Towards an accurate rolling resistance: Estimating intra-cycle load distribution between front and rear wheels during wheelchair propulsion from inertial sensors.

Accurate assessment of rolling resistance is important for wheelchair propulsion analyses. However, the commonly used drag and deceleration tests are reported to underestimate rolling resistance up to 6% due to the (neglected) influence of trunk motion. The first aim of this study was to investigate the accuracy of using trunk and wheelchair kinematics to predict the intra-cyclical load distribution, more particularly front wheel loading, during hand-rim wheelchair propulsion. Secondly, the study compared the accuracy of rolling resistance determined from the predicted load distribution with the accuracy of drag test-based rolling resistance. Twenty-five able-bodied participants performed hand-rim wheelchair propulsion on a large motor-driven treadmill. During the treadmill sessions, front wheel load was assessed with load pins to determine the load distribution between the front and rear wheels. Accordingly, a machine learning model was trained to predict front wheel load from kinematic data. Based on two inertial sensors (attached to the trunk and wheelchair) and the machine learning model, front wheel load was predicted with a mean absolute error (MAE) of 3.8% (or 1.8 kg). Rolling resistance determined from the predicted load distribution (MAE: 0.9%, mean error (ME): 0.1%) was more accurate than drag test-based rolling resistance (MAE: 2.5%, ME: -1.3%).

Machine Learning Approach for Pitch Type Classification Based on Pelvis and Trunk Kinematics Captured with Wearable Sensors.

The large stream of data from wearable devices integrated with sports routines has changed the traditional approach to athletes' training and performance monitoring. However, one of the challenges of data-driven training is to provide actionable insights tailored to individual training optimization. In baseball, the pitching mechanics and pitch type play an essential role in pitchers' performance and injury risk management. The optimal manipulation of kinematic and temporal parameters within the kinetic chain can improve the pitcher's chances of success and discourage the batter's anticipation of a particular pitch type. Therefore, the aim of this study was to provide a machine learning approach to pitch type classification based on pelvis and trunk peak angular velocity and their separation time recorded using wearable sensors (PITCHPERFECT). The Naive Bayes algorithm showed the best performance in the binary classification task and so did Random Forest in the multiclass classification task. The accuracy of Fastball classification was 71%, whilst the accuracy of the classification of three different pitch types was 61.3%. The outcomes of this study demonstrated the potential for the utilization of wearables in baseball pitching. The automatic detection of pitch types based on pelvis and trunk kinematics may provide actionable insight into pitching performance during training for pitchers of various levels of play.

Management of displaced humeral surgical neck fractures in daily clinical practice: hanging does not re-align the fracture.

INTRODUCTION: It is unclear if the collar and cuff treatment improve alignment in displaced surgical neck fractures of the proximal humerus. Therefore, this study evaluated if the neckshaft angle and extent of displacement would improve between trauma and onset of radiographically visible callus in non-operatively treated surgical neck fractures (Boileau type A, B, C). MATERIALS AND METHODS: A consecutive series of patients (≥ 18 years old) were retrospectively evaluated from a level 1 trauma center in Australia (inclusion period: 2016-2020) and a level 2 trauma center in the Netherlands (inclusion period: 2004 to 2018). Patients were included if they sustained a Boileau-type fracture and underwent initial non-operative treatment. The first radiograph had to be obtained within 24 h after the initial injury and the follow-up radiograph(s) 1 week after trauma and before the start of radiographically visible callus. On each radiograph, the maximal medial gap (MMG), maximal lateral gap (MLG), and neck-shaft angle (NSA) were measured. Linear mixed modelling was performed to evaluate if these measurements would improve over time. RESULTS: Sixty-seven patients were included: 25 type A, 11 type B, and 31 type C fractures. The mean age (range) was 68 years (24-93), and the mean number (range) of follow-up radiographs per patient was 1 (1-4). Linear mixed modelling on both MMG and MLG revealed no improvement during follow-up among the three groups. Mean NSA of type A fractures improved significantly from 161° at trauma to 152° at last follow-up (p-value = 0.004). CONCLUSIONS: Apart from humeral head angulation improvement in type A, there is no increase nor reduction in displacement among the three fracture patterns. Therefore, it is advised that surgical decision-making should be performed immediately after trauma. LEVEL OF CLINICAL EVIDENCE: Level IV, retrospective case series.

