Exercise is medicine, but have you ever wondered how much exercise is needed to heal the body?
Studies show exercise is a powerful tool for treating knee pain and delaying or preventing future surgery. As a physical therapist, I have witnessed these benefits firsthand. Patients destined for the knife are able to delay and sometimes permanently postpone surgery through exercise.
In each case, I work with the patient to develop a comprehensive, long-term exercise plan to build the body’s resilience. In each case, I have to determine what type and how much exercise is needed.
A recent study looked at how little exercise can be used to ward off surgery.
The QUADX-1 trial
The QUADX-1 trial assessed whether home-based exercise therapy could prevent future knee surgery.
This is not the first trial attempting to prevent knee surgery through exercise. It is, however, the first to assess how much exercise is needed to prevent surgery.
The QUADX-1 trial divided participants into three groups. Each participant was deemed eligible for a knee replacement by an orthopedic surgeon due to knee osteoarthritis, had confirmed osteoarthritis on x-rays, reported an average knee pain of 3/10 over the past week, and was at least 45 years old.
All three groups were assigned 12 weeks of exercise but with differing numbers of sessions each week — 2, 4, or 6 sessions. Here is where it gets interesting.
They all performed a single exercise — the knee extension.
Why only one exercise? Poor adherence to home-based exercise programs is their greatest undoing. If you hand someone a sheet full of exercises, the chances they won’t complete the exercises is substantial. A single exercise, however, is easy to remember and knock out, even on a busy day.
The magic of the knee extensor exercise
The trial participants didn’t use the knee extension machine like the one in the image above. Instead, all participants sat on a chair with an exercise band wrapped around their ankle and fixed the other end of the band behind a door to serve as an anchor. Much simpler and cheaper.
The participants were not able to grab a yellow band (the lightest resistance) and quickly crank out three sets of ten. The exercise needed to be challenging.
The participants were instructed to find the right amount of tension — influenced by band color and the length of the band relative to the chair and wall positions — that caused failure at 12 reps. They then completed three sets of twelve reps with each rep lasting eight seconds — three seconds for extending the leg, one second pause at the top, four seconds for lowering the leg.
That’s it.
Did it work?
Yes.
Quadriceps strength increased in all three groups, but that’s not the most interesting finding.
There was no difference between the three groups. Doing a single exercise only twice a week led to the same improvements in knee strength and greater improvements in knee pain and functional outcome questionnaires compared to four and six times a week.
Two times a week was the winner.
Does this mean I barely need to exercise?
No.
The study is not looking at muscle mass, cardiovascular health, bone mineral density, or any other health benefits exercise provides. You can’t do one exercise twice a week to get in shape. A single exercise can, however, provide some benefits.
Pain is complex and relies heavily on psychological and social influences. This trial minimized the burden of exercise but still encouraged challenging exercise directly targeted to a painful area.
By performing a challenging exercise directed at the knee, the participants were shown their knee was not fragile. They built confidence in their ability to use their knee.
Knee osteoarthritis often causes people to become inactive, leading to muscle wasting and deconditioning. A single challenging exercise can improve strength — through the nervous system, not building muscle. Challenging exercise can also reduce pain through hormonal and neural mechanisms.
This study challenged my biases
I am a huge proponent of exercise. As a physical therapist, exercise and education about pain and lifestyle habits are the foundation of my treatment.
If you had shown me the plan for the trial without the results, I would have been pessimistic about the outcomes. Having seen the benefits and reflecting on the results, I understand how a single exercise can help.
There is no best way to exercise. At the end of the day, it’s about empowering people and facilitating movement. Adherence to an exercise plan is the first step.
This study does not mean all knee osteoarthritis can be prevented or reversed with two exercise sets a week. It does, however, show a single exercise can be a powerful first step towards achieving health and wellness.
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