Participating in a group exercise class challenges you to work out beyond your perceived limitations. The instructor observes your body for signs of fatigue and pushes you to your limits. You are likely to work out harder, as everyone is exercising toward the same goal than you would on your own.
The ladies within the charity meet and have a fitness class (Zumba) every Saturday. This is to help them be fit while they deepen their friendships so that they can fit in.