Shoulder kinematics and muscle activity following latissimus dorsi transfer for massive irreparable posterosuperior rotator cuff tears in shoulders with pseudoparalysis.

BACKGROUND: The aim of this study was to evaluate the thoracohumeral (TH) and glenohumeral (GH) motion with muscle activity after latissimus dorsi transfer (LDT) in a shoulder with a massive irreparable posterosuperior rotator cuff tear (MIRT) and pseudoparalysis compared with the asymptomatic contralateral shoulder (ACS). METHODS: We recruited and evaluated 13 patients after LDT in a shoulder with preoperative clinical pseudoparalysis and an MIRT on magnetic resonance imaging, with a minimum follow-up period of 1 year, and with a Hamada stage of 3 or less. Three-dimensional electromagnetic tracking was used to assess shoulder active range of motion in both the LDT shoulder and the ACS. The maximal active elevation of the shoulder (MAES) was assessed and consisted of forward flexion, scapular abduction, and abduction in the coronal plane. Maximal active internal rotation and external rotation were assessed separately. Surface electromyography (EMG) was performed to track activation of the latissimus dorsi (LD) and deltoid muscles during shoulder motion. EMG was scaled to its maximal isometric voluntary contraction recorded in specified strength tests. RESULTS: In MAES, TH motion of the LDT shoulder was not significantly different from that of the ACS (F1,12 = 1.174, P = .300) but the GH contribution was significantly lower in the LDT shoulder for all motions (F1,12 = 11.230, P = .006). External rotation was significantly greater in the ACS (26° ± 10° in LDT shoulder vs. 42° ± 11° in ACS, P < .001). The LD percentage EMG maximum showed no significant difference between the LDT shoulder and ACS during MAES (F1,11 = 0.005, P = .946). During maximal active external rotation of the shoulder, the LDT shoulder showed a higher percentage EMG maximum than the ACS (3.0% ± 2.9% for LDT shoulder vs. 1.2% ± 2.0% for ACS, P = .006). CONCLUSIONS: TH motion improved after LDT in an MIRT with pseudoparalysis and was not different from the ACS except for external rotation. However, GH motion was significantly lower after LDT than in the ACS in active-elevation range of motion. The LD was active after LDT but not more than in the ACS except for active external rotation, which we did not consider relevant as the activity did not rise above 3% EMG maximum. The favorable clinical results of LDT do not seem to be related to a change in LD activation and might be explained by its effect in preventing proximal migration of the humeral head in active elevation.

Using Wearable Sensors to Estimate Mechanical Power Output in Cyclical Sports Other than Cycling-A Review.

More insight into in-field mechanical power in cyclical sports is useful for coaches, sport scientists, and athletes for various reasons. To estimate in-field mechanical power, the use of wearable sensors can be a convenient solution. However, as many model options and approaches for mechanical power estimation using wearable sensors exist, and the optimal combination differs between sports and depends on the intended aim, determining the best setup for a given sport can be challenging. This review aims to provide an overview and discussion of the present methods to estimate in-field mechanical power in different cyclical sports. Overall, in-field mechanical power estimation can be complex, such that methods are often simplified to improve feasibility. For example, for some sports, power meters exist that use the main propulsive force for mechanical power estimation. Another non-invasive method usable for in-field mechanical power estimation is the use of inertial measurement units (IMUs). These wearable sensors can either be used as stand-alone approach or in combination with force sensors. However, every method has consequences for interpretation of power values. Based on the findings of this review, recommendations for mechanical power measurement and interpretation in kayaking, rowing, wheelchair propulsion, speed skating, and cross-country skiing are done.

Individualised Ball Speed Prediction in Baseball Pitching Based on IMU Data.

