A good workout routine will test you, but shouldn't damage you. As muscles get used, especially somewhat beyond their usual range, lactic acid, micro-tears and other physiological changes occur that result in muscles being built up stronger than before.
But if you are experiencing back pain, neck aches, knee joint soreness and other symptoms, you should consult with an expert. Your technique may be wrong, you may be trying to do too much, too soon, or you may have a medical problem that should be addressed.
Work up to any vigorous routine slowly. How slowly will vary from person to person, depending on age, experience, prior exercise routines and overall fitness. Get muscles warm and limber before cranking it up. Most strains and rips result from being too cold and not stretching, or extending more than you're ready for.
Warm-ups should take at least 15 minutes and include very gentle jogging in place or jumping jacks to get the cardio and lung systems working well. They should include some slow, gradual stretching to get joints lubricated and muscles relaxed and gently lengthened. Warm-ups that are too short can easily lead to stretched or torn cartilage that takes a long time to heal.
Don't let inexperienced trainers, or so-called 'friends' embarrass you into believing you have to get out and run five miles two weeks after an injury, surgery or other debilitating condition. Physical therapy and exercise sometimes requires that you work against discomfort, but you don't leap over tall buildings the first day out.
Every person committed to fitness will want to push him or herself to achieve excellence. But an attitude that leads to overdoing it is counter-productive to your goal. You're working to improve or maximize health and overall body tone and strength - not proving you are 'mentally tough'.
Before you begin a new routine that involves activities that are unfamiliar, get guidance from an expert. Next to bad warm-ups or overdoing it, incorrect technique is the leading cause of injury. If you don't know how to use a station at the weight machine correctly, don't be embarrassed to ask. No one is born with this knowledge. Anyone who mocks you for ignorance isn't someone whose opinions you have reason to heed.
Be aware of your environment while you go through your routine. It's easy to get into a rhythm, get concentrated on your workout and end up crashing into a wall or a nearby person. Jogging especially requires that you pay attention to the surface you run on and the people and cars around you. No shoe in existence will keep you from slipping on a muddy patch. Only awareness and good reflexes can help.
Stay within your comfort zone as you gradually expand it. One of the foremost reasons people give up on workouts is injury produced by working beyond their capacity. That makes working out no longer fun. Building up, while you build out, to increase your ability to do more, faster will keep you going for years to come.
Your health will thank you for exercising common sense, while you exercise your body.
