What will exercise do for you? Well, here's just a few things to think about: exercise will boost your sex life, improve erectile strength, improve your memory and brain function, build new synapses in your brain, decrease your risk of cardiovascular disease and make your body look twenty plus years younger. Any other questions?!?
I can't think of anything better for your sex life and erectile strength than exercise. Other than a Low Fat Diet or possibly a Mediterrean Diet, you can't beat exercise to boost your bedroom performance. Exercise boosts all the stuff you want for erections, testosterone and nitric oxide for starters, and lowers all the stuff that's hard on erections - no pun intended - including blood pressure and triglycerides. The list of benefits could go on and on and I've covered that extensively in my link on How Exercise Can Cure Erectile Dysfunction and Improve Your Sex Life.
Besides an improved sex life and better erections, exercise also gives you the potential to literally rebuild your brain. Any exercise is good in this respect, but probably the most important in terms of your cognition is probably Interval Training combined with aerobics. (By the way, science has discovered how you can literally rebuild your Memory and Brain at any age.) Interval Training increases Growth Hormone and IGF-1, which in turn has been shown in the research to cause neurogenesis, a scientific term for building new neurons. 
Straight aerobics is also fantastic for the brain: multiple studies have shown that it raises levels of a brain chemical called BDNF, which can actually promote the formation of new neurons and synapses.  And, by the way, this is NOT just for the young. Remarkably, the studies show that both young and old can rebuild their brain.
Okay, so we can add new neurons to our brains. Does that really translate to more brain power? Can we actually make ourselves smarter through exercise?? The research says, "Yes!" A large meta-analysis in 2003 showed that found that exercise actually improved many of the cognitive areas in seniors that are most likely to show age-related decline such as ï¿½planning, scheduling, working memory, inhibitory processes, and multitaskingï¿½.  Furthermore, one recent MRI study of older adults found that exercisers had significant increases in grey matter, i.e. these individuals actually increased their brains! Again, this is seniors we are talking about here. 
Anyone who exercises hard and consistently for any length of time can feel this. Endurance training "clears your mind" and makes you ready for action. Menï¿½s Health in the October 2005 issue covered this and described it as "the kind of smart that leads to faster and more accurate decision making, yields greater productivity and inspires innovation. If you want to be calculating about it, itï¿½s the kind of smart that makes you money." This same article goes on to document an elite group of corporate executives that enter the CEO Challenge, which is an Ironman Triathlon. Most of these executives believe that exercise completely transformed their careersoup of co and that without it, they would not still be CEOs today.
Those CEOs, who have been doing this for quite awhile, were years ahead of their time: research is pouring in showing almost unbelievable gains in mental capabilites from exercise.
All of this has been shown in multiple studies. I cover this in my How to Raise Your Kid's IQ page. (See number 9.)
It should not be suprising that exercise is also one of the few proven preventors of Alzheimer's and dementia. One analysis of the Canadian Study of Health and Aging, for example, found that "Compared with no exercise, physical activity was associated with lower risks of cognitive impairment, Alzheimer disease, and dementia of any type. Significant trends for increased protection with greater physical activity were observed. High levels of physical activity were associated with educed risks of cognitive impairment, Alzheimer disease, dementia of any type".  And this appears, by the way, to occur not just because of exercise's neuron-building and neuron-promoting properties. A study at the University of Chicago showed mice that exercised had 80% less Alzheimer's plaque than mice that did not exercise.
Exercise is also a proven mood-enhancer and - let's face it - a decent mood is essentially to libido, self-confidence and relationships in general. One study on the toughest case possible, those with major depression, found that exercise was as clinically effective as the blockbuster antidepressant Zoloft.  This is important to keep in mind because so many of the antidepressants cause or exacerbate erectile dysfunction. A follow up study verified that the results were just as impressive after 10 months!  And all with no side effects...
And donï¿½t leave out strength training. It is true that past 40 it's harder to gain muscle and it takes longer to recover. Is that any shock? Your testosterone isn't 800 any more, so that shouldn't surprise you too much. But what you may not realize is that your nightmare is not the fact that you have trouble putting on muscle. Your nightmare is losing muscle.
Each pound of muscle literally burns the fat right off your body. Consider this: if you add ten pounds of muscle somehow: it will burn off 62 pounds of fat over the next year! And for anyone past middle age a more relevant comment: if you let your body lose ten pounds of muscle, you are opening yourself up to potentially gaining 62 pounds of fat unless you drastically change your caloric intake (which requires nerves and discipline of steel).
Check this link out for details:
The major point is that you definitely do not want to lose muscle. If you do, you will inevitably begin to put on weight more easily because your "metabolism" shifts to where you keep those pounds more easily. For some of you this sounds VERY familiar. Have you ever felt like you just canï¿½t lose weight even when you cut back on calories? Well, if youï¿½ve lost a lot of your muscle mass, what do you expect? Muscle is your bodyï¿½s fat burner.
So, yes itï¿½s time to hit the iron. There are added bonuses by the way. Recent research shows that weight lifting burns off many more calories than previously thought. So not only does weight training burn fat while you're lifting, it helps your body burn fat all day long after your training session.
Plus, Weight Lifting in particular has been shown in several studies to increase baseline testosterone. No wonder that exercise so completelky transforms the body. Even those middle aged and beyond bodies out there can transform themselves. Itï¿½s a fact that those who lift weights with even moderate intensely will turn back the clock dramatically. Someone who lifts weights will have the body of someone 15-20 years younger.