Ball velocity is considered an important performance measure in baseball pitching. Proper pitching mechanics play an important role in both maximising ball velocity and injury-free participation of baseball pitchers. However, an individual pitcher's characteristics display individuality and may contribute to velocity imparted to the ball. The aim of this study is to predict ball velocity in baseball pitching, such that prediction is tailored to the individual pitcher, and to investigate the added value of the individuality to predictive performance. Twenty-five youth baseball pitchers, members of a national youth baseball team and six baseball academies in The Netherlands, performed ten baseball pitches with maximal effort. The angular velocity of pelvis and trunk were measured with IMU sensors placed on pelvis and sternum, while the ball velocity was measured with a radar gun. We develop three Bayesian regression models with different predictors which were subsequently evaluated based on predictive performance. We found that pitcher's height adds value to ball velocity prediction based on body segment rotation. The developed method provides a feasible and affordable method for ball velocity prediction in baseball pitching.

Physiological and biomechanical comparison of overground, treadmill, and ergometer handrim wheelchair propulsion in able-bodied subjects under standardized conditions.

BACKGROUND: Handrim wheelchair propulsion is often assessed in the laboratory on treadmills (TM) or ergometers (WE), under the assumption that they relate to regular overground (OG) propulsion. However, little is known about the agreement of data obtained from TM, WE, and OG propulsion under standardized conditions. The current study aimed to standardize velocity and power output among these three modalities to consequently compare obtained physiological and biomechanical outcome parameters. METHODS: Seventeen able-bodied participants performed two submaximal practice sessions before taking part in a measurement session consisting of 3 × 4 min of submaximal wheelchair propulsion in each of the different modalities. Power output and speed for TM and WE propulsion were matched with OG propulsion, making them (mechanically) as equal as possible. Physiological data and propulsion kinetics were recorded with a spirometer and a 3D measurement wheel, respectively. RESULTS: Agreement among conditions was moderate to good for most outcome variables. However, heart rate was significantly higher in OG propulsion than in the TM condition. Push time and contact angle were smaller and fraction of effective force was higher on the WE when compared to OG/TM propulsion. Participants used a larger cycle time and more negative work per cycle in the OG condition. A continuous analysis using statistical parametric mapping showed a lower torque profile in the start of the push phase for TM propulsion versus OG/WE propulsion. Total force was higher during the start of the push phase for the OG conditions when compared to TM/WE propulsion. CONCLUSIONS: Physiological and biomechanical outcomes in general are similar, but possible differences between modalities exist, even after controlling for power output using conventional techniques. Further efforts towards increasing the ecological validity of lab-based equipment is advised and the possible impact of these differences -if at all- in (clinical) practice should be evaluated.

Wearable Wheelchair Mobility Performance Measurement in Basketball, Rugby, and Tennis: Lessons for Classification and Training.

Athlete impairment level is an important factor in wheelchair mobility performance (WMP) in sports. Classification systems, aimed to compensate impairment level effects on performance, vary between sports. Improved understanding of resemblances and differences in WMP between sports could aid in optimizing the classification methodology. Furthermore, increased performance insight could be applied in training and wheelchair optimization. The wearable sensor-based wheelchair mobility performance monitor (WMPM) was used to measure WMP of wheelchair basketball, rugby and tennis athletes of (inter-)national level during match-play. As hypothesized, wheelchair basketball athletes show the highest average WMP levels and wheelchair rugby the lowest, whereas wheelchair tennis athletes range in between for most outcomes. Based on WMP profiles, wheelchair basketball requires the highest performance intensity, whereas in wheelchair tennis, maneuverability is the key performance factor. In wheelchair rugby, WMP levels show the highest variation comparable to the high variation in athletes' impairment levels. These insights could be used to direct classification and training guidelines, with more emphasis on intensity for wheelchair basketball, focus on maneuverability for wheelchair tennis and impairment-level based training programs for wheelchair rugby. Wearable technology use seems a prerequisite for further development of wheelchair sports, on the sports level (classification) and on individual level (training and wheelchair configuration).

