High-intensity vs. low-intensity strength training fails to reduce OA knee pain
High-intensity strength training failed to significantly reduce knee pain, or knee joint compressive forces, at 18 months when compared to low-intensity regimens or attention control in patients with osteoarthritis, according to data.
“Both high- and low-intensity strength training significantly increase strength in an older osteoarthritic population,” Stephen P. Messier, PhD, of Wake Forest University, in Winston-Salem, North Carolina, told Healio Rheumatology. “However, the increase in muscle strength did not translate into significantly better thigh muscle volume. Hence, strength training in this population will increase strength but has little effect on thigh composition.”
In their findings published in JAMA, Messier and colleagues observed that a previous study in 2001 by Baker and colleagues had suggested that short-term, high-intensity strength training was safe and well-tolerated by older adults with knee OA. Noting that long-term improved strength could improve clinical outcomes, the researchers aimed to analyze whether high-intensity training in patients with OA reduced knee pain, as well as joint compressive forces, more than low intensity routines or attention control.
Messier and colleagues conducted an assessor-blinded, randomized clinical trial of 377 community-dwelling adults aged 50 years with radiographic knee OA, knee pain and a BMI ranging from 20 to 45. Enrollment was carried out at Wake Forest University between July 2012 and February 2016, with follow-up assessments completed by September 2017. Participants were randomly assigned to one of three routines, with 127 in the high-intensity strength training group, 126 in the low-intensity strength training group, and 124 in the attention control arm.
Participants in the strength training groups worked out three times weekly over a period of 18 months. Sessions included a 5-minute warm-up, training for 40 minutes, followed by a 15-minute cool-down. After the first four sessions, each participant was given a test to determine the maximum amount they were capable of lifting in a single repetition (1RM). This amount was used as their starting resistance. Exercises included leg curl, leg extension and leg press; seated calf; hip abduction and adduction; compound row; vertical chest; lower back; and abdomen.
The high-intensity group performed three sets of each exercise beginning at 75% 1RM, with eight repetitions per set for 2 weeks, before moving on to 80% 1RM with eight repetitions per set for weeks 3 and 4, then 85% 1RM with six repetitions per set for weeks 5 and 6, and then 90% 1RM with four repetitions per set for weeks 7 and 8. Week 9 was a taper week, with alternate exercises and establishing new 1RMs for each exercise. This 9-week block was then repeated using the new 1RM values. Meanwhile, the low-intensity group used the same 9-week block pattern, but with three sets of 15 repetitions at 30% to 40% 1RM for the same exercises.
Participants in the attention control group attended 60-minute, biweekly group workshops for 6 months, followed by monthly sessions for 18 months.
Primary outcomes included Western Ontario McMaster Universities Osteoarthritis Index (WOMAC) knee pain and knee joint compressive force — defined as the maximal tibiofemoral contact force exerted along the long axis of the tibia during walking — at 18-month follow-up. Analyses adjusted for sex, baseline BMI and baseline outcome values. A total of 320 participants completed the trial.
According to the researchers, mean adjusted WOMAC pain scores at 18 months were not statistically different between the high-intensity group, at 5.1, and the control group, at 4.9, (adjusted difference = 0.2; 95% CI, –0.6 to 1.1). Similarly, there was little difference between the high-intensity group and the low-intensity arm, which had a mean adjusted WOMAC score of 4.4 (adjusted difference = 0.7; 95% CI, –0.1 to 1.6).
There was also no statistically significant difference in mean knee joint compressive forces, with 2,453 N recorded for the high-intensity group and 2,512 N for the control group (adjusted difference = –58; 95% CI, –282 N to 165 N), and 2,475 N for the low intensity arm (adjusted difference compared with high intensity = –21; 95% CI, –235 N to 193 N).
There were 87 nonserious adverse events — including 53 in the high-intensity group, 30 in the low-intensity arm and 4 in the control — and 13 serious adverse events — five in the high-intensity group, 3 in the low-intensity group and five among the controls — unrelated to the study.
“Neither high- nor low-intensity strength training exacerbate joint space narrowing. Hence, strength training does not accelerate osteoarthritis progression,” Messier said. “Strength training has a modest, but consistent effect on pain reduction of about 30%. Some of this improvement could be attributed to attention, placebo response, and regression to the mean. An excellent healthy living education intervention can result in similar outcomes.”
“Overall, low-intensity strength training had better short term — 6 months — results than high intensity strength training, including less pain, better function and better mobility,” he added. “However, by 18 months these differences were absent. Should older adults with knee OA incorporate strength training into their exercise routine? Without any intervention, adults lose strength with aging, so yes, strength training would be excellent to include. However, high-intensity strength is not necessary since similar results are obtained with low-intensity strength training.”