Workouts warm up your soft tissues that respond to exertion and movement by becoming more elastic. This means your connective tissues, myofascia, not just your muscles. Collagen becomes softer, just like hard butter that warms up, so your movements are eased.
Here is a short demonstration of stretching/fitness exercises by Miranda Esmonde White, author of the best seller "Aging Backwards Miranda Esmonde White". This one is for upper body pain.
Many people get worse aches and pains in cold and/or damp weather, so keeping up the winter time workouts is crucial. Seasonally, our hormones accommodate the fall and winter cycles, and most people feel like hibernating. We may not have sunshine in the evenings to get us motivated for exercising. If we do, it may be too cold to go out and do it, if that is what you prefer.
And sometimes it is too hot in the summer to exercise outdoors!