Single finger movements in the aging hand: changes in finger independence, muscle activation patterns and tendon displacement in older adults.

With aging, hand mobility and manual dexterity decline, even under healthy circumstances. To assess how aging affects finger movement control, we compared elderly and young subjects with respect to (1) finger movement independence, (2) neural control of extrinsic finger muscles and (3) finger tendon displacements during single finger flexion. In twelve healthy older (age 68-84) and nine young (age 22-29) subjects, finger kinematics were measured to assess finger movement enslaving and the range of independent finger movement. Muscle activation was assessed using a multi-channel electrode grid placed over the flexor digitorum superficialis (FDS) and the extensor digitorum (ED). FDS tendon displacements of the index, middle and ring fingers were measured using ultrasound. In older subjects compared to the younger subjects, we found: (1) increased enslaving of the middle finger during index finger flexion (young: 25.6 ± 12.4%, elderly: 47.0 ± 25.1%; p = 0.018), (2) a lower range of independent movement of the index finger (youngmiddle = 74.0%, elderlymiddle: 45.9%; p < 0.001), (3) a more evenly distributed muscle activation pattern over the finger-specific FDS and ED muscle regions and (4) a lower slope at the beginning of the finger movement to tendon displacement relationship, presenting a distinct period with little to no tendon displacement. Our study indicates that primarily the movement independence of the index finger is affected by aging. This can partly be attributed to a muscle activation pattern that is more evenly distributed over the finger-specific FDS and ED muscle regions in the elderly.

Improving Mobility Performance in Wheelchair Basketball.

OBJECTIVE: This study aimed to investigate which characteristics of athlete, wheelchair and athlete-wheelchair interface are the best predictors of wheelchair basketball mobility performance. DESIGN: A total of 60 experienced wheelchair basketball players performed a wheelchair mobility performance test to assess their mobility performance. To determine which variables were the best predictors of mobility performance, forward stepwise linear regression analyses were performed on a set of 33 characteristics, including 10 athlete, 19 wheelchair, and 4 athlete-wheelchair interface characteristics. RESULTS: A total of 8 of the characteristics turned out to be significant predictors of wheelchair basketball mobility performance. Classification, experience, maximal isometric force, wheel axis height, and hand rim diameter-which both are interchangeable with each other and wheel diameter-camber angle, and the vertical distance between shoulder and rear wheel axis-which was interchangeable with seat height-were positively associated with mobility performance. The vertical distance between the front seat and the footrest was negatively associated with mobility performance. CONCLUSION: With this insight, coaches and biomechanical specialists are provided with statistical findings to determine which characteristics they could focus on best to improve mobility performance. Six out of 8 predictors are modifiable and can be optimized to improve mobility performance. These adjustments could be carried out both in training (maximal isometric force) and in wheelchair configurations (eg, camber angle).

Development, construct validity and test-retest reliability of a field-based wheelchair mobility performance test for wheelchair basketball.

The aim of this study was to develop and describe a wheelchair mobility performance test in wheelchair basketball and to assess its construct validity and reliability. To mimic mobility performance of wheelchair basketball matches in a standardised manner, a test was designed based on observation of wheelchair basketball matches and expert judgement. Forty-six players performed the test to determine its validity and 23 players performed the test twice for reliability. Independent-samples t-tests were used to assess whether the times needed to complete the test were different for classifications, playing standards and sex. Intraclass correlation coefficients (ICC) were calculated to quantify reliability of performance times. Males performed better than females (P < 0.001, effect size [ES] = -1.26) and international men performed better than national men (P < 0.001, ES = -1.62). Performance time of low (≤2.5) and high (≥3.0) classification players was borderline not significant with a moderate ES (P = 0.06, ES = 0.58). The reliability was excellent for overall performance time (ICC = 0.95). These results show that the test can be used as a standardised mobility performance test to validly and reliably assess the capacity in mobility performance of elite wheelchair basketball athletes. Furthermore, the described methodology of development is recommended for use in other sports to develop sport-specific tests.

