Relationship of Clubhead Speed With Explosive Power and Muscle Strength of the Hip and Trunk Joints of Elite Golfers.

ABSTRACT: Suhara, H, Nariai, M, Takagi, T, Akiyama, K, Nagashima, J, and Shiraki, H. Relationship of clubhead speed with explosive power and muscle strength of the hip and trunk joints of elite golfers. J Strength Cond Res 37(4): 859-865, 2023-In golf, the driving distance of the ball is affected by the clubhead speed (CHS) on impact. We aimed to clarify the relationship between CHS and explosive power and muscle strength of the hip and trunk muscles in elite golfers (male age: 19.6 ± 1.9 years, male handicap: 4.4 ± 0.9, female age: 17.7 ± 1.4 years, and female handicap: 6.2 ± 0.7). A correlational design was used to assess the relationships between CHS and strength (hip extension-flexion and trunk rotation of peak torque at an isokinetic 60 and 180°·s -1 angular velocity) and CHS and power (countermovement jump [CMJ]; peak power and jump height; backward overhead medicine ball [BOMB] throw). Fourteen each of male and female elite golfers were included. The CHS during the golf swing was measured using a Doppler radar measurement device (Trackman). A correlation analysis between each measurement and CHS ( p ≤ 0.05) was conducted. We found that the peak torque of right hip extension at an angular velocity of 180°/s (male, r = 0.67; female, r = 0.61), peak CMJ power (male: r = 0.63, female: r = 0.75), and BOMB throw distance (male, r = 0.6; female, 0.6) were positively correlated with CHS in both male and female golfers. These results suggest that the extensor strength of the lower extremities and trunk, centered on the hip joint in the sagittal plane, is important for physical fitness and muscle strength measurement related to CHS. Conversely, concentric trunk rotator strength and CHS were not correlated, suggesting that concentric trunk rotator strength may not be actively involved in CHS.

Difference of Hamstring Activity Between Bilateral and Unilateral Nordic Hamstring Exercises With a Sloped Platform.

CONTEXT: This study aimed to examine the differences in electromyographic (EMG) activity of the biceps femoris long head (BFlh) and semitendinosus (ST) muscles, break-point angle (BPA), and the angle at peak BFlh EMG activity between bilateral and unilateral Nordic hamstring exercise (NHE) on a sloped platform. DESIGN: This study was designed as a case-control study. METHODS: Fourteen men participated in the study. The participants initially performed maximum voluntary isometric contraction (MVIC) on the prone leg curl to normalize the peak hamstring EMG amplitude as the %MVIC. Then, participants were randomized to perform the following 3 variations of NHE: bilateral (N40) or unilateral (N40U) NHE with a platform angle of 40°, and unilateral NHE with a platform angle of 50° (N50U). The EMG activities of the BFlh and ST and the knee flexion angle during the NHE variations were recorded to calculate the EMG activity of the BFlh and ST in terms of the %MVIC, the angle at peak BFlh EMG, and BPA. RESULTS: The BFlh %MVIC was significantly higher in N40U (P < .05) and N50U (P < .05) than in N40. A significant difference in BFlh %MVIC and ST %MVIC was observed between N40U (P < .05) and N50U (P < .05). The mean values of BPA and the angle at peak BFlh EMG were <30° for all NHE variations. CONCLUSIONS: In the late swing phase of high-speed running, BFlh showed higher EMG activity; thus, unilateral NHE may be a specific hamstring exercise for hamstring injury prevention.

Liver choline metabolism and gene expression in choline-deficient mice offspring differ with gender.

Choline is an important nutrient during pregnancy and lactation. Maternal choline deficiency in CD-1 mice lowers liver betaine levels in male offspring. By contrast, it increases elovl3 and vanin-1 mRNA levels in female offspring. Taken together, these observations suggest gender-specific responses to a choline-deficient diet.

Effect of Different Slopes of the Lower Leg during the Nordic Hamstring Exercise on Hamstring Electromyography Activity.

