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. Author manuscript; available in PMC: 2023 Feb 1.
Published in final edited form as: Sports Biomech. 2019 Aug 27;21(2):165–178. doi: 10.1080/14763141.2019.1649452

Three-dimensional kinematics in healthy older adult males during golf swings

Anna C Severin 1, Stewart A Tackett 1, C Lowry Barnes 1, Erin M Mannen 1,*
PMCID: PMC7044058  NIHMSID: NIHMS1536180  PMID: 31453740

Abstract

The biomechanics of the golf swing has received considerable attention in previous research. However, existing studies have focused on young athletes, while the kinematics of older golfers remain poorly documented. This study presents kinematic data for healthy senior golfers during swings performed with a driver and six-iron. Seventeen male golfers (62.2±8.8 years) volunteered for participation and a 10-camera Vicon system (Oxford, UK) recorded kinematic data (500 Hz). A launch monitor (TrackMan, Vedbæk, Denmark) recorded club head speed and initial ball speed. Joint angles and peak velocities of the trunk and lower body were extracted at the top of the backswing, ball contact, and end of the swing. Intraclass correlations and standard error of measurement determined reliability, and pairwise statistics determined between-club differences. Swings with the driver had 7.3° less trunk extension and 4.3° less X-factor at backswing, and 10.5° less trunk flexion and 3.2° less X-factor at ball impact. Older adults portray several differences in lower body kinematics between a six-iron and driver but maintain good to excellent reliability (0.728-0.997) during the swings. Comparisons with previous research also showed senior athletes produce slower club head and ball speeds than younger golfers, and that kinematic differences exist between the populations.

Keywords: seniors, biomechanics, reliability, performance

Introduction

Golf is an increasingly popular sport and is practiced by individuals of all ages (Marta, Silva, Castro, Pezarat-Correia, & Cabri, 2012). It is considered a low impact activity with both physical and social benefits (Gulgin, Armstrong, & Gribble, 2009; Marta et al., 2012), and is therefore often suggested for older adults to meet recommended levels of physical activity (ACSM’s guidelines for exercise testing and prescription, 2013). Golf offers enjoyment, has a distinct purpose, and supports socialization, which are factors known to encourage older individuals in particular to adhere to physical activity (Costello, Kafchinski, Vrazel, & Sullivan, 2011). However, in order to safely prescribe and recommend regular golf practice to older individuals, it is important to have a comprehensive understanding of the demands it places upon the aging body.

The golf swing motion has frequently been examined by biomechanical researchers and has been analysed from both a performance (Betzler, Kratzenstein, Schweizer, Witte, & Shan, 2006; Joyce, Burnett, Cochrane, & Ball, 2013) and injury perspective (Cole & Grimshaw, 2016; Goebel, Drollinger, & Drollinger, 2018). However, these reports have focused on young individuals, providing limited understanding on the mechanics of older golfers. To produce successful golf swings, the athlete must generate fast club head speeds (Hume, Keogh, & Reid, 2005), generally through powerful trunk and body rotations (Joyce et al., 2013; Peterson & McNitt-Gray, 2018). The swing is a fast and powerful motion, its outcome is strongly dependent on the performers’ strength, coordination and power (Lewis, Ward, Bishop, Maloney, & Turner, 2016), and it places high demands on hand-eye coordination, postural control and balance (Peterson, Wilcox, & McNitt-Gray, 2016). Many of these abilities are known to decline with age (Alcock, O’Brien, & Vanicek, 2015; Brooks & Faulkner, 1994), which likely have consequences on golfing performance and mechanics.

Several biomechanical variables have been highlighted in the literature as important contributors for club head speed and performance, including the transverse plane separation between the trunk and pelvis (termed the X-factor) (Joyce, 2017a), the rotations about the hips (Gulgin et al., 2009), and ground reaction forces (Peterson & McNitt-Gray, 2018). The X-factor has been of particular interest in the biomechanical literature with strong scientific evidence highlighting its importance for performance (Brown, Selbie, & Wallace, 2013; Joyce, 2017a; Joyce, Burnett, & Ball, 2010). In addition, skilled golfers have been described to initiate the forward rotation of the hips while the shoulders lag behind and thereby creating an ‘X-factor stretch’, which is thought to utilise a recoil effect and thus result in even faster club head speeds and improved performance (Cheetham, Martin, Mottram, & St Laurent, 2001; Joyce, 2017a; Joyce et al., 2010). These variables have frequently been quantified in young golfers (Betzler et al., 2006; Egret, Vincent, Weber, Dujardin, & Chollet, 2003; Gulgin et al., 2009; Peterson & McNitt-Gray, 2018), but the literature on senior golfers’ mechanics is limited. Most reports involving older adults have quantified their golfing activity following orthopaedic surgeries (Jacobs, Christensen, & Berend, 2009; Papaliodis, Photopoulos, Mehran, Banffy, & Tibone, 2017). It has been reported that older golfers utilise reduced shoulder range of motion (ROM) compared to younger golfers (Mitchell, Banks, Morgan, & Sugaya, 2003), and it is known that age affects the mechanics of tasks such as gait (Alcock et al., 2015), however, research to quantify the golf swing mechanics of healthy older adults is lacking.

