Effects of left thigh blood flow restriction exercise on muscle strength and golf performance in amateur golfers

Ahn, Hyun; Bae, Sea-Hyun; Kim, Kyung-Yoon; Hyun Ahn; Sea-Hyun Bae; Kyung-Yoon Kim

doi:10.12965/jer.2346302.151

J Exerc Rehabil > Volume 19(4);2023 > Article

Ahn, Bae, and Kim: Effects of left thigh blood flow restriction exercise on muscle strength and golf performance in amateur golfers

Original Article

Journal of Exercise Rehabilitation 2023; 19(4): 237-244.

Published online: August 22, 2023

DOI: https://doi.org/10.12965/jer.2346302.151

Effects of left thigh blood flow restriction exercise on muscle strength and golf performance in amateur golfers

Hyun Ahn¹, Sea-Hyun Bae², Kyung-Yoon Kim^2,^*

¹Department of Physical Therapy, Samsung Electronic Musculoskeletal Disorders Prevention Center, Gwangju, Korea

²Department of Physical Therapy, Dongshin University, Naju, Korea

^*Corresponding author: Kyung-Yoon Kim, https://orcid.org/0000-0002-8670-9664, Department of Physical Therapy, Dongshin University, 67 Dongshindae-gil, Naju 58245, Korea, Email: redbead7@daum.net

Received July 3, 2023 Accepted August 1, 2023

(open-access):

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (https://creativecommons.org/licenses/by-nc/4.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

This study aimed to investigate the effect of lower-extremity strengthening exercise (LSE) with and without blood flow restriction (BFR) on the left thigh on golf performance. Eighteen amateur golfers with more than 1 year of golf experience participated in the study and were randomly divided into two groups: LSE+BFR group (LSE with BFR on the left thigh, n=9) and LSE group (LSE without BFR, n=9). The LSEs consisted of squats, lunges, and standing leg curls. All exercises were performed 3 times a week for 6 weeks. Changes in thigh muscle strength, plantar foot pressure (weight transfer), and golf performance, such as club head speed, ball speed, and carry distance were measured before and after the exercise program. Right knee extension (P<0.001) and left knee extension and flexion (P<0.001) strength were higher in the LSE+BFR group than in the LSE group. The changes in plantar foot pressure confirmed that smooth weight transfer appeared in E1 (event 1) (address) (P<0.05) of the LSE+BFR group, which confirmed that the carry distance (P<0.05) of the LSE+BFR group improved after the exercise program. The results of this study showed that BFR muscle strengthening exercise are more effective than basic simple muscle strengthening exercise in improving golf performance through muscle strength and weight transfer improvement.

Keywords: Amateur golfer, Muscle strengthening exercise, Blood flow restriction, Lower-extremity strength, Weight transfer, Golf performance

INTRODUCTION

Muscle strength and conditioning exercises are recognized as a crucial component of a multidimensional approach for optimizing golf performance; combined with improvements in technology, proper biomechanics integrated with technological improvements are considered an important strategy to improve the golf swing (Doan et al., 2006; Lephart et al., 2007). Marta et al. (2012) and Marta et al. (2016) were able to score higher levels by including leg exercises in muscle strength and conditioning programs. Furthermore, Driggers and Sato (2018) and Oranchuk et al. (2020) confirmed the importance of these physical characteristics by reporting positive results in increased club head speed (CHS) and distance. Myers et al. (2008) reported that leg muscle strength is a major source of energy for golf swing speed and that leg muscle strength is important for creating a strong rotational force that unravels the upper body and pelvis rotation during the golf swing. In particular, the muscle strength of the left leg is important in increasing golf performance ability, such as carry distance (CD), which affects the shot accurate and rotational force at the moment of impact during a golf swing (Lee et al., 2010).

