Jessica Zendler

University of Michigan | U-M · School of Kinesiology

Estimating external workload in baseball pitchers is important for training and rehabilitation. Since current methods of estimating workload through pitch counts and rest days have only been marginally successful, clubs are looking for more sophisticated methods to quantify the mechanical loads experienced by pitchers. Among these are the use of we...

Many runners seek health professional advice regarding footwear recommendations to reduce injury risk. Unfortunately, many clinicians, as well as runners, have ideas about how to select running footwear that are not scientifically supported. This is likely because much of the research on running footwear has not been highly accessible outside of th...

Background Frailty commonly complicates cirrhosis and associates with poorer outcomes. While patients with cirrhosis may be sedentary, there are few comprehensive descriptions of their physical activity (PA) patterns related to frailty. Our aim was to identify PA characteristics that may be used in interventions to improve PA and reduce frailty. M...

Elite middle distance runners present as a unique population in which to explore biomechanical phenomena in relation to running speed, as their training and racing spans a broad spectrum of paces. However, there have been no comprehensive investigations of running mechanics across speeds within this population. Here, we used the spring-mass model o...

Background Non-tackle football (ie, flag, touch, 7v7) is purported to be a lower-risk alternative to tackle football, particularly in terms of head injuries. However, data on head injuries in non-tackle football are sparse, particularly among youth participants. Purpose To describe the epidemiology of emergency department visits for head injuries...

Objectives Non-tackle American football is growing in popularity, and it has been proposed as a safer alternative for young athletes interested in American football. Little is known about the nature of head contact in the sport, which is necessary to inform the extent to which protective headgear is warranted. The objective of this study was to ide...

Footwear assessment is thought to be influenced by shoe comfort and the feeling of the ground-shoe interface during contact, sometimes called the ride of the shoe. Runners are often asked to rate the ride quality of smoothness as an indicator of comfort. However, previous work has shown that smoothness does not directly map to preference or comfort...

Research question: The current study investigated stride-to-stride fluctuations of step rate and contact time in response to enforced step frequency perturbations as well as adaptation and de-adaptation behavior. Methods: Forty distance runners ran at a self-selected speed and were asked to match five different enforced step frequencies (150, 16...

Step frequency (SF) in running has received substantial interest from researchers, coaches, therapists, and runners. It has been widely studied in controlled settings, but no published study has measured it continuously in elite-level competition. The present study used wrist-based accelerometers in consumer-grade watches to monitor SF and SF varia...

Ground reaction force measurements are a fundamental element of kinetic analyses of locomotion, yet they are traditionally constrained to laboratory settings or stationary frames. This study assessed the validity and reliability of a new wireless in-shoe system (Novel Loadsol/Pedoped) for field-based ground reaction force measurement in hopping, wa...

Biomechanical response to running footwear has been studied with regard to traditional shoes and, more recently, minimalist (MIN) shoes. Maximalist (MAX) shoes have grown in popularity as a highly-cushioned counterpoint to MIN shoes. However, little is known about the influence of MAX shoes on running biomechanics alone or in comparison to a MIN sh...

Purpose: Increased running experience and more time spent running appears to be advantageous in reducing injury risk, although the reason behind this is unclear. It is plausible that more experience results in better running mechanics leading to less injuries. Running mechanics are often screened during clinical assessments and targeted for correc...

Purpose: To compare passive and real-time active hip range of motion (ROM) in asymptomatic collegiate pitchers, to investigate whether differences in hip morphology and ROM exist between lead and trail hips, and to relate active hip ROM during the pitch to hip morphology and femoroacetabular impingement. Methods: Eleven collegiate baseball pitch...

Femoroacetabular impingement (FAI) is particularly prevalent in ice hockey. The butterfly goalie technique is thought to involve extreme ranges of hip motion that may predispose goaltenders to FAI. To quantify hip mechanics during 3 common goaltender movements and interpret their relevance to the development of FAI. Descriptive laboratory study. Fo...