However, please don't think that you have to become a bodybuilder to take a couple of decades off of your appearance. Looking twenty years younger requires only modest effort and even that level of training will boost your Self-Image and Mental Outlook, which in turn can directly boost your testosterone, which builds more muscle and improves your mental being which in turn burns more fat and so on. I think you get the idea: this all ties together and one discipline will help the other.
CAUTION: New research shows that aerobics/cardio should always be done after weight training. A recent study out of Japan  has potentially uncovered the fact that weight training actually stiffens arteries - and you don't want stiff arteries if you want anything else to be stiff if you know what I mean - unless followed by cardio or aerobics. Furthermore, weight training without cardiovascular training leads to decreased Nitric Oxide production from the endothelium, which is bad - very bad. Intense weight training leads to very high, albeit brief, blood pressure levels.  These pressures may "stun" the lining of our blood vessels and arteries and possibly even do long term damage. Again, do NOT do aerobics before your weight workout - do it after. This will nullify any negative effects on the endothelium of the weight training. (Note: Some studies have not shown weight training in a negative fashion, but it is best to play it safe. ) News Flash: A recent study showed that intense weight training hardened the arteries but did not seem to damage the endothelium. To test this, they immersed the weight lifters foot in icy water and then measured artery expansion in the neck. 
CAUTION #2: Be careful with the heavy, Olympic-type lifts that is advocated by most body building magazines. It is very easy to injure yourself. Fitness Rx is one of the few that is honest with its readers and cites a recent journal article that reports that almost all lifters who do regular and heavy bench pressing experience shoulder injuries.  By the way, I have put on mass using much-easier-on-the-joints Isolation and Volume Techniques. These lifts will not as significantly raise your blood pressure as high either and you will find yourself.
For heart health, nothing beats exercise (and a Low Fat Diet). How exercise works its magic is somewhat of a mystery. Scientists have discovered that it does some rather suprising and near miraculous things such as increase the secretion of enzymes that extract cholesterol and fatty acids from the blood.  This may be the reason that exercise lowers inflammation , decreases blood pressure , improves insulin sensitivity , decreases arterial stiffness  and raises HDL, the good cholesterol.  The HDL-improving aspect of exercise was re-verified in a recent meta-analysis, which is a study of previous studies, showing significant increases in HDL for anyone who exercised over 120 minutes per week and/or burned over 900 calories per week.  One could say truthfully that exercise improves significantly almost every know risk factor for heart disease (and therefore erectile dysfunction and brain/cognitive/memory issues).
The bottom line is that there is no discipline more important to your sex life, your health, your mental capabilites and even your survival than exercise. Find an exercise program that you enjoy and get started. If you haven't exercised in years, go easy at first. (If you have health issues, check with your doctor of course!) But get started: there is nothing more important that you can do to enjoy the next decades of your life.
Several studies have shown that sedentary people have less energy than exercisers.  It might seem that sitting around and "resting up" would give you more energy, but the research shows that the opposite is actually the case. You middle aged and beyond guys out there: you can have the energy of someone in their 20's if you'll start exercising. The transformation will shock you.
Exercise, as long as you don't do it right before bed, is a powerful sleep-inducer. In one study, researchers reported that exercisers experienced "better sleep patterns including higher sleep quality, shortened sleep onset latency, and fewer awakenings after sleep onset, as well as less tiredness and increased concentration during the day".  Another study found similar results and went a step further to find that it improved brain wave patterns including prolonged (and restorative) slow-wave sleep.  Read here about Sleep Increases Testosterone and Growth Hormone.
What if I told you I could give you a way to reduce your risk of dying by 50% or more? Well, I can and you can probably guess what I am going to say: exercise is your best life insurance policy. Exercise has been shown in numerous studies to reduce your risk of dying by heart disease, cancer and all causes. One study, the Honolulu Heart Program, grouped Japanese non-smoking males aged 61 to 81 according to whether they walked < 1 mile/day, 1 - 2 miles/day or 2+ miles/day. As might be expected, the 1-2 miles/day group beat out the death rates of the < 1 mile/day group in cancer, heart disease and all causes. Similary, the 2+ miles/day group beat out the death rates of the 1 - 2 mile/day group in every category.  And if you compare the 2+ group to the < 1 mile group, the death rates in cancer, heart disease and all causes is approximately half!
Another study of Finnish middle and senior aged twins found much the same result: the group doing the most exercise had about half - actually in this case about 60% less - the death rate of the cohort doing the least exercise.  There are numerous other studies that show similar results. One interesting one showed that exercise was an even better predictor, or perhaps a better way to put it is an even stronger factor, than waist circumference. And we all know that extra body fat is deadly. 
One 2008 study in the British Medical Journal had an interesting twist: it showed that those with greater strength compared to those with weakest had a 32% reduced death rate from all causes.  This is an incredible reduction, especially considering they are just looking at one factor isolated by itself. Even more remarkable is the fact that the results showed that there was a 50% reduction in heart deaths and 32% from cancer.
I don't know what else to say except that there is nothing more important that you can do to enjoy the next decades of your life than exercise. Exercise not only gives life, but it increases your ability to process and enjoy it.
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