Existing resistance exercises for golfers include progressive overload protocols using machine weights, free weights, and barbells. Progressions is made by increasing repetitions and load or adding new and more difficult exercises (Smith et al., 2011). However, the slow contraction speeds used in resistance exercises do not improve power production or reflect the dynamic nature of the sport (Sheehan et al., 2019). Recently, it was reported that muscle adaptation, which is induced by applying blood flow restriction (BFR) during low-load resistance exercise, cardiovascular endurance exercise, and other types of exercise that do not improve muscle mass and strength (Mouser et al., 2017; Slysz et al., 2016), and exercise stimulation combined with BRF, showed the most effective muscle increase during resistance exercise (Slysz et al., 2016).

BFR is a method of inducing hypoxia environment in tissues by limiting muscle blood flow using an air-injectable cuff during exercise, and even short-term low-intensity exercise can have effects similar to those of high-intensity exercise (Pope et al., 2013). BFR exercises improve the strength of muscles distal to the point of restriction by increasing the amplitude of the corticomotor evoked potential, which changes the motor output at the applied site (Patterson and Ferguson, 2011). In addition, BFR exercises can be used on their own and in various populations, such as athletes, older individuals, and patients undergoing rehabilitation, given their positive effects, such as increased muscle strength and muscle cross-sectional area, improved endurance, and promoted hormone such as growth hormone (Buford et al., 2015; Scott et al., 2015; Segal et al., 2015). Athletes and sports participants are more likely to be injured during practice, training, and games every day, and sports damage is also an important disadvantage of exercise (Okobi et al., 2022). Some attempts have been made to select exercises based on the best muscle strength and conditioning studies to prevent sports injuries and improve performance; however, a lack of research on such exercises remains (Lehman, 2006), and there are insufficient studies to explain the kinematic contribution of the legs, which takes into account golf performance during golf swing (McNally et al., 2014).

This study assumed that scientific evidence and an understanding of the physical characteristics that improve golf performance could suggest effective exercise methods for designing more efficient exercise programs for professional sports workers. Therefore, the purpose of this study was to investigate the effect of lower-extremity strengthening exercise (LSE) with and without BFR on the left thigh on golf performance.

MATERIALS AND METHODS

Participants

Twenty volunteers who met the selection criteria and understood the study purpose were recruited. The inclusion criteria were as follows: (a) no leg strength exercise in the last 6 months, (b) no experience in BFR exercise, (c) smooth golf swing, and (d) more than 1 year of golfing experience. The exclusion criteria were as follows: (a) blood pressure >120/80 mmHg, (b) joint or muscle inflammatory disease, (c) central and peripheral neurological symptoms, and (d) uncontrolled drug use. Except for the two who dropped out (refused to participate) in the middle of the study period, 18 people completed the measurement through exercise over a period of 6 weeks, and the general characteristics of the participants are presented in Table 1. This study was approved by the Institutional Review Board of Dongshin University (1040708-202205-BM-020).

Study procedure

Participants who agreed to participate in the study were randomly assigned to either the LSE+BFR group (LSE with BFR on the left thigh, n=9) or the LSE group (LSE without BFR, n=9). This study included two measurements before (pretest) and after (posttest) LSE for 6 weeks. All the data were collected between June and August 2022. The participants were allowed to adapt to all experimental equipment and exercise. Participants could adapt to all equipment and training before the lower-extremity exercise, which were conducted individually according to their personal visit schedule. The participants were asked to avoid exercise other than LSEs conducted in this study.

Sample size calculation

The a priori sample size was calculated with an estimated effect size of 1.6, an alpha level of 0.05, and desired power of 0.8 using G*Power v3.1.9.7. Based on our estimated sample size, a minimum of 16 participants (n=8/group) were required.

