|On the one hand there is no problem with a manager exercising during a meeting unless he or she exercises bad judgment because of a failure to pay attention. With this in mind, if questions are not being answered or promised actions are not being taken, then you and your associates should mention your concern to your manager.|
On the other hand, even if your manager is not distracted by his exercises, the same cannot automatically be said for those who meet with him. The effectiveness of any meeting is going to be undermined if you and your associates are annoyed by his "uplifting" behaviors. On the psychological side, flexing muscles can easily be perceived as flexing power, and that alone can be a mighty distraction. Either way, he might be concentrating on the meeting, but you are not.
There is also the question of where to draw the line. If a manager can lift weights during a meeting, what else can he or she do? Polish shoes? Clip fingernails? Crack every knuckle? All of these behaviors, including exercising, can be barriers in the communication process, but this really depends on the players involved.
If you believe that communication is suffering because of your manager's strong-arm behaviors, then you and your associates should discuss this with him before something snaps.