Strength athletes often eschew cardio. On the other side of the coin, endurance athletes often ignore strength training. If we do this, we do so at our peril.
With one of the rising causes of death in the USA being isolated old folks who fall over and can't get up again, being strong is even more important. And it's not just the USA; my elderly neighbour fell over one morning and was only discovered on the floor by her son when he returned home at 10pm!
Five Reasons Why You Should Lift Heavy Stuff Regularly
Maintenance of muscular balance and basic human movement patterns
Most endurance sport takes place in very small ranges of movement, using a number of muscle groups in preference to others. This results in muscular imbalances that make you prone to injury but are very effectively reversed by doing compound (whole body) strength training.
Prevention of muscle loss (sarcopenia) into old age
Muscle loss as we age is perfectly normal if we don't undertake activities to prevent it. "Use it or lose it" is a great motto in this regard. Most people become progressively more sedentary as they age and this simply makes matters worse. Regular strength training, in conjunction with solid nutrition, will help you to maintain, if not improve your muscle mass at any age.
Improves sports performance
Muscle is what what drives us during those performances. A stronger muscle will fatigue more slowly under the same load, allowing you to maintain that all-important form. It'll also give you a bit of a reserve for those moments when you need a surge of speed along the way.
Improved insulin sensitivity and thus staving off type 2 diabetes
Similar to cardiovascular training but perhaps a little different. It might be a small distinction but, whilst cardio clears sugar from the blood by using it for energy, strength training makes muscles more sensitive to insulin, reducing how much the body pancreas needs to secrete to deal with blood sugar.
Strength training makes you look good, feel good and able to be useful in the world
A muscular physique simply looks good, and who doesn't want to look good? You don't need to be built like Arnie to have a great physique, just have some muscle. Being in shape fells good too. Finally, it's great to have a level of strength that allows you to do whatever you please, simply because you can.
I knew a world-champion athlete who could not pick his 5-year-old daughter up off the floor; how disappointing to be that fast & that weak. What's more, he was only on his 40's.
Consider what he could be facing in his 80's. Unable to get in and out of a chair without pain? Unable to get up off the floor if he falls over?
Life is about more than just the now. A long life should not simply be a long death, remembering what you used to able to do in your 20's, 30's and 40's.
Bottom line: That's why you need strength training.