Length/Tension Relationship

Ever notice how a pull up gets a lot harder once you pass the 90 degree angle of your elbow?  Every muscle has a length/tension relationship, ie there are lengths that create more or less tension (force) based on the angle of the joint.  This has to do with how much actin and myosin (proteins) overlap in the contractile units (sarcomeres) of your muscle cells.  There is an ideal amount of overlap of these proteins, you don't want too much or too little.  For the arm (elbow), 90 degrees is the angle that provides the length of bicep that creates the most amount of force.  Once you pass that 90 degree point, the length of your bicep is not able to generate as much force (too much overlap of actin and myosin).  Here is a photo of Heather fighting through that difficult length/tension relationship of her bicep. 

Workout:

10 Rounds:
3 Bench Press within first 30 seconds
5 Strict Pull Ups within next 30 seconds

21 Box Jumps (24/20in)
200 Meter Run
15 Box Jumps
400 Meter Run
9 Box Jumps
800 Meter Run
15 Box Jumps
400 Meter Run
21 Box Jump
200 Meter Run