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September 28th 2006
Moderate to severe osteoarthritis affects more than 22 million American
adults between the ages of 25 and 74 and knee osteoarthritis (OA) can lead
to disability in daily activities. Weakness in the quadriceps can be a risk
factor for knee OA, but it may be the easiest one to prevent. Previous studies
have rarely investigated whether quads strengthening exercises prevent or
slow progression of knee OA or changes that are visible in X-rays. None
have used
the highly standardized x-ray procedures employed in a new study published
in the October 2006 issue of Arthritis Care & Research , which examined
the effects of strength training on the incidence and progression of knee
OA in older adults.
Led by Alan E. Mikesky, PhD, of Indiana University and Purdue University
in Indianapolis, IN, researchers conducted a study of 221 patients divided
into 4 groups (OA/pain, OA/no pain, no OA/pain, no OA/no pain) that were
then randomly assigned to either a strength training (ST) program or a range-of-motion
(ROM) regimen for 30 months. Patients initially trained at a fitness center
twice a week and at home once a week; the sessions at the fitness center
were gradually decreased until patients were doing all of the workouts at
home after the first year. The ST program included upper-body exercises,
but was focused on resistance training for the lower-body. The ROM exercises
consisted of simple movement exercises without weights.
Strength was measured and X-rays were taken at the beginning of the study
and at 30 months. The severity of OA features on the X-rays was rated independently
by two different readers who didn’t know to which group each patient
belonged. In addition, patients were asked to
return to the fitness center for strength testing and assessment of pain
and function every 6 months after the first year. Of the 221 patients, 67
did not complete the exercise program, mostly because of time and travel
constraints; 174 patients were evaluated at 30 months.
The results showed that patients in both groups lost lower extremity strength
over 30 months, but the rate of loss was slower with ST than with ROM. In
patients with OA at the beginning of the study, the average loss of joint
space width as seen on X-rays was 37% less in the ST group than in the ROM
group, although this was not considered to be significant. However, progression
of joint space narrowing occurred less often in the ST group. In addition,
neither
group showed a decrease in knee pain, although this is not particularly
surprising in light of the fact that half of the patients did not have any
knee pain when the study
began. Patients in the ST group did begin to show better function during
the last six months of the trial.
The researchers note that resistance exercise has consistently been shown
to maintain or increase muscle mass, as well as improve strength. “In
light of several previous positive studies in this area, the present study’s
failure to demonstrate gains in isokinetic quadriceps strength in the ST
group is difficult to explain,” the authors state. One explanation
might be that adherence to the exercise programs was only moderate during
the first year, although it increased slightly during the remainder of the
study. The fact that patients showed gains in isotonic strength (i.e. weight
lifted with exercise machines such as leg presses) but not isokinetic strength
(i.e. the speed at which weight is lifted) may have to do with the fact
that isotonic strength was measured in a way that closely resembled the
exercises patients were familiar
with.
Despite the lack of gains in isokinetic strength, a beneficial effect of
strength training, namely less progressive joint space narrowing in the
ST group, was suggested in the X-ray results. However, negative effects
were also noted: in knees that were normal at the beginning of the study,
joint space narrowing was more common in the ST group than the ROM group.
The authors do not believe, however, that strength training is harmful for
adults without knee OA, citing other studies that have shown benefits from
these types of exercises. “In any event,”
they conclude, “this finding requires confirmation in future trials
of resistance exercise programs for older adults, which should include serial
standardized radiographic or MRI examination to monitor possible adverse
effects of lower-extremity resistance on articular cartilage in the knee.”
Article: “Effects of Strength Training on the Incidence and Progression
of Knee Osteoarthritis,” Alan E. Mikesky, Steven A. Mazzuca, Kenneth
D. Brandt, Susan M. Perkins, Teresa Damush, Kathleen A. Lane, Arthritis
Care & Research, October 2006; (DOI: 10.1002/art.22245).
SOURCE: John Wiley & Sons, Inc.
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