medwireNews: High-intensity strength training does not significantly reduce pain or knee joint compressive forces among people with knee osteoarthritis, suggest findings from the START trial.
“Thigh muscle weakness is associated with knee discomfort and osteoarthritis disease progression,” and “[t]he study premise was that long-term high-intensity strength training would affect the biomechanical pathway via reduced knee joint compressive forces,” leading to attenuated pain and disease progression, explain the investigators.
To test this hypothesis, 377 participants aged 50 years or older with knee pain and radiographic knee osteoarthritis were randomly assigned to take part in high- or low-intensity strength training three times per week for 18 months or to receive a control intervention involving 24 educational group workshops covering topics such as foot care, nutrition, and sleep practices.
Both strength training programs comprised six lower body and four upper body/core exercises; the high-intensity program involved lifting 75–90% of the maximum amount of weight a participant could lift in a single repetition, while the low-intensity program involved lifting 30–40% of the maximum.
As reported in JAMA, average WOMAC pain scores at baseline were 7.0, 7.4, and 7.2 points in the high-intensity, low-intensity, and control groups, respectively, and these scores improved over the study period in all groups.
At 18 months, the adjusted mean WOMAC pain score was 5.1 points in the high-intensity group, compared with 4.4 points in the low-intensity group and 4.9 points in the control arm. There were no significant between-group differences in WOMAC pain scores at 18 months, but the researchers note that the 95% confidence intervals around the pairwise differences “included worse scores for the high-intensity group of between 1 and 2 points that are of uncertain clinical importance.”
Therefore, “clinically important levels of increased pain with high-intensity training cannot be ruled out,” they say.
The team also found that the adjusted average maximum knee joint compressive force at 18 months was comparable in the high-intensity compared with the low-intensity and control groups, at 2453 N versus 2475 N and 2512 N, respectively.
Despite the lack of impact of strength training on pain and compressive forces, post-hoc analysis demonstrated that average knee flexor strength at 18 months was significantly greater in the high- and low-intensity exercise groups than the control arm, at 51.5 Nm and 52.6 Nm versus 43.8 Nm, respectively.
Therefore, “significant increases in muscle strength were not associated with improvement in knee joint loads,” say Stephen Messier (Wake Forest University, Winston-Salem, North Carolina, USA) and co-investigators.
They conclude that their results “do not support the use of high-intensity strength training over low-intensity strength training or [a control intervention] in adults with knee osteoarthritis.”
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