Kimitake Sato

Baseball Resistance Training: Should Power Clean Variations Be Incorporated?

Baseball Resistance Training: Should Power Clean Variations Be Incorporated? nThe power clean and its variations are prescribed by many collegiate and professional strength and conditioning coaches in order to train lower body muscular power. Lower body muscular power is an essential component to the overall performance of athletes in their respective sports. Although baseball is a sport that requires lower body power to be successful, it has not followed the trend of other sports that use Olympic lifts and their variations to train lower body power. Speculation leads practitioners to believe that baseball players consider Olympic lifts to be harmful to their shoulders and wrists because of the traditional over-head catch position of the snatch and jerk and the catch position of the power clean respectively. There are several power clean variations that produce high amounts of lower body power and may decrease the chance for injury to the shoulders and wrists. The high pull, jump shrug, and mid-thigh pull are three power clean variations that are used in the teaching progression of the power clean. Previous research indicated that the high pull, jump shrug, and mid-thigh pull can produce high amounts of lower body power that may be superior to a power clean variation that includes the catch phase. Because of the simplistic nature of these variations, it is likely the chance of injury to the shoulders and wrists will decrease.

Comparison of the Relationship between Lying and Standing Ultrasonography Measures of Muscle Morphology with Isometric and Dynamic Force Production Capabilities

The purpose of the current study was (1) to examine the differences between standing and lying measures of vastus lateralis (VL), muscle thickness (MT), pennation angle (PA), and cross-sectional area (CSA) using ultrasonography; and (2) to explore the relationships between lying and standing measures with isometric and dynamic assessments of force production—specifically peak force, rate of force development (RFD), impulse, and one-repetition maximum back squat. Fourteen resistance-trained subjects (age = 26.8 ± 4.0 years, height = 181.4 ± 6.0 cm, body mass = 89.8 ± 10.7 kg, back squat to body mass ratio = 1.84 ± 0.34) agreed to participate. Lying and standing ultrasonography images of the right VL were collected following 48 hours of rest. Isometric squat assessments followed ultrasonography, and were performed on force platforms with data used to determine isometric peak force (IPF), as well as RFD and impulse at various time points. Forty-eight hours later, one-repetition maximum back squats were performed by each subject. Paired-samples t-tests revealed statistically significant differences between standing and lying measurements of MT (p < 0.001), PA (p < 0.001), and CSA (p ≤ 0.05), with standing values larger in all cases. Further, standing measures were correlated more strongly and abundantly to isometric and dynamic performance. These results suggest that if practitioners intend to gain insight into strength-power potential based on ultrasonography measurements, performing the measurement collection with the athlete in a standing posture may be preferred.

The Use of an Optical Measurement System to Monitor Sports Performance

The purpose of this study was to compare ground contact time between an optical measurement system and a force platform. Participants in this study included six collegiate level athletes who performed drop jumps and sprint strike steps for a total of 15 repetitions each. Ground contact data was simultaneously collected from an optical measurement system and a force platform, at a sampling frequency of 1000 Hz. Data was then analyzed with Pearson’s correlation and paired sample t-tests. The measures from the optical measurement system were found to be significantly higher (p < 0.001) than measures from the force platform in both conditions. Although significantly different, the extremely large relationships (0.979, 0.993) found between the two devices suggest the optical sensor is able to detect similar changes in performance to that of a force platform. Practitioners may continue to utilize optical sensors to monitor performance as it may provide a superior user-friendly alternative to more traditional based monitoring procedures, but must comprehend the inherent limitations due to the design of the optical sensors.

Validation of inertial sensor to measure velocity of medicine balls

Objectives: The purpose of this study was to examine the validity of a wireless device measuring velocity via inertial sensor medicine ball. Design and Methods: Sixteen healthy adults volunteered in the study. Each participant performed a series of three static and countermovement (CM) medicine ball chest throws. All throws were performed using 8-lb and 12-lb medicine balls inlayed with a wirelessly transmitted accelerometer and gyroscope. Reflective markers were placed on both sides of medicine ball and data were collected using a three-dimensional (3D) motion analysis system as the criterion measure. Pearson correlations and paired samples t-tests were calculated to assess the accuracy of the medicine ball peak velocity to that of the 3D motion analysis. Additionally, intraclass correlation coefficients (ICC) were calculated within each device to determine reliability. The alpha level was set as p ≤ 0.05. Results: Pearson correlations indicated the medicine ball device to be relatively accurate with 3D motion analysis for static throws (r = 0.85-0.94) and CM throws (r = 0.62-0.89). There were no statistically significant differences between the two devices. ICC indicated trial-to-trial reliability of the medicine ball device to be acceptable (ICC = 0.74-0.98) compared to the 3D motion analysis (ICC = 0.67-0.98). Conclusion: Overall, the study demonstrated that relatively accurate data may be obtained from an inertial sensor medicine ball, indicated from the strong and very strong correlations with 3D motion analysis. Additionally, similar ICC values between the medicine ball and 3D motion analysis suggest the device yields acceptable reliability. (Journal of Trainology 2018;7:16-20)

Increases in Variation of Barbell Kinematics Are Observed with Increasing Intensity in a Graded Back Squat Test

The purpose of the current study was two-fold: (1) To examine the variation in velocity and power with increasing intensity in the back squat among subjects; and (2) To explore individual subject characteristics as possible explanations for variations of velocity in the back squat. Fourteen recreationally trained male subjects with experience in the back squat agreed to participate in the study (age = 25.0 ± 2.6 years, height = 178.9 ± 8.1 cm, body mass = 88.2 ± 15.8 kg). One-repetition maximums (1RM) were performed for each subject on force platforms with four linear position transducers attached to the barbell. The 1RM assessment was immediately preceded by warm-up sets at 65%, 75%, 85%, and 95% of estimated 1RM for 5, 3, 2, and 1 repetitions, respectively. Mean concentric velocity (MCV) and mean power were recorded for each intensity condition and were analyzed using Pearson correlation to determine the relationship between each variable and relative intensity (%1RM). Statistically significant negative relationships existed between %1RM and MCV (r = −0.892) and mean power (r = −0.604). Between-subject coefficient of variation tended to increase as %1RM increased for both MCV and mean power. These results suggest that MCV is superior to mean power as an indicator of relative intensity in the back squat. Additionally, the between-subject variation observed at higher intensities for MCV and mean power support the use of velocity ranges by strength and conditioning coaches.