The Effect of Dynamic versus Isometric Resistance Training on Pain and Functioning among Adults with Osteoarthritis of the Knee

Magdy MA Shabana

Published on: 2019-02-28

Abstract

Study support the efficacy of prescribing various resistance-training programs with mechanical resistance to patients with OA of the knee as a method to enhance their functional ability and to reduce their knee joint pain.

Keywords

Osteoarthritis; Knee

Introduction

Osteoarthritis (OA) is a common progressive health problem among adults [1]. It is a widespread, slowly developing disease, with a high prevalence increasing with age [2]. It is estimated that 80% of all adults at or over the age of 65 years exhibit radiographic evidence of OA [3,4]. A majority have OA-related pain, which is thought to contribute to 10% to 25% of all visits to primary care physicians [5,6] and is the second most common cause of disability among older adults [7]. The relationship between joint pain and declines in muscle strength are beginning to be recognized as more complex than simply disuse because of joint pain contributing to muscle atrophy and muscle weakness surrounding joint [8].

Investigators have speculated that progression of knee OA may be a result of declines in quadriceps motor and sensory [9]. In patient with knee osteoarthritis various pathophysiological disorders are present, such as quadriceps weakness, decrease in joint range of motion and joint instability [10,11]. Muscle strengthening is a key component of exercise for osteoarthritis because of the relation between the muscle weakness and pain and function [12,13]. Previous investigators have found that the strength declines among older adults can be reversed through regular resistance training, even among frail older adults [14,15]. Deyle reported knee OA patients who participated in 8 weeks of a leg stretching and strengthening program significantly improved their walking speed and their perceived levels of functioning. Petrella and van Baar reviewed 33 studies and reported that exercise treatment had small to moderate effects on joint pain. Small effects on functional outcome measures and more moderate effects on self-perceived measures of functioning [16].

Interventions that use either isometric of dynamic resistance training positively impact the symptoms of OA [17]. A significant limitation of the studies on isometric resistance training is that the training took place at discrete joint angles, which may explain the limited improvements in functional ability [18]. Isometric resistance training improves muscle strength only at the joint angle at which the training takes place. A possible advantage of isometric training may be that it does not stress the joint over a functional range of motion (ROM). Reduced joint movement may result in less pain during and after the resistance training. In contrast, dynamic resistance training in non-OA subjects improves the strength of the trained muscle over the entire ROM at which resistance training took place. It has been reported that dynamic resistance training correlates with improved knee strength [19], increased neuromuscular performance. Light to moderate knee osteoarthritic patients will benefit from regular exercise, which leads to improvement in muscle strength, endurance and speed [18].

Although dynamic resistance training improves strength and functioning over the training ROM, the joint is being loaded while it is moved, which may result in pain among OA patients. Lane NE, and Buckwalter JA concluded that exercise reduces pain and improves function in patients with osteoarthritis of the knee, but the optimal exercise regimen has not been determined [20]. Fitness walking, aerobic exercise, and strength training have all been reported to result in functional improvement in patients with osteoarthritis of the knee. It is stated that pain is related to muscle weakness, and functional impairment to ROM, pain, muscle weakness and physiological changes [21]. Recent meta-analyses support the recommendations of exercise therapy in two published papers in 2004 focus specifically on the efficacy of strengthening published evidence-based recommendations for exercise in managing knee osteoarthritis [22,23].

Patients And Methods

Sample of 8 patients with age between 40 to 60 years old and have history of chronic unilateral knee osteoarthritis between 1 to 3 years, randomly selected and previously diagnosed with knee osteoarthritis volunteered and participated in the present program of exercises, 4 patients will follow dynamic resistive training and the other 4 patients will follow the isometric resistive training program. Subjects will be recruited from physician offices with medical report of a moderate degree of knee pain because of OA as evidenced by a score of 5 or greater on the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) pain subscale. A physician validated the knee pain and diagnosis of OA of the knee using previously established criteria [24]. Evaluation has always been an important component of any health intervention program. The impact of chronic disease and therapeutic interventions must be evaluated from the patient’s perspective in addition to more traditional measures of medical outcomes [25].