LSE program

LSE consisted of squats, lunges, and standing leg curls, and were conducted 3 times a week for 6 weeks. The LSE program consisted of an initial stage (1–2 weeks), improvement stage (2–3 weeks), and maintenance stage (5–6 weeks) (Table 2). In the squat, both feet were spread shoulder-width apart, and with the ankle joint at 15° of abduction, the knees were kept from going over the toes while sitting down or rising up. In the study by Luna et al. (2021), the hip joint was leveled with the knee joint to maintain a certain sitting angle during squatting, and the hip, knee, and ankle positions were checked until the participant returned to the starting position. The lunge was performed in a position where both feet were shoulder-width apart, the forward leg was bent at 90°, and the knees of the rear leg touched the ground such that the body was lowered. Adapting the study of Doma et al. (2020), the rear and front legs positions were marked on the floor at regular intervals during lunge exercise. Referring to Taylor et al. (2010) and Bowman et al. (2019), the standing leg curl was performed with the feet slightly wider than shoulder-width apart, hands supported on a chair, the upper body in a straight position, bending one knee, and raising the heel towards the hip.

Blood flow restriction

The LSE+BFR group applied a BFR cuff on the left thigh and then performed LSE. The 3-cm wide and 60-cm long BFR cuff was applied between the hip joint (proximal part of the thigh area) and the greater trochanter of the left thigh.

Before performing the exercise, the cuff was expanded to 120 mmHg for 30 sec so that the participant could get accustomed to the cuff pressure, the pressure was released for 10 sec, and the cuff inflated again. The pressure was then increased by 20 mmHg, maintained for 30 sec, relaxed for 10 sec during occlusion stimulation, and repeated until a final occlusion pressure of 160 mmHg was reached (Renzi et al., 2010). A BFR pressure of 160 mmHg was applied using a biofeedback press unit, depending on the equipment use. After wearing the cuff, the capillary reaction time was set between 2 and 3 sec when the skin color returned to normal by applying pressure to the quadriceps muscle using a finger (Amano et al., 2016). If abnormal symptoms appeared during exercise, the cuff was immediately removed.

Outcome measures

Thigh muscle strength, plantar foot pressure (weight transfer), and golf performance were measured before and after exercise. By modifying the study of Marta et al. (2016), the golf swing phase was set to four events: E1: address, E2: backswing top, E3: impact, and E4: finish and the foot pressure test was measured at four events during the golf swing.

Thigh muscle strength test

Thigh muscle strength was measured using a hand-held dynamometer (Micro FET2; Hoggan Scientific, Salt Lake City, UT, USA). The measurement was performed with the participants sitting on a chair with the hip and knee at 90° flexion. A strap (Movement Belt, Balance Body Co., Seoul, Korea) was fixed to the legs behind the chair to apply the dynamometer in front of the participant’s ankle. Extension strength was measured at the command of “stretch your knees and maintain for 3 seconds” (Bohannon et al., 2011). For knee flexion strength measurement, the participants were placed in the prone position with the knee at 90° flexion, a strap was fixed to a pillar, and the dynamometer was fixed to the calf. Flexion strength was measured at the command of “flex your knees and maintain for 3 seconds” (Reurink et al., 2016). There was a 10-sec break between the extension and flexion strength measurements; all measurements were calculated after five repetitions, and the average value was used.

Plantar foot pressure (weight transfer) test

Plantar foot pressure was measured using a smart insole (Salted Golf; Salted, Hanam, Korea). After removing the existing insole from the golf shoes, the participants had an adaptation time of 3 min after inserting the smart insole. Referring to study of Marta et al. (2016), the data values calculated from four events (E1, E2, E3, and E4) among data values collected at the time of “swing please” signal were collected. When calculating the pressure values, movement towards the left sole was negative (-), and movement towards the right sole was positive (+) based on the center value (0). All measurements were determined by taking the average value from a total of five repetitions.

Golf performance ability test

A golf simulator (QED EyeXo, Uneekor, Irvine, CA, USA) was used to measure golf performance. CHS, ball speed (BS), and CD were used as indicators of golf performance. After 3 min of swing practice, the participants performed swing measurements 5 times, and the data collected from the golf simulator were used. The CHS and BS values were calculated by averaging the data from the five swings. The distance was calculated as an average value by selecting three data points with high accuracy and excluding data that deviated from the fairway among the five swings.

