An investigation into the effects of the Mojoband on segmental accelerations and peak club head speed in golf.
By Dr Mark Bull - PHD in Sport Exercise and Rehabilitation Science and fully qualified PGA Golf coach
This study will explore and investigate the effects of the Mojoband on segmental accelerations and peak club head speed in golf. Participants will hit five golf shots wearing both the Mojoband and no band in a random order, participants will wear the Mojoband and/or no band both blind to themselves and the researcher. Pre and post analysis will then be carried out exploring any influence the Mojoband has on segmental accelerations and peak club head speed compared to wearing no band.
2.0 Literature Review
Improving golf swing performance and club head speed has long been an objective of many golfers. Golf ball carry distance/displacement is innately connected to club head speed (allowing for the five impact conditions, Langdown, 2012), therefore long tee shots explain Bull & Bridge (2012) have been found to contribute 44% of strokes gained against the field measure for the top ten long game players on the PGA Tour between 2003 and 2010 (Broadie, 2012). To provide an example of the influence of driving distance, during 2012 Tiger Woods gained 2.08 strokes or 65% of his total of 3.20 strokes gained on the field from his long game (Broadie, 2012).
When examining the influence of the golf swing’s contribution on club head speed and subsequent ball carry distance, multiple physiological influences need considering, amongst them suggest Hellström (2009) is how the golfer requires strong and powerful lower limb muscles to generate high forces and torques against the ground and alongside this, high rotational, powerful movements in the thorax and arms. Additionally state Brown et al (2011) the pelvis and thorax are likely to have an important and influential role in accelerating the clubhead towards impact. Much of this mechanism connects back to the summation of speed principle described by Bunn (1972) and later by Putnam (1993) who discussed the influence of the proximal segment acceleration and reaching peak speed first within chain of movement, then slowing down to allow the acceleration/deceleration of the more distal segments in a sequential way to allow for maximum distal speed and optimal timing of the application of this force, Bull and Bridge (2012).
The proximal segment in golf would be considered to be the pelvis whereas the distal segment would be considered to be the club head. Research by Cheetham et al. (2001), Cheetham et al. (2008) and Cheetham (2010) and has shown this occurs through the power of the leg muscles rotating the pelvis forward towards the target, the pelvis then accelerates, but quickly decelerates, transferring energy to the thorax (Cheetham, 2010, Cheetham et al., 2001). This pattern is continued with an acceleration and deceleration of the thorax which transfers energy to the lead arm and finally to the club (Cheetham, 2010). Additionally, Callaway et al. (2012) add how this sequential order should continue throughout the downswing, at which all body segments are accelerating and then decelerating with the specific objective to deliver the club to impact with the ball at maximum speed. Therefore it could be considered that the acceleration and deceleration of the body’s segments could be of influence on club head speed and subsequent ball carry distance.
A repeated measures design was used to study the effect of the intervention on golf swing segmental peak accelerations and peak club head speed at impact. Using a dependant T test, the dependant variables investigated are pelvis, thorax, lead arm, lead hand acceleration and club head speed with the independent variable being the wearing/non wearing of the Mojoband.
Fifty participants (category one – handicap <5) were chosen as the sample population for the study as they have been shown to have a reduced variability in their swing mechanics and would therefore produce more reliable swing mechanics increasing the internal validity of the results. Mean handicap was 1.1 SD± 1.76. Participants were recruited from local golf clubs, by word of mouth and from the clientele of local professional golf coaches.
Participant breakdown consisted of forty eight right hand a nd two left hand participants consisting of 49 males and 1 female. Participants mean age was 29.42 years SD ±7.02 years. Participants expressing an interest in the study were given written information about the study covering its purpose and commitment required from them should they participate. They were also given the opportunity to question the investigator about the study.
4.0 Common data collection procedure
Participants were asked to hit ten 6 iron shots onto an open-air driving range. Each participant wore typical golf attire and golf shoes and went through their normal warm up routine prior to all testing. Once fully warmed up, participants hit shots from a driving range mat at full speed toward a designated target on the driving range with all testing carried out using full compression balls. The target was located so that a line drawn between it and the position of the ball on the driving range mat was parallel to the x-axis of the global frame. Each participant hit five shots with a Mojoband secured to the thorax sensor bracket and five shots without any band secured to the bracket, making ten shots in total. The bands were attached blind to the participant by a 3rd party therefore blind to the researcher, therefore neither the researcher or participant knew if a band or no band had been attached, see picture 1. The order the band was applied changed between each participant therefore the sequence of each participant was participant one no band – Mojoband, participant two Mojoband – no band with this sequential pattern continuously applying to all participants throughout the study.