A game of golf requires several clubs and it is not uncommon that researchers include more than one type of club in their analysis to examine the effect on the golf swing (Egret et al., 2003; Joyce et al., 2013; Peterson & McNitt-Gray, 2018). These reports agree that different clubs generate different club head speeds and affects the kinematics of the trunk, shoulders and lower body. However, the research on the effects of different clubs on swing mechanics is also limited to young athletes (Egret et al., 2003; Joyce et al., 2013), leaving the understanding of these effects on the mechanics of senior golfers unknown.

The aim of this study was therefore to examine the golf swing kinematics of healthy older experienced golfers using a driver and a six-iron. It was hypothesised that (1) kinematic differences would exist between the two clubs, and (2) older adults would use different kinematics during swing than those reported in the literature for younger individuals.

Methods

Participants

Seventeen healthy older male golfers (1.77±0.07 m, 91.3±11.1 kg, 62.2±8.8 years) volunteered for participation in this study. All participants were right handed, active golfers with a self-reported handicap of 15 or less (8.7±4.9) and were free from previous orthopaedic surgeries and injuries within the last six months. Written informed consent was obtained before any data collection in agreement with the University of Arkansas for Medical Sciences’ Institutional Review Board study approval.

Procedure

The motion capture system was calibrated before each data collection, with the criteria that the global error was less than 0.2 mm for every camera. The participants were fitted with low-mass retroreflective markers (14mm) on the following landmarks: C7, T5, T10, manubrium, xiphoid process, and bilaterally on the anterior superior iliac spine, posterior superior iliac spine, iliac crest, greater trochanter, medial and lateral epicondyle of the femur, medial and lateral malleolus, calcaneus, and the heads of the 1st, 3rd, and 5th metatarsals. Additionally, marker clusters were attached laterally on the mid-thighs and shanks and all participants wore the same model Nike Trophy golf shoes. Kinematic data were recorded using a 10-camera motion capture system (Vicon, Oxford, UK) operating at 500 Hz, and a dual radar golf launch monitor (TrackMan 4, TrackMan A/S, Vedbæk, Denmark) was set up behind the participant to record club and ball performance parameters.

The floor was covered in a layer of artificial turf (Peterson & McNitt-Gray, 2018) that, combined with the golf shoes, provided frictional characteristics similar to that of a golf course. A static trial was performed with each participant standing in the anatomical position. Participants were then instructed to hit the golf ball into a net placed 5 metres in front of them, aiming at a piece of string on the net that provided a target. Each participant was allowed as many practice swings as they wanted to warm up and then performed shots using their own driver and six-iron. Eight shots were recorded for each club (Severin, Barnes, Tackett, Barnes, & Mannen, 2019).

Data processing

All kinematic data were imported into Visual3D (C-motion, Germantown, MD, USA) for processing and analysis. The data were filtered using a 4th order Butterworth filter at 4 Hz, based on a residual analysis (Winter, 2009). The global coordinate system was designed so that the positive X-axis pointed left to right from the participants’ perspective, the positive Y-axis pointed anteriorly, and the positive Z-axis pointed vertically. The static trial was used to establish zero joint angles (Joyce et al., 2013) and all joint angles were constructed in accordance with ISB standards (Wu et al., 2002) where flexion, adduction and internal rotation were considered positive. All joint data from the left side of the body were modified to conform to these conventions. Based on recommendations from previous research, the X-factor was defined by determining the motions of the thoracic segment (defined between the shoulders and T10 marker) (Joyce et al., 2013) with the segmental coordinate system of the pelvis as reference (Brown et al., 2013), in a Cardan coordinate system of YXZ (lateral bending, flexion/extension, axial rotation) (Joyce et al., 2013). For consistency, the trunk angles about all planes of motion were derived using this method, however, since the term ‘X-factor’ is limited to describe transverse plane motions only, the term ‘trunk’ will be used throughout this paper to describe trunk motion in flexion, extension and lateral bending.

Three key events were identified throughout the swing motion: the top of the backswing, which was defined as the point where the trunk rotation changed direction in relation to the global coordinate system, the ball impact, which was the point at which the club impacted the ball, and the end of the swing which was the point of peak trunk rotation to the left after ball impact. The ball impact was identified using a time-synchronised digital video camera (Vicon, Oxford, UK). Using these events, the golf swing was divided into three phases: (1) the backward swing – from address to the top of the backswing, (2) the downward swing – from the top of the backswing to ball impact, and (3) the follow through – from ball impact to end of the swing. Kinematic variables of interest included three dimensional joint angles of the trunk, pelvis, hips, knees and ankles at each of the identified events as well as the peak velocities for each joint between the top of the backswing and end of the swing. The X-factor stretch was also extracted as the maximal X-factor value during the downward swing phase. In addition, club head speed and initial ball speed were extracted from the launch monitor for each shot to indicate performance.