Effects of Offense, Defense, and Ball Possession on Mobility Performance in Wheelchair Basketball.

The aim of this study was to determine to what extent mobility performance is influenced by offensive or defensive situations and ball possession and to what extent these actions are different for the field positions. From video analysis, the relative duration of the various wheelchair movements during team offense/defense and individual ball possession was compared in 56 elite wheelchair basketball players. A two-way analysis of variance indicated that during offense, the guards and forwards performed longer driving forward than during defense. Overall, centers stood still longer during offense than during defense. Without ball, centers performed driving forward longer than with ball possession. It is concluded that offense, defense, and ball possession influenced mobility performance for the different field positions. These differences can be used to design specific training protocols. Furthermore, field positions require potentially different specific wheelchair configurations to improve performance.

Do field position and playing standard influence athlete performance in wheelchair basketball?

Improved understanding of mobility performance in wheelchair basketball is required to increase game performance. The aim of this study was to quantify the wheelchair-athlete activities of players in different field positions and of different playing standard during wheelchair basketball matches. From video analysis, absolute and relative duration and frequency of wheelchair movements and athlete control options were examined in 27 national standard and 29 international standard players during entire wheelchair basketball matches. Between-group factorial analysis of variances identified that national players drove more forward (42.6 ± 6.8 vs. 35.4 ± 3.7%; effect size Cohen's d (ES) = 1.48) and started more often driving forward (33.9 ± 2.6 vs. 31.8 ± 2.8; ES = 0.77) during a match while the mean activity duration for a single driving forward activity was longer (4.3 ± 0.9 vs. 3.7 ± 0.6 s; ES = 0.75) than for international players. Furthermore, national players performed fewer rotational movements (21.8 ± 4.0 vs. 28.9 ± 7.8%; ES = -1.30) and started less often with the rotational movements (35.0 ± 3.6 vs. 40.5 ± 5.5; ES = -1.21) while the mean activity duration for a single rotation activity was shorter (2.1 ± 0.3 vs. 2.3 ± 0.3 s; ES = -0.67) than for international players. Differences in mobility performance among guard, forward and centre players were minimal. The results should help wheelchair basketball coaches specify wheelchair-handling training techniques and means to optimise wheelchair-athlete configurations.

Early motor learning changes in upper-limb dynamics and shoulder complex loading during handrim wheelchair propulsion.

BACKGROUND: To propel in an energy-efficient manner, handrim wheelchair users must learn to control the bimanually applied forces onto the rims, preserving both speed and direction of locomotion. Previous studies have found an increase in mechanical efficiency due to motor learning associated with changes in propulsion technique, but it is unclear in what way the propulsion technique impacts the load on the shoulder complex. The purpose of this study was to evaluate mechanical efficiency, propulsion technique and load on the shoulder complex during the initial stage of motor learning. METHODS: 15 naive able-bodied participants received 12-minutes uninstructed wheelchair practice on a motor driven treadmill, consisting of three 4-minute blocks separated by two minutes rest. Practice was performed at a fixed belt speed (v = 1.1 m/s) and constant low-intensity power output (0.2 W/kg). Energy consumption, kinematics and kinetics of propulsion technique were continuously measured. The Delft Shoulder Model was used to calculate net joint moments, muscle activity and glenohumeral reaction force. RESULTS: With practice mechanical efficiency increased and propulsion technique changed, reflected by a reduced push frequency and increased work per push, performed over a larger contact angle, with more tangentially applied force and reduced power losses before and after each push. Contrary to our expectations, the above mentioned propulsion technique changes were found together with an increased load on the shoulder complex reflected by higher net moments, a higher total muscle power and higher peak and mean glenohumeral reaction forces. CONCLUSIONS: It appears that the early stages of motor learning in handrim wheelchair propulsion are indeed associated with improved technique and efficiency due to optimization of the kinematics and dynamics of the upper extremity. This process goes at the cost of an increased muscular effort and mechanical loading of the shoulder complex. This seems to be associated with an unchanged stable function of the trunk and could be due to the early learning phase where participants still have to learn to effectively use the full movement amplitude available within the wheelchair-user combination. Apparently whole body energy efficiency has priority over mechanical loading in the early stages of learning to propel a handrim wheelchair.

