Effects of Lift Velocity on Muscle Activation During Leg Extension

It is not known if manipulating velocity within a prescribed resistance training mode will improve muscle activation. Muscle activations of the Rectus Femoris (RF), Vastus Lateralis (VL), Vastus Medialis (VM) and Bicep Femoris (BF) were examined during a leg extension exercise at 3 different velocities on 15 subjects (10men, 5 female, Age = 21.5 ± 1.8 yrs, Height = 171.2 ± 12.5 cm, Mass = 75.5 ± 16.3 kg). Trials of 1 set of 10 repetitions at 60% of 1RM, were performed at 15, 30 and 60º/s. Bipolar surface electrodes were placed over the BF, RF, VL, and VM. Micro-switches were utilized to identify the concentric (CON) and eccentric (ECC) phases of the lift. Data were sampled at 1024 Hz, filtered, rectified and the mean, integrated EMG calculated. One 2 x 4 x 3 (action x muscle x velocity) ANOVA with bonferonni adjustment was run and significance was followed by Tukey HSD post hoc analysis. Results indicated significantly greater activation of the VL, RF and VM for ECC extension at 60º/s compared to 15º/s. While 60º/s was also greater than 30º/s for the VL and VM during ECC. While comparing muscle action, CON VL, VM and RF were greater than ECC at 30º/sec, meanwhile VM CON was also greater at 15º/sec. No differences in muscle activation at any velocity or muscle action for BF were identified. We conclude that muscle recruitment while training with a 60% 1RM load is maximized at a velocity of 60º/s during ECC activity and 15 or 30º/sec during CON

The Effect of Foam Rolling Duration on Hamstring Range of Motion

Musculoskeletal health benefits from flexibility training and maintaining a functional, or sport specific, range of motion is important to one’s overall fitness. Commercial foam rollers are commonly used in gyms, therapy clinics and homes, yet data are lacking on the optimal rolling duration and effect on range of motion

Determination of Energy Expenditure during Pregnancy and its Comparison to the Compendium of Physical Activity Values: A Pilot Study

Current exercises recommended during pregnancy are prescribed at the same intensity as the general adult population, 3-6 METs. It is unclear whether these MET values can be applied to the pregnant population. Purpose: To determine energy expenditure of pregnant women while participating in three exercises (walking, stationary biking, and prenatal aerobics) during the second and third trimesters. And second, to determine whether the energy expenditure of the exercises would change from the second to third trimester. Methods: Participants were 3 women, ages 23-32, in their second trimester (weeks 14-26) of pregnancy at commencement of the study. Subjects reported to the Human Performance Lab twice, once during the second trimester and once during the third trimester with at least 6 weeks between visits. During each visit, subjects were in a resting state for 30 minutes and then participated in stationary biking, walking, and prenatal aerobics for 10 minutes each with a break between exercises. Data was analyzed using a sample t-confidence interval test to compare the average energy expenditure of each activity during the 2nd and 3rd trimester to recommended values. A paired t-test was used to compare values between the trimesters. Results and Discussion: Results from the statistical analysis cannot be determined as significant at this point. While numbers were highly or moderately correlated, the p-values were not significant due to the low sample size. This indicates that there is potential for significant data but more subjects are needed to be able to draw any conclusive evidence

The Influence of Hip and Shoulder Range of Motion on Shoulder Function in Collegiate Baseball and Softball Players.

The influence of Hip and Shoulder Range of Motion on Shoulder Function in Collegiate Baseball and Softball Players

Pre-participation Electrocardiography as part of the Pre-participation Physical Examination: A Systematic Review