Statistical analysis

All data measured in this study were analyzed using IBM SPSS Statistics ver. 22.0 (IBM Co., Armonk, NY, USA). Descriptive statistics were used to determine the general characteristics of the subjects, and homogeneity tests were conducted for each group. The Shapiro–Wilk test was used to check whether the data were normally distributed. To test the difference between exercise groups, a Mann–Whitney U-test was used. The statistical significance level was set at 0.05.

RESULTS

Changes in thigh muscle strength

An intergroup comparison was conducted to determine the difference in thigh muscle strength changes with and without a BFR cuff applied to the left thigh. Compared with the LSE group, the LSE+BFR group showed significant differences in right knee extension (P<0.001) and left knee extension and flexion (P<0.001) (Table 3).

Changes in plantar foot pressure (weight transfer) during the golf swing

An intergroup comparison was conducted to determine the difference in the change in plantar foot pressure for each event during the golf swing according to whether the BFR was applied to the left leg. There was a significant difference in the event of the LSE+ BFR group E1 (address) (P<0.05) compared with the LSE group (Table 4).

Changes in golf performance ability

An intergroup comparison was conducted to determine whether the difference in golf performance changes with or without the application of a BFR cuff to the left thigh. Compared with the LSE group, the LSE+BFR group showed significant differences in CD (P<0.05) (Table 5).

DISCUSSION

It is important to develop new exercise methods that can increase joint tolerance to the load induced by golf when designing golf-specific lower-extremity strengthening protocols while simultaneously reducing the risk of potential injuries and increasing performance. This study aimed to determine how left thigh BFR muscle strengthening exercises alter thigh muscle strength, plantar foot pressure (weight transfer), and golf performance (evaluated using CHS, BS, and CD) in amateur golfers. Changes in thigh muscle strength in this study were compared and analyzed using a digital muscle dynamometer between the knee extension and flexion muscles. The LSE and LSE+BFR groups showed a significant difference in right knee extension (P<0.001), and the left knee showed a significant difference in extension and flexion. Therefore, the improvement in the left thigh muscle strength was confirmed to be greater than that in the right thigh.

In general, BFR exercises consist of low-intensity resistance or aerobic exercise (May et al., 2022) along with BFR, by applying air pressure or an elastic cuff to the arms and legs, Takada et al. (2012) reported that BFR exercises resulted in greater muscle strength and muscular hypertrophy than those performed at the same intensity without BFR. May et al. (2022) interpreted muscle exercise after BFR resistance exercise as a neurological adaptation involving central activation, spinal excitability, and peripheral nerve root adaptation. Fujita et al. (2007) reported that growth-promoting factors and satellite cells increase owing to environmental changes in muscles caused by BFR. Loenneke et al. (2011) reported that an acute increase in growth hormones level had a positive effect on muscle strength improvement through the stimulation of muscle protein synthesis. Cook et al. (2017) reported improvements in muscle strength and cross-sectional area after 12 weeks of lower-extremity BFR training in older adults at risk of mobility limitations, and Kang et al. (2015) reported an improvement in muscle strength and muscular hypertrophy of the right leg during bodyweight leg muscle exercise after 6 weeks of right-leg BFR, which is consistent with the results of the LSE+BFR group results in this study.

