Answer
Fig. 11.16
The gluteus maximus and the quadriceps femoris.
Work Step by Step
There are two forms of isotonic muscle contraction. In concentric isotonic contraction, a muscle shortens as it maintains tension. On the contrary, in eccentric isotonic contraction, a muscle lengthens as it maintains tension. The process of lowering the buttocks to contact the seat of a chair involves flexion of both hip and knee joints. The gluteus maximus, and hamstring muscles contract eccentrically in the flexing of the hip; the flexing of the knee joint involves eccentric contraction of the quadriceps femoris muscles.
