Muscle strategies for leg extensions on a "Reformer" apparatus

Looped Elastic Resistance during Squats: How Do Band Position and Stiffness Affect Hip Myoelectric Activity?

Looped elastic bands around the thigh are commonly used during squats and result in increased hip activation. Due to the closed kinetic chain nature of the squat exercise, one may expect that placing the elastic band on distal segments, close to the floor contact, may not result in the same increase in hip muscle activation as that achieved with a looped band around the thigh. We analyzed the effects of band position (thigh, lower leg, and forefoot) and band stiffness on the myoelectric activity of the tensor fascia latae, gluteus medius, gluteus maximus, biceps femoris, vastus medialis, and vastus lateralis during squats in 35 healthy subjects (18 men and 17 women). The greatest myoelectric activity of hip muscles was observed when the stiffest band was positioned around the forefeet with an increase in 24% for the tensor fascia latae, 83% for the gluteus medius, and 68% for the gluteus maximus compared to free (without resistance band) squatting. Contrary to previous thinking, the use of elastic bands around the forefeet during squats can elicit increased myoelectric activity of hip muscles, with a magnitude often greater than when the band is placed around the thigh segments.

Hip torques and the effect of posture in side-stepping with elastic resistance

BACKGROUND

The way movement-based exercises affect targeted muscles is not always obvious. Side stepping with an elastic band around the forefeet is aimed at strengthening hip abductors and lateral rotator muscles, with the premise that it creates an external torque of adduction and medial rotation of the femur around the pelvis that needs to be counteracted by hip muscles. However, hip torques during this exercise have not been previously quantified.

RESEARCH QUESTION

Is the premise that the side-stepping exercise creates an external torque of adduction and medial rotation of the femur around the pelvis correct?

METHODS

Thirty-six adults performed the exercise in an upright and a squat posture while 3D kinetic and kinematic data were collected. Hip muscle torques were calculated using inverse dynamics. The effect of posture and potential interactions with sex, side-stepping phases, and trailing/leading directions were analyzed using Pearson correlation and mixed-model ANOVAs.

RESULT

A hip net muscle torque of extension, abduction and medial rotation was required to perform the exercise, regardless of phase and direction. The net muscle torque towards medial rotation required during the exercise was smaller (P < 0.001) in the upright (0.05-0.12 N m kg^-1 m^-1 across phases) compared to the squat posture (0.10-0.24 N m kg^-1 m^-1). In contrast, hip abductor torque was not affected by posture. When averaged across phases and directions, the normalized hip medial rotator muscle torque was highly correlated with knee flexion (r = 0.93, P < 0.001).

SIGNIFICANCE

The assumption that the side-stepping with the elastic band on the forefeet creates an external hip torque of medial rotation is erroneous. The resistance imposed to the hip during this exercise is consistent with the goal of strengthening the muscles that contribute to hip abduction and hip medial (not lateral) rotation. Changing the knee flexion angle is an effective way to manipulate hip rotator torque when prescribing this exercise in strength training and rehabilitation programs.

Analysis of lower limb force in foot work exercise of Pilates

Abstract Introduction: Pilates is a physical exercise method that uses the resistance of springs to modulate the overload from exercises. Objective: To characterize the force versus time curve of the foot work exercise; verify and compare the force applied by the same limb during the foot work exercise against the resistance of two types of springs with different elastic constants, and verify and compare the asymmetry of force applied by right and left lower limbs during the foot work exercise against the resistance of the same type of spring. Methods: Twenty healthy adult individuals familiarized with Pilates were evaluated. Two extensometric force plates adapted to the Reformer apparatus were used. Each participant performed 10 repetitions of the exercise against the resistance of two pairs of springs with different elastic constants. Descriptive and inferential statistics were used with significance levels of p < 0.05. Results: The exercise's standard curve showed that the peak force is reached in the point of maximum hip and knee extension during the execution of the exercise. There were differences between force production by the same limb for different springs (p < 0.001) and between left and right limb when spring with lower elastic constant was used (p = 0.006). No differences were found between right and left limb when spring with higher elastic constant was used (p = 0.108). Conclusion: The knowledge of the force versus time curve and the quantification of unilateral force are important elements in the evaluation and prescription of exercises.