In golf, the method used to perform weight transfer directly affects the swing pattern, the club’s trajectory, and consequently, the ball’s direction, distance, and height (Smith et al., 2017). In addition, smooth body rotation and translational weight transfer during golf swing are among the ways to CHS during impact, and it is important to understand how to most efficiently transfer the energy generated during swing to the ball (Queen et al., 2013). For the change in plantar foot pressure in this study, four events were compared and analyzed during the swing operation using a pressure-measuring instrument with a built-in sensor. When comparing the LSE and LSE+BFR groups, a significant difference was observed in the E4 (finish) of the LSE+BFR group compared to the LSE group. In the LSE group, pressure was maintained on the left foot during all events, and there was little weight movement between the right and left sides. Although not statistically significant, in the LSE+BFR group, the right plantar foot pressure in E1 (address) and E2 (backswing top) was transferred to the left plantar foot pressure in E3 (impact) and E4 (finish). Golf-coaching literature emphasizes the importance of smooth weight transfer when swinging, constituting a prerequisite for a solid and strong swing. Many golf coaches believe that weight transfer is the most important factor in golf swing, and that smooth weight movement affects golf swing and performance (Ball and Best, 2012).

McHardy et al. (2006) and Williams and Cavanagh (1983) reported an increase in the weight ratio applied to the trailing leg (right foot) during the backswing phase (E2), and 75%–80% of the body weight transfer to the leading leg (left foot) during the downswing phase (E3) and finishing phase (E4), resulting in a compressive force of up to 756 N. A study by Okuda et al. (2010) on the weight transfer patterns of professional golfers reported that approximately 80% of their weight moves to the trailing leg (right foot) during the backswing (E2) phase, which is consistent with the results of E1 (address) and E2 (backswing) of this study’s experimental group. Additionally, regarding earlier weight transfer to the lead leg during the downswing for skilled golfers, Okuda et al. (2010) and Navarro et al. (2021) reported that the weight on the trailing leg (right foot) can transfer more force to the ball as it moves to lead leg (left foot) while lowering the club at impact. Williams and Cavanagh (1983) reported that at impact (E3), the weight transferred to the lead leg (left foot) during the downswing, while the golfer’s weight reached 81%–141%, and the results of E3 (impact) and E4 (finish) were matched in this study’s LSE+ BFR group. The BFR LSE conducted in this study may have affected the weight transfer pattern necessary for each stage of the golf swing.

The changes in golf performance in this study were analyzed by comparing the CHS, BS, and CD using a golf simulator. When comparing the LSE and the LSE+BFR groups, a significant difference (P<0.05) was observed in the CD in the LSE+BFR group. In particular, the CD in the LSE+BFR group showed a significant increase after exercise, which is believed to have had a meaningful effect on golf performance due to smooth weight transfer to the left side, based on the improvement of thigh muscle strength during golf swing movements. Okuda et al. (2010) reported that weight transfer from the trail leg (right foot) to the lead leg (left foot) is an important factor in hitting the ball far away, and McNally et al. (2014) reported that lower-extremity muscle strength is an important factor in CHS and that improved CHS directly affects distance (Wells et al., 2019). The lead leg (left foot) and the trail leg (right foot) are both related to CHS; however, the lead leg in golf swing shows a stronger relationship than the trail leg, emphasizing the importance of the lead leg for greater energy transfer in sports with rotational elements to the upper extremity (McNally et al., 2014).

Based on the data from this study, BFR LSE affected thigh muscle strength improvement by providing a positive environment that led to increased exercise mobilization in both the muscle fiber mobilization rate and the number of stimulated fibers. In particular, it was confirmed that smooth weight transfer to the left leg during golf swing movements had a meaningful effect on golf performance based on the improvement in left thigh muscle strength.

Therefore, LSEs using BFR improve the golf performance of amateur golfers. In addition, appropriate muscle exercise using BFR is considered an effective way to strengthen muscles in patients with musculoskeletal diseases under conditions where it is difficult to perform lower-extremity exercise or in athletes who need sports rehabilitation under conditions that require potential injury prevention and high-intensity rehabilitation.

Notes

CONFLICT OF INTEREST

No potential conflict of interest relevant to this article was reported.

ACKNOWLEDGMENTS

The authors received no financial support for this article.

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Table 1

General characteristics of the study participants

Characteristic	LSE	LSE+BFR	U	P-value
Age (yr)	40.2±9.59	42.2±6.80	34.5	0.627
Height (cm)	176.4±5.13	176.6±4.74	38.0	0.863
Weight (kg)	80.3±3.27	80.6±3.46	38.0	0.860

Values are presented as mean±standard deviation.

