Many people like to go to the weight room and start performing the standard isolation exercises either using a machine weight system or even free weights.  Afterwards, they do a 20-30 minute cycle of cardio vascular exercise.  Then, after a normal day of picking up groceries in/out of the car and into the house and some moderate yard work, they find themselves injured.  Usually, this injury involves the lower back.

I have found after a few decades of training that the body really performs best when it is accustomed to movements not joint isolation exercises.   There are training programs out there that focus on Core Development yet really perform standard isolation exercises like crunches or sit-ups and some back extensions.

Now, do not get me wrong, isolation exercises have their place as they are safe, effective ways to train muscles that need rehabilitating.  They are also a great way to build a foundation of training that should inevitably lead to tougher movement exercises.

Since a picture is worth a thousand words, check out how you can turn a bicep curl, military press, triceps extension into one steady movement involving several joints and balance if you try in standing on one leg.
I call this one Multi-Joint Dumbbell #1 or MJDB#1:

Now add in a squat to the exercise and a real life movement of picking up something off the floor and lifting it over your head is developing into MJDB#2:

It may take some time to build up to MJDB#3, but as you can see all it took was some imagination and you turned a tired old set of dumbbells into a harder exercise full body movement program.  As you progress with your program, add Olympic weight lifting, yoga, and any martial arts movements and you will see a difference in your entire body.  Remember fitness is a journey - not a destination so visit a variety of programs.

Other related programs I recommend that teach movements compared to isolation exercises:

TRX - Suspension Training

The Pre-Habit Workout DVD

Stew Smith is a former Navy SEAL, and author of several fitness and self defense books such as The Complete Guide to Navy SEAL Fitness , Maximum Fitness , and SWAT Workout . Certified by the National Strength and Conditioning Association as a Strength and Conditioning Specialist (CSCS) and as military fitness trainer, Stew has trained hundreds of students for Navy SEAL, Special Forces, SWAT, FBI, ERT and many other law enforcement professions.  See him at StewSmith.com