Contractions can be observed under two different conditions Isometric - muscle is fixed therefore no change in muscle length. Measures the tension developed. Isotonic - muscle shortens and lifts a load. Measures distance shortened. Lengthening contraction - an additional state.
Load is larger than the tension generated, pulls crossbridges towards Z-line.
Can lead to detachment of cross bridges. Characteristics of isotonic and isometric twitches Latent period - period of time between the action potential and the onset of contraction. Shorter for isometric vs. isotonic. In isometric conditions it represents time for EC coupling. In isotonic conditions it also represents a period of isometric contraction.