Rafael Escamilla

• Doctor of Philosophy
• California State University, Sacramento

Background While one-legged and two-legged bodyweight squats on unstable and stable surfaces are commonly used during patellofemoral rehabilitation, patellofemoral loading during these exercises is unknown. Understanding how patellofemoral force and stress magnitudes affects different squat variations will aid clinicians in determining how and when...

Background: The forward lunge is a closed-chain weight-bearing multi-joint exercise simulating the activities of daily living, such as walking or stair climbing, which mainly activates hip, knee, and ankle musculature and is also used by athletes and other individuals to train lower-extremity musculature. Objectives: The purpose of this study is to...

Purpose] Compare four quick (approximately 60 s), reliable methods of assessing %body-fat (%BF) among young (Y, 18–34 years), middle-age (M, 35–59 years), and older (O, 60–88 years) healthy-adults. [Participants and Methods] One-hundred-eighty healthy males-and-females were equally (n=30) divided into Y, M, and O age groups to assess %BF. The %BF m...

Background Historically, it was assumed by some that high leg lift with windup pitching generated more ball velocity whereas pitching from the stretch was quicker to reduce the risk of base stealing but also more stressful on the arm. However, many now believe that velocity and stress do not differ between windup and stretch and always pitching fro...

Given there are no known studies which have examined multiple lower extremity muscles between different ankle positions during bridging activities, the objective was to assess how employing two different ankle positions (PF versus DF) while performing five common bridging exercises (three bipedal and two unipedal) used in rehabilitation and athleti...

Foot stance and club type's relationship with lead knee joint biomechanics and possible involvement with injury incidences in amateur golfers have not been evaluated. This study included 16 male right-handed amateur golfers who performed golf swings with 2 different foot stances (straight and open) using 4 different club types (driver, 3 iron, 6 ir...

Introduction: While bodyweight wall and ball squats are commonly used during patellofemoral rehabilitation, patellofemoral loading while performing these exercises is unknown, which makes it difficult for clinicians to know how to use these exercises in progressing a patient with patellofemoral pathology. Therefore, the purpose was to quantify pat...

Background: Baseball pitchers employ various contralateral trunk tilt (CTT) positions when pitching depending on if they have an overhand, three-quarter, or sidearm delivery. There are no known studies that have examined how pitching biomechanics are significantly different in professional pitchers with varying amounts of CTT, which may provide in...

This clinical commentary will address five key concepts that can be used by clinicians as criteria for selecting lower extremity weight bearing exercises (WBE) and non-weight bearing exercises (NWBE) employed for cruciate ligament and patellofemoral rehabilitation. The following will be discussed for both cruciate ligament and patellofemoral rehabi...

The objective was to assess how patellofemoral loads (joint force and stress) change while lunging with step length and step height variations. Sixteen participants performed a forward lunge using short and long steps at ground level and up to a 10-cm platform. Electromyography, ground reaction force, and 3D motion were captured, and patellofemoral...

Purpose: The optimal surgical technique for unstable acromioclavicular (AC) and coracoclavicular (CC) joint injuries has not yet been established. The biomechanical and radiographic effect of the LockDown device, a synthetic ligament for AC joint reconstruction, was evaluated to assess the optimal surgical technique for unstable AC and CC joint in...

Background: Forward and side lunge exercises strengthen hip and thigh musculature, enhance patellofemoral joint stability, and are commonly used during patellofemoral rehabilitation and training for sport. Hypothesis/purpose: The purpose was to quantify, via calculated estimates, patellofemoral force and stress between two lunge type variations...

The flow of mechanical energy of segmental motion during baseball pitching is poorly understood, particularly in relation to the valgus torque at the elbow which is prone to pitching-related injuries. This study employed an induced power analysis to determine the components of muscle and velocity-dependent torques that contribute to the power of th...

Background It is unclear how a glenohumeral internal rotation (IR) loss (GIRLoss), a glenohumeral external rotation (ER) gain (GERGain), or a total rotational motion (TRM) deficit (TRMD) predict medial ulnar collateral ligament (MUCL) injury risk among high school (HS), college (COLL), and professional (PRO) baseball pitchers with and without MUCL...

