Abstract
972 Analyses of 3 knee extensors, vastus medialis, rectus femoris, and vastus lateralis, were conducted to examine the reliability of (a) a maximal voluntary isometric contraction (MVIC) measured across trials (2), days (5), and joint angles (5); and (b) normalized EMG responses during dynamic knee extension at 2 submaximal work loads. Strength (cable tension) and integrated peak EMG (surface electrodes) were measured during the MVIC. Men and women( n = 44) performed 2 consecutive MVICs with 2 min rest between trials at 110 °, 90 °, 70 °, 50 °, and 30 ° of knee flexion, followed by the 2 submaximal dynamic knee extension exercises. Intraclass correlation (R) values for the average score across trials or days(R1) and for a single trial or a single day (R2) were calculated using two-way ANOVA. Sample results for integrated peak EMG scores (vastus medialis), showed R values for trials ranged from.84 to.99 for R1 and from.73 to.98 for R2. Sample results for the integrated peak EMG scores(vastus medialis), showed R values across days ranged from.95 to.96 for R1 and from.79 to.83 for R2. Similar analyses were conducted on MVIC strength measures and normalized dynamic EMG responses. The investigators concluded that cable tension strength can be reliably measured at all tested angles and maximal strength occurred at 110 ° of knee flexion. For MVIC peak EMG measures, reliability of the mean of 2 trials was higher than for a single trial; the highest occurred at 30 ° of knee flexion. For all muscies and joint angles, the reliability of the mean of MVIC peak EMG scores for 5 days was higher than the reliability of a single day. The lowest reliabilities occurred on Day 1, but high, yet comparable, reliabilities occurred on Days 2-5. Reliabilities of normalized dynamic EMG scores were lower and more random than MVIC peak EMG scores for trials, days, angles, and loads.
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