The Effect of Volitional Preemptive Abdominal Contraction on Biomechanical Measures During A Front Versus Back Loaded Barbell Squat.

Background: Weightlifting is growing in popularity among recreational and competitive athletes. The barbell back squat (BackS) is commonly included in these training programs, while the barbell front squat (FrontS) is commonly performed as a component of other lifts such as the power clean or clean and jerk, it is less commonly practiced in isolation. Hypothesis/Purpose: The purpose of this study was to examine the effects of VPAC performance on trunk muscle and LE biomechanical responses during loaded BackS versus FrontS in healthy subjects. Study Design: Controlled Laboratory Study. Methods: Healthy male subjects with the ability to perform a sub-maximal loaded barbell squat lift were recruited. Subjects completed informed consent, demographic/medical history questionnaires and an instructional video. Subjects practiced VPAC and received feedback. Surface electromyography (sEMG) electrodes and kinematic markers were applied. Muscles included were the internal oblique (IO), external oblique (EO), rectus abdominis, iliocostalis lumborum (ICL), superficial multifidi, rectus femoris, vastus lateralis, biceps femoris, and gluteus maximus. Maximal voluntary isometric contractions established reference sEMG values. A squat one-rep-max (1RM) was predicted by researchers using a three to five repetition maximum (3RM, 5RM) load protocol. Subjects performed BackS trials at 75% 1RM while FrontS trials were performed at 75% BackS weight, both with and without VPAC. Subjects performed three repetitions of each condition with feet positioned on two adjacent force plates. Significant interactions and main effects were tested using a 2(VPAC strategy) x 2(squat variation) and 2(VPAC strategy) x 2(direction) within-subject repeated measures ANOVAs. Tukey's Post-Hoc tests identified the location of significant differences. Results: Trunk muscle activity was significantly higher during FrontS versus BackS regardless of VPAC condition. (IO: p=0.018, EO: p<0.001, ICL: p<0.001) VPAC increased performance time for both squat variations (p=.0011), which may be associated with decreased detrimental force potential on the lumbar spine and knees. VPAC led to improved ability to maintain a neutral lumbar spine during both squat variations. This finding is associated with decreased detrimental force potential on the lumbar spine. Conclusions: Findings could help guide practitioners and coaches to choose squat variations and incorporate VPAC strategies during their treatments and/or training programs. Level of Evidence: Level 3©The Author(s).

The effect of forearm position on elbow flexion strength in nursing, occupational, and physical therapy students.

BACKGROUND: Novice nurses, occupational and physical therapist's injury rates are alarming. OBJECTIVE: To test for differences in peak elbow flexion forces (PEFF) by profession using different forearm positions. METHODS: Entry-level RN, OT, and PT students performed 3-repetitions of standing PEFF in forearm supination, pronation, and neutral. A one-way repeated measures ANOVA determined the forearm position with the greatest PEFF. A one-way ANOVA assessed differences in PEFF between professions. The alpha level was set at p≤0.05 for all analyses. RESULTS: Thirty 30 RN, 25 OT, and 30 PT students (x = 23.27 + /-3.29 yrs.) were studied. A one-way repeated measures ANOVA revealed a significant difference in PEFF between positions (F(2,168) = 144.3, p < 0.0001). A significant (p < 0.0001) pairwise comparison revealed neutral produced the greatest (28.15 + /-12.64 kg) and pronation the least PEFF (17.27 + /-7.40). PEFF was significantly different between position by profession (supination: F(2,82) = 10.14, p < 0.0001; pronation: F(2,82) = 10.33, p < 0.0001; neutral: F(2,82) = 13.39, p < 0.0001). PTs were significantly stronger than OTs and RN students in all forearm positions (p < 0.01). CONCLUSIONS: Neutral PEFF was greatest and PT students demonstrated greater PEFF than OT and RN students.

Effect of overground locomotor training on ventilatory kinetics and rate of perceived exertion in persons with cervical motor-incomplete spinal cord injury.

Study design: Pre-post, pilot study. Objectives: To characterize ventilatory (VE) responses to exercise following warm-up walking in individuals with chronic incomplete spinal cord injury (iSCI) during constant work rate (CWR) exercise. Secondarily, to investigate VE and tidal volume (VT) variability, and ratings of perceived exertion (RPE) before and after overground locomotor training (OLT). Setting: Research laboratory. Methods: A 6-min CWR walking bout at preferred pace was used as a warm-up followed by 6 min of rest and a second 6-min CWR bout at above preferred walking pace. The second CWR bout was analyzed. Breath-by-breath ventilatory data were examined using a curvilinear least squares fitting procedure with a mono-exponential model. VE and VT variability was calculated as the difference between the observed and predicted values and RPE was taken every 2 min. Results: Participants (n = 3, C4-C5) achieved a hyperpneic response to exercise in VE and VT. OLT resulted in faster ventilatory kinetics and reductions of 24 and 29% for VE and VT variability, respectively. A 30% reduction in RPE was concurrent with the reductions in ventilatory variability. Conclusions: OLT may improve ventilatory control during CWR in patients with cervical motor-iSCI. These data suggest that in some participants with iSCI, ventilation may influence RPE during walking. Future research should investigate mechanisms of ventilatory variability and its implications in walking performance in patients with iSCI.