Statistical analysis

All statistical analyses were performed in SPSS Statistical software v. 25 (IBM Corp., Armonk, NY, USA). The within-trial reliability of each variable was determined with intra-class correlation coefficients (ICC (3,1)) and standard error of the mean (SEM) (Joyce et al., 2013). ICC values >0.750 were considered excellent, values between 0.600 and 0.750 were considered good, values between 0.400 and 0.750 were considered fair, and values <0.400 were considered poor (Joyce et al., 2013). Shapiro-Wilk’s test determined normality and Levine’s test assessed the equality of variances. Where appropriate, a paired samples T-test or Wilcoxon signed ranks test was performed to test for differences in joint angles and velocities between clubs. Cohen’s d effect sizes were calculated and were considered large if d >0.8, moderate if 0.5< d <0.8 and small if d <0.5 (Cohen, 1988). The alpha level was set at p<0.05.

Results

The results showed that the driver produced higher club head speed (driver: 39.4 ± 4.4 m/s, six-iron: 33.8 ± 4.4 m/s, p=0.001, d=1.28) and ball speed (driver: 56.1 ± 7.3 m/s, six-iron: 45.1 ± 6.0 m/s, p<0.001, d=1.66) compared to the six-iron. However, the X-factor stretch was not different between the clubs (driver: 35.8 ± 11.6°, six-iron: 37.9 ± 8.1°, p=0.270, d=0.22).

The analysis showed several differences in joint orientation at the key events between the two clubs (Table 1, 2 and 3). Particularly, at the top of the backswing, the golfers had on average 7.3° more trunk extension and 4.3° more X-factor when swinging with the 6-iron. At ball impact, the driver had on average 10.5° less trunk flexion and 3.2° less X-factor than the 6-iron. The analysis also revealed that the amount of pelvic anterior tilt was less with the driver and that the amount of axial rotation towards the lead leg was greater when using the driver (top of backswing: average 1.1° less anterior tilt and 2.0° more axial rotation, ball impact: average 1.7° less anterior tilt and 5.2° more axial rotation, and end of swing: average 1.0° less anterior tilt and 6.4° more axial rotation). Significant differences also existed about the sagittal and frontal plane motions of both hips, and the frontal plane motions of both ankles (Table 1 and 2). The only significant transverse plane differences were those about the pelvis and trunk. The analysis also showed that the participants had consistently good to excellent reliability during the swings with lowest values in the frontal plane (driver ICC range: 0.780-0.985, 6-Iron ICC range: 0.721-0.997) (Tables 1-3).

Table 1.

Mean ± SD for sagittal plane joint angles during three key events of the golf swing. Positive angles represent flexion/posterior tilt/dorsiflexion and negative values represent extension/anterior tilt/plantarflexion.

Driver 6-iron
Event Segment/Joint Angle (°) ICC SEM Angle (°) ICC SEM d p-value
BS Trunk −28.3 ± 5.6 0.946 1.40 −35.6 ± 6.6 0.980 1.27 1.20 <0.001
Pelvis −14.2 ± 3.8 0.908 0.92 −15.3 ± 4.3 0.885 1.04 0.25 0.021
Lead hip 17.7 ± 10.5 0.960 2.54 19.1 ± 11.1 0.991 2.68 0.13 0.398
Lead knee 45.2 ± 10.0 0.968 2.43 48.6 ± 8.4 0.992 2.03 0.37 0.026
Lead ankle −0.9 ± 5.6 0.931 1.36 0.3 ± 4.8 0.986 1.17 0.22 0.094
Trail hip 27.8 ± 9.7 0.977 2.36 26.6 ± 7.7 0.983 1.86 0.12 0.519
Trail knee 26.6 ± 12.5 0.962 3.02 23.7 ± 11.0 0.989 2.67 0.25 0.074
Trail ankle −14.4 ± 7.6 0.971 1.84 −16.2 ± 6.4 0.985 1.55 0.26 0.043
BI Trunk 30.4 ± 5.9 0.971 1.79 40.9 ± 5.8 0.991 1.33 1.82 <0.001
Pelvis −0.5 ± 6.1 0.977 1.47 −2.2 ± 6.4 0.932 1.55 0.27 0.010
Lead hip 11.7 ± 7.5 0.971 1.81 13.4 ± 7.6 0.990 1.83 0.24 0.046
Lead knee 23.5 ± 9.2 0.874 2.23 23.7 ± 8.7 0.962 2.10 0.02 0.922
Lead ankle −15.2 ± 9.1 0.932 2.20 −14.3 ± 9.7 0.989 2.36 0.09 0.599
Trail hip 7.1 ± 8.4 0.981 2.03 12.4 ± 8.4 0.992 2.03 0.65 0.001
Trail knee 33.4 ± 9.6 0.967 2.34 33.3 ± 7.9 0.979 1.92 0.01 0.671
Trail ankle −14.7 ± 10.5 0.974 2.55 −12.1 ± 7.7 0.985 1.87 0.28 0.147
ES Trunk −4.0 ± 7.5 0.976 2.34 −9.1 ± 9.2 0.995 1.92 0.61 <0.001
Pelvis −4.4 ± 3.4 0.906 0.83 −5.4 ± 3.4 0.839 0.81 0.30 0.004
Lead hip 5.2 ± 10.3 0.978 2.49 4.3 ± 7.6 0.993 1.85 010 0.540
Lead knee 10.3 ± 11.8 0.967 2.87 12.7 ± 8.8 0.987 2.12 0.23 0.686
Lead ankle −22. 2 ± 7.9 0.926 1.92 −21.0 ± 9.1 0.984 2.21 0.08 0.272
Trail hip −12.5 ± 7.4 0.971 1.79 −10.7 ± 5.5 0.981 1.33 0.27 0.303
Trail knee 34.0 ± 8.2 0.925 1.99 36.8 ± 8.4 0.967 2.03 0.33 0.162
Trail ankle −37.1 ± 26.0 0.984 6.30 −38.6 ± 21.4 0.935 5.19 0.06 0.710
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Bolded values indicate statistical significance at p<0.05 or large effect size at d>0.8. BI – ball impact, BS – top of backswing, d – Cohen’s d effect size, ES – end of swing ICC – Intra-class correlation coefficient (3,1)