The purpose of this study was to quantify ball flight kinematics (ball speed, spin rate, spin axis orientation, seam orientation) and release location variability in the four most common pitch types in baseball and relate them to in-season pitching performance. Nine NCAA Division I pitchers threw four pitching variations (fastball, changeup, curveb...

Background: Femoroacetabular impingement (FAI) is a major cause of performance inhibition in elite-level athletes. The condition is characterized by pain, osseous abnormalities such as an increased alpha angle, and decreased range of motion at the affected hip joint. Arthroscopic surgical decompression is useful in reshaping the joint to alleviate...

Although inter-and intra-tester reliability has been a common theme in Functional Movement Screen (FMS) research, the criterion validity of manual grading is yet to be comprehensively examined. This study aimed to compare the FMS scores assigned by a certified FMS tester to those measured by an objective inertial-based motion capture system (IMU)....

Background: Femoroacetabular impingement is a debilitating hip condition commonly affecting American football athletes. Femoroacetabular impingement is associated with reduced hip range of motion; however, little is known about the range-of-motion demands of football athletes. This knowledge is critical to effective management of this condition. Pu...

INTRODUCTION Modeling articular cartilage (AC) poses a challenge due to the tissue's complex physiology and its equally complex non-linear viscoelastic loading response [1, 2]. Under the relative short loading times associated with walking, the mechanical response of knee joint AC is primarily driven by the collagen network of the superficial zone...

INTRODUCTION Knee osteoarthritis (OA) debilitates 10% of the world's population [1]. Since knee articular cartilage (AC) lesions associated with OA manifest in common regional patterns [2, 3], accurate characterization of AC mechanical properties across the joint surface could reveal important insight into the disease process. A previous study by o...

The relative contribution of medial and lateral hamstring torque during high impact landings are posited to contribute to ACL injury risk. In particular, disparate torque production between these muscles precipitates hazardous female knee abduction motions (Palmieri-Smith, J Athl Train 2009). This risk is governed in part by the moment arms of the...

Knowledge of the extent to which tibial plateau cartilage displays non-uniform mechanical topography under physiologically relevant loading conditions is critical to evaluating the role of biomechanics in knee osteoarthritis. Cartilage explants from 21 tibial plateau sites of eight non-osteoarthritic female cadaveric knees (age: 41-54; BMI: 14-20)...

Non-contact anterior cruciate ligament (ACL) injuries sideline approximately 80,000 athletes annually, yet the underlying cause remains unknown. A much touted contributor to the ACL injury mechanism is the interaction of quadriceps' and hamstrings' torques produced about the knee joint during high-impact landings. At low knee flexion angles at whic...

Knee osteoarthritis is one of the most common musculoskeletal pathologies. With no cure other than total joint replacement, and the incidence of osteoarthritis rising worldwide, the need to understand how the disease develops has reached a critical level. Alterations in the spatial loading pattern on the joint???s articular cartilage, for example,...

Nearly 3% of individuals worldwide experience pain, immobility, and compromised quality of life due to knee osteoarthritis (OA)1. It has been widely accepted that joint mechanics play a critical role in the initiation and progression of knee OA2. A shift away from the normal joint motion, for example due to injury or malalignment, is believed to pr...

INTRODUCTION Knee osteoarthritis (OA) afflicts approximately 3% of individuals worldwide, leading to serious joint pain, debilitation, and morbidity [1]. Abnormal knee joint mechanics are believed to play a critical role in the development and progression of the disease, by placing loads on the joint cartilage that it cannot safely sustain [2]. Alt...

Abnormal 3-dimensional tibiofemoral joint kinematics have been identified in anterior cruciate ligament-reconstructed knees during functional gait tasks, which is suggested to directly affect risk of knee osteoarthritis. However, the extent to which similar high-risk abnormalities are present during more demanding maneuvers, such as single-legged h...

Rotator cuff tears are a common injury that have a major impact on function, comfort, and medical care costs. Treatment procedures rely implicitly on the belief that restoring normal glenohumeral joint (GHJ) mechanics is necessary to obtain a satisfactory clinical result. However, it is unknown if rotator cuff repair restores and maintains normal G...