Isokinetics and Exercise Science

Acoustic myography (AMG) is the technique of recording muscle sounds and is potentially useful as an indicator of force. This review provides a background of the history, basic physical principles, and methodology of recording muscle sounds. Some obvious limitations of the technique are addressed, but others need to be investigated. Guidelines for the appropriate use and potential applications of AMG are discussed. Use of the AMG technique in the clinical situation would be premature at this early stage of its development.

An analysis was conducted of the movement that takes place in the glenohumeral joint while a subject performs shoulder flexion/extension on the Cybex isokinetic dynamometer (CYBEX, Ronkonkoma, NY). The initial position of the glenohumeral joint was extrapolated from bony landmarks. Light-emitting diodes associated with the Watsmart three-dimensional optoelectronic motion analysis system were placed on the subject's arm and traced while he worked on the Cybex. Nine subjects took part in the experiment, and pooling their data showed that on average the joint elevated 8 cm. This constitutes 12.5% of the distance from the glenohumeral joint to the wrist. A combination of elbow flexion and protraction/distraction of the shoulder complex compensated for glenohumeral joint movement. Because the perpendicular distance from the shoulder to the handle of the Cybex has been reduced by 12.5%, so should the value recorded by the Cybex data reduction computer.

Movement of the glenohumeral joint while subjects performed shoulder abduction/adduction on the Cybex dynamometer (CYBEX, Ronkonkoma, NY) was analyzed with a procedure similar to that described for the analysis of shoulder flexion/extension. The axis of the glenohumeral joint was aligned with the axis of the Cybex and verified by construction of a special frame that fit directly over the dynamometer spindle and thus revolved with the Cybex lever arm. Five subjects were studied, one of whom performed the movement on three separate occasions. Distinct from the first experiments, the subjects were only tested at one speed of movement: 60 deg/sec. As previously, the glenohumeral joint was found to traverse approximately 8 cm from its position of initial alignment with the axis of the Cybex dynamometer to its position with the arm in full elevation.

The purpose of this study was to determine the effects of hip position and angular velocity on quadriceps and hamstring peak torque and on the hamstring/quadriceps (H/Q) ratio during maximal eccentric force. The dominant knee of 14 normal subjects (seven males and seven females) was tested in seated and supine positions at velocities of 60 and 180 deg/sec. Testing was completed using the Kinetic Communicator isokinetic dynamometer (Chattex Corp., Chattanooga, TN) and peak torque was corrected for gravity. The results showed that (a) the quadriceps (p < .001) produced significantly greater peak torque than the hamstrings, (b) both muscle groups produced significantly greater peak torque in the seated position (p < .001) than in the supine position and at 180 deg/sec (p < .05) than at 60 deg/sec, and (c) H/Q ratios were significantly greater in the seated position (p < .01) and at 180 deg/sec (p < .05) than in the supine position and at 60 deg/sec. The findings of this study suggest that the quadriceps and hamstring peak eccentric torque and H/Q ratio are influenced by hip position and angular velocity.

Torque measures were compiled from 4,541 men and women (17 to 62 years of age) as pre-employment and job advancement screening in various industries. Cybex dynamometers measured flexion and extension of the knees (30, 180, and 300 deg/sec, where 1 deg/sec = 0.01745 rad/sec) and shoulders (60 and 180 deg/sec), and back extension (60 deg/sec). Percentile scores are reported by age and gender. Torque differences between genders across ages suggested a faster strength loss in women. For example, women over 50 years of age had 22% lower torque than women 41 to 50 years of age, whereas men demonstrated a corresponding 9% difference. Flexion/extension ratios increased with speed in both genders for the knee, but not for the shoulder. These data may be useful for comparative purposes in strength evaluations used in clinical settings (i.e., injury prevention and rehabilitation), as well as for screening in the industrial setting.

The purpose of this study was to determine the effect of a 24-hour and 48-hour interval on test-retest reliability of the Biodex isokinetic dynamometer. Sixty-three healthy, 18- to 35-year-old men and women were tested for unilateral concentric knee flexion and extension at 60, 180, and 300 deg/sec. Subjects completed a 5-minute cardiovascular warmup, three submaximal and one maximal pretest contractions, and five maximal test contractions. Testing was performed at the aforementioned speeds with a 30-second rest between each speed. Data from initial tests was compared with that from final tests. Statistical analysis of data showed highly reliable correlation coefficients of 0.94, 0.92, and 0.93 for peak flexion torque at 60, 180, and 300 deg/sec, respectively. Peak extension torque correlation coefficients were 0.97, 0.94, and 0.95 for the same respective speeds. Correlation coefficients for total flexion work at the aforementioned speeds were 0.90, 0.85, and 0.87. Total extension work correlation coefficients were 0.95, 0.94, and 0.94, respectively. The results of this study demonstrated (1) no statistically significant difference in the 24- or 48-hour interval between tests, and (2) a high overall degree of reliability for Biodex test-retest measurements of peak torque and total work.

The purpose of this study was to biomechanically analyze the lower extremity during exercise using the Kinetron II (Lumex, Cybex, Ronkonkoma, NY, USA). Two subjects performed a variety of exercise sequences while being recorded on videotape. Video analysis allowed a review of the alterations in joint angles seen at the hip, knee, and ankle. Recommendations for clinical application of the Kinetron II were determined.

The purpose of this study was to determine if 6 weeks of training on the Shuttle 2000 (Contemporary Design, WA, USA) would change quadriceps strength or vertical leap measurements. Thirty university women were assigned randomly to one of two groups. The training group exercised for 6 weeks, with three sets of 15 repetitions of a horizontal squat against resistance. Pretests and posttests of vertical leap and quadriceps strength, measured eccentrically and concentrically on the Kin Com (Chattex Corp., Chattanooga, TN) at 60 and 180 deg/sec, were used for analysis. t Tests were used to determine significant differences between the two groups. Percent change was defined as [(posttest) − (pretest)/pretest] × 100. Results of the t test on the percent change in vertical leap showed a significant difference between the groups at p < 0.01. Moderate increases in quadriceps strength were found in the training group for each speed and type of contraction, but no statistically significant change was seen between the two groups at either speed or type of contraction. The improved performance could be related to enhanced neural activation/control.