Table 2.

Mean ± SD for frontal plane joint angles during three key events of the golf swing. Positive angles represent adduction/lateral tilt to the right/varus, and negative values represent abduction/lateral tilt to the left/valgus.

Driver 6-iron
Event Segment/Joint Angle (°) ICC SEM Angle (°) ICC SEM d p-value
TBS Trunk 1.9 ± 7.2 0.962 1.63 −0.4 ± 8.3 0.997 1.15 0.30 0.003
Pelvis −4.7 ± 3.4 0.946 0.91 −8.1 ± 3.0 0.740 0.74 1.00 <0.001
Lead hip −35.8 ± 5.2 0.963 1.26 −37.6 ± 5.8 0.986 1.41 0.31 0.115
Lead knee −5.8 ± 5.3 0.970 1.29 −6.8 ± 5.2 0.962 1.27 0.19 0.266
Lead ankle 16.3 ± 6.4 0.947 1.56 16.1 ± 6.4 0.958 1.55 0.05 0.677
Trail hip 12.5 ± 6.6 0.956 1.60 15.8 ± 6.3 0.989 1.54 0.50 <0.001
Trail knee −3.2 ± 4.7 0.972 1.14 −1.7 ± 2.9 0.950 0.70 0.37 0.200
Trail ankle 11.6 ± 5.3 0.974 1.28 10.6 ± 5.0 0.985 1.21 0.18 0.037
BI Trunk 20.7 ± 7.6 0.956 1.25 23.1 ± 8.2 0.998 1.40 0.30 0.014
Pelvis 7.5 ± 4.9 0.981 1.18 6.8 ± 5.8 0.939 1.40 0.13 0.283
Lead hip 0.1 ± 7.8 0.966 1.88 2.9 ± 7.2 0.992 1.75 0.38 0.013
Lead knee 2.0 ± 3.7 0.953 0.91 0.2 ± 2.9 0.844 0.70 0.55 0.010
Lead ankle 10.6 ± 6.9 0.939 1.67 7.4 ± 5.1 0.983 1.24 0.53 0.034
Trail hip −18.5 ± 7.7 0.973 1.88 −21.5 ± 6.0 0.968 1.46 0.44 0.217
Trail knee −2.8 ± 4.1 0.780 0.98 −2.7 ± 4.3 0.929 1.03 0.02 0.994
Trail ankle 17.9 ± 7.6 0.977 1.85 20.2 ± 6.2 0.981 1.51 0.33 0.226
ES Trunk 5.8 ± 5.5 0.969 2.34 9.3 ± 5.6 0.979 1.03 0.63 <0.001
Pelvis 5.4 ± 3.7 0.952 0.90 6.4 ± 4.8 0.721 1.15 0.25 0.156
Lead hip 9.8 ± 5.6 0.981 1.36 10.8 ± 3.6 0.982 0.86 0.23 0.397
Lead knee 5.8 ± 4.3 0.913 1.03 4.5 ± 3.7 0.947 0.88 0.34 0.110
Lead ankle 7.5 ± 6.9 0.959 1.68 5.0 ± 5.5 0.951 1.33 0.39 0.088
Trail hip −6.4 ± 5.2 0.957 1.25 −11.7 ± 5.8 0.973 1.40 0.96 <0.001
Trail knee −3.1 ± 4.7 0.959 1.13 −4.2 ± 5.9 0.952 1.42 0.21 0.226
Trail ankle 14.9 ± 6.6 0.973 1.59 17.3 ± 6.1 0.954 1.49 0.37 0.430
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Bolded values indicate statistical significance at p<0.05 or large effect size at d>0.8. BI – ball impact, BS – top of backswing, d – Cohen’s d effect size, ES – end of swing ICC – Intra-class correlation coefficient (3,1)

Table 3.

