Neuromuscular phenotyping <i>in vivo</i>.

<p><b>A... </b><u>Voluntary exercise capacity:</u> Mice (CASQ1 null; n = 6) and WT; n = 6) were singly housed in a cage with a mouse running wheel (Lafayette Instruments, Lafayette, IN) in a 12/12 hour light/dark animal facility with <i>ad libitum</i> access to food and water. The number of wheel revolutions were computer analyzed per 24 hour period and data was converted to mean number of meters per day and reported as descriptive data. When compared to the WT group (8.64±0.99 km), the CASQ1 null animals (4.75±1.41 km) exhibited a significant deficit in total daily running distance (t-test, p<0.05) <b>B... </b><u>Treadmill exercise capacity</u> (i.e., non-voluntary) was evaluated in previously sedentary CASQ1 null (n = 6) and WT (n = 6). Following an a 3 day acclimation period (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0027036#s4" target="_blank">methods</a>), mice were exercised at 10 meters/minute for the first 10 min then ramped to 20 m/min over 1 min and held there until volitional exhaustion. Volitional exhaustion was assessed by a single rater, blinded to mouse genotype, who determined the time point at which the mouse was unable to maintain treadmill pace after two successive startles. After the trial, total time was converted to distance covered. Exercise naïve WT mice performed significantly better (490±80 m; n = 6) than age matched CASQ1 null mice (280±130 km; n = 6). <b>C... </b><u>Forepaw grip strength</u> was determined on a commercial rodent grip strength meter (Columbus Inst., USA) as described (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0027036#s4" target="_blank">methods</a>). CASQ1 null mice (n = 8) exhibited a significant deficit in grip strength (C; left panel) compared to WT (n = 8) mice when normalized to bodyweight (3.68±0.17 vs. 4.24±0.14 g·bdwt⁻¹; t-test, p<0.05). The body weight of the WT mice was approximately 18% larger than those of the CASQ1 null animals (34.58±0.26 g vs. 28.14±1.36; t-test, p<0.05). The decrement in force between the peak value and the value of the 7^th trial was evaluated as an index of fatigue (C; right panel) and expressed as % of initial.CASQ1 null animals exhibited more fatigue than did their WT counterparts.