Exclusion criteria

Potential subjects are excluded if they show any contraindications for exercise, including a history of uncontrolled angina, cardiomyopathy severe enough to compromise cardiac functioning, electrolyte or metabolic disturbances, disabilities that prohibited resistance training of the lower extremities, or if they are currently taking nitrates, digitalis, or phenothiazine. Individuals are also excluded if they are currently participating in an organized exercise program or exercised more than 1 hour per week. Subjects are excluded from further participation if their history, physical examination, or electrocardiogram indicated that they might have difficulty with the testing procedures or if they are found to have knee pain attributable to a cause other than OA, including fibromyalgia, bursitis, tendonitis, a tear of the articular cartilage as evidence by a positive McMurray sign or underlying arthropathy of the knee or pain in the lower back, hips, or ankles. Subjects will complete these assessments at the beginning of the treatment and after 3 weeks and at the end of 6 weeks of participation in their respective treatment group.

Measurements for assessment

Perceived pain and functional ability were assessed by means of the WOMAC. The WOMAC is a multidimensional, disease-specific, self-administered health status instrument for patients with OA of the knee [26]. It is composed of the subscales of perceived pain, and functional ability. The individual completing the instrument rates his/her perceived pain, and functional ability on a 5-point (none, slight, moderate, severe, extreme) Likert scale, which is scored from 0 to 4. The scores for each dimension were determined by summing the items contributing to each of the sub scores. Higher scores on these subscales indicated higher degrees of joint pain, and functional limitations. Bellamy reported acceptable reliability coefficients (Cronbach α ≥.85) for all of the WOMAC subscales [27]. Construct validity of the WOMAC was considered acceptable compared with other instruments that measured pain, physical capacity, and joint tenderness and it is the most widely used disease-specific instrument for assessment of patients with knee osteoarthritis [28]. The sub scores of joint pain, and functional limitations subscales obtained from the WOMAC was used in the statistical analyses (Table 1).

The timed 6- minute walk test measures the distance a patient walks in 6 minutes and has been demonstrated to be a reliable measurement of functional exercise capacity [29]. Knee pain and performance of functional tasks included the time to perform an individual functional task and the subject's report of knee pain while performing the functional task. These tasks were selected as measures of functional ability because they have been cited as representing a significant functional challenge to osteoarthritic patients [30]. These tasks included ascending and descending a set of 27 stairs and ambulation for 6-minutes.

1-Descending and ascending stairs

Each subject was asked to descend and then ascend a flight of twenty-seven 15.24-cm steps. The subject started the task standing facing the stairs, with hands at sides. Timing began with the subject's firs movement. Subjects were told to descend and then ascend the stairs as quickly and as safely as possible; the time taken to complete the task was measured by using a stopwatch. Subjects were allowed to use the handrails if needed. Subjects completed each trial up to 3 times and the fastest time recorded for ascend and descend was used in the analysis. The subjects were allowed to rest 15 to 30 seconds between each trial.

2-Ambulation

Each subject is asked to ambulate for 6 minutes with relaxed and normal cadence. Timing begins with the subject’s first movement. Subjects are asked to perform walking as safe as possible; the time taken to complete the task is measured by using stopwatch. Subjects will be required to complete each trial up to 3 times and the further distance achieved for the 6 minutes’ walk will be used in analysis. Subjects will be allowed to rest for 15 to 30 seconds between each trial. Pain while performing the functional task was operationalized by having the subject rate his/her knee pain in the affected knee on a 10-cm horizontal visual analog scale (VAS) ranging from no pain (0) to the worst pain possible (10). VAS as a measure of self-reported pain has high test-retest reliability and validity [31,32]. The knee pain while performing the functional task was the sum of the 2 knee pain ratings with higher scores indicating higher degrees of pain while performing the specific functional task (Table 2).

Interventions
 

After baseline testing, subjects were randomly assigned and divided even to the 2 treatment groups; dynamic resistance training (dynamic group), isometric resistance training (isometric group), subjects assigned to the 2 resistance training groups began their respective treatments, documenting their exercise compliance on the first day of the week after their baseline testing. Both resistance-training interventions trained the same muscle groups. All resistance training occurred bilaterally, with both resistance-training interventions exposing the subjects to the same duration of muscle tension and rest during each exercise session. Both interventions of resistance training included the same scheduled increases in repetitions and sets over the 8-week training protocol. Subjects were requested to complete the 2 muscle-strengthening exercises unilaterally 3 times weekly. Under the supervision of the project staff physical therapist in an outpatient clinic. Subjects recorded their compliance with this prescribed exercise in an exercise log. The exercise log was checked by project staff physical therapist after each supervised session of resistance training (Table 3).

resistance training and 5 minutes cool down. The warm-up consisted of mild un-weighted leg movements to increase blood flow to the leg muscles. Subjects completed the dynamic resistance-training exercises, which were designed to develop the knee flexors and extensors, weeks 1 and 2; each subject performed 1 set of 8 repetitions of each exercise using rating of perceived exertion of mild fatigue after 8 repetitions. Subjects increased the number of repetitions and/or sets of repetitions every week in a scheduled progression of training outlined in their exercise program. Progression of training continued until during 3 to 6 weeks each subject performed 3 sets of 12 repetitions of each exercise with to produce a perceived exertion rating of moderate fatigue at the end of each set of 12 repetitions with a 2-minute rest between sets (approximately 50 min). The cool-down consisted of 5 minutes of stretching exercises.