The purpose of this study was to examine whether the NHE with an increased lower leg slope angle would enhance hamstring EMG activity in the final phase of the descend. The hamstring EMG activity was measured, the biceps femoris long head (BFlh) and the semitendinosus (ST). Fifteen male volunteers participated in this study. Subjects performed a prone leg curl with maximal voluntary isometric contraction to normalize the hamstring EMG activity. Subsequently, subjects performed the NHE, with the help of a certified strength and conditioning specialist, while the lower leg slope angle were randomly set at 0° (NH), 20° (N20), and 40° (N40). To compare hamstring EMG activity during the NHE variations, the knee flexion angle was set in the range from 0° to 50°, divided into five phases (0-10°, 10-20°, 20-30°, 30-40° and 40-50°), where 0° indicated that the knee was fully extended. To calculate the knee extension angular velocity, the knee flexion angle divided by time, and break point angle (BPA) was the angle at which 10°/s was exceeded. In the statistical analysis, a two-way repeated measures ANOVA was used for the hamstring EMG activity and a one-way repeated measures ANOVA was used for the BPA. The EMG activity of the BFlh and the ST in N20 and N40 was significantly higher than in NH at knee flexion angle of 0-20° (p < 0.05). For the BPA, NH (57.75° ± 13.28°), N20 (36.27° ± 9.89°) and N40 (16.26° ± 9.58°) were significantly higher in that order (p < 0.05). The results of this study revealed that the NHE with an increased lower leg slope angle shifted the BPA to the lower knee flexion angle and enhanced the hamstring EMG activity in the final phase of the descent.

Elite Male Lacrosse Players' Match Activity Profile.

Match demands in international men's lacrosse have yet to be explored. Therefore, this investigation quantified positional match demands of international men's lacrosse. This study quantified activity profiles of 50 lacrosse players [attack (AT): 11, midfield (MD): 22, defense (DF): 17] on Japan's national team, using a global positioning system (GPS), players' acceleration, and a heart rate (HR) apparatus to investigate their movement and physiological load. The study revealed that in thirteen international matches, distance, walk distance, jog distance, low-intensity acceleration, and low-intensity deceleration for the AT and DF groups was significantly greater than for the MD group, but the MD group's average speed and sprint distance were the highest. Multiple comparison tests showed that measurements for the AT and DF groups were significantly greater than the MD group for distance, low-intensity acceleration, medium-intensity decelerations, and low-intensity deceleration. This data can become the physical data for helping coaches with strength and conditioning training at the international level. For MD players, anaerobic power and load condition (long rest, high intensity) should be emphasized. In addition, coaches can decide on tactics and a running-quantity target for the next game by acquiring continuous activity data.

The Validity and Reliability of a Smartphone Application for Break-Point Angle Measurement during Nordic Hamstring Exercise.

Background: A recently developed smartphone application (Nordic Angle) allows the automatic calculation of the break-point angle (BPA) during Nordic hamstring exercise (NHE) without transferring the collected data to a computer. The BPA is the point at which the hamstrings are unable to withstand force. However, the validity of the BPA values obtained by this method has not been examined. Hypothesis/Purpose: This study aimed to evaluate the validity and reliability of the Nordic Angle by comparing the BPA values of the Nordic Angle with those of two-dimensional motion analysis software that can calculate the angles and angular velocities of various joints. Study Design: Cohort assessing Validity and Reliability. Methods: The validity of the Nordic Angle BPA data was verified by Spearman's correlation test for consistency with the movement analysis data, and the magnitude of the correlation was indicated by rs. The agreement between these measurements was examined using the Bland-Altman analysis. The reliability of the Nordic Angle and motion analysis was examined using the intraclass correlation coefficient (ICC) (1,k) based on data from repeated trials within a day. Results: Although the spearman correlation between the Nordic angle and the angle determined using motion analysis did not reach statistical significance (p = 0.052), a very large correlation was present (rs = 0.75). The difference between the mean values of the Nordic Angle and motion analysis was 0.4 ± 2.1°, and the limits of agreement ranged from -3.9° to 4.6°. In two BPA measurements, the Nordic Angle showed perfect reliability (ICC = 1.00, p < 0.001), while motion analysis showed nearly perfect reliability (ICC = 0.97, p < 0.001). Conclusion: The Nordic Angle, which has both validity and reliability, may be appropriate for field measurement because it allows immediate feedback of BPA and the measurement of many athletes. Level of evidence: 3b©The Author(s).

The effect of pads on foot morphology in athletes with medial tibial stress syndrome.

BACKGROUND: Evaluation of the effect of a pad on foot morphologies in patients with medial tibial stress syndrome (MTSS) requires more reliable and objective methods, rather than conventional subjective observations. OBJECTIVE: The objective of this study was to investigate the effect of pads on foot morphologies during quiet standing in athletes with MTSS. METHODS: We measured three-dimensional foot morphologies in 30 feet with MTSS and 40 healthy feet. RESULTS: The analysis showed that Hallux valgus degree, calcaneal angle, arch height, and arch height ratio differed significantly as a result of the pad support, compared to no pad support in the MTSS group. The pad support only resulted in significant differences in arch height, compared to no support in the control group. Furthermore, thumb side angle, calcaneal angle, and arch height ratio were significantly different between the MTSS and control groups. CONCLUSIONS: Our study results suggest that changes in foot morphologies because of the use of a pad can be measured objectively in patients with MTSS.

