Um estudo de caso sobre treinamento isocinético: o esforço máximo é suficiente para o aumento de força? / A case study of isokinetic training: is maximal effort enough to increase strength?

INTRODUÇÃO: Dinamômetro isocinético é um equipamento eletrônico e mecânico, capaz de medir o torque gerado por um determinado segmento, bem como a potência e estimar fadiga, observando-se a variação do torque ao longo tempo. Este dispositivo também controla a velocidade do movimento angular, seja ele gerado por uma contração excêntrica ou concêntrica. Este tipo de equipamento tem sido utilizado tanto para avaliação como para treinamento de força. OBJETIVO: Verificar o efeito do treinamento de força, realizado exclusivamente no dinamômetro isocinético, na capacidade de gerar torque isométrico. MÉTODO: 2 homens, sedentários, saudáveis com idade de 23 e 24 anos realizaram 16 sessões de treinamento de força (sempre em esforço máximo e no modo concêntrico utilizando-se um dinamômetro isocinético) para os músculos flexores da articulação do cotovelo do membro dominante. As sessões foram compostas por um treinamento de quatro séries de oito repetições em uma amplitude de movimento de 130º, com velocidade fixada em 45º/s. As avaliações de contração isométrica voluntária máxima (CIVM) a 90º de flexão da articulação do cotovelo foram realizadas na primeira, oitava e décima sexta sessão. Espessura dos músculos flexores da articulação do cotovelo também foi medida, com ultrassonografia, nas mesmas sessões em que o torque máximo isométrico foi medido. RESULTADOS: Não houve diferença significativa no ganho de torque tam pouco na espessura muscular, ao final do treinamento. CONCLUSÃO: Treinamento de força, exclusivamente realizado no modo concêntrico no dinamômetro isocinético não provocou aumento da capacidade de gerar força isométrica, tam pouco aumento da espessura muscular. [AU]

INTRODUCTION: Isokinetic dynamometer is an electromechanical device that allows measuring the torque of a segment, as well as estimating power and fatigue by observing the variation of torque over time. This device also controls the speed of the angular movement, whether it is generated by an eccentric or concentric contraction. This equipment is utilized for both evaluation and strength training. OBJECTIVE: Verify the effects of strength training performed on an isokinetic dynamometer on the capacity to generate isometric torque. METHOD: Two healthy, sedentary men, aged 23 e 24 performed 16 strength training sessions (always at maximum effort) for elbow joint flexor muscles of the dominant limb. The sessions were composed by a training of four sets of eight repetitions in a range of movement of 130°, at 45º/s. The evaluations of maximal voluntary isometric contraction (MVIC) in a 90º of elbow flexion was realized in the first, eighth and sixteenth sessions. Thickness of the flexor muscles of the elbow joint was also measured with ultrasonography at the same sessions in which the maximum isometric torque was measured. RESULTS: There was no significant difference in torque gain or in muscle thickness at the end of the training protocol. CONCLUSION: Strength training, exclusively performed in the concentric mode on an isokinetic dynamometer did not caused an increase in the capacity to generate isometric torque and did not change muscle thickness. [AU]

Isometric and isokinetic testing of core muscles during trunk rotation / 中华物理医学与康复杂志

Objective To quantify the correlation between isometric and isokinetic tests of core muscles during trunk rotation. Methods The strength of the core muscles of 38 healthy males was measured isometrically and isokinetically ( at 60°/s) during trunk rotation.The left and right peak rotation torque ( LPT,RPT) and the ratio of left to right torque (L/R) were analyzed using correlation and regression analysis and paired t-tests. Results The subjects' LPTs and RPTs were positively correlated ( rL =0.644,P ≤ 0.01 ;rR =0.566,P≤0.01 ) There were significant differences in the L/R ratios determined using the two tests (r=0.663,P≤0.01 ).The regression equations predicting LPT and RPT were yL =22.330 + 0.937x and yR =32.752 +0.847x,respectively.Paired t-tests showed that tL =4.562,P≤0.01 and tR =3.855,P≤0.01 during left or right rotation.There was a significant difference,but there was no significant difference in LPT/RPT. Conclusion Isometric and isokinetic tests of core muscles during trunk rotation give results which are strongly correlated.Either can correctly reflect the maximal strength of core muscles during trunk rotation.Clinicinas may reasonably choose either testing method to assess patients and guide treatment according to the patient's clinical symptoms and the severity of the problem.