Three-dimensional kinematic data was collected using a Polhemus G4 dual hub electromagnetic tracking system (Polhemus Inc., Colchester, VT, USA), sampling at 120 Hz. Polhemus G4 trackers provides realtime, six degrees of freedom motion tracking that according to Polhemus has a static RMS of 2.0 mm for sensors X, Y and Z in position and orientation RMS of 0.50mm orientation (https://polhemus.com/_assets/img/Polhemus_Tracking_Performance_Comparison_Chart.pdf). Polhemus G4 works through the use of electromagnetic sensors distorting an electromagnetic field created by a global transmitter (source) located 25cm behind the golfer. See picture two. Sensors were secured to the participant by using a small, slim body harness, which offered little or no resistance or interference to the participant during their swing.
Sensors were placed on the participants at the following body landmarks; middle of second metacarpal on dorsal side of the hand, lateral and proximal section of the humerus, centre of forehead, third vertebrae thoracic spine, lumbo-sacral joint and attached to the club shaft using a lightweight plastic clasp just below the base of the grip, however this sensor was not used to collect and data throughout the study as it primary use was to calibrate each body segment and provide an accurate representation of the club within the animation. Peak impact club head speed was captured and produced using a Trackman 4.0 launch monitor radar. Trackman is a dual radar tracking device that provides club head delivery and ball flight and dispersion data (https://trackmangolf.com/products/trackman-4). Trackman was calibrated and aligned to the target prior to data capture and placed precisely on the X axis, 5ft directly behind the ball. See picture two.
Bull3D motion capture were used in this study, this transformed the raw sensor data into anatomical segmental data, and these are outlined below. Table 1 shows the points digitised during the calibration using a 10 cm pointer pen. This allowed the sensors to be located within the magnetic field created by the transmitter, and the resultant construction of anatomical segment axes.
5.0 System set up, participant calibration and data collection
Subjective error was minimised by having the same person (the researcher) perform system set up, sensor placement, calibration and swing capture on all participants throughout all captures allowing for reduced chance of error and enhance reliability and accuracy of data.
The same 3rd party independently attached the band (or no band) to the participants, therefore, reducing any subjective error allowing for greater validity and repeatability throughout testing.
Based on the literature review, variables were selected that showed the closest association to the production of club head speed alongside the actual impact club speed as well. Selected variables were calculated for each shot from the 3D swing data using the Bull3D software. The following variables were calculated: Axial rotational (rot) accelerations for the following segments: pelvis, thorax, lead upper arm, and lead hand. Club head impact speed was produced via Trackman data.
5.2 Common variable calculations
The angular velocity of the pelvis and thorax segments were the axial rotational velocity about the z axis of the local (anatomically referenced) coordinate systems. This axis was normal to the plane of the medial-lateral and anterior-posterior unit vectors that run from left to right greater trochanters (for the pelvis) and from posterior to anterior. The centres of the two shoulder joints defined the medial-lateral axis for the thorax. The z-axis of the thorax had an approximate vertical orientation when the body is in an erect posture. Segment accelerations are calculated based on the segment angular velocity. By taking the differential of the same therefore if the angular velocity is w(t) and in discrete time w(n) then the acceleration is Lim(w(t + delt)-w(t))/delt , delt tends to 0 in continuous time. Angular acceleration is the derivative of angular velocity. In discrete time angular acceleration is (w(n)-w(n-1))/delt, delt – is the time difference between two samples, from this peak acceleration is produced.
5.3 Critical events
Peak pelvis, thorax, lead arm and lead hand accelerations were defined as the peak acceleration values produced during the downswing phase in the golf swing. Downswing is defined by the phase between top of backswing (minimum negative pelvis rotation) and impact (peak club head speed), (Bull3D, n.d).