The relationship between shot velocity and physical characteristics of lacrosse players.

BACKGROUND: This study was designed to quantify the relationship between the velocity at which lacrosse players can shoot a lacrosse ball (shot velocity) with a lacrosse stick and a variety of physical strength attributes. METHODS: Twenty lacrosse athletes were recruited to participate in the study. We measured shot velocity with a microwave, speed-measuring apparatus. RESULTS: Shot velocity showed significant and moderate correlations with the distance a player can throw a medicine ball (r=0.58-0.66), the height at which a player could jump vertically from a crouching position (r=0.44-0.46), a player's hand grip strength (r=0.33-0.46), and the isokinetic concentric strength of player knees (r=0.20-0.45). The thrown distance of a medicine ball was significantly and moderately correlated with vertical jump height (r=0.32-0.47) and hand grip strength (r=0.33-0.53), respectively. CONCLUSIONS: Strength and conditioning coaches should train lacrosse players in strengthening their core, lower extremities and in movements that link their arms with the lower part of the body. The muscular strength of trunk rotation, which relies on the strength of the arms and lower limbs, greatly enhances a player's ability to shoot a lacrosse ball at high velocities.

Shear Modulus of the Lower Leg Muscles in Patients with Medial Tibial Stress Syndrome.

This study aimed to investigate the in vivo kinematics of shear modulus of the lower leg muscles in patients with medial tibial stress syndrome (MTSS). The study population included 46 limbs with MTSS and 40 healthy limbs. The shear modulus of the medial head of the gastrocnemius, lateral head of the gastrocnemius, soleus, peroneus longus and tibialis anterior muscles were measured using shear wave ultrasound elastography. As a result, the shear modulus of the lower leg muscles was significantly greater in patients with MTSS than in healthy patients (p < 0.01). Based on the differences in shear modulus of lower leg muscles between the patients with MTSS and healthy patients, the measurements obtained via shear wave ultrasound elastography could be used to evaluate risk factors of MTSS.

Analysis of the talocrural and subtalar joint motions in patients with medial tibial stress syndrome.

BACKGROUND: The rearfoot motion during sports activities in patients with the medial tibial stress syndrome (MTSS) is unknown. This study aimed to investigate the difference in kinematics of the rearfoot in MTSS patients (eight male soccer players) and control participants (eight male soccer players) during a forward step. METHODS: Sixteen male soccer players, including eight players with MTSS, participated. Forward step trials were recorded with cineradiographic images obtained at a sampling rate of 60 Hz. Geometric bone models of the tibia and talus/calcaneus were created from computed tomography scans of the distal part of one lower limb. Following a combination of approaches, anatomical coordinate systems were embedded in each bone model. The talocrural joint motion (relative motion of the talus with respect to the tibia) and subtalar joint motion (relative motion of the calcaneus with respect to the talus) were examined. RESULTS: A significantly larger range of internal/external rotation and inversion/eversion motion was observed in the subtalar joint of MTSS patients compared to healthy controls (P < 0.05) from heel contact to heel off. There were no significant differences between the MTSS patients and healthy participants in the ranges of all talocrural joint angles during the forward step. CONCLUSION: Our results indicate that the range of subtalar joint motion is greater in patients with MTSS during the stance phase of the forward step. The kinematic results obtained of this study may have important clinical implications and add quantitative data to an in vivo database of MTSS patients.

Structural deformation of longitudinal arches during running in soccer players with medial tibial stress syndrome.

The purpose of this study was to compare angular change and translational motion from the medial longitudinal arch (MLA) and lateral longitudinal arch (LLA) during running between medial tibial stress syndrome (MTSS) and non-MTSS subjects. A total of 10 subjects volunteered, comprising 5 subjects with MTSS and 5 subjects without injury (non-MTSS) as the control group. All subjects performed the test movement that simulated running. Fluoroscopic imaging was used to investigate bone movement during landing in running. Sagittal motion was defined as the angular change and translational motion of the arch. A Mann-Whitney U-test was performed to determine the differences in the measured values between the MTSS and non-MTSS groups. The magnitude of angular change for the MLA and LLA was significantly greater for subjects with MTSS than for control subjects. Translational motion of the MLA and LLA of the MTSS group was also significantly greater than that of the non-MTSS group (all p < 0.05). Soccer players with MTSS have an abnormal structural deformation of foot during support (or stance) phase of running, with a large decrease in both the MLA and LLA. This abnormal motion could be a risk factor for the development of MTSS in these subjects.