Letters to the Editor-in-Chief of JOSPT as follows:

• "Manual Magic: The Method Is Not the Trick" and Authors' Response
• "Moving Past Sleight of Hand" and Authors' Response
• "Core Muscle Activation During Swiss Ball and Traditional Abdominal Exercises" and Authors' Response

J Orthop Sports Phys Ther 2010;40(8):535-541. doi:10.2519/jospt.2010.0201

STUDY DESIGN: Controlled laboratory study using a repeated-measures, counterbalanced design. OBJECTIVES: To test the ability of 8 Swiss ball exercises (roll-out, pike, knee-up, skier, hip extension right, hip extension left, decline push-up, and sitting march right) and 2 traditional abdominal exercises (crunch and bent-knee sit-up) on activating core (lumbopelvic hip complex) musculature. BACKGROUND: Numerous Swiss ball abdominal exercises are employed for core muscle strengthening during training and rehabilitation, but there are minimal data to substantiate the ability of these exercises to recruit core muscles. It is also unknown how core muscle recruitment in many of these Swiss ball exercises compares to core muscle recruitment in traditional abdominal exercises such as the crunch and bent-knee sit-up. METHODS: A convenience sample of 18 subjects performed 5 repetitions for each exercise. Electromyographic (EMG) data were recorded on the right side for upper and lower rectus abdominis, external and internal oblique, latissimus dorsi, lumbar paraspinals, and rectus femoris, and then normalized using maximum voluntary isometric contractions (MVICs). RESULTS: EMG signals during the roll-out and pike exercises for the upper rectus abdominis (63% and 46% MVIC, respectively), lower rectus abdominis (53% and 55% MVIC, respectively), external oblique (46% and 84% MVIC, respectively), and internal oblique (46% and 56% MVIC, respectively) were significantly greater compared to most other exercises, where EMG signals ranged between 7% to 53% MVIC for the upper rectus abdominis, 7% to 44% MVIC for the lower rectus abdominis, 14% to 73% MVIC for the external oblique, and 16% to 47% MVIC for the internal oblique. The lowest EMG signals were consistently found in the sitting march right exercise. Latissimus dorsi EMG signals were greatest in the pike, knee-up, skier, hip extension right and left, and decline push-up (17%-25% MVIC), and least with the sitting march right, crunch, and bent-knee sit-up exercises (7%-8% MVIC). Rectus femoris EMG signal was greatest with the hip extension left exercise (35% MVIC), and least with the crunch, roll-out, hip extension right, and decline push-up exercises (6%-10% MVIC). Lumbar paraspinal EMG signal was relative low (less than 10% MVIC) for all exercises. CONCLUSIONS: The roll-out and pike were the most effective exercises in activating upper and lower rectus abdominis, external and internal obliques, and latissimus dorsi muscles, while minimizing lumbar paraspinals and rectus femoris activity.

J Orthop Sports Phys Ther 2010;40(5):265-276, Epub 22 April 2010. doi:10.2519/jospt.2010.3073

KEY WORDS: crunch, EMG, low back pain, lumbar spine, rectus abdominis, sit-up

SYNOPSIS: The biomechanical analysis of rehabilitation exercises has led to more scientifically based rehabilitation programs. Several investigators have sought to quantify the biomechanics and electromyographic data of common rehabilitation exercises in an attempt to fully understand their clinical indications and usefulness. Furthermore, the effect of pathology on normal shoulder biomechanics has been documented. It is important to consider the anatomical, biomechanical, and clinical implications when designing exercise programs. The purpose of this paper is to provide the clinician with a thorough overview of the available
literature relevant to develop safe, effective, and appropriate exercise programs for injury rehabilitation and prevention of the glenohumeral and scapulothoracic joints. LEVEL OF EVIDENCE: Level 5.

