It's hard to think of a training method that offers so many benefits as progressive strength training. No one other method can enhance every facet of fitness;
Run faster, jump higher, cycle longer, hit harder, increase endurance, bigger muscles, stronger bones etc.
Any athlete that strength trains is a better athlete for it. In fact, any person that strength trains is better off for having done so.
Muscles are our own personal movement motors - they propel every movement we make. If your motors are withered and weak, it reflects in every aspect of your life. Strong muscles make movement and life in general more enjoyable and easier.
When you strengthen a muscle you increase it's ability to produce force, which in turn can be trained into a specific sports related skill.
Not only that, a stronger muscle is harder to hurt (sprain) and as a result, the joints that they surround are more stable for it and thus also harder to damage.
SO thus far we have:
1) Strengthening your muscles increases force potential and thus movement performance
2) Strength training reduces the chance of injury and strengthens joints which in turn keep your bones and posture healthy.
For the majority of people, training with weights is considered reserved for those that want bigger muscles - think body building. I would like to educate a person right now that is a possibility, if that is want you want to do, however it is not something that has to happen. Getting big muscles is not as easy as simply lifting weights.
When you do lift weights/ strength train you are toning your muscles - tone simply means the residual electrical energy running through a relaxed muscle, holding it in a state of readiness. So when someone asks to "tone" an area, what they are actually seeking, is a way to strengthen that area. They may not know it, but strength training is the best and fastest way to tone a muscle.
Not only is it the best way to tone a muscle, it also happens to be one of the most overlooked ways to increase endurance too.
Taking cycling as an example (Us Brits like our cycling after Beijing) to help explain and how and why strength training helps your endurance capacity;
Your maximum strength level is 100 units in this example.
To keep the crank turning at 100 revolutions per minute you need to produce a force of 60 units each rotation. (Numbers are purely for illustrative purposes).
60 units out of a possible maximum of 100 units has you working at 60% of your maximum to hold that speed and your place in the pack.
Now fast forward 6 months and some serious, well programmed strength training later and you have increase your maximum strength level to 200 units.
That same effort of 60 units to keep the crank rotating at 100 revs per minute is now only 33% of your maximum effort and thus much easier leaving you more energy and strength for a spectacular sprint finish.
You could continue to work at 60% of your maximum strength levels which would now have you able to be pushing 120 units of effort through that crank - I'll leave you experiment with how many more revs you will get out of it (or what gear you can now work in) and how much further up the pack you are now you have added a well designed strength program to your training!
I don't know how Lance Armstrong trained but I am willing to bet he lifts weights to get the edge.
So now we have 2 more
3) Progressive strength training is the quickest and safest way to tone a muscle.
4) Strength training is a hugely beneficial method to increase your performance in endurance based events
But wait, there's more.
When a muscle has been well toned and strengthened, it needs more energy to help hold it in that readied state - it burns more calories. Bad for your food bill, great for your waist line and getting lean. The stronger you are, the more calories you will burn. Don't get the image of a super heavyweight power lifter in your mind, yes they are strong and yes they are fat, however, they choose to be fat to stay in their weight class and the extra fat around joints helps store energy and reduce the range of motion they lift a weight over and thus allows them to lift more.
Power lifters and weight lifters that stay in a lighter weight class to show off huge power to weight ratios are super lean for sure.
Strong muscles hold a better shape and are more pleasing to the eye. I am not suggesting we all look like body builders or that is even pleasing to the eye. I am suggesting that the muscles of a well trained athlete are far more pleasing than the soft out of shape muscles of your average person. Strength training can literally transform your shape - saggy bingo wings, get them stronger. "Relaxed" abs, strength train. Smaller tighter bum, strength train!
When you have a strong body you feel more confident, this leads to less stress, that leads to better health and lower levels of stress hormones, leading to better sleep and quicker recovery - bonus for sure.
As a happy side not worthy of mention strength training will also keep the muscles of you cardiovascular system strong, elastic and clear from junk.
To add to this list:
5) Strength training causes your body to burn more calories per day through an increased metabolic rate.
6) Strong muscles look better
7) Strength training reduces stress through increased confidence and better sleep.
8) Progressive strength training also helps keep your heart and vessels strong.
No other one mode of training offers so much from so little.