Calf Strength and Plantar Flexion: Straight-Knee vs Bent-Knee Raises

Name the ankle action precisely

Plantar flexion is the ankle action that points the forefoot away from the shin. The gastrocnemius crosses both the knee and ankle, whereas the soleus crosses the ankle. That anatomy explains why knee position changes a calf-raise task; it does not make a straight-knee raise a test of one muscle or a bent-knee raise a cure for a movement problem. OpenStax lists both muscles among the plantar flexors of the lower leg. OpenStax

Compare support and knee position

In a standing calf raise, the knees are commonly near straight and the hands may need to manage balance. In a seated raise, the knees are bent and a pad or machine supplies external resistance. A bent-knee standing variation can land between those choices. The important distinction is practical: if wobbling ends a standing set long before the ankle work is challenging, hold a rail, use a machine, or choose a seated variation. Support can make range and tempo more repeatable.

Use a stable edge or machine platform only when it lets the heel move through a range you can control. The bottom position should be a deliberate ankle position, not a bounce off the floor. At the top, finish the ankle movement without rolling hard to the outside of the foot or rushing to the next repetition. The height of the lift is less useful than whether the same foot position and range recur.

Select a range you can own

Place the ball of the foot on the platform, establish light contact with a support if needed, and let the heel lower only as far as you can reverse smoothly. Rise by pressing through the forefoot, pause for a count, then lower at a similar pace. A shoe, platform height, and machine design can all change how the movement feels. Record those details before deciding that a later set was stronger or weaker.

Illustrative: two calf tasks in one week

Illustrative example: On one day, perform three sets of ten supported straight-knee raises with a two-second lower and a one-second top pause. On another day, perform three sets of twelve seated raises at a load that permits the same pauses. Log the variation, load, range cue, and whether the final repetition matched the first. Progress one variable at a time: a small load increase, an extra repetition, or a longer pause. This is a training comparison, not a claim that the two exercises measure identical capacities.

Build progression from records, not folklore

ACSM’s resistance-training position stand describes progression as dependent on training status and goals, with exercise choice and loading adjusted over time. ACSM position stand For calf work, that can be as ordinary as choosing a repeatable version, doing it consistently, and increasing demand after the present dose is controlled. There is no need to turn every raise into a balance challenge or to chase an arbitrary burn.

Calf raises train ankle plantar flexion under the conditions you choose. They do not by themselves establish a runner’s stride quality or predict performance. Keep the claim at the scale of the exercise and make each set legible enough to compare later.