Club head speed is defined by the club speed, the linear speed of the club head’s geometric centre just prior to first contact with the golf ball, https://blog.trackmangolf.com/club-speed/
5.4 Definition and unit
Table 2 lists the definition of key variables and unit used.
6.0 Data analysis
Individual participant variables were measured and calculated and any effects of the intervention on these variables were examined. This was carried out by using a repeated measures paired dependant samples t-test on the mean scores between groups – Mojoband, No band. The overall type I error rate for each analysis was set at α=0.05. All data are reported as mean ± standard deviation and with 95% confidence intervals unless otherwise stated.
Peak pelvis acceleration. Mojoband produced a significantly different peak pelvis acceleration 2237.4 d/s/s compared to no band 2175.2 d/s/s (t49=2.98, p=.004 r=.95).
Peak thorax acceleration. Mojoband produced a significantly different peak thorax acceleration 3495.2 d/s/s compared to no band 3415.4 d/s/s (t49=2.16, p=.04 r=.95).
Peak lead arm acceleration. There was no significant lead peak arm acceleration difference between Mojoband 4361.7 d/s/s compared to no band 4291 d//s/s (t49=1.81, p=.7 r=.94).
Peak lead hand acceleration. There was no significant lead peak hand acceleration difference between Mojoband 7339.8 d/s/s compared to no band 7330.6 d//s/s (t49=0.19, p=.9 r=.94).
Peak club head speed. Mojoband produced a significant different peak clubhead speed 86.04 mph compared to no band 85.1 mph (t49=2.95, p=.005 r=.97).
The purpose of this study was to investigate the influence of Mojoband on segmental accelerations and peak club head speed in golf. Previous research by Cheetham et al (2001), Cheetham (2010) and Brown et al. (2011) have discussed how segmental acceleration in golf has shown an association to increased ball displacement. Langdown et al. (2012) describe how golf ball displacement which inherently relates to driving distance is essentially controlled by club head speed (allowing for impact conditions) therefore it may be fair to state that increased segment acceleration and club head speed in golf leads to increased ball displacement/distance.
Broadie (2012) findings provide a connection between increased driving distances to strokes gained on The PGA Tour between 2003-10.
When wearing the Mojoband, participants showed a statistically significant increase in peak pelvis acceleration compared to no band (2237 d/s/s vs. 2175 d/s/s), increased thorax peak speed compared to no band (3495 d/s/s vs. 3415 d/s/s) and in increase in peak club head speed compared to no band (86.04mph vs. 85.09mph). There was no significant change in both peak lead arm and peak lead hand acceleration. Although the gains were small, they were considered of statistical significance. Trackman (https://blog.trackmangolf.com/ball-speed/_) suggest for every 1 mph change in club head speed (allowing for no change in ball/club impact conditions) this equates to an increase in 2 yards driving distance. All segment accelerations showed large standard deviations, much of this could be related to the variability in age of the participants as this was the main variable throughout as all participants were category one golfers which reduces the influence of swing and movement variability as they have shown to have more predictable and reliable golf swings. However, despite being classified as category one golfers, there was much variability in each participants golf swing movement/technique which could lead to evident and notable differences In segmental movement and acceleration alongside club head speed as suggested by Neal et al (2008) who reported how movement can remain the same however the outcome can be variable whereas Tucker et al (2013) showed how movement can be variable however the outcome remains the same. In addition, participants can respond individually therefore more time may be required to allow any such influence to show any tangible changes. Additionally, a 6 iron was used throughout the study, using different clubs, mainly a driver may produce different results as despite explicit guidance provided to the participants before testing, iron clubs are typically associated with accuracy and control whereas the driver is more commonly connected to driving distance.
9.0 Future research
Future research may wish to explore the neurophysiological properties and behaviours when wearing the Mojoband as what is not currently known is what changed neurologically and physiologically to produce the increases in pelvis peak speed, thorax peak speed and peak club head speed. Alongside this, wearing the Mojoband over increased periods of time to plot and assess more accurately the influence the band may have as well as inverting this process – removing the Mojoband from participants that have worn the band for lengthened periods of time to see if any regression exists, therefore providing and allowing for an A-B and B-A exploration both ways – no band/wear band measure and wear band/remove band measure.
Although small, wearing the Mojoband has shown to statistically increase peak pelvis acceleration, peak thorax acceleration and peak club head speed.
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