Assessment of resistance torque and resultant muscular force during Pilates hip extension exercise and its implications to prescription and progression.

BACKGROUND: The understanding of the external mechanics of Pilates exercises and the biomechanics of the joints may guide the prescription of rehabilitation exercises. OBJECTIVES: To evaluate the resistance torque (Γ(R)) during hip extension (HE) exercises performed on the Pilates Cadillac. To perform a biomechanic analysis of the Γ(R) and the weighted mean moment arm (WMMA) in order to calculate the resultant muscle force (FM(R)) of the hip extensors and flexors. To present a mechanical criteria for progression of HE exercise on the Pilates Cadillac. METHODS: Fourteen participants performed HE exercises on the Cadillac in four randomly assigned situations - using two springs (blue and red), which were attached in two positions (high and low). Angular positions were measured using an electrogoniometer. In order to calculate Γ(R), the muscle torque (Γ(M)) and FM(R), free-body diagrams and movement equations were used. The WMMA of the hip extensors and flexors were estimated from the literature. RESULTS: The Γ(R) and FM(R) presented a similar behavior during all situations; however, the maximum Γ(R) values did not occur at the same joint position as the FM(R) maximum values. The WMMA of the hip flexors presented an increased- decreased behavior with greatest values around 55º of flexion, while the hip extensors presented a similar behavior with greatest values around 25º of flexion. CONCLUSION: Biomechanic analysis of HE exercises and the evaluation of mechanical features in relation to the hip joint may be used as an objective criteria for the prescription and progression of HE exercise in Pilates.

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 / Assessment of resistance torque and resultant muscular force during Pilates hip extension exercise and its implications to prescription and progression

CONTEXTUALIZAÇÃO: A análise da mecânica externa dos exercícios de Pilates e da biomecânica das articulações pode subsidiar a prescrição de exercícios na reabilitação. OBJETIVOS: Avaliar o comportamento do torque de resistência (ΓR) do exercício de extensão de quadril (EQ) realizado no Cadillac; realizar uma análise biomecânica a partir do comportamento do ΓR e das distâncias perpendiculares médias ponderadas (DPMPs) para estimar a força muscular resultante (FM R) dos extensores e flexores e propor critérios mecânicos para progressão do exercício de EQ realizado no Cadillac. MÉTODOS: Catorze praticantes de Pilates realizaram EQ no aparelho Cadillac em quatro situações em ordem aleatorizada - usando duas molas (vermelha e azul) fixadas em duas posições (alta e baixa). As posições angulares foram coletadas por meio de eletrogoniometria. Para o cálculo do ΓR, torque muscular (ΓM) e da FM R foram usados diagramas de corpo livre e equações de movimento. Os valores de DPMP dos músculos flexores e extensores do quadril foram quantificados usando dados da literatura. RESULTADOS: O ΓR e a FM R apresentaram comportamentos semelhantes em todas as situações, entretanto os valores máximos de ΓR não ocorrem na mesma posição articular que a FM R máxima. A DPMP dos flexores de quadril apresentou um comportamento crescente-decrescente, com máximo próximo aos 55º de flexão, enquanto os extensores de quadril apresentaram comportamento semelhante, com máximo próximo aos 25º de flexão. CONCLUSÃO: A análise biomecânica do exercício e a avaliação das características mecânicas associadas à articulação do quadril podem ser usadas como critérios objetivos de prescrição e progressão do exercício de EQ no Pilates.

BACKGROUND: The understanding of the external mechanics of Pilates exercises and the biomechanics of the joints may guide the prescription of rehabilitation exercises. OBJECTIVES: To evaluate the resistance torque (ΓR) during hip extension (HE) exercises performed on the Pilates Cadillac. To perform a biomechanic analysis of the ΓR and the weighted mean moment arm (WMMA) in order to calculate the resultant muscle force (FM R) of the hip extensors and flexors. To present a mechanical criteria for progression of HE exercise on the Pilates Cadillac. METHODS: Fourteen participants performed HE exercises on the Cadillac in four randomly assigned situations - using two springs (blue and red), which were attached in two positions (high and low). Angular positions were measured using an electrogoniometer. In order to calculate ΓR, the muscle torque (ΓM) and FM R, free-body diagrams and movement equations were used. The WMMA of the hip extensors and flexors were estimated from the literature. RESULTS: The ΓR and FM R presented a similar behavior during all situations; however, the maximum ΓR values did not occur at the same joint position as the FM R maximum values. The WMMA of the hip flexors presented an increased- decreased behavior with greatest values around 55º of flexion, while the hip extensors presented a similar behavior with greatest values around 25º of flexion. CONCLUSION: Biomechanic analysis of HE exercises and the evaluation of mechanical features in relation to the hip joint may be used as an objective criteria for the prescription and progression of HE exercise in Pilates.

