Table 1. Additional in vitro contractile properties of directly stimulated EDL muscles.

	+/+	−/−
Body weight (g) [BW]	8.1±.0.2	3.3±0.4**
Muscle weight (mg) [MW]	2.7±0.2	1.1±0.2**
MW:BW ratio %	0.034±0.0023	0.033±0.0029
Pt (g)	1.2±0.4	0.32±0.06*
Pt (N/g)	4.3±1.5	2.9±0.9
TPT (ms)	21.1±1.1	25.1±2.6*
1/2RT (ms)	32.2±3.7	36.9±7.5

*<0.03.

**<0.0001.

Muscle twitches recorded in mutant mice are smaller and have a longer time-to-peak tension. Reduced absolute values are due to smaller muscles in mutants because normalized twitch forces are not different from wild-type. Similar outcome is shown for tetanic force in Figure 3. MW:BW ratio%, percent muscle to body-weight; Pt(g), absolute twitch force; Pt (N/g), twitch force normalized to muscle weight; TPT, time-to-peak twitch tension; 1/2RT-twitch half-relaxation time; N, Newtons (force); ms, milliseconds.