Look at a home exercise plan and you will see two kinds of instruction. Some lines say "10 repetitions". Others say "hold for 30 seconds". The first is a dynamic exercise: the joint moves through a range. The second is a static, or isometric, exercise: the muscle works hard while the joint stays still. Therapists prescribe both on purpose, and the mix usually changes as you recover.
What an isometric hold does
A wall sit, a plank, or pressing the back of your knee into a rolled towel are all isometric. Because the joint does not travel, a hold can load a muscle or tendon at one tolerable angle while avoiding the part of the range that hurts. That makes holds useful early, when movement is restricted or painful.
There is also a short-term pain effect. In a small 2015 study in the British Journal of Sports Medicine, six volleyball players with patellar tendinopathy did five 45-second holds at 70 percent of their maximum. Pain during a decline squat fell from about 7 out of 10 to under 1, and the relief was still present 45 minutes later. A matched set of repetitions reduced pain by less and the effect did not last. Six people and one session is a thin base, and later studies have not always reproduced the finding, so read it as the reason some therapists use holds before heavier work, not as a guarantee.
What repetitions do that holds can't
Moving through a range trains the muscle at every angle in that range, trains control of the movement, and rebuilds the capacity for the things you actually need: stairs, standing up, reaching overhead. The longer-term evidence favours this kind of progressive loading. A 2020 systematic review of ten randomised trials found isometric exercise was not superior to isotonic (moving) exercise for chronic tendinopathy, either immediately after treatment or at up to 12 weeks, though the authors rated the evidence as limited. A 2025 meta-analysis of nine knee osteoarthritis trials with 688 participants found isometric exercise beat no exercise for pain, function, and strength, but showed no advantage over isotonic exercise. Holds are an effective option. They are not a better one.
Why your plan has both
- Early on, holds let you load a joint that cannot yet move far or move comfortably, for instance after surgery or during a flare.
- For pain-sensitive tendons, a set of holds before repetitions can make the repetitions more tolerable.
- Repetitions are the main progression. Over weeks, the balance usually shifts from holds toward reps, then toward heavier or faster reps.
- The same exercise can be either. A wall sit is a held squat; a squat is a moving wall sit. Your therapist picks the version that fits the week.
Doing each one well at home
- For holds: breathe steadily, count the seconds honestly, and stop when your form gives out rather than when the timer does. A 20-second hold with good position beats a 30-second hold that collapses at the end.
- For reps: use the full range you were shown, control the lowering phase, and rest between sets. Speeding through reps to finish is the most common way they stop working.
- For both: note how it felt. Pain during, and pain the next morning, tell your therapist whether the dose is right.
How KineTrue tracks them
KineTrue treats the two types differently. Dynamic exercises are counted in reps; static exercises are timed in seconds. Each logs range of motion, a movement quality signal, and your pain rating. Your therapist can see that you held for 25 seconds rather than 30, or that your reps slowed down in the last set, which says far more than a tick in a box. If you want the related question of stretching answered, read our guide to static vs dynamic stretching.
Holding your breath during a hold pushes blood pressure up. Breathe through every hold, and if you have a heart condition or high blood pressure, ask your therapist how long and how hard you should be holding.