Brian Hatzel

Activation of the trapezius muscle during varied forms of Kendall exercises

UNLABELLED The trapezius muscle plays a crucial role in maintaining proper shoulder mechanics and is often considered a source of weakness and dysfunction in patients. OBJECTIVES The purpose of this study was to investigate the activation patterns of the middle and lower trapezius during four prone horizontal abduction exercises of the glenohumeral joint (GHJ). METHODS The muscle activation patterns of 19 female and 13 male volunteers were measured using surface EMG during horizontal arm abduction exercises commonly used in rehabilitative settings. Each subject performed 10 repetitions of horizontal abduction (ABD) at each position using only the weight of the arm. Function was assessed during shoulder horizontal abduction while positioned at: 75 degrees , 90 degrees , 125 degrees and 160 degrees of GHJ ABD. Electromyographic activity was collected during the concentric phase during each test repetition in the lower (LTRAP) and middle trapezius (MTRAP). A repeated measure ANOVA was performed followed by Bonferronis post hoc test. RESULTS The MTRAP had significantly greater recruitment at 90 degrees and 125 degrees , compared to 160 degrees . Similarly, results for the lower trapezius indicated that recruitment at 90 degrees and 125 degrees was significantly greater than 160 degrees . CONCLUSION Most significant muscle activation for the middle and lower trapezius occurred at 90 degrees and 125 degrees of GHJ ABD. For the clinician, training at 90 degrees is easy to identify, and provides maximal activation, negating the need for multiple training angles.

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. Purpose : The purpose of this study was to examine the effect of varied durations of a commercial foam roller treatment on hamstring range of motion. Methods : The knee extension range of motion of 33 college aged men and women (age= 20±1.5y, mass= 72.2±10.8 kg) was assessed after a short (2 sets of 10s) and long (4 sets of 30s) duration of hamstring self-administered myofascial release using a commercial foam roller. A one way ANOVA was performed to compare the mean knee extension angle for each condition to baseline measures. Results : Results indicated that neither the short duration (67.30 ± 10.60 deg) nor long duration (67.41 ± 10.81 deg) rolling condition produced significant increases in knee extension compared to baseline (67.70 ± 9.90 deg). Conclusion : Self-administered foam rolling for a total duration of up to 2 minutes is not adequate to induce improvements in knee joint flexibility. Contributing factors may include the amount of pressure imparted by the commercial roller as well as duration of treatment.

Effects of weightlifting and breathing technique on blood pressure and heart rate.

Lepley, AS and Hatzel, BM. Effects of weightlifting and breathing technique on blood pressure and heart rate. J Strength Cond Res 24(8): 2179-2183, 2010-Weight training is a method commonly used to increase strength. The purpose of this investigation was to examine the effect of breathing technique during weight training on heart rate (HR) and blood pressure (BP). After completing a health history questionnaire, 30 subjects (16 men: 21.25 ± 1.21 years, 180.26 ± 2.36 cm, 84.31 ± 19.32 kg; and 14 women: 21.29 ± 2.37 years, 170.08 ± 2.15 cm, 137.36 ± 62.31 kg) were familiarized and tested for an estimated 1 repetition maximum, on the chest press and leg press lifts using each of the 2 breathing techniques, hold breath (HB), and controlled breathing. Lifts were examined using each breathing technique with 1 set of 10 repetitions on separate days. Data were collected during the push phase on average of 3.72 times per set and again at 1 and 5 minutes post lift. Resting, during lift (peak, average); 1-minute and 5-minute post lift BP; and HR values were measured using the NIBP100A noninvasive BP system (Biopac Systems, Inc), for both breathing technique within each lift. The HB technique posted higher but statistically insignificant (p < 0.05) values for systolic BP (p = 0.420), diastolic BP (p = 0.531), and HR (p = 0.713) than the controlled breath technique. The HB technique used in this investigation produced minimal elevations in HR and BP and appears to be safe when performing the chest press and leg press lifts at a moderate resistance. Education on proper weight training techniques can help limit unwanted risks during these exercises.

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.