Effect of proximal exercises of lower extremity on static balance parameters during quiet standing

ABSTRACT

Purpose:

People who suffer from knee osteoarthritis (KOA) face reduced balance, which causes increased falling and many serious complications and injuries. The purpose of the extant study was to determine the effect of proximal exercises of lower extremity on static balance parameters during quiet standing.

Materials and Methods:

In the present randomized controlled trial, 36 patients were divided into intervention and control groups (n = 18 in each group). Both groups received routine physiotherapy in three sessions per week for 6 weeks, while the intervention group did proximal exercises in addition to physiotherapy routine. In the extant study, the pain intensity was measured through a visual analog scale (VAS), and individuals’ static balance parameters were measured using Biodex Balance System. All measurements were done before and after the intervention, and then statistical data analysis was performed with Statistical Package for the Social Sciences (SPSS) 24 software.

Results:

Intergroup comparison indicated significant progress of pain intensity, anterior–posterior (AP), and Overall balance stability in both studied groups (P < 0.05). There was a significant increase in medial–lateral (ML) balance stability only in the intervention group (P < 0.05). Intergroup comparison showed that there was not any significant difference between variables before the intervention (P > 0.05). The results showed more progress in the intervention group than the control group after they received the intervention, which was significant in terms of ML balance stability (P < 0.05).

Conclusion:

Adding proximal exercises to physiotherapy had more effect on ML balance stability in KOA patients; however, 6 weeks of these exercises in addition to physiotherapy had also the same effect on pain intensity, Overall, and AP balance stability.

Introduction

Knee osteoarthritis (KOA) is an important factor of disability among the older population.[1] The global prevalence of KOA is about 3.8%, and it is more prevalent among women (4.8%) than men.[2] KOA affects all joint structures, causing pain and joint stiffness, weak lower extremity, impaired balance, and physical function.[3] Patients with KOA have more postural instability than healthy people. Increased anterior–posterior and lateral oscillations have been reported in KOA patients.[4]

Balance requires interaction between the nervous–musculoskeletal system and the environmental effects. Muscular strength is one of the factors associated with the musculoskeletal system.[5] Possible reasons for increased balance caused by strengthening exercise training may stem from increase in muscular power of lower extremity, facilitation of large and fast-shrinking motor units, increase in muscular harmony, and removal of spontaneous inhibition.[3] Evidence indicates the benefit of exercise training, including general and purposeful resistance exercises that reduce the pain intensity and improve the function of patients with KOA.[1]

On the other hand, weakness of the muscles of the lower extremities is one of the complications of KOA.[1] The damage caused by KOA to articular mechanoreceptors evokes abnormal sensory information; afferent fibers from articular mechanoreceptors evoke abnormal afferent information and affect the excitability of a- and g-motor neurons, which in turn decrease their excitability and impair both motor control and sensory appreciation. Changed sensory input from articular mechanoreceptors may decrease quadriceps strength proprioceptive acuity, thereby accelerating articular damage.[6]

Muscular impairments are not just limited to quadriceps muscle in KOA patients.[1] A cohort study suggested that patients with smaller external adductor moments (or weaker hip abductor) experience a rapid KOA progression.[7] Chang et al.[8] postulated that weak hip abductor muscles allow greater contralateral pelvic drop, which could shift the center of mass away from the stance limb, resulting in high loading across the medial knee compartment and acceleration of disease progression. Proximal muscular weakness may result from KOA. Deasy et al.[9] systematically revealed defects in hip muscle strength and weaker isometric and isokinetic muscle strength of hip abduction in KOA patients. KOA patients use some strategies to reduce the pain intensity, including slow walking, increasing abduction moment in the last standing stages, and some alternative patterns such as lateral bending. A weak hip abductor may be a reason for taking such strategies. However, alternative patterns for walking can reduce the use of hip abductor muscles, making them weaker. The same is likely to occur due to weak quadriceps muscles, that is, inactivation and atrophy caused by KOA and muscular weakness. The reduced activity level resulting from KOA may lead to general weakness of all hip joint muscles.[10]

Since muscular weakness may cause some disorders, including postural instability,[4] knee instability,[1] and falling,[3] the extant study aimed to examine the effect of proximal exercises of lower extremity on static balance parameters during quiet standing.

Materials and Methods

This study was a randomized controlled trial (approval code: IR.ZAUMS.REC.1400.078).

KOA patients based on the American College of Rheumatology’s criteria, superior pain/tenderness of knee medial, no surgical experience or intra-articular injection of corticosteroids or physiotherapy history 6 months before the study, no severe articular symptoms in lateral rather than medial in radiography, and no abnormal conditions affecting the balance were enrolled in the study. The data, including patients’ demographic characteristics, pain intensity, and individuals’ static balance parameters, were collected through personal characteristics, visual analog scale (VAS) questionnaires, and Biodex Balance System (Balance System SD 950-304, Model SW 45-30D-E6N; Biodex Medical System Inc., New York, USA).