Mean ± SD for transverse plane joint angles during three key events of the golf swing. Positive angles represent internal rotation/rotation to the left and negative values represent external rotation/rotation to the right.

Driver 6-iron
Event Segment/Joint Angle (°) ICC SEM Angle (°) ICC SEM d p-value
TBS X-factor −33.0 ± 11.0 0.981 1.56 −37.3 ± 8.3 0.997 1.73 0.29 0.069
Pelvis −43.8 ± 9.9 0.966 2.41 −41.8 ± 10.2 0.909 2.48 0.20 0.017
Lead hip −22.7 ± 11.4 0.985 2.76 −25.4 ± 8.9 0.988 2.16 0.27 0.356
Lead knee 24.1 ± 12.0 0.964 2.91 24.2 ± 12.1 0.995 2.93 0.01 0.961
Lead ankle −2.8 ± 5.7 0.941 1.35 −3.7 ± 6.0 0.977 1.46 0.16 0.275
Trail hip 6.1 ± 4.1 0.975 0.98 5.6 ± 3.8 0.970 0.92 0.12 0.469
Trail knee −5.2 ± 11.1 0.980 2.69 −5.3 ± 9.1 0.993 2.21 0.01 0.116
Trail ankle 18.4 ± 4.7 0.976 1.13 19.9 ± 6.7 0.978 1.63 0.25 0.551
BI X-factor −14.9 ± 9.5 0.983 1.89 −18.1 ± 8.9 0.995 2.63 0.21 0.023
Pelvis 20.8 ± 10.6 0.961 2.57 15.6 ± 11.1 0.887 2.69 0.34 0.001
Lead hip −15.8 ± 7.6 0.970 1.85 −16.6 ± 6.0 0.979 1.44 0.12 0.540
Lead knee 4.4 ± 12.2 0.909 2.96 3.5 ± 11.0 0.982 2.67 0.08 0.866
Lead ankle 11.8 ± 7.1 0.877 1.71 12.6 ± 10.2 0.966 2.48 0.08 0.727
Trail hip −11.6 ± 6.6 0.921 1.59 −8.1 ± 6.2 0.964 1.51 0.54 0.029
Trail knee −21.6 ± 11.2 0.973 2.72 −22.0 ± 10.7 0.991 2.60 0.04 0.830
Trail ankle 6.6 ± 11.7 0.974 2.83 2.3 ± 6.6 0.935 1.61 0.46 0.259
ES X-factor 29.7 ± 10.6 0.965 2.72 33.4 ± 7.9 0.996 2.60 0.28 0.104
Pelvis 88.8 ± 16.1 0.906 3.91 82.4 ± 15.5 0.856 3.75 0.40 <0.001
Lead hip 2.8 ± 13.5 0.967 3.28 7.5 ± 9.6 0.989 2.33 0.40 0.055
Lead knee −6.4 ± 12.5 0.949 3.04 −6.4 ± 10.3 0.980 2.50 0.00 0.338
Lead ankle 33.8 ± 15.0 0.939 3.64 35.5 ± 14.6 0.962 3.53 0.11 0.646
Trail hip −19.3 ± 10.2 0.957 2.48 −18.7 ± 10.9 0.982 2.63 0.05 0.710
Trail knee −23.2 ± 15.0 0.961 3.63 −21.0 ± 16.4 0.993 3.97 0.13 0.345
Trail ankle 4.8 ± 14.1 0.981 3.42 3.1 ± 13.9 0.987 3.38 0.12 0.408
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Bolded values indicate statistical significance at p<0.05 or large effect size at d>0.8. BI – ball impact, BS – top of backswing, d – Cohen’s d effect size, ES – end of swing ICC – Intra-class correlation coefficient (3,1)

The trunk and pelvis also exhibited significant differences between the clubs in the peak velocities in all three planes of motion (Table 4). The analysis showed that the peak velocities of both hips differed in both the sagittal and frontal plane, while the lead knee differed between the clubs in the transverse plane. Further, the peak velocity most often occurred during the downward swing phase of the motion, however the peak trunk velocities occurred during the follow through in all planes of motion for both clubs. The frontal plane velocity for the trail ankle also peaked during the follow through with both clubs, while the trail knee sagittal plane velocity reached its peak during the downward swing for the driver and during the follow through for the six-iron.

Table 4.

Mean ± SD for peak joint velocities during the golf swing in the three planes of motion. Positive velocities in the sagittal, frontal and transverse planes represent flexion/posterior tilt/dorsiflexion, obliquity/lateral bending to the right/adduction/varus, and axial rotation to the left/internal rotation.