J Orthop Sports Phys Ther. 2009;39(2):105-117. doi:10.2519/jospt.2009.2835

KEY WORDS: electromyography, infraspinatus, serratus anterior, supraspinatus, trapezius

STUDY DESIGN: Controlled laboratory biomechanics study using a repeated-measures, counterbalanced design. OBJECTIVES: To compare patellofemoral joint force and stress between a short- and long-step forward lunge both with and without a stride. BACKGROUND: Although weight-bearing forward-lunge exercises are frequently employed during rehabilitation for individuals with patellofemoral joint syndrome, patellofemoral joint force and stress and how they change with variations of the lunge exercise are currently unknown. METHODS AND MEASURES: Eighteen subjects used their 12-repetition maximum weight while performing a short- and long-step forward lunge both with and without a stride. Electromyography, ground reaction force, and kinematic variables were put into a biomechanical optimization model, and patellofemoral joint force and stress were calculated as a function of knee angle. RESULTS: Visual observation of the data show that during the forward lunge, patellofemoral joint force and stress increased progressively as knee flexion increased, and decreased progressively as knee flexion decreased. Between 70° and 90° of knee flexion, patellofemoral joint force and stress were significantly greater when performing a forward lunge with a short step compared to a long step (P<.025). Between 10° and 40° of knee flexion, patellofemoral joint force and stress were significantly greater when performing a forward lunge with a stride compared to without a stride (P<.025). CONCLUSIONS: When the goal is to minimize patellofemoral joint force and stress during the forward lunge performed between 0° to 90° knee angles, it may be prudent to perform the lunge with a long step compared to a short step and without a stride compared to with a stride, because patellofemoral joint force and stress magnitudes were greater with a short step compared to a long step at higher knee flexion angles and were greater with a stride compared to without a stride at lower knee flexion angles.

J Orthop Sports Phys Ther. 2008; 38(11):681-690, Epub 24 October 2008. doi:10.2519/jospt.2008.2694 

KEY WORDS: knee, knee kinetics, patella, rehabilitation

Underhand pitching has received minimal attention in the sports medicine literature. This may be due to the perception that compared with overhead pitching, the underhand motion creates less stress on the arm, which results in fewer injuries. The purpose of this study was to calculate kinematic and kinetic parameters for the pitching motion used in fast pitch softball. Eight female fast pitch softball pitchers were recorded with a four-camera system (200 Hz). The results indicated that high forces and torques were experienced at the shoulder and elbow during the delivery phase. Peak compressive forces at the elbow and shoulder equal to 70-98% of body weight were produced. Shoulder extension and abduction torques equal to 9-10% of body weight x height were calculated. Elbow flexion torque was exerted to control elbow extension and initiate elbow flexion. The demand on the biceps labrum complex to simultaneously resist glenohumeral distraction and produce elbow flexion makes this structure susceptible to overuse injury.

J Orthop Sports Phys Ther. 1998;28(6):405-414.

Key Words: biomechanics, underhand pitching, softball, shoulder, elbow

Study Design: A repeated-measures, counterbalanced design. Objectives: To test the effectiveness of 7 commercial abdominal machines (Ab Slide, Ab Twister, Ab Rocker, Ab Roller, Ab Doer, Torso Track, SAM) and 2 common abdominal exercises (crunch, bent-knee sit-up) on activating abdominal and extraneous (nonabdominal) musculature. Background: Numerous abdominal machine exercises are believed to be effective in activating abdominal musculature and minimizing low back stress, but there are minimal data to substantiate these claims. Many of these exercises also activate nonabdominal musculature, which may or may not be beneficial. Methods and Measures: A convenience sample of 14 subjects performed 5 repetitions for each exercise. Electromyographic (EMG) data were recorded for upper and lower rectus abdominis, external and internal oblique, pectoralis major, triceps brachii, latissimus dorsi, lumbar paraspinals, and rectus femoris, and then normalized by maximum muscle contractions. Results: Upper and lower rectus abdominis EMG activities were greatest for the Ab Slide, Torso Track, crunch, and Ab Roller, while external and internal oblique EMG activities were greatest for the Ab Slide, Torso Track, crunch, and bent-knee sit-up. Pectoralis major, triceps brachii, and latissimus dorsi EMG activities were greatest for the Ab Slide and Torso Track. Lumbar paraspinal EMG activities were greatest for the Ab Doer, while rectus femoris EMG activities were greatest for the bent-knee sit-up, SAM, Ab Twister, Ab Rocker, and Ab Doer. Conclusions: The Ab Slide and Torso Track were the most effective exercises in activating abdominal and upper extremity muscles while minimizing low back and rectus femoris (hip flexion) activity. The Ab Doer, Ab Twister, Ab Rocker, SAM, and bent-knee sit-up may be problematic for individuals with low back pathologies due to relatively high rectus femoris activity.

J Orthop Sports Phys Ther. 2006;36(2):45-57. doi:10.2519/jospt.2006.2054 

Key words: EMG, low back pain, lumbar spine, rectus abdominis, sit-up