The isometric resistance-training group was given strength-training instructions that explained the resistance-training exercises by using standard isometric training techniques [33]. These techniques required the individual to generate tension in the muscle without changing the joint angle. Subjects generated this muscle tension by using maximum-resistance. Subjects performed the isometric resistance-training exercises unilaterally 3 times a week while positioning the targeted muscle and joint at a predetermined joint angle (at 30&60&90 flexion degree respectively) under the supervision of the project staff physical therapist in an outpatient clinic. Subjects recorded their compliance with this prescribed exercise in an exercise log. The exercise log was checked by the exercise leader after each supervised session of resistance training,after positioning the joint to the prescribed angle, the subject generated tension in the muscle group against the sub-maximum resistance for 3 to 5 seconds without moving the joint angle. Training joint angles 30°, 60°&90° of knee flexion when performing knee flexion and extension. During training weeks 1 and 2, each subject performed 1 set of 8 repetitions while producing sub-maximum muscle tension during the exercise. After these first 2 weeks, each subject is told to complete each isometric repetition while producing maximum muscle tension for 3 to 5 seconds. This intensity of training was designed to produce a moderate degree of muscle fatigue at the end of the final repetition of the set for each exercise. Subjects increase the number of repetitions and/or sets of repetitions every week in a scheduled progression of training outlined in their exercise instructions. Progression of training continue until during weeks 3 to 6 each subject performed 3 sets of 12 repetitions of each exercise with a 2-minute rest between sets (approximately 50 min). The cool-down consisted of 5 minutes stretching exercises [34].

Results

Analysis of data were conducted in three steps by using paired sample tests for each, the first step was to examine the group of isometric strengthening ex's between different intervals of treatment (initial, after three weeks and after six weeks) and results have shown P. value<0.05 means there is difference between before and after treatment and accepting the alternative hypothesis for the effect of treatment, second step for the group using dynamic strengthening exercises an also have shown level of confident > 95% with the use of paired sample test and in the third step using the two groups in one sample as both groups are statistically similar and the results were P value<0.05.

Conclusions

The results of the present study support the efficacy of prescribing various resistance-training programs with mechanical resistance to patients with OA of the knee as a method to enhance their functional ability and to reduce their knee joint pain.

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Tables

Table 1: Paired samples statistics.

Variable

Groups

Mean

N

Std.Deviation

WOMAC pain scale

Pair

Prest

8.125

8

0.8345

1

Interst

4.875

8

1.3562

Pair

Prest

8.125

8

0.8345

2

Postst

2.125

8

0.8345

Pair

Interst

4.875

8

1.3552

3

Postst

2.125

8

0.8345

WOMAC pain scale

Pair

Prewa

7.375

8

0.5176

4

Interwa

3.75

8

0.7071

Pair

Prewa

7.375

8

0.5176

5

Postwa

1.5

8

0.5345

Pair

Interwa

3.75

8

0.7071

8

Postwa

1.5

8

0.5345

Table 2: Paired Sample test.

Variable

 

Groups

 

Paired Differences

mean

Std. Deviation

95% Confidence interval of the Difference

   

Lower

Upper

WOMAC pain scale

Pair 1

Prest-Interst

3.25

1.16496

2.27607

4.22393

Pair 2

Prest-postst

6

1.30931

4.90539

7.09461

Pair 3

Interst-postst

2.75

1.16496

1.77607

3.72693

WOMAC pain scale

Pair 4

Prewa-interwa

3.625

0.51755

3.19232

4.05768

Pair 5

Prewa-postwa

5.875

0.35355

5.57942

6.17058

Pair 6

Interwa-postwa

2.25

0.70711

1.65884

2.84116

Table 3: Paired Sample test.

Variable

Groups

Df

Sig.(2-tailed)

WOMAC pain scale

Pair 1

Prest-Interst

7

0

Pair 2

Prest-postst

7

0

Pair 3

Interst-postst

7

0

WOMAC pain scale

Pair 4

Prewa-interwa

7

0

Pair 5

Prewa-postwa

7

0

Pair 6

Interwa-postwa

7

0