Exercise Substitutions and Unit Conversion in Strength Builder

I would like to suggest two improvements to the Strength Builder that would significantly improve usability for coaches and athletes.

1. Ability to Program Exercise Substitutions

Coaches should be able to assign up to two substitute exercises for each programmed strength exercise. In practice, athletes often encounter situations where they cannot perform the exact exercise prescribed (equipment limitations, minor injuries, gym restrictions, etc.). Currently, this creates confusion because athletes do not know what alternative movement the coach prefers.

Allowing coaches to pre-assign one or two substitute exercises would solve this issue. If the primary exercise cannot be performed, the athlete could simply select a substitute that the coach has already approved. This would maintain training intent while preventing unnecessary communication delays.

1. Ability for Athletes to Switch Between Kilograms and Pounds

The Strength Builder currently lacks a simple way for athletes to select weights between kilograms and pounds. Many coaches program in kilograms, but athletes in some countries primarily use pounds. Because the platform does not allow athletes to switch units, they must manually convert every weight prescription.

This creates unnecessary friction and increases the chance of input errors. Athletes should be able to toggle between kilograms and pounds for each exercise so the displayed load automatically converts to their preferred unit.

These two changes would make the Strength Builder much more practical for coaches managing athletes across different gyms, equipment setups, and countries.