return to biology 105 syllabus
Biology of Exercise
Quiz 1, part 5 answer.
Muscles produce the most force when they are at an optimal length. This is much longer than the length at maximal shortening and much shorter than a maximally stretched muscle. The reason for this is that overlap between myosin head groups and actin is optimal at an intermediate length. At short lengths, the sarcomere filaments are jammed together, reducing overlap and creating mechanical obstruction during contraction. At longer length, the filaments slide apart and thus have less overlap. Because the myosin-actin interaction is responsible for creating force, the length at which these interactions is optimized is the optimal length for force production.