Task variation during simulated, repetitive, low-intensity work--influence on manifestation of shoulder muscle fatigue, perceived discomfort and upper-body postures.

Work-related musculoskeletal disorders are increasing due to industrialisation of work processes. Task variation has been suggested as potential intervention. The objectives of this study were to investigate, first, the influence of task variation on electromyographic (EMG) manifestations of shoulder muscle fatigue and discomfort; second, noticeable postural shoulder changes over time; third, if the association between task variation and EMG might be biased by postural changes. Outcome parameters were recorded using multichannel EMG, Optotrak and the Borg scale. Fourteen participants performed a one-hour repetitive Pegboard task in one continuous and two interrupted conditions with rest and a pick-and-place task, respectively. Manifestations of shoulder muscle fatigue and discomfort feelings were observed throughout the conditions but these were not significantly influenced by task variation. After correction for joint angles, the relation between task variation and EMG was significantly biased but significant effects of task variation remained absent. PRACTITIONER SUMMARY: Comparing a one-hour continuous, repetitive Pegboard task with two interrupted conditions revealed no significant influences of task variation. We did observe that the relation between task variation and EMG was biased by posture and therefore advise taking account for posture when investigating manifestations of muscle fatigue in assembly tasks.

The influence of task variation on manifestation of fatigue is ambiguous - a literature review.

Task variation has been proposed to reduce shoulder fatigue resulting from repetitive hand-arm tasks. This review analyses the effect of task variation, both 'temporal (i.e. change of work-rest ratio)' and 'activity (i.e. job rotation)' variation, on physiological responses, endurance time (ET) and subjective feelings. Pubmed was searched and complemented with references from selected articles, resulting in 17 articles. Temporal variation had some positive effects on the objective parameters, as blood pressure decreased and ET increased, and on the subjective feelings, as perceived discomfort decreased. The observed findings of activity variation showed both positive and negative effects of increased activity variation, while hardly any effects were found on electromyography manifestations of fatigue. In conclusion, the evidence for positive effects of increasing the level of variation is scarce. The number of studies on variation is limited, while in most studies the findings were not controlled for the amount or intensity of work.

Predicting elbow load based on individual pelvis and trunk (inter)segmental rotations in fastball pitching.

The baseball pitch is a repetitive, full-body throwing motion that exposes the elbow to significant loads, leading to a high incidence of elbow injuries. Elbow injuries in pitching are often attributed to high external valgus torques as these are generally considered to be a good proxy for the load on the Ulnar Collateral Ligament. The aim of the study is to contribute to elbow load monitoring by developing a prediction model based on the pelvis and trunk peak angular velocities and their separation time. Eleven male youth elite baseball pitchers (age 17 ± 2.2 years) threw 25 fastballs at full effort off a mound. Two-level varying-intercept, varying-slope Bayesian models were used to predict external valgus torque based on (inter)segmental rotation in fastball pitching with pitcher's weight and height added to strengthen the individualisation of the prediction. The results revealed the high predictive performance of the models including a set of kinematic parameters trunk peak angular velocity and the separation time between the pelvis and trunk peak angular velocities. Such an approach allows individualised prediction of the external valgus torque for each pitcher, which has a great practical advantage compared to group-based predictions in terms of injury assessment and injury prevention.

Trunk motion influences mechanical power estimates during wheelchair propulsion.