In VAS, the patient determines the pain level on a line with two extreme limits, including no pain and severe pain.[11] This is a valid and reliable method used for pain intensity measurement.[12] To measure balance, the patient stands on the circular screen of Biodex Balance System can eliminate while his/her hands are on the body with eyes open. The patient tries to keep a certain point on the respective range determined in the monitor, while keeping body balance. Each 20-s test is repeated three times with 10 s rest between them. The average rate of three tests is shown as the final score. The respective information included Overall, anterior–posterior (AP), and medial–lateral (ML) parameters, so that the higher the score, the more the oscillations in quiet standing position. Postural stability test was selected in the device. The test was done with 2 ft in quiet standing, open eyes, and static force.[13,14,15]

In this study, 36 patients were assigned randomly to two groups using the replacement block-stratified randomized method.[16] Both groups received interventions three sessions per week (for 6 weeks). The control group received routine physiotherapy treatments,[17,18,19,20,21,22] including transcutaneous electrical nerve stimulation (TENS) with 60–100 Hz frequency, hot pack, ultrasound with 1.5 W/cm² dose, and therapeutic exercises, including stretching anterior, posterior, and lateral thigh, posterior leg, knee, and short arc knee extension (SAKE) while the patients were lying down. Stretches were repeated three times (30 s active, 15 s rest). SAKE was done progressively from one set in the first session to three sets in the last session using a weight cuff (with 50%–65% dose) based on patients’ one repetition maximum (1RM).[22] In addition to the exercises mentioned above, the intervention group did hip abduction exercises using a weight cuff lying on the side and with a similar SAKE diet.[22]

The considered variables were measured before and after the treatment. Paired t-test was used to compare within group data; an independent t-test was used to compare between group data, including normal data and their equivalents for non-normal data. P < 0.05 was considered as statistically significant.

Results

Normality of contextual variables, including patients’ demographic characteristics, was examined by Shapiro–Wilk test in each group. Contextual data were normal. According to the results of matching the variables (age, weight, height) in the two groups based on the independent t-test, before therapeutic protocols, there was no significant difference between these variables (P > 0.05) [Table 1].

Table 1.

Description and comparison of context variables at the baseline

Variable	Intervention group	Control group	P
Age	53.56±8.83	53.06±7.08	0.85
Weight	70.78±12.66	71.06±9.05	0.94
Height	1.64±0.10	1.66±0.07	0.48

Data are expressed as mean and standard deviation

There was a similar gender distribution in the two groups, with females comprising 66.7% and males comprising 33.3% in the two groups (P = 1).

At the end of the 6^th week, the average pain intensity, Overall, and AP balance stability significantly improved in the control group; however, there was not any significant improvement in ML balance stability average. In this case, pain intensity average reduced and Overall and AP average rates decreased (P < 0.05). However, ML average rate indicated no significant improvement (P > 0.05). Moreover, at the end of the 6^th week in the intervention group, the pain intensity average and the mean values of Overall and AP parameters were improved significantly (P < 0.05) [Table 2].

Table 2.

Results of within and between group comparisons of variables of interest

Variable	Group	Before	After	P
Pain intensity	Intervention	6.28±1.49	1.89±1.02	<0.001
	Control	6.33±1.53	2.06±1.00	<0.001
	P	0.884	0.719
Overall	Intervention	0.75±0.33	0.57±0.33	<0.001
	Control	0.74±0.34	0.66±0.31	<0.001
	P	0.960	0.439
AP	Intervention	0.53±0.28	0.43±0.27	0.005
	Control	0.54±0.24	0.44±0.25	0.001
	P	0.990	0.910
ML	Intervention	0.40±0.17	0.22±0.15	<0.001
	Control	0.38±0.24	0.37±0.20	0.547
	P	0.811	0.015

AP=anterior-posterior balance stability, ML=medial-lateral balance stability, Overall=overall balance stability. Data are expressed as mean and standard deviation

Among the examined variables, the mean value of ML of the intervention group was significantly different from the ML rate in the control group (P < 0.05). Although the Overall variable indicated a relative improvement in the intervention group compared to the control group, it was not significant (P > 0.05). The other variables, including pain intensity and AP, showed no significant intergroup difference (P > 0.05) [Table 2].

