We examined and clarified the relationship between the maximum squat depth and the range of motion of the ankle, knee, and hip joints, and the knee and hip muscle strength. [Participants and Methods] Nine healthy males participated in this study and performed a deep squat with the upper extremities raised; the movement was analyzed by two-dimensional motion analysis. We measured the ankle dorsiflexion, hip flexion, and knee flexion ranges of motion, as well as the knee extension and hip flexion muscle strengths and analyzed the relationship between the squatting motion, the range of motion, and the muscle strength of each joint. [Results] The right ankle dorsiflexion range of motion was a significant predictor of the ankle dorsiflexion angle on both sides. The right knee flexion range of motion was a significant predictor of the knee flexion angle, and the left knee flexion range of motion was a significant predictor of the trunk anterior tilt angle on both sides. The right ankle dorsiflexion range of motion was a significant predictor of the right hip flexion angle and vice versa. [Conclusion] This study reveals that movement on one side affects contralateral movement, which is important when evaluating the deep squat motion as a functional test.

This study aimed to clarify the relationship between the distance measurements in the Star Excursion Balance Test and participants' posture and lower limb muscle strength. [Participants and Methods] Nine healthy male college students participated in this study. Star Excursion Balance Test distance was measured in both lower limbs by performing anterior, posterolateral, and posteromedial trials; measuring the maximum reach; and performing three-dimensional motion analysis to determine the posture at maximum reach. Isokinetic muscle strength for knee flexion/extension, hip flexion/extension, and hip adduction/abduction were measured using an isokinetic machine.[Results] The hip extension strength, reach side ankle dorsiflexion angles, stance side knee flexion, reach side knee flexion, and knee flexion strength were selected as significant explanatory variables in the anterior direction. For the posteromedial direction, hip adduction and hip extension strength, reach side hip flexion angle, and stance side hip flexion angle were selected. For the posterolateral direction, reach side knee flexion angle and stance side ankle dorsiflexion, knee flexion strength and reach side hip flexion angle were selected. [Conclusion] The related factors differed between the dominant and non-dominant legs even in the same reach direction.

Abstract. We explored the extent to which fair knee extensors might be judged to be weaker than the normal knee extensors of healthy young adults. To obtain quantitative data for normal strength of knee extensors, we recorded knee torque in 20 healthy young subjects using an isokinetic dynamometer, and calculated muscle strength equivalent to fair, including the effect of inertial force, using a rigid body model. The results showed that fair torque as a percentage of actual normal torque at 60 degrees per second was 4.8 ± 1.2% (mean ± standard deviation) among the men and 4.6 ± 1.0% among the women. This difference in per cent strength was not statistically significant between men and women. In manual muscle testing, the grade of fair for knee extensors is thus very far below the midpoint of the scale from no activity to normal. This means that the good range between grade fair and normal is too wide to connote one particular state of strength. We believe that other methods are needed, for example using a dynamometer, to evaluate intermediate muscle weakness in detail. Key words: manual muscle testing, knee extensor strength, biomechanics (J Jpn Phy Ther Assoc 2: 1-5, 1999)Manual muscle testing arose from the idea of being able to move against gravity, which forms the central idea of this form of evaluating muscular strength. The grade of fair, which signifies ability to move a given body part through its full available range of motion against gravity with no external resistance manually applied, does not simply express a certain degree of muscle weakness, but also bears a functional connotation about whether or not a certain minimum of work can be performed in everyday life. The language of the different stepwise grades of strength in manual muscle testing thus contains useful information other than simply degree of muscular weakness 1) . In spite of this functionally meaningful form of assessing muscular strength, the quantitative meaning of fair in relation, for example, to normal is vague. If a muscle has only fair strength, how much weaker is it than a muscle with normal strength?Since fair is in the middle of the scale for this manual grading system, the examiner may misunderstand it to mean 50% of maximum strength 2) . Resnick et al. 3) reported that the ratio of fair to normal means 4% for the biceps femoris, 17-22% for the hip abductors, and 2% for the supinator muscle. None of these values is close to half of maximum strength, thus posing a problem to the physical therapist, who should think of fair not simply as a grade, but also as an approximate quantity of muscle strength.In the present study, we explored the extent to which fair knee extensors might be judged to be weaker than normal knee extensors of healthy young adults. The purpose of this study was to clarify the following: 1) How weak is fair strength as a percentage of normal strength in the knee extensors? 2) Is this ratio different between men and women? Methods Measuring muscle strength equivalent to normalTo obtain quantitative data fo...

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