Efeitos de diferentes intervalos de recuperação no desempenho muscular isocinético em idosos / Effects of different rest intervals on isokinetic muscle performance among older adults

OBJETIVO: Comparar os efeitos de diferentes intervalos de recuperação (IR) entre séries de contração isocinética no desempenho muscular em idosos. MÉTODOS: Vinte idosos voluntários (66,9±3,9 anos, 76,1±13,4kg, 169±5,2cm) foram submetidos a três sessões de exercício resistido isocinético unilateral da musculatura extensora do joelho com diferentes IR (1 minuto, 2 minutos, e 3 minutos) na velocidade de 60°•s-1. Cada sessão consistia em três séries de 10 repetições durante as quais foram avaliados o pico de torque (PT), trabalho total (TT) e índice de fadiga (IF). ANOVA fatorial para medidas repetidas, com a análise de Post hoc por Bonferroni, foi utilizada para identificar possíveis diferenças entre os IR. O nível de significância estatístico utilizado foi de p<0,05. RESULTADOS: Não foram observadas diferenças no desempenho muscular entre as 1as séries nos diferentes IR (p>0,05). Apesar de ter sido observado menor desempenho muscular na 3ª série em todos os IR, maiores quedas no PT, TT e IF foram observadas quando adotado o IR de 1minuto (p<0,05). CONCLUSÃO: Os resultados mostraram que a variável IR exerce importante influência sobre o desempenho muscular isocinético em idosos, principalmente a partir da 3ª série, o que sugere incrementos no IR à medida que séries subsequentes forem executadas durante a mesma sessão de exercícios.

OBJECTIVE: To compare the effects of different rest intervals (RI) between sets of isokinetic contractions on muscle performance in older adults. METHODS: Twenty older participants (66.9±3.9 years; 76.1±13.4kg; 169±5.2cm) underwent three sessions of unilateral isokinetic training for the knee extensor muscles, with different RI (1 minute, 2 minutes and 3 minutes) at an angular velocity of 60°•s-1. Each session consisted of three sets of 10 repetitions, during which the peak torque (PT), total work (TW) and fatigue index (FI) were evaluated. Factorial ANOVA for repeated measurements, with Bonferroni post-hoc analysis, was used to identify possible differences between the RI. The statistical significance level was set at p<0.05. RESULTS: No differences in muscle performance during the first sets were observed between the different RI (p>0.05). Although muscle performance was lower during the third sets with all RI, the greatest decreases in PT, TW and FI occurred with the 1 minute RI (p<0.05). CONCLUSIONS: The results showed that the RI variable has an important influence on isokinetic muscle performance in older adults, particularly from the third sets onwards, which suggests that RI should be increased as successive sets are performed within the same exercise session.

Mechanical properties of dynamic muscle contraction against viscosity resistance(isoviscous contraction). Its comparison with isotonic and isokinetic contraction / 体力科学

The present study attempted to define a dynamic muscle contraction against viscosity resistance in which force is proportional to velocity of movement, and to determine its mechanical properties in comparison with isotonic and isokinetic muscle contraction. This dynamic contraction was referred to as the “isoviscous contraction” . A loading mechanism consisting of a directly-driven electromagnetic motor and an electronic control circuit was developed to enable three patterns of dynamic contraction to be performed. The torque, joint angle and joint angular velocity in the three types of dynamic contraction were measured in 8 healthy male volunteers during knee joint extension. The isoviscous contraction was not accompanied by any abrupt change in torque during the movement observed regularly in isotonic and isokinetic contraction. The instructed movement for isoviscous contraction could be performed over a wide range of joint motion at all levels of contraction. In addition to its unique mechanical properties, since the viscosity resistance produces a better damping effect against an abrupt change in torque, isoviscous contraction is considered to be a useful method of rehabilitation training in disabled patients and aged individuals. However, the great inertial force produced by isoviscous contraction corresponding to that in isotonic contraction should be further investigated.

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.