Discussion

There has not been any study on the effect of proximal exercises on the average stability of static balance in different ML, AP, and Overall directions. The results of the extant study indicated 6 weeks of routine physiotherapy treatment alone and along with proximal exercises led to significant improvement in pain intensity, average Overall, and AP stability in static balance, while the average rate of ML stability of static balance in quiet standing became significant only when proximal exercises were added to the protocol. Other studies have also reported the positive and efficient effect of routine physiotherapy treatments on KOA patients. In their review, Kus and Yeldan[18] indicated that strengthening the quadriceps femoris muscle provided pain reduction and improved the function of KOA patients, so combination of these exercises with other electrotherapy modalities led to higher effectiveness. This review examined the pain intensity and balance function of patients.[18]

On the other hand, pain intensity and higher strength of the quadriceps muscle affect balance oscillations in KOA patients.[23] Therefore, pain intensity reduction and improved balance parameters of patients can be justified by applying electrotherapy modalities and strengthening the quadriceps muscle. Moreover, pain intensity reduction itself plays a vital role in improving balance parameters.[24] Despite the intragroup progress of variables, the present paper did not indicate any significant intragroup difference in the control group after treatment in terms of ML stability of static balance within quiet standing. This result was in line with findings obtained by Pua et al.[25] considering the strengthening quadriceps muscle in the control group. Pua et al. (2013)[25] explained the quiet standing balance by indicating significant effects of knee extensor strength on AP stability variables but not on the ML stability variables. In other words, the central nervous system uses different strategies to control balance in AP and ML levels. Furthermore, since knee extensors are mainly the sagittal plane movers, these muscles seemingly participate more in AP’s balance parameters than ML plane in two feet static balance.

On the other hand, the results of this study indicate a significant difference in ML stability of static balance in the intervention group. In a systematic review, Orr[26] mentioned better balance and power after doing resistance exercises, pointing to the significant difference between higher strength and better balance after doing resistance exercises. Some studies[27,28] have mentioned the more important role of hip muscles than other lower extremity muscles in keeping balance.[27,28] Moreover, it has been shown that fatigue of hip abductor muscles increased ML oscillations in the mass center of healthy people.[29] Deasy et al.[9] indicated obvious hip abduction weakness in Osteoarthritis (OA) patients in their systematic review.

Moreover, muscular strength is a factor that highly affects balance.[26] Therefore, it was expected to see a significant intergroup difference between the control group and the intervention group that received proximal hip abduction exercises. Biomechanically, the gluteus medius moment is longer than other lower limb muscles (ankle muscles) to control motion in the frontal plane. Moreover, hip abductors effectively change the mass center while responding to ML oscillations.[30]

Most studies have shown the significant effect of proximal exercises on pain intensity reduction, while the present paper did not indicate the same result.[31,32,33] The difference may stem from the lack of electrotherapy application in treatment groups. Consistent with the results obtained by Pouradeli et al.,[34] the extant study showed a significant indifference between groups in terms of pain intensity after adding proximal exercises. Moreover, there was no significant difference between the two main groups regarding 2 ft static balance.[34] Nevertheless, previous studies have not measured balance measurements (e.g., AP and ML) of quiet standing in the considered interventions.

Ashok[31] compared the abduction strengthening with routine exercises alone for patients with KOA and found more progression of patients’ pain and function in the hip abduction strengthening group. Sled et al.[35] studied the effect of hip abductor strengthening on knee load, muscular power, pain, and function of people with KOA. Results showed a reduction in knee pain that was not statistically significant. There was not also any significant decline in other indicators. Bennell et al.[32] studied hip abduction and adduction strengthening exercises among OA patients and healthy people. Their results indicated significant progress of pain and physical function. Bagheri et al.[33] examined the effect of combined hip abductor–quadriceps strengthening and quadriceps strengthening alone among women with OA and indicated a significant difference between the progress rates of function, pain intensity, timed up and go, and single leg balance tests in assessing functional balance. Pouradeli et al.[34] studied the effect of electrotherapy and strength training of selected lower limb muscles on pain and functional balance in older women (60–80 years old), emphasizing the type of focus of attention. The results indicated a lack of significant difference between the main groups without consideration of focus of attention, while changing the focus of attention led to a significant difference in dynamic balance.

The present study faced some constraints, including small sample size, a control group with healthy people, and an intervention group with only proximal muscle strengthening. It is recommended to consider the abovementioned points in further studies and conduct studies with a longer follow-up for longer intervention and more follow-up after the intervention to achieve long-lasting effects of exercise on the selected muscles.

Conclusion

The results indicated significant progress in ML stability of the static balance of individuals who received proximal hip exercises. At the same time, the difference between groups was not affected by some factors such as pain intensity (i.e., pain intensity progress was not significantly different between the two studied groups). Therefore, it is suggested to add proximal exercise programs to the routine physiotherapy of OA patients to achieve a better balance level regarding both AP and ML directions in the static balance of quiet standing and obtain a perfect treatment.

Financial support and sponsorship

The study was a part of the MSC. thesis of Mahla Rakhshani at the Zahedan University of Medical Sciences, Zahedan, Iran.

Conflicts of interest

There are no conflicts of interest.