Background Pitching-related elbow injuries remain prevalent across all levels of baseball. Elbow valgus torque has been identified as a modifiable risk factor of injuries to the ulnar collateral ligament in skeletally mature pitchers. Purpose To examine how segmental energy flow (power) influences elbow valgus torque and ball speed in professional...

Background Throwing athletes with ulnar collateral ligament (UCL) injury and symptomatic valgus instability can expect to return to the same or higher level of play. Reconstruction with tendon graft is the dominant method of surgical treatment. Recent evidence suggests that spanning the joint with a suture anchored on both sides is biomechanically...

The purpose of this study was to assess biomechanical differences among overhand, three-quarter, and sidearm arm-slot professional baseball pitchers. It was hypothesized that kinematic-and-kinetic differences would be found among the three groups, with sidearm pitchers demonstrating greater movement along the transverse plane, and overhead pitchers...

Context: Hip abductor musculature contributes to the stability of the pelvis, which is needed for efficient energy transfer from the lower extremity to the upper extremity during overhead throwing. Objective: The purpose of this study was to examine the effects of a hip abduction fatigue protocol on overhead throwing kinematics and hip passive r...

Background: In professional baseball pitchers, pitching biomechanics have not been examined for the slider, and the only known study for the curveball and changeup examined limited kinetics. Moreover, no known studies have investigated pitching biomechanics between strikes and balls. Purpose/Hypothesis: The purpose was to compare pitching biomecha...

Background: A glenohumeral internal rotation (IR) deficit or a total rotational motion (IR plus external rotation [ER]) deficit in the throwing shoulder compared with the nonthrowing shoulder has been shown to increase the risk of shoulder and elbow injuries. After a pitching session, both IR and total rotational motion deficits have been shown to...

Background Prone, supine, and side position exercises are employed to enhance core stability. Hypothesis Overall core muscle activity would be greater in prone position exercises compared with supine and side position exercises. Study Design Controlled laboratory study. Methods Eighteen men and women between 23 and 45 years of age served as subj...

Background: In spite of the bodyblade (BB®) being used in clinical settings during shoulder and trunk rehabilitation and training for 24 years, there are only five known scientific papers that have described muscle recruitment patterns using the BB®. Moreover, there are no known studies that have examined muscle activity differences between males...

A relatively high number of active professional baseball pitchers have a history of ulnar collateral ligament reconstruction (UCLr) on their throwing elbow. Controversy exists in the literature about whether professional baseball pitchers regain optimal performance after return from UCLr. It has been suggested that pitchers may have different biome...

Muscle recruitment patterns of lumbopelvic-hip musculature, which is commonly referred to as the core, and loading of the lumbar spine during core exercises common used during core strengthening programs are described in the literature. The orthopaedic surgeon should be knowledgeable about why the core is important, what muscles comprise the core a...

Shoulder impingement is a progressive orthopedic condition that occurs as a result of altered biomechanics and/or structural abnormalities. An effective nonoperative treatment for impingement syndrome is aimed at addressing the underlying causative factor or factors that are identified after a complete and thorough evaluation. The clinician devises...

Cruciate ligament injuries are common and may lead to dysfunction if not rehabilitated. Understanding how to progress anterior cruciate ligament and posterior cruciate ligament loading, early after injury or reconstruction, helps clinicians prescribe rehabilitation exercises in a safe manner to enhance recovery. Commonly prescribed therapeutic exer...

Throwing velocity is an important baseball performance variable for baseball pitchers, because greater throwing velocity results in less time for hitters to make a decision to swing. Throwing velocity is also an important baseball performance variable for position players, because greater throwing velocity results in decreased time for a runner to...

There is a growing body of evidence documenting loads applied to the anterior cruciate ligament (ACL) for weight-bearing and non-weight-bearing exercises. ACL loading has been quantified by inverse dynamics techniques that measure anterior shear force at the tibiofemoral joint (net force primarily restrained by the ACL), ACL strain (defined as chan...

Effects of a 4-week youth baseball conditioning program on throwing velocity. This study examined the effects of a 4-week youth baseball conditioning program on maximum throwing velocity. Thirty-four youth baseball players (11-15 years of age) were randomly and equally divided into control and training groups. The training group performed 3 session...

Controlled laboratory study using a repeated-measures, counterbalanced design. 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 compl...