Determinação da força das linhas do kite sobre um praticante em terra, utilizando o trapézio e a cadeirinha do kitesurfing / Ascertainment of the kite’s lines forces on an athlete in land, using trapeze harness and seat harness of Kitesurfing

No Kitesurfing, o indivíduo utiliza o vento para deslizar com uma prancha sobre a água por meio de um kite, que pode ser preso ao praticante pelos equipamentos: trapézio (posicionado em volta da cintura) ou cadeirinha (posicionada em volta do quadril). A diferença entre eles consiste no ponto em que o kite exerce força sobre o indivíduo. O objetivo do presente estudo foi medir a força das linhas do kite (FLK) exercida sobre um praticante em terra, utilizando o trapézio e a cadeirinha em diferentes posições angulares entre o tronco do indivíduo e as linhas do kite. Um praticante foi preso às cordas de um kite, que foram fixadas à parede e ao teto de uma sala. Ele foi solicitado a manter por 8 s o corpo com certa inclinação em relação ao solo de modo a formar ângulos próximos de 35, 45, 60 e 90° entre a linha de ação da FLK e o seu corpo (medidos com um goniômetro manual), utilizando a cadeirinha e o trapézio. Com uma célula de carga foi registrado a FLK exercida sobre o indivíduo (normalizada pelo seu peso) e com uma câmera de vídeo foram verificadas a sua posição angular. Com o trapézio, a força avaliada foi 43,4±0,2%, 48,5±0,5%, 57,1±0,3% e 25,4±0,11% para os ângulos avaliados em ordem crescente; com a cadeirinha, a força foi 51,9±0,2%, 62,1±1,5%, 57,9±0,2% e 28,3±0,1% para os mesmos ângulos. A FLK sobre o praticante variou de 25 a 60% do peso corporal.

During kitesurfing, the athlete propels himself and his board across the water by transferring the energy of the wind into speed by a large controllable kite, which can be attached to the athlete by 2 equipment: the trapeze harness (placed around the waist) or the seat harness (placed around the hip). The difference between them consist on the point where the kite apply force on the athlete, changing the sailing conditions. However, measuring this force is not easy, due to the environment in which the sport is practiced, therefore to evaluate this force on earth is the first step towards the development of a methodology. To measure the Kite’s lines forces (KLF), applied on the athlete in land, using a trapeze harness and a seat harness in different angular positions between his trunk and the kite’s lines. One practitioner (22years old; 76kg; 1,79m) was attached to the kite’s lines, which were linked to the wall and to the ceiling of a room. The practitioner was asked to keep during 8 s the body with determined inclination in relation to the ground to form angles close to 35, 45, 60 and 90 ° between the line of action of KLF and his body (measured by a manual goniometer and similar to the angles that occur in the sport) using a trapeze harness and a seat harness. The KLF was recorded with a dinamometer. Later this force was normalized by the practitioner weight. And with a video camera the body position and angles desired were checked. With the trapeze harness, the forces evaluated were 43,4±0,2%, 48,5±0,5%, 57,1±0,3% e 25,4±0,11% for the angles measured in ascending range; with the seat harness the forces were 51,9±0,2%, 62,1±1,5%, 57,9±0,2% e 28,3±0,1% for the same angles. The KLF on the practitioner ranged from 25 to 60% of the practitioners weight. The next step will be evaluate the forces and practitioner’s the body position in land with the kite, to later perform measurements in terms of the sport.

Análise mecânica e estimativa da força muscular resultante no aparelho flexor dorsal do pé / Mechanical analysis and estimation of muscle strength resulting in apparatus flexor dorsal foot

Embora a importância do reforço dos dorsiflexores seja conhecida, muitas vezes esses músculos são negligenciados em um programa de treinamento. O objetivo desse estudo é analisar o comportamento do torque resistente do “aparelho flexor dorsal do pé” e analisar o comportamento da força muscular resultante durante o exercício. Para tanto, foram elaborados diagramas de corpo livre da parte móvel do aparelho e do segmento humano e, também, foram determinadas equações de equilíbrio de torque, em que a velocidade foi considerada constante. Os resultados indicam que o torque de resistência do aparelho é crescente até chegar à horizontal e decrescente a partir desse ponto. A força muscular resultante é crescente durante todo o movimento e mais notadamente após a horizontal.

Although the importance of the dorsiflexors muscle work is well known, very often these muscles are neglected in a workout-training program. The aim of this study is to analyze the behavior of the resistant torque on the “dorsiflexors machine” and, also, analyze how the muscle force output during the exercise is. For that, there were designed free body diagrams of the movable part of the machine and human segment. There were made torque equilibrium equations where the velocity was considered to be steady. Our results suggest the resistant torque increases till it gets at the horizontal line and it decreases from this spot on. As for the muscle force output it increases for all over the range of movement and it is more evident after the horizontal line.