Driver 6-iron
Plane Segment/Joint Velocity (°/s) ICC SEM Velocity (°/s) ICC SEM d p-value
Sagittal
Trunk 164.9 ± 41.6c 0.878 10.09 138.9 ± 30.4c 0.858 7.37 0.75 0.003
Pelvis 86.7 ± 28.8b 0.876 6.86 85.2 ± 32.1b 0.948 7.79 0.05 0.891
Lead hip −126.6 ± 54.0b 0.934 13.09 −154.7 ± 51.1b 0.943 13.39 0.40 0.001
Lead knee −219.7 ± 87.4b 0.954 21.19 −231.3 ± 90.5b 0.976 21.94 0.05 0.699
Lead ankle −121.4 ± 57.4b 0.952 13.91 −127.5 ± 53.0b 0.892 12.85 0.15 0.640
Trail hip −175. 6 ± 35.4b 0.901 8.59 −148.8 ± 38.5b 0.931 9.34 0.76 0.001
Trail knee 108.7 ± 35.0b 0.920 8.49 82.0 ± 47.0c 0.936 11.39 0.62 0.075
Trail ankle −60.5 ± 25.2b 0.968 6.11 −30.3 ± 17.6b 0.930 4.27 1.33 <0.001
Frontal
Trunk 223.4 ± 60.5c 0.959 14.67 254.2 ± 74.8c 0.953 18.14 0.45 0.004
Pelvis 113.3 ± 32.5b 0.855 7.89 136.0 ± 38.8b 0.913 9.40 0.61 0.005
Lead hip 201.8 ± 55.0b 0.912 13.34 228.8 ± 63.5b 0.919 15.40 0.41 0.043
Lead knee −90.2 ± 33.6b 0.912 8.15 −107.5 ± 37.5b 0.946 9.09 0.41 0.238
Lead ankle 91.0 ± 42.7b 0.968 10.36 93.7 ± 40.6b 0.863 9.83 0.01 0.837
Trail hip −132.0 ± 42.9b 0.729 10.41 −163.5 ± 49.5b 0.899 12.01 0.65 0.035
Trail knee −38.5 ± 35.6b 0.972 8.57 −54.6 ± 30.7b 0.860 7.45 0.42 0.359
Trail ankle −98.3 ± 67.7c 0.976 16.43 −79.7 ± 50.9c 0.977 12.34 0.32 0.224
Transverse
X-factor 155.2 ± 55.9c 0.969 13.56 133.5 ± 37.6c 0.942 9.13 0.43 0.050
Pelvis 315.0 ± 52.5b 0.933 12.74 283.2 ± 54.1b 0.957 13.11 0.59 <0.001
Lead hip 112.2 ± 28.7b 0.873 6.97 108.6 ± 43.1b 0.942 10.45 0.11 0.539
Lead knee 152.3 ± 28.1b 0.874 6.81 121.9 ± 42.9b 0.970 10.41 0.81 0.002
Lead ankle 127.7 ± 42.5b 0.921 10.31 127.0 ± 39.4b 0.945 9.56 0.09 0.706
Trail hip −135.9 ± 34.4b 0.882 8.35 −136.3 ± 37.5b 0.933 9.09 0.01 0.442
Trail knee −101.7 ± 33.4b 0.885 8.09 −54.6 ± 30.7b 0.823 7.45 0.52 0.132
Trail ankle −114.7 ± 51.1b 0.950 12.39 −119.0 ± 19.0b 0.804 4.62 0.04 0.875
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Bolded values indicate statistical significance at p<0.05 or large effect size at d>0.8. BI – ball impact, BS – top of backswing, d – Cohen’s d effect size, ES – end of swing ICC – Intra-class correlation coefficient (3,1). Symbols indicate during what phase of the swing the peak velocity occurred;

a

backward motion

b

downswing motion

c

follow through

Discussion and Implications

This study reported trunk and lower body kinematic data for older adults performing a golf swing with a driver and a six-iron. Our first hypothesis, that the driver and six-iron would produce different kinematics, was supported by the data. Several differences were seen between the clubs in the joint displacements at the key events, and in both the magnitude and timing of peak velocities. This agrees with previous research that reported differences in the kinematics of the trunk, hips, knees, and shoulders in young populations while hitting with a driver and a five-iron (Egret et al., 2003; Joyce, 2017b; Joyce et al., 2013). One study suggested that the differences in kinematics between drivers and irons may be caused by the intent of different types of shots; the driver is used to maximise the ball flight distance and irons are used when accuracy is more important (Joyce, 2017b). However, it is important to consider that during both the current and the previous studies, the testing was performed in a laboratory without the external incentive of hitting a golf ball towards a physical flag on a course, but rather to hit the ball into a net. It is uncertain how specific shot characteristics expected on a course are replicated within the laboratory setting. It is also likely that differences in club characteristics, such as shaft flex, length and weight, contributed to altered mechanics. Regardless, understanding of the different kinematics produced by the different clubs is important for any healthcare professional suggesting golf as a form of physical activity for older adults.

Our second hypothesis, that the older population in this study would use different mechanics than younger populations described in previous research was also supported. Several differences in both performance and mechanics were observed between our data and published reports on younger golfers. Unsurprisingly, our older population had slower club head speeds and ball speeds compared to young golfers reported in previous reports (Table 5). This was expected as declines in strength and flexibility are normal consequences of the aging process (Alcock et al., 2015; Brooks & Faulkner, 1994). It must be acknowledged that the handicaps of the participants in the studies presented in Table 5 were lower than those of our participants. It has been shown that skill affects club head speed (Fradkin, Sherman, & Finch, 2004), so differences in club head and ball speed between ours and previous studies may partially be attributed to skill differences. Regardless, kinematic differences existed, with smaller overall X-factor and X-factor stretch in the senior athletes compared to what has been reported in younger adults (Cheetham et al., 2001; Joyce, 2017b).