The purpose of this study was to compare cruciate ligament forces between the forward lunge with a short step (forward lunge short) and the forward lunge with a long step (forward lunge long). Eighteen subjects used their 12-repetition maximum weight while performing the forward lunge short and long with and without a stride. EMG, force, and kinema...

Although weight bearing lunge exercises are frequently employed during anterior cruciate ligament and posterior cruciate ligament rehabilitation, cruciate ligament tensile forces are currently unknown while performing forward and side lunge exercises with and without a stride. Eighteen subjects used their 12 repetition maximum weight while performi...

The rotator cuff performs multiple functions during shoulder exercises, including glenohumeral abduction, external rotation (ER) and internal rotation (IR). The rotator cuff also stabilizes the glenohumeral joint and controls humeral head translations. The infraspinatus and subscapularis have significant roles in scapular plane abduction (scaption)...

A motion system collected 120-Hz data from 14 baseball adult hitters using normal and choke-up bat grips. Six swings were digitized for each hitter, and temporal and kinematic parameters were calculated. Compared with a normal grip, the choke-up grip resulted in 1) less time during stride phase and swing; 2) the upper torso more opened at lead foot...

We propose that learning proper hitting kinematics should be encouraged at a young age during youth baseball because this may help reinforce proper hitting kinematics as a player progresses to higher levels of baseball in their adult years. To enhance our understanding between youth and adult baseball hitting, kinematic and temporal analyses of bas...

To compare patellofemoral compressive force and stress during the one-leg squat and two variations of the wall squat. Eighteen subjects used their 12 repetition maximum (12 RM) weight while performing the wall squat with the feet closer to the wall (wall squat short), the wall squat with the feet farther away from the wall (wall squat long), and th...

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 eff...

Purpose: To compare cruciate ligament forces during wall squat and one-leg squat exercises. Methods: Eighteen subjects performed the wall squat with feet closer to the wall (wall squat short), the wall squat with feet farther from the wall (wall squat long), and the one-leg squat. EMG, force, and kinematic variables were input into a biomechanical...

Understanding when and how much shoulder muscles are active during upper extremity sports is helpful to physicians, therapists, trainers and coaches in providing appropriate treatment, training and rehabilitation protocols to these athletes. This review focuses on shoulder muscle activity (rotator cuff, deltoids, pectoralis major, latissimus dorsi,...

Controlled laboratory biomechanics study using a repeated-measures, counterbalanced design. To compare patellofemoral joint force and stress between a short- and long-step forward lunge both with and without a stride. Although weight-bearing forward-lunge exercises are frequently employed during rehabilitation for individuals with patellofemoral jo...

Although weight bearing lunge exercises are frequently employed during patellofemoral rehabilitation, patellofemoral compressive force and stress are currently unknown for these exercises. Eighteen subjects used their 12 repetition maximum weight while performing forward and side lunges with and without a stride. EMG, force platform, and kinematic...

The primary purpose of this project was to examine whether lower extremity joint kinetic factors are related to the walk-run gait transition during human locomotion. Following determination of the preferred transition speed (PTS), each of the 16 subjects walked down a 25-m runway, and over a floor-mounted force platform at five speeds (70, 80, 90,...

The purpose of this study was to compare the kinematics of kuzushi/tsukuri (KT) phases of the harai-goshi throw under competitive and non-competitive conditions. A third degree black belt subject served as the tori (thrower) for both conditions. Two black belt participants ranked as first degree and fourth degree served as the uke (faller) for the...

Although the preferred transition speed (PTS) reported by various researchers is relatively consistent, the amount of observed hysteresis (difference between the walk-run and the run-walk transition speed) varies considerably. Variations in reported hysteresis appear to be related to the protocol used to determine the transition speeds. This invest...

When a treadmill accelerates continuously, the walk-run transition has generally been assumed to occur at the instant when a flight phase is first observed, while the run-walk transition has been assumed to occur at the instant of the first double support period. There is no theoretical or empirical evidence to suggest that gait transitions occur a...

The effects of approaching muscular fatigue on pitching biomechanics are currently unknown. As a pitcher fatigues, pitching mechanics may change, leading to a decrease in performance and an increased risk of injury. As a pitcher approaches muscular fatigue, select pitching biomechanical variables will be significantly different than they were befor...

