Biomedical subjects

Duane Knudson

Publications and source records attributed to Duane Knudson.

6 recordsLinked to original sources

PubMed2006

Biomechanics Concept Inventory.

A third version of a biomechanics concept inventory was developed and administered to 41 kinesiology majors before and after an introductory biomechanics class to build a larger pool of questions for course evaluation. The test measured understanding of four prerequisite and eight competencies based on national standards. Mean and standard deviation normalized gain was 29% (21) of maximum possible improvement and was similar to previous versions of the test given to students at the same university. Biomechanics instructors can use questions from all versions of the Biomechanics Concept Inventory to customize tests for evaluating instructional techniques in biomechanics.

Biomechanical Phenomena↗

PubMed2005

Time course of stretch-induced isometric strength deficits.

Stretching in the warm-up has been shown to decrease several muscular performance variables, but the dose-response of this effect is unknown. This study documented the change in isometric grip strength over ten trials in a convenience sample of young adults randomly assigned to control (n=22) or repeated bouts of 10-s static stretches of the wrist flexors (n=35). There was a significant (P<0.05) difference in the change in mean normalized grip strength between the control and stretching groups that was not significantly different across gender. Grip strengths in the control group were consistent with a linear trend, while the grip strengths in the stretching group declined in a logarithmic fashion to 88.8% with 100 s of stretching. Statistically significant (P<0.05) differences in normalized grip strength between the two groups appeared after 40 s of stretching. Meaningful decreases in isometric grip strength following static stretching are likely to appear in young adults following 20-40 s of static stretching.

Female↗

PubMed2005

Accuracy of visual estimates of joint angle and angular velocity using criterion movements.

A descriptive study to document undergraduate physical education majors' (22.8 +/- 2.4 yr. old) estimates of sagittal plane elbow angle and angular velocity of elbow flexion visually was performed. 42 subjects rated videotape replays of 30 movements organized into three speeds of movement and two criterion elbow angles. Video images of the movements were analyzed with Peak Motus to measure actual values of elbow angles and peak angular velocity. Of the subjects 85.7% had speed ratings significantly correlated with true peak elbow angular velocity in all three angular velocity conditions. Few (16.7%) subjects' ratings of elbow angle correlated significantly with actual angles. Analysis of the subjects with good ratings showed the accuracy of visual ratings was significantly related to speed, with decreasing accuracy for slower speeds of movement. The use of criterion movements did not improve the small percentage of novice observers who could accurately estimate body angles during movement.

Adult↗

PubMed2003

Development and evaluation of a biomechanics concept inventory.

To help instructors in evaluating innovations in biomechanics instruction, a standardised test of the key concepts taught in the introductory biomechanics course was developed. The Biomechanics Concept Inventory (BCI) consists of 24 questions that test four prerequisite competencies and eight biomechanics competencies. Three hundred and sixty seven students from ten universities throughout the United States took the test at the beginning and the end of the introductory biomechanics course. Analysis of a sub-sample of the students showed that the BCI was reliable with typical errors in internal consistency and test-retest conditions of 1.4 and 2.0 questions, respectively. Mean pre-test scores (8.5 +/- 2.0) significantly (p < 0.0001) improved to 10.5 +/- 3.2 in the posttest (n = 305). Typical biomechanics students could correctly answer half of the prerequisite questions on the pre-test. Instruction resulted in a mean normalised gain (g) of 13.0% of maximum possible improvement that was consistent with research on traditional instruction in introductory physics courses. It was concluded that the BCI could be an effective tool to evaluate the overall effect of pedagogical strategies on student learning of key biomechanical concepts in the introductory biomechanics course.

Biomechanical Phenomena↗

PubMed2003

Effect of elastic-cord towing on the kinematics of the acceleration phase of sprinting.

We studied the specificity of elastic-cord towing by measuring selected kinematics of the acceleration phase of sprinting. Nine collegiate sprinters ran two 20-m maximal sprints (MSs) and towed sprints (TSs) that were recorded on high-speed video (180 Hz). Sagittal plane kinematics of a 4-segment model of the right side of the body were digitized for a complete stride at the 15-m point for the fastest trial. Significant (p < 0.001) differences were observed for horizontal velocity of the center of mass (CoM), stride length (SL), and horizontal distance from the CoM of the foot to the CoM of the body. There was no significant difference in stride rate between the MS and TS conditions. Omega-squared analysis showed that elastic-cord towing accounted for most of the variance in acute changes in horizontal velocity (73%), SL (68%), and horizontal position of the CoM at foot contact (64%). Elastic-cord tow training resulted in significant acute changes in sprint kinematics in the acceleration phase of an MS that do not appear to be sprint specific. More research is needed on the specificity of TS training and long-term effects on sprinting performance.

Adult↗

PubMed2002

Effect of type 3 (oversize) tennis ball on serve performance and upper extremity muscle activity.

This study investigated the effect of the larger diameter (Type 3) tennis ball on performance and muscle activation in the serve. Sixteen male advanced tennis players performed serves using regular size and Type 3 tennis balls. Ball speed, surface electromyography, and serve accuracy were measured. There were no significant differences in mean initial serve speeds between balls, but accuracy was significantly greater (19.3%) with the Type 3 ball than with the regular ball. A consistent temporal sequence of muscle activation and significant differences in mean activation of different muscles were observed. However, ball type had no effect on mean arm muscle activation. These data, combined with a previous study, suggest that play with the larger ball is not likely to increase the risk of overuse injury, but serving accuracy may increase compared to play with the regular ball.

Acceleration↗