Figure 8.

Simulation of an exercise session involving three sets of ten 10-s repetitions. (a) All repetitions are performed at the same force per titin, but their duration is cut short upon reaching exhaustion. As the number of titins increases, we assume that the training regime adapts by proportionately increasing the repetition force. (b) The depletion of ATP leads to a temporary drop in phosphorylated TK during exercise. However, the sum of open, phosphorylated, and signaling complex-bound TK steadily increases during the exercise. Because the closing rate of TK is quite low (of the order of 10⁻⁵ s⁻¹, depending on the number of attempts at crossing the energy barrier and the barrier height ΔG₀), the baseline concentrations of phosphorylated and signaling TK conformations remain elevated after exercise. To see this figure in color, go online.