In wheelchair sports, there is an increasing need to monitor mechanical power in the field. When rolling resistance is known, inertial measurement units (IMUs) can be used to determine mechanical power. However, upper body (i.e., trunk) motion affects the mass distribution between the small front and large rear wheels, thus affecting rolling resistance. Therefore, drag tests - which are commonly used to estimate rolling resistance - may not be valid. The aim of this study was to investigate the influence of trunk motion on mechanical power estimates in hand-rim wheelchair propulsion by comparing instantaneous resistance-based power loss with drag test-based power loss. Experiments were performed with no, moderate and full trunk motion during wheelchair propulsion. During these experiments, power loss was determined based on 1) the instantaneous rolling resistance and 2) based on the rolling resistance determined from drag tests (thus neglecting the effects of trunk motion). Results showed that power loss values of the two methods were similar when no trunk motion was present (mean difference [MD] of 0.6 ± 1.6 %). However, drag test-based power loss was underestimated up to -3.3 ± 2.3 % MD when the extent of trunk motion increased (r = 0.85). To conclude, during wheelchair propulsion with active trunk motion, neglecting the effects of trunk motion leads to an underestimated mechanical power of 1 to 6 % when it is estimated with drag test values. Depending on the required accuracy and the amount of trunk motion in the target group, the influence of trunk motion on power estimates should be corrected for.

The ulnar collateral ligament response to valgus stress, repetitive pitching, and elbow muscle contraction in asymptomatic baseball pitchers.

Background: In baseball, repetitive pitching leads to medial elbow injuries, particularly to the ulnar collateral ligament (UCL). To prevent pitchers from UCL injuries, it is important to quantify the response to elbow stress. Repetitive elbow external valgus torque and muscular fatigue induced by repetitive pitching could affect markers of the response, that is, humeroulnar joint gap and UCL morphology. The aims of the study were three-folded: to investigate the effect of (1) exerted handgrip force on the humeroulnar joint gap, (2) repetitive pitching on the humeroulnar joint gap and the UCL morphology, and (3) exerted handgrip force on the humeroulnar joint gap for different levels of elbow valgus stress is different after compared to before repetitive pitching in asymptomatic baseball pitchers. Methods: Medial elbow ultrasound images were collected in 15 asymptomatic male baseball pitchers. Three levels of static elbow valgus stress (0N, 50N, 100N) were applied with a TELOS device before and after repetitive pitching and with or without handgrip force. These images were used to assess the humeroulnar joint gap size and UCL length and thickness. After 110 fastball pitches or when 80% self-perceived fatigue on a VAS scale was reached, participants were instructed to stop throwing. Repeated measures ANOVAs were used to statistically test significant differences. Results: Handgrip force did not significantly affect the humeroulnar joint gap. The UCL thickness and length and the humeroulnar joint gap were also not different after compared to before repetitive pitching. While higher levels of applied valgus stress significantly increased the humeroulnar joint gap (P < .001), this effect was not significantly different in the interaction with handgrip force and repetitive pitching. Conclusion: The humeroulnar joint gap changes for different levels of elbow valgus stress. However, adult baseball pitchers did not respond to elbow stress after a single pitching session with or without submaximal handgrip force in the humeroulnar joint gap and UCL morphology.

Automatic identification of radius and ulna bone landmarks on 3D virtual models.

BACKGROUND: For bone morphology and biomechanics analysis, landmarks are essential to define position, orientation, and shape. These landmarks define bone and joint coordinate systems and are widely used in these research fields. Currently, no method is known for automatically identifying landmarks on virtual 3D bone models of the radius and ulna. This paper proposes a knowledge-based method for locating landmarks and calculating a coordinate system for the radius, ulna, and combined forearm bones, which is essential for measuring forearm function. This method does not rely on pre-labeled data. VALIDATION: The algorithm is validated by comparing the landmarks placed by the algorithm with the mean position of landmarks placed by a group of experts on cadaveric specimens regarding distance and orientation. RESULTS: The median Euclidean distance differences between all the automated and reference landmarks range from 0.4 to 1.8 millimeters. The median angular differences of the coordinate system of the radius and ulna range from -1.4 to 0.6 degrees. The forearm coordinate system's median errors range from -0.2 to 2.0 degrees. The median error in calculating the rotational position of the radius relative to the ulna is 1.8 degrees. CONCLUSION: The automatic method's applicability depends on the use context and desired accuracy. However, the current method is a validated first step in the automatic analysis of the three-dimensional forearm anatomy.