Neck injuries signify a physical fitness and human system problem with high operational significance. The prevalence of injuries in tactical aviators has been reported to be as high as 84%, although few report engaging in neck-specific strengthening exercises. It is generally believed that neck strengthening may result in fewer neck injuries. This...

Four black belt throwers (tori) and one black belt faller (uke) were filmed and analyzed in three-dimensions using two video cameras (JVC 60 Hz) and motion analysis software. Average linear momentum in the anteroposterior (x), vertical (y), and mediolateral (z) directions and average resultant impulse of uke's center of mass (COM) were investigated...

Performing nontraditional abdominal exercises with devices such as abdominal straps, the Power Wheel, and the Ab Revolutionizer has been suggested as a way to activate abdominal and extraneous (nonabdominal) musculature as effectively as more traditional abdominal exercises, such as the crunch and bent-knee sit-up. The purpose of this study was to...

PURPOSE: Although the wall squat, forward lunge, side lunge, and one-leg squat are common exercises, there are limited EMG data regarding muscle recruitment patterns. The purpose of this study was to compare muscle activity among these exercises and between technique variations (short and long foot positions). METHODS: Nineteen healthy males (29±7...

Background and Purpose. Performing nontraditional abdominal exercises with devices such as abdominal straps, the Power Wheel, and the Ab Revolutionizer has been suggested as a way to activate abdominal and extraneous (nonabdominal) musculature as effectively as more traditional abdominal exercises, such as the crunch and bent-knee sit-up. The purpo...

Controversy exists about whether breaking pitches are more stressful than are fastballs. Previous biomechanical studies compared kinematics but not kinetics. Elbow and shoulder forces and torques are statistically different among the fastball, curveball, change-up, and slider. Descriptive laboratory study. Twenty-one healthy collegiate pitchers wer...

A repeated-measures, counterbalanced design. 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. Numerous abdominal machine exercises are beli...

Some aspects of backward locomotion are similar to forward locomotion, while other aspects are not related to their forward counterpart. The backward preferred transition speed (BPTS) has never been directly compared to the energetically optimal transition speed (EOTS), nor has it been compared to the preferred transition speed (PTS) during forward...

INTRODUCTION Several researchers [1,2,3,4] have hypothesized that the gait transitions of quadrupeds are triggered by kinetic factors, such as musculoskeletal stresses, particularly at joints. Utilizing invasive techniques, it has been shown [1,2,4] that small horses, dogs, and goats reduced bone and joint strain when changing gait from a trot to a...

The purpose of this study was to compare the shoulder and elbow joint loads during the tennis serve. Two synchronised 200 Hz video cameras were used to record the service action of 20 male and female players at the Sydney 2000 Olympics. The displacement histories of 20 selected landmarks, were calculated using the direct linear transformation appro...

Strength athletes often employ the deadlift in their training or rehabilitation regimens. The purpose of this study was to compare muscle activity between sumo and conventional style deadlifts, and between belt and no-belt conditions. Six cameras collected 60-Hz video data and 960-Hz electromyographic data from 13 collegiate football players who pe...

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The specific aim of this project was to quantify knee forces and muscle activity while performing squat and leg press exercises with technique variations. Ten experienced male lifters performed the squat, a high foot placement leg press (LPH), and a low foot placement leg press (LPL) employing a wide stance (WS), narrow stance (NS), and two foot an...

The aim of this study was to compare and evaluate the kinematics of baseball pitchers who participated in the 1996 XXVI Centennial Olympic Games. Two synchronized video cameras operating at 120 Hz were used to video 48 pitchers from Australia, Japan, the Netherlands, Cuba, Italy, Korea, Nicaragua and the USA. All pitchers were analysed while throwi...

Improper lifting techniques may increase injury risks and decrease performance. The aim of this study was to compare and contrast biomechanical parameters between sumo and conventional style deadlifts and between high- and low-skilled lifters who participated in the powerlifting event during the 1999 Special Olympics World Games. Two synchronized v...

The purpose of this study was to quantify biomechanical parameters employing two-dimensional (2-D) and three-dimensional (3-D) analyses while performing the squat with varying stance widths. Two 60-Hz cameras recorded 39 lifters during a national powerlifting championship. Stance width was normalized by shoulder width (SW), and three stance groups...