinetic dynamometer (Cybex II<SUP>+</SUP>) in three different angular velocities of 60, 180, 300 deg/sec. Moreover, the isometric torque (0 deg/sec) was measured in 39 athletes, 120 and 240 deg/sec of contraction were performed in 12 out of 39 athletes.<BR>The exponent equation (<I>F = F<SUB>o</SUB>× e<SUP>av</SUP>- kv</I> : Fenn 1935) was applied to normalize the torquevelocity curve without including the coefficient of viscosity (<I>k</I>) . The maximal power and its optimal velocity was presumed from this torque-velocity curve. The average of measured torque at 0 deg/sec contraction (<I>F<SUB>0</SUB></I>) was lower than that of 60 deg/sec, therefore<I>F<SUB>0</SUB></I>was presumed as the same as the maximal power. Those parameters were not significantly different when calculated from 3 velocities (60, 180, 300 deg/sec) and 5 velocities (plus 120, 240 deg/sec) in 12 athletes. For this reason, each parameter was calculated from 3 velocities.<BR>The maximal torque (<I>F<SUB>0</SUB></I>/BW) was the same between elite and non-elite group (4.0 Nm/kg) . Nevertheless, the coefficient of torque loss (<I>a</I>), maximal power and its optimal velocity were significantly different (-0.1586 : -0.1908, 9.6 : 7.8 watt/kg, 373: 309 deg/sec, respectively. P<0.01 Student-t) . It was said that to normalize the torque-velocity curve or to presume the maximal knee extension power and its optimal velocity were useful to assess the muscle function or the performance of athletes under isokinetic contraction.