Estimativa das forças na articulação tíbio-femoral no exercício de extensão dos joelhos em cadeia cinética aberta realizado em máquina de musculação

Abstract

RESUMOOs objetivos do presente estudo foram: (1) avaliar o torque de resistência (TR) de uma máquina de musculação para a realização do exercício de extensão dos joelhos em cadeia cinética aberta e (2) realizar um ensaio teórico a partir do comportamento do TR com o intuito de estimar as forças internas na articulação tíbio-femoral. O estudo foi realizado em dois momentos: (1) medições da máquina utilizada e (2) estimativa das forças externas (na máquina) e internas (no membro inferior). Foram utilizadas equações baseadas em um modelo mecânico bi-dimensional para o cálculo das componentes perpendiculares e axiais da força muscular (FMp e FM", respectivamente) e da força articular (FAp e FA", respectivamente), assim como de suas resultantes (forças muscular, FM; articular, FA e humana, FH). As variáveis foram mensuradas em cinco ângulos de fl exão do joelho (zero, 30, 45, 60 e 90 graus). Observou-se uma redução da FH com o aumento do ângulo de fl exão do joelho, enquanto FM e FA apresentam aumento. O valor da FH apresentou-se sempre menor ao valor da força resistiva (FR), indicando que a máquina reduz a sobrecarga imposta ao executante. Observa-se uma redução da FMp e FAp nos maiores ângulos de fl exão do joelho, indicando uma redução da força de cisalhamento anterior da tíbia sobre o fêmur. Percebeu-se um aumento da FA", devido ao aumento de FM", principalmente de 45 a 90 graus. Palavras-chave:Reabilitação, Força articular no joelho, Treinamento de força. ABSTRACTThe objectives of this study were to: (1) evaluate the resistive torque of an open kinetic chain strength-training machine for performing knee extensions, and (2) perform an analysis estimating internal forces in the tibiofemoral joint. During a fi rst phase of the study, measurements were taken of the machine under analysis (external forces), and then calculations were performed to estimate forces on the lower limb (internal forces). Equations were defi ned to calculate human force (HF), and the moment of muscular force (MMF). Perpendicular muscular force (MFp) and joint force (JFp), axial muscular force (MF") and joint force (JF"), and total muscular force (MF) and joint force (JF) were all calculated. Five knee angles were analyzed (zero, 30, 45, 60, and 90 degrees). A reduction was observed in HF at higher knee angles, while MF and JF also increased at the same time. HF was always lower than the load selected on the machine, which indicates a reduced overload imposed by the machine. The reduction observed in MFp and JFp at higher knee angles indicates a lower tendency to shear the tibia in relation to the femur. At the same time, there was an increase in JF" due to higher MF". The biomechanical model proposed in this study has shown itself adequate for the day-to-day needs of professionals who supervise orient strength training.

Análise do torque de resistência e da força muscular resultante durante exercício de extensão de quadril no Pilates e suas implicações na prescrição e progressão

“…The WMMA is the result from the sum of the products between the perpendicular distance of each muscle (d ┴ ) and its respective physiological cross-sectional area (PCSA) divided by the sum of the cross-sectional areas of the muscles 13,14 (Equation 4). In the present study, HE muscles included: biceps femoris, semitendinosus, semimembranosus and gluteus maximus and flexor muscles included: rectus femoris, psoas, iliacus, sartorius and tensor fasciae latae.…”

“…The reason for this is that the sping's strength (given by the constant of strain and the variation of its length) in addition to its respective perpendicular distance (directly determined by the fixation site of the spring) compose the resistance torque (T R ) offered by this exercise, during the exercise range of motion (ROM). Thus, in clinical practice, Γ R assessment (which considers the variations in the constant of strain and the fixation height of the spring) may provide useful quantitative data for progressing the intensity of the program over the course of the treatment and also indicate in which joint position the external load is maximum 11,[13][14][15] , allowing clinicians to prioritize strength gains in specific ranges of motion.…”

Comparative study between two elbow flexion exercises using the estimated resultant muscle force

“…Many different types of equipment are commonly used to adjust the external load of an exercise to the demand required for muscle stimulation 4 . Free weights 5,6 (dumbbells, barbells, plates and ankle and wrist weights), elastic resistance 7,8 (bands, rubber bands, tubes and springs), machines 9,10 (devices with pulleys and/or torque transmission bars) and equipment for aquatic exercise 11,12 (paddles, fins and buoys) are some of the items used while performing exercises. Different items have distinct resistance force characteristics due to the physical laws that cause these forces.…”

“…These variations produce differentiated external resistance, and consequently require distinct muscle efforts in each case. Although the organization of different activation strategies for muscle groups is highly complex and is not fully understood 16 , mechanical analysis has recently been used to understand exercises 10 , and even to choose one exercise over another 17,18 . Hence, in an attempt to understand the elbow flexion exercise from a mechanical perspective, the objective of the present study was to compare the estimated resultant muscle force required throughout the full ROM in two distinct elbow flexion exercises.…”

Avaliação da Força de Atrito em máquina de musculação durante exercícios de extensão de joelho

“…Muitos estudos já realizaram estimativas de força durante a realização de exercícios em máquinas de musculação, no entanto, não levaram em consideração o efeito da FA sobre o exercício. Aparelhos de remada (DE TOLEDO;DE OLIVEIRA;LOSS, 2007), extensão de joelhos (BINI et al, 2008), flexão dorsal (CANTERGI et al, 2010), entre outros são alguns dos exemplos onde o atrito normalmente não foi levado em consideração na estimativa de forças, tendo seu efeito subestimado.…”