Regression analysis for prediction: understanding the process.

Research related to cardiorespiratory fitness often uses regression analysis in order to predict cardiorespiratory status or future outcomes. Reading these studies can be tedious and difficult unless the reader has a thorough understanding of the processes used in the analysis. This feature seeks to "simplify" the process of regression analysis for prediction in order to help readers understand this type of study more easily. Examples of the use of this statistical technique are provided in order to facilitate better understanding.

Grip strength of Texas Special Olympians.

Little is known about the physical fitness parameters of individuals who participate in the Special Olympics. The purpose of this study was to assess the grip strength of 104 Special Olympians participating in the winter Olympic Games. Men were significantly stronger than women across age groups 20 to 59 yr. Women's right hands were stronger than their left, while the opposite was true for men, despite the fact that 78.8% of the subjects reported right hand dominance. Mean right and left grip strengths were 25-40% less than the 1985 normative data of Mathiowetz, et al. by age groups. Special Olympian men and women have grip strengths comparable to elderly people rather than age-matched men and women.

Isometric strength and dynamic back extensor endurance are unrelated in children ages 6-10 years: a pilot study.

This study assessed the correlation between back extensor isometric force and dynamic endurance in 69 children 6-10 years of age. Subjects were positioned prone with legs and hips supported and restrained on two folded 6-in. mats. 42 subjects (20 girls; 22 boys) performed three 5-sec. isometric back extension efforts against a calibrated dynamometer and peak force values were averaged. An additional 27 subjects (9 girls; 18 boys) also performed a dynamic (0 degrees --> 45 degrees flexion-->0 degrees) back extension test at a frequency of 20 per minute, and the number of repetitions was recorded. Both tests were repeated at a 1-wk. interval. Pearson correlations for the endurance, the isometric force test, and test-retest, and between the functional concentric endurance vs isometric force were .55, .79 (both p<.01), and .03, respectively. These tests have moderate to high reliability but they examine different aspects of back muscle fitness. They should not be used interchangeably to assess back extensor muscle fitness. Further investigation must determine whether different dynamic test frequencies and mat heights yield different results.

Mismatch of school desks and chairs by ethnicity and grade level in middle school.

OBJECTIVE: The purpose of this study was to compare anthropometric measurements of children/adolescent (6th grade - 8th grade) and use these measurements to determine fit by ethnicity and grade level across three common classroom desks and chairs. STUDY DESIGN: Eighty-eight Caucasian-American (CA), 65 Mexican-American (MA), and 58 African-American (AA) 6th, 7th, and 8th graders participated in the study (n = 211 students). Students were seated (shoeless) on a horizontal seating surface with an adjustable footrest to obtain 90 degrees angles at the hips, knees, and ankles. Standing height and five seated measurements were obtained using a stadiometer. Desk measurements were obtained from the most common desks used for each grade level. Six measurements (seat height, seat depth, seat slope, desk height, desk clearance, desk slope) were obtained with a tape measure and angle finder. Mismatch was operationalized apriori to determine fit of student dimensions and desks. RESULTS: Multivariate analysis (SPSS 10.1) revealed significant differences in anthropometric dimensions at each grade level for ethnicity and gender (p < 0.05). Only one 6th grade MA male fit both seat height and depth criteria. One-way ANOVA's and Scheffe post hoc tests revealed significant differences between fit by ethnicity for chair 1 and chair 2. No students experienced knee/desk clearance problems. Only one student was able to find a desk surface that did not exceed their maximum functional elbow height. CONCLUSIONS: AA's had longer lower extremity lengths versus their ethnic counterparts at all grade levels. Subjects did not fit chairs and desks regardless of age or ethnicity. Ethnicity played a significant role in seat height fit for two of the three chairs. These disparities may create a generation with an increased incidence of musculoskeletal problems carrying over to adulthood and the adult workplace.

Wheelchair coasting downhill is a reliable work task.

OBJECTIVE: To measure test-retest reliability of physiological responses during submaximal wheelchair downhill and horizontal treadmill ergometry. DESIGN: A test-retest design was used on a convenience sample. Four male and three female non-wheelchair users, (22-43 years of age) propelled or coasted in a wheelchair under steady-state conditions. Four minute work bouts were performed at 1, 2, 3, and 4 km/hr. (0.62, 1.24, 1.86 and 2.5 mph, respectively) at 0 degrees, -2 degrees, and -4 degrees. Subjects were studied twice under each of the 12 conditions. Six tests were performed daily, with testing occurring over four days. Dependent variables included oxygen consumption, minute ventilation and heart. Intraclass correlation coefficients were determined for each set of paired tests. RESULTS: Intraclass correlation coefficients were high for absolute VO_{2}(R=0.84-0.99), V_{E} (R=0.86-0.98) and HR (R=0.95-1.0) over the range of 4 speeds and 3 inclinations studied. On average, % differences from test 1 to test 2 were less than 3%. CONCLUSION: At the treadmill speeds and inclinations (positive and negative) studied in this investigation, untrained wheelchair users responded in a physiologically reliable manner.