Table 5.

Club head and ball speed reported previously for young male golfers

Study population
Study N Age Handicap Club CH speed (m/s) Ball Speed (m/s)
Egret et al. (2003) 7 17-34 0-3 Driver NR 44.9±2.6
5-Iron 40.8±2.0
Gulgin et al. (2009) 15 19.7± 1.4 5.2±3.3 Driver 37.3±3.5 NR
Horan et al. (2010) 19 26±7 0.6±1.1 Driver 49.1±3.6 69.5±5.2
Joyce et al. (2017) 15 22.7±4.3 2.5±1.9 Driver 46.7±4.5 64.8±4.2
5-Iron 43.9±4.7 54.0±3.8
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CH – club head speed, NR – not reported

Interestingly, our older participants had a greater X-factor at the top of the backswing when swinging with the six-iron than with the driver. Further, the X-factor stretch was not different between the clubs and was small for both clubs (driver: 1.6°, 4.7%, six-iron: 0.7°, 1.8%). This is different from what has been reported for young populations, where the X-factor at the top of the backswing was similar between clubs, and the stretch was considerable (Cheetham et al., 2001; Joyce, 2017b; Joyce et al., 2010). It is often regarded in the literature that the X-factor and X-factor stretch may be the most important contributors to club head and ball speed (Brown et al., 2013; Hume et al., 2005; Myers et al., 2008). For example, Joyce (2017b) reported only a 0.6° difference in X-factor at the top of the backswing between a driver and five-iron, but reported an X-factor stretch of 4.6° (7.7%) for the driver and 3.4° (5.8%) for the five-iron. Similarly, Cheetham et al. (2001) reported an X-factor stretch of 19% in highly skilled young golfers and 13% in recreational younger golfers, but without a corresponding difference in X-factor at the top of the backswing. The authors therefore suggested that the degree of X-factor stretch was a more important contributor to an effective swing than simply the degree of X-factor.

The lack of an X-factor stretch in older golfers is a previously unreported observation that may indicate a caution within the population when swinging a heavier driver in order to control the swinging motion. Interestingly, the older golfers produced a lateral trunk flexion at ball impact that was similar to what has been reported for high-level young females, albeit with less angular displacement (Horan, Evans, Morris, & Kavanagh, 2010). It has been highlighted that even though the lateral trunk flexion probably contributes to the force applied to the ball (Joyce, 2017a), lateral tilt velocity contributes to lumbar spine loads, and the role of lateral trunk motions in the golf swing is not yet well understood (Horan et al., 2010). However, it has been suggested that less lateral trunk flexion may allow for increased axial rotation and potentially faster club head speed (Joyce, 2017a), but this suggestion was based on research performed on younger golfers and it is still unknown how this may transfer to older adults.

In addition, the senior athletes in this study had an increased amount of pelvic axial rotation at the top of the backswing when swinging with the driver, which may suggest a compensatory mechanism to shift the high demands from the trunk to other segments down the kinetic chain. Although the analysis showed that the older golfers had slower peak velocities about the pelvis than younger golfers (Horan et al., 2010), the increased amount of rotation suggests that the older golfers relied more on the pelvis to contribute to the golf swing. This may be a consequence of reduced flexibility and power needed to perform the golf swing in the manner younger players do. This is an important consideration for clinicians as it may shift the mechanical demands that are usually seen in golfers to other segments.

Our analysis further showed that the older golfers had faster transverse plane rotations about the trail hip than the lead hip with both clubs. This was surprising as one of the few other studies reporting on hip rotation velocities during golf swings reported considerably higher velocities in the lead hip in high level female golfers (Gulgin et al., 2009). Further, although the lead hip velocities were lower in our older male golfers compared to the young females, the external rotation velocity about the trail hip was comparable between the populations. This was an unexpected observation that supports the suggestion of a compensatory mechanism in the older population. Our participants had faster velocities about the lead hip for both clubs in the frontal plane and in the sagittal plane for the six-iron compared to the driver; however, the study by Gulgin et al. (2009) only addressed transverse plane velocities which prevents further comparisons. The literature on fast rotational kinematics about the hips during closed kinetic chain movements is limited so it is difficult to speculate on reasons behind the increased rotational trail hip velocity in the older golfers, or comment on possible repercussions. However, it has been highlighted that the rapid external hip rotation coupled with hip extension that occurs at the trail limb during the golf swing may place golfers at increased risk of hip joint injury (Gulgin et al., 2009). In fact, individuals who regularly perform activities that place large axial demands on the hips may be more likely to develop labral or chondral disorders which may contribute to degeneration later in life (McCarthy et al., 2003). It is therefore possible that older golfers with years’ of playing experience are particularly susceptible to degenerative hip joint disorders such as osteoarthritis. Practitioners working with golfers should therefore emphasise appropriate hip function and aim to minimise the risk of future degeneration and subsequent surgery. Further, transverse plane hip joint angles of younger golfers have been described at the top of the backswing as 52.9±9.0° with a driver, and 50.9±7.4° with a five-iron (Egret et al., 2003). Although the study did not define whether this referred to the trail or lead hip, the reported values are considerably higher than seen in our older adult population (lead hip: 22.7°±11.4°, trail hip: 6.1°±4.1°). This may be a sign of reduced flexibility in our participants due to the aging process, though it is also possible that reduced hip motion is a strategy to reduce the rotational loading during the swing. The combination of reduced X-factor increased pelvic motion and reduced hip motion suggests a different movement strategy with unclear consequences. Future research should assess the joint moments in older golfers to examine whether these differences in the kinematics are reflected in the kinetic profile.