Context: Sudden cardiac death (SCD) in athletes most often occurs in those with underlying heart abnormalities that havent been identified during the pre-participation exam (PPE). In the US, the PPE recommendations include a cardiovascular (CV) medical history and physical examination (H/P). The ability of the CV medical history and H/P to identify cardiac abnormalities has been questioned for some time... There is debate as to whether mandatory electrocardiography (EKG) testing should be added to the PPE. Objective: To determine whether an EKG as part of the standard PPE for young athletes is a cost effective and diagnostically appropriate option. Data Sources: Searches were conducted using Proquest, Ovid Journals, Academic Search Premier, and ScienceDirect with key words: sudden cardiac death, hypertrophic cardiomyopathy, electrocardiogram, athletic pre-participation exam, sensitivity, specificity, and cost-effectiveness. Limits included peer-reviewed studies less than 30 years old and English language. Study Selection: Studies were initially chosen based on the inclusion of relevant information in the title or abstract, which were: athletic PPE guidelines, SCD prevalence and associated CV conditions, diagnostic effectiveness of EKG screening in detecting SCD-related abnormalities, and cost-effectiveness of cardiac screening methods. A subsequent evaluation of the full-text articles resulted in 11 original studies being selected for inclusion spanning 3 specific areas (CV screening procedures, Diagnostic Capabilities of EKG, and Cost Effectiveness of EKG). Data Extraction: The methodological quality of selected articles was evaluated independently by two raters using the PEDro scale and ranged from 4-8. Data related to sensitivity, specificity and cost effectiveness were extracted and utilized. Data Synthesis: Related to CV screening protocols; an EKG-mandated protocol decreased the incidence of SCD by 89% in the young competitive athletes (YCA) vs. the general population while also bringing person years from 3.6/100,000 to 0.4/100,000 in YCA. Diagnostic capabilities showed that H/P + EKG = 99.8% sensitivity, EKG alone = 90.9% sensitivity while H/P alone was 45.5% sensitive. Others reported sensitivity to range from 60-70%, specificity to be 97.8%, with false positives equaling 2.2%. Cost-effectiveness of implementing mandatory EKG testing showed $44,000/year of life saved in comparison to the AHA-recommended H/P at$84,000/year of life saved. Conclusions: One of the main arguments against PPE EKG testing historically is that it has a low specificity, which is negatively associated with cost-effectiveness as unnecessary referrals are made due to higher false positives. It has been suggested that adjusting diagnostic criteria to be more representative of YCAs can increase specificity to as high as 97.8%. Despite numerous variations in study methods and results, the data generally suggests that PPE EKG testing has the potential to be an acceptable and cost-effective addition to the PPE and ultimately decreases SCD. Word Count: 43

The Efficacy of Instability Resistance Training on Shoulder Muscle Firing Characteristics

PURPOSE: The glenohumeral joint is the most mobile joint in the body. Due to the anatomical makeup and range of motion demands, the shoulder is at risk for instability. The purpose of this research was to examine the effects of instability resistance training on muscle activation on the shoulder in healthy subjects. SUBJECTS: Fifteen adults (10 females, 5 males; 21.5 years ± 1.5) without previous shoulder injury were included. METHODS AND MATERIALS: D2 shoulder flexion/extension and wrist flexion/extension exercises were performed supine using a resistance device (unstable and stable). The unstable condition was a water-filled pipe device that caused dynamic resistance during exercise. The stable condition was a similar pipe device filled with stationary weights. The Biopac MP 150 EMG system was used to measure muscle activity for the middle deltoid (DELT), pectoralis major (MAJ), and latissimus dorsi (LAT). Subjects performed 10 repetitions of exercise following a metronome. Exercise and condition were randomly assigned. ANALYSES: Four separate repeated measures ANOVAs (Muscle x Condition) were performed to evaluate differences in the coefficient of variance for each exercise (D2 flexion, D2 extension, Wrist flexion, Wrist extension). RESULTS: No significant differences were identified across any exercise for muscle or condition, alpha \u3e 0.05. Despite no significant main or interaction effect being realized, higher EMG activity was noted for the unstable PEC and LAT (2.96±0.31 vs. 2.44±0.12, 2.6± 0.19 vs. 2.31±0.11). CONCLUSIONS: Data did not indicate significance, however, subjects experienced varied applications of load during D2 flexion. Further investigation is warranted to explore instability resistance training and potential benefits in the shoulder

Kinesiology for dummies

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