Force Angle Relationship Lab Report

Lab 2: Force Angle relationship 250 words 4 marks

In this lab we concentrated on investigating the relationship between joint angle and consequential ability of muscles to produce force. The knee joint was focused on with the quadriceps (rectus femoris, vastus lateralis, vastus intermedialis vastus medialis) and hamstrings (semitendinosus, semimembranosus. biceps femoris lomg head and short head) being the main muscle groups studied.

A relationship exists between the length of the muscle before the onset of contraction and the tetanic tension that each contracting fibre can subsequently develop at that length (Sherwood 2010). For every muscle there is an optimal length at which maximal force can be achieved on a subsequent tetanic contraction.

The thin actin filaments optimally overlap the regions of thick myosin filaments from which the cross bridges project. At this length, a maximal number of cross bridges and actin molecules are accessible to each other for cycles of binding and bending

Lengths greater than optimal length- the thin filaments are pulled out from between the thick filaments, decreasing the number of actin sites available for cross-bridge binding. Actin sites and cross bridges no longer “matches up” and so “go

Decreases in voluntary torque generation at the extremes of the functional joint range of motion (0° to90° flexion) may be attributed to mechanical and/or muscle activation factors. Also as discussed, at this extended range the muscle is not at optimal length and the numbers of actin sites available for cross-bridge binding is limited. Brownstein et al. (1985) found that peak torque was coincident with maximum IEMG at 50° for males and 70° in females of knee flexion. With Subject 1’s (male) maximum quadriceps isometric contraction occurring at a 60° knee joint angle and Subject 2’s (female) occurring at 75°, our results correlate quite closely with these