Michael Bird

Electromyographic activity of the pectoralis major and anterior deltoid muscles during three upper-body lifts.

The purpose of this study was to examine the differences in activation levels and times of activation for the pectoralis major and anterior deltoid when performing the concentric phase of 3 upper-body lifts. Twelve college-age men and women with various degrees of lifting experience performed 3 repetitions using the 6 repetition maximum in a barbell bench press, dumbbell bench press, and dumbbell fly while being monitored for electromyographic activity in both muscles. Motor unit activation of both muscles was not significantly different during all 3 lifts. However, dumbbell flys had significantly less relative time of activation than did barbell or dumbbell bench presses. Therefore, dumbbell flys may be better suited as an auxiliary lift, whereas barbell and dumbbell bench presses may be used interchangeably in training programs. The compatibility of the barbell and dumbbell bench presses may aid lifters in overcoming training plateaus by alternating exercises for the same muscle groups.

Comparison of the backward overhead medicine ball throw to power production in college football players.

The purpose of this study was to determine the relationship of the backward overhead medicine ball (BOMB) throw to power production in college football players. Forty National Collegiate Athletic Association Division II college football players were studied at the end of an 8-week off-season conditioning program for power output determined from a counter-movement vertical jump on a force plate and for maximal distance in the standing BOMB throw. Although the reliability of the BOMB test was high (interclass correlation coefficient = 0.86), there was a significant learning effect across 3 trials (p < 0.01). Peak and average powers generated during the vertical jump correlated moderately but significantly with the best BOMB throw distance (r = 0.59 and 0.63, respectively). Considering power relative to body mass or lean body mass failed to produce significant correlations with BOMB throw distance (r = 0.27 and 0.28, respectively). Therefore, the BOMB throw may have limited potential as a predictor of total body explosive power in college football players.

Development and evaluation of a biomechanics concept inventory

Abstract 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 post‐test (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.

THE AGING MOVER: A PRELIMINARY REPORT· ON CONSTRAINTS TO ACTION'"

Locomotion by older adults is typically characterized by performance declines. Older individuals walk more slowly, take shorter steps, and spend a longer time in support than young individuals. Investigators assumed implicitly that declines are related to an inevitable aging process. The purpose of this investigation was to examine constraints that might result in the declines described, outside or in addition to, the general process of aging. We examined two types of terrain over which locomotion might occur, level ground and stairs, and two movement speeds, preferred and fast. Healthy, active females between twenty to eighty years were videotaped. Individuals over sixty years walked at significantly slower speeds, particularly climbing stairs. They used a smaller range of speeds than younger individuals. Despite this slowing, the pattern of coordination between limbs remained essentially the same across the ages tested. The small magnitude of declines observed was attributed to the good health and active lifestyles of these individuals.

Electromyographic comparison of the ab-slide and crunch exercises.

The purpose of this study was to compare the Ab-Slide with crunch abdominal exercises for electromyographic activity for selected muscles. Forty-five subjects who regularly performed abdominal exercises participated. Subjects completed 5 trials for each exercise, with repetition rate controlled by the tester. Electromyographic activity for the external oblique (EO), upper rectus abdominis (URA), and lower rectus abdominis (LRA) was collected. Raw data for each muscle were rectified and integrated over 100-millisecond time intervals. For each muscle, the average concentric and eccentric integrated amplitudes of the middle 3 trials were compared with a dependent t-test. During concentric movement, the EO and LRA had significantly higher integrated activation amplitudes for the crunch exercise. During the eccentric movement, the URA, LRA, and EO had significantly higher average integrated activation amplitudes for the Ab-Slide exercise. The Ab-Slide is a credible abdominal exercise variation, but the crunch should remain the standard abdominal exercise.

Measurement of elastic-like behaviour in the power squat

Because traditional procedures of evaluating elastic-like behaviour have yielded mixed results, the purpose of this work was to explore two methods of measuring elastic-like behavior in the power squat. The entire concentric time method was based on traditional procedures. The initial concentric time method was developed to examine elastic-like behavior for the beginning 0.2 s of concentric movement. The present study compares a power squat performed maximally by nine subjects at 70% of their 1 repetition maximum. Squats were performed with rebound (REB) and without rebound (NRB). For the entire concentric time method only concentric time was significantly greater (p < 0.05) in the NRB than the REB. For the initial concentric time method the relative displacement, velocity, net work, & peak power of the center of mass were significantly greater (p < 0.05) in the REB than the NRB. Some subjects had theoretically infeasible negative results for elastic enhancement in the entire concentric time method, but not the initial concentric time method. It seems that measuring elastic-like behavior near the end of the movement can be confounded by the constraints of the task. Based on its success, the initial concentric time method appears to be more appropriate for measurement of elastic-like behavior in lifting.

Influence of Knee-to-feet Jump Training on Vertical Jump and Hang Clean Performance

Abstract Stark, L, Pickett, K, Bird, M, and King, AC. Influence of knee-to-feet jump training on vertical jump and hang clean performance. J Strength Cond Res 30(11): 3084–3089, 2016—From a motor learning perspective, the practice/training environment can result in positive, negative, or neutral transfer to the testing conditions. The purpose of this study was to examine the training effect of a novel movement (knee-to-feet [K2F] jumps) and whether a 6-week training program induced a positive transfer effect to other power-related movements (vertical jump and hang clean [HC]). Twenty-six intercollegiate athletes from power-emphasized sports were paired and counter-balanced into a control (i.e., maintained their respective sport-specific lifting regimen) or an experimental group (i.e., completed a 6-week progressive training program of K2F jumps in addition to respective lifting regimen). A pre- and posttest design was used to investigate the effect of training on K2F jump height and transfer effect to vertical jump height (VJH) and 2-repetition maximum (RM) HC performance. A significant increase in K2F jump height was found for the experimental group. Vertical jump height significantly increased from pre- to posttest but no group or interaction (group × time) effect was found, and there were nonsignificant differences for HC. Posttest data showed significant correlations between all pairs of the selected exercises with the highest correlation between K2F jump height and VJ H (R 2 = 0.40) followed by VJH and 2RM HC (R 2 = 0.38) and 2RM HC and K2F jump height (R 2 = 0.23). The results suggest that K2F jump training induced the desired learning effect but was specific to the movement in that no effect of transfer occurred to the other power-related movements. This finding is value for strength and condition professionals who design training programs to enhance athletic performance.