Neurotoxin (or neuromodulator like botox) injections target the muscle to weaken or paralyze the muscle. It is FDA approved for injections on the face to weaken or paralyze the muscles of the face that make wrinkles. Injections of toxins elsewhere on the body can be used "off-label" - meaning not FDA approved for injections in those areas, calf muscles being one of those areas. If you are constantly working out, then the muscle will swell and grow in size (hypertrophy). Toxin injections can help the size and hypertrophy of the muscle like it does with other muscles (masseter muscle of jaw), but it may cause weakness and functional loss. The amount of botox needed to reach this threshold depends on each individual patient and the amount of bulk there is. Starting with a lower dose toxin is usually a better idea than starting at a high dose, since botox is not reversible. More toxin can always be added later, but if too much is injected initially, there is nothing that can be done to reverse it, and you will have the effect linger for 2-3 months (typical duration of effect of most toxins). Too much toxin injections in the calves can can cause weakness in walking, running and even standing for a long period of time. This in turn will lead to compensatory changes in your gait, and compensatory changes in other muscles chipping in to do the work the calf muscles are supposed to do, further leading to muscle imbalances and potential injuries when training. It is possible that even in small doses, these compensatory changes may happen, and it is unpredictable as to what extent it will happen. If you are working out everyday, it may affect your training and your overall fitness goals. The risk of losing your function should be weighed against the benefit of the contour and appearance of the muscle. Toxin injections in the calf is a double edged sword and the risks and benefits should be carefully considered.