Monitoring workload in athletes is on the rise due to the increased prevalence of throwing related injuries.1 However, most workload monitors are applied on a gross scale or measure whole body workload.2 Gross workload based on full body movement can provide significant information, but there is a direct need for a joint specific workload measures in overarm throwing athletes.
The motusBASEBALL sensor is an inertial measurement unit that monitors stress on the ulnar collateral ligament (UCL) of the elbow through a measure of valgus torque. As prevalence of UCL tears in pitchers has sky-rocketed in the last decade3, monitoring joint specific workloads for pitchers has become a necessity. The importance of measuring these workloads is further supported as this sensor is the first wearable technology to be approved by MLB for in game use for pitchers.
However, football quarterback throwing can also use joint specific workloads to monitor performance and reduce injury risk. Football quarterbacks (QB) exhibit over arm throwing injuries due to overuse4 and often have to rehab from throwing arm injuries caused by contact. This technology would prove invaluable to football QBs to monitor workloads for performance, injury prevention, and rehabilitation purposes.
A high school male who played both baseball pitcher and football QB (age 15.0; 72 kg; and 180 cm) reported to the Motus Biomechanics lab for testing. The subject was instrumented with 46 reflective markers on anatomical land markers. Kinematic data were collected at 480 Hz using a twelve-camera 3D motion capture system (Motion Analysis Corp., Santa Rosa, CA, USA). The subject was also instrumented with a motusBASEBALL sensor on the inside of the forearm placed approximately 3 cm distal to the medial elbow epicondyle. The subject was allowed unlimited time to warm-up and then threw ten fast balls down the middle, with game-emulated effort. The subject pitched off a mound into a net at a distance of approximately 6 m away from the pitching rubber. Following this, the subject was allowed to take as many warm-up throws as desired with a football. Once ready, 7 throws were made in a shotgun stance with no drop prior to throwing the ball.
All marker motion data were filtered through a low-pass 14 Hz Butterworth filter. Full body kinematics were calculated and used to calculate elbow valgus torque. The motusBASEBALL sensor simultaneously collected elbow valgus torque for all trials. The physics of the sensor that calculate elbow valgus torque were adjusted to account for the different weights of a regulation baseball (6 oz.) and a regulation football (15 oz.).
Condition torque averages were calculated. T-test were run to compare difference between motion capture and sensor for both conditions. The predetermined level of significance was set at p < 0.01.
RESULTS AND DISCUSSION
The elbow valgus torque profiles for baseball pitching and quarterback throwing are presented in Figure 2. Peak torque in both throwing motions occur slightly prior to maximum external rotation or when the throwing arm is fully cocked back.
Table 1. Peak valgus torques for each throwing motions using motion capture (MoCap) and motusBASEBALL (Sensor)
Average peak elbow valgus torques and standard deviations for baseball pitching and quarterback throwing are reported in Table 1 and Figure 1. Although the motusBASEBALL sensor read slightly higher peak elbow valgus torque for baseball pitching (3%) and slightly lower in football throwing (5%) there were no significant differences between motion capture and sensor torque for both conditions (baseball p = 0.38 and football p = 0.44)
Figure 1. Average peak valgus torque
These results found that the motusBASEBALL sensor was successful in calculating maximum elbow valgus torque in both throwing conditions. The differences that exist between motion capture calculations of torque and sensor calculations of torque are minor.
Monitoring workload in baseball pitching and football pitching is a vital and effective tool for trainers, coaches, and athletes to use in order to ensure maximal performance and reduce risk of injury.
The motusBASEBALL sensor can accurately measure torque for both baseball pitching and football throwing to within a 5% error of torques measured by motion capture.
This case study shows that the motusBASEBALL sensor provides an accurate measure of elbow valgus torque for both baseball pitching and football throwing. This allows Motus to utilize the torque readings from the sensor to create measures of acute and chronic workloads that are joint specific to the throwing arm. This information will prove to be an invaluable tool for preventing throwing arm injury, maximizing throwing performance, and rehabbing from injury to the throwing arm with maximal efficiency.
1. Black GM, at al. Sports Medicine. 2016: 1-14.
2. Hulin BT, et al. Br J Sport Med. 2016
3. Conte SA, et al. Am J Sport Med 43(7), 1764-1769, 2015
4. Kelly BT, et al. Am J Sport Med, 32(2), 328-331, 2004.
Figure 2. Average valgus torque on the elbow for baseball pitching and football throwing between foot contact and maximum internal rotation.