Because the golf swing is predominantly performed in the transverse plane and power is generated through trunk and hip rotations, most kinematic research has focused on transverse motions about these joints (Brown et al., 2013; Cheetham et al., 2001; Gulgin et al., 2009; Joyce, 2017a, 2017b; Joyce et al., 2010; Joyce et al., 2013; Myers et al., 2008). Compared to existing knee-related golf research, our results suggest that older athletes perform a golf swing with larger flexion angles at both knees (Egret et al., 2003), and less transverse plane rotations about the lead knee (Purevsuren et al., 2017) compared to younger golfers. It is possible that the increased knee flexion was a balance strategy employed to maintain a lower position of the centre of mass during the swing as balance reduces with age (Alcock et al., 2015; Brooks & Faulkner, 1994). Our study did not analyse balance and further research is needed to understand the balance strategies used by older golfers. It seems, however, reasonable to suggest that older golfers employ increased limb flexion angles to lower their centre of mass. This is an important consideration for practitioners as it has been highlighted that balance strategies used during a golf swing may translate to balance strategies during other weight-baring activities (Peterson et al., 2016).

The reduced transverse plane rotations support other observations that the older population performs the golf swing with decreased motion in all planes compared to younger golfers. However, further research that allows more direct comparisons with younger populations of similar skill level is needed to clarify the differences and identify possible compensatory movement strategies within the older population.

The primary limitation to this study is that the testing took place in an indoor biomechanics’ laboratory, with the participants wearing spandex, which is atypical to golf practice. Further, each participant used their own clubs which may have affected the results. However, allowing the participants to use their own clubs is common in the literature (Brown et al., 2013; Joyce, 2017a; Joyce et al., 2013; Kwon, Como, Singhal, Lee, & Han, 2012; Kwon, Han, Como, Lee, & Singhal, 2013) and prevents altered mechanics due to unfamiliarity with the club. It should also be recognised that the excessive trunk rotation during the golf swing creates a degree of skin artefact, which may affect the accuracy of the motion capture data. However, skin artefact is an acknowledged limitation of motion capture systems and these systems are common practice for biomechanical golf swings (Gulgin et al., 2009; Joyce, 2017b; Kwon et al., 2013). Although it is not uncommon in this research area to enrol participants of the same sex (Egret et al., 2003; Gulgin et al., 2009; Joyce et al., 2013), kinematic differences have been reported between male and females (Horan et al., 2010). Future work should focus expand upon this report and examine the kinematics of older female golfers, as this study only assessed males. In addition, this study examined kinematics at discrete time points of a dynamic task, and since important information can be learned from assessing continuous data, this should be addressed in future research.

Conclusions

This study provided kinematic trunk, pelvis, hip, knee and ankle data for healthy older male golfers performing golf swings with a driver and a six-iron. The clubs generated different swing mechanics, particularly about the trunk and pelvis. The senior adult population had slower club head speed and ball speed than what has been reported for younger individuals. The kinematic analysis suggested that the emphasis on large and fast transverse plane motions of the trunk and hips that are typically seen in golf swings performed by young athletes may be beyond what the aging male population are able to perform. The data further indicated strategies to shift the demands from the trunk and hips to the pelvis and to lower the centre of mass during the swing. It is likely that such strategies are consequences of reduced muscle strength, flexibility and balance that are known to occur during the aging process, but further research is needed to clarify these strategies. It is also likely that altered mechanics combined with age-related declines in strength and flexibility contributed to the slower club and ball speeds. Regardless, it is important for practitioners to recognise the movement demands of the golf swing and consider the potential compensation strategies when discussing continued golf practice or recommending including golf as a form of physical activity for older adults.

Acknowledgements

The authors would like to thank the participants in this study and the HipKnee Arkansas Foundation.

Funding statement

Research reported in this publication was supported by the National Institute Of General Medical Sciences of the National Institutes of Health under Award Number P20GM125503. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health

Footnotes

Data availability statement

The data that support the findings of this study are available from the corresponding author, EM, upon reasonable request.

Disclosure statement

The authors declare no conflict of interest and that no financial interest or benefit has arisen from the direct applications of this research.

Conflict of Interest Disclosure: None

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