I often need to talk to clients about switching them to endurance training at the gym. Usually, they have noticed that their usual strength training workout isn’t working: it feels too intense, it feels exhausting “and not in a good way,” they don’t seem to be making progress anyway, and they are worried that training may be a problem for a current injury or pain problem. Often, they have already stopped working out altogether.
If you enjoy the gym, this is an exasperating situation. You are eager for a solution. You want to get back to work!
If you don’t especially enjoy the gym — if you are only strength training for weight loss, or as part of a general fitness program that your doctor put you up to — then you are eager for an excuse to stop!
What’s going on here? Why do strength training workouts sometimes seem to stop working? And how can a switch to endurance training help?
If you’ve spent any time at the gym, you will have heard people talking about “reps” for repetitions and “loads” for the heaviness of a weight. Strength training refers to “high load, low rep” exercises — lifting weights so heavy that you can only manage a few repetitions. Endurance training is the opposite: lifting light weights lots of times.
Endurance training and strength training are the top half of a spectrum of intensity in basic rehabilitation exercises:
|PF-ROM Exercises||25–100||extremely low||painless|
|Endurance Training||12–50||low to moderate||moderate exertion discomfort|
|Strength Training||6–12||moderate to high||strong exertion discomfort|
Strength training may not work well on muscles that contain significant muscle knots.1 The evidence is circumstantial, not direct: to the best of my knowledge, the subject has never been studied. However, it is a reasonable theory, based on what is known about muscle knots.
Common muscle knots — technically known as a myofascial trigger points — are involved in virtually every pain problem or injury. They either cause it, or complicate it, or both.
Trigger points may develop for months or years before causing obvious symptoms. These “latent” trigger points may interfere with strength training long before you are aware of any problem, whether you are injured or not.
A trigger point is a small, dysfunctional patch of muscle tissue, a localized spasm. It is unhealthy: usually painful to press on, full of waste metabolites. Muscle cells affected by trigger points may not be as neurologically responsive, and probably cannot recover from training as well as unaffected muscle cells.
More importantly, trigger points actually weaken a muscle.2
Although the physiology is complex and imperfectly understood, there is a straightforward “mechanical” reason why trigger points probably make you weaker.
The smallest functional unit of muscle physiology is the sarcomere, which is like a microscopic muscle: a bundle of overlapping protein fibres that can grab onto each other and pull, like living Velcro that can suck itself together. A muscle is basically several million sarcomeres working in together.3
In a trigger point, the sarcomeres are over-contracted … which means that the sarcomeres up and down the line are, to some extent, over-stretched.4
The over-stretched sarcomeres on either side of a trigger point cannot contract efficiently. Their fibres, barely overlapping, cannot get a “grip” on each other. It’s like trying to start a car in third gear.Contracting a muscle with trigger points is like trying to start a car in third gear.
Anyone experienced with weight training knows that it’s harder to start a lift with stretched out muscles. In a muscle with trigger points, it’s like the muscle is always stretched out.
For a much more detailed explanation of how this all works, see Micro Muscles and the Dance of the Sarcomeres.
At the very least, strength training when you have significant trigger points is probably futile. But it can certainly be hazardous as well.
There is also probably an increased risk of muscle strain (tear). This situation tends to result in poorly coordinated muscle contraction, and inappropriate muscles trying to “pinch hit” for the ones you are trying to use. But the most likely consequence is simply that your trigger points will get worse, which can lead to surprisingly intense flare-ups of pain that your trainer, doctor, or even physiotherapist will usually misinterpret.
Disturbances of motor function caused by trigger points include weakness of the involved muscle function, loss of coordination by the involved muscle, and decreased work tolerance of the involved muscle. Weakness and the loss of work tolerance are often interpreted as an indication for increased exercise, but if this is attempted without inactivating the responsible trigger points, the exercise is likely to encourage and further ingrain substitution by other muscles, with further weakening and deconditioning of the involved muscle.
Muscle pain, by Siegfried Mense, David G Simons, and IJ Russell, p. 214
Trainers simply aren’t aware of trigger point physiology, doctors have been proven by other doctors to be incompetent at physical therapy,5 and physiotherapists, although generally competent rehabilitation coaches, are not well-informed about trigger points specifically.6 I think they probably often misinterpret poor results in strength training as a natural, unavoidable part of the challenge of rehabilitation. This is a daily frustration for me as a therapist.
But there is an alternative!
Gentler, more repetitive usage of the muscle is the solution. If you are in pain, mobilizations are even gentler than endurance training, and often more appropriate. But endurance training is simply a terrific way for enthusiastic weight lifters not just to safely continue training, but to actually help to relieve the trigger points and get back to strength training.Endurance training can actually help to relieve the trigger points so that you can get back to strength training.
The low loads of endurance training simply minimize the risk of aggravating trigger points or tearing muscle, while the high repetitions provide the stimulation that is needed for healing. No tissue can thrive without some stimulation! A good endurance workout creates a significant metabolic demand, which increases circulation more than any massage ever could.7
Injury rehabilitation is all about taking “baby steps.” Understanding endurance training gives you another increment to work with, a way of using the gym without banging your head against a brick wall. Good luck!
I am a science writer, former massage therapist, and I was the assistant editor at ScienceBasedMedicine.org for several years. I have had my share of injuries and pain challenges as a runner and ultimate player. My wife and I live in downtown Vancouver, Canada. See my full bio and qualifications, or my blog, Writerly. You might run into me on Facebook or Twitter.