LSE, lower-extremity strengthening exercise; BFR, blood flow restriction on the left thigh.

Table 2

Lower-extremity strengthening exercise program

Initial stage (1–2 weeks)	Improvement stage (3–4 weeks)	Maintenance stage (5–6 weeks)
Each exercise (squat, lunge, standing leg curl) performed for 3 sec; 12 rep.×3 sets 30-sec rest between sets	Each exercise (squat, lunge, standing leg curl) performed for 4 sec; 10 rep.×3 sets 60-sec rest between sets	Each exercise (squat, lunge, standing leg curl) performed for 5 sec; 8 rep.×3 sets 60-sec rest between sets

Table 3

Comparison of lower-extremity muscle strength changes between groups

Group	Right				Left

	Knee extension		Knee flexion		Knee extension		Knee flexion

	Pre	Post	Pre	Post	Pre	Post	Pre	Post
LSE	44.06±5.08	44.64±4.66	44.46±5.64	45.27±5.94	41.93±5.40	42.76±5.65	42.56±5.37	43.35±5.55

LSE+BFR	41.54±5.68	43.17±5.45	45.22±7.79	46.46±7.72	40.76±4.18	44.07±4.43	43.17±4.58	45.84±5.46

LSE (Δ)	0.58±1.15		0.80±1.34		0.84±1.32		0.79±1.30

LSE+BFR (Δ)	1.63±1.29		1.24±1.66		3.32±1.83		2.67±2.13

U	510		891		278		446

P-value	0.001^***		0.329		0.001^***		0.001^***

Values were presented as mean±standard deviation.

LSE, lower-extremity strengthening exercise; BFR, blood flow restriction on the left thigh; Δ, post-pre.

^*** P<0.001.

Table 4

Comparison of plantar foot pressure (weight transfer) changes during the golf swing between groups

Group	E1		E2		E3		E4

	Pre	Post	Pre	Post	Pre	Post	Pre	Post
LSE	0.01±0.16	0.01±0.16	0.03±0.29	0.02±0.20	0.46±0.42	−0.50±0.27	0.68±0.30	0.71±0.17

LSE+BFR	0.06±0.26	0.05±0.28	0.26±0.39	0.30±0.36	0.74±0.12	0.85±0.08	0.90±0.08	0.96±0.06

LSE (Δ)	−0.01±1.50		−0.01±0.27		−0.04±0.16		−0.03±0.09

LSE+BFR (Δ)	0.11±0.41		0.04±0.32		−0.11±0.25		−0.14±0.25

U	738		950		885		785

P-value	0.027^*		0.613		0.305		0.066

Values were presented as mean±standard deviation.

LSE, lower-extremity strengthening exercise; BFR, blood flow restriction on the left thigh; E1, address; E2, backswing top; E3, impact; E4, finish; Δ, post-pre.

^* P<0.05.

Table 5

Comparison of golf performance changes between groups

Group	CHS (m/sec)		BS (m/sec)		CD (m)

	Pre	Post	Pre	Post	Pre	Post
LSE	92.38±5.93	94.18±6.17	117.47±15.13	118.81±15.68	193.48±19.92	195.12±19.78

LSE+BFR	94.55±7.57	97.09±6.35	124.22±6.51	126.84±4.96	177.88±17.28	184.92±13.46

LSE (Δ)	1.81±4.83		1.33±4.66		1.63±8.64

LSE+BFR (Δ)	2.55±5.07		2.62±5.32		7.05±11.66

U	915		872		759

P-value	0.434		0.257		0.041^*

Values were presented as mean±standard deviation.

CHS, club head speed; BS, ball speed; CD, carry distance; LSE, lower-extremity strengthening exercise; BFR, blood flow restriction on the left thigh; Δ, post-pre.

^* P<0.05.