People lift for many reasons: to add muscle or to lose weight. Ignoring those reasons, what does science say about lifting for longevity?
I'm a runner, I've been going to the gym for a year to two, but I'm getting bored of it and questioning why I should bother.
You say family history of heart disease, what is your history? Just because there is family history doesn't mean you have it. I would definitely recommend a doctor's exam first, and discuss your training plans with him/her.
That being said, the science is heavily in favor of weightlifting in the elderly, as it helps preserve and/or restart muscle mass retention (And yes, elderly can build muscle, just not the mass that you can get when younger), keeps or increases mobility, and allows normal functions of daily living.
Just going through some of the studies on Google Scholar, here are a few items:
Protein synthesis and muscle adaptive response maintained even in frail elderly populations.
Strength training in the elderly builds muscle, normalizes blood pressure, increases metabolism but does not increase O2 uptake, flexibility or improve lipid profiles.
Single arm training resulted in large gains in the main arm, as well as corollary gains in the non training arm (Which also gives corroboration to the crossover training theory for injuries at all levels).
That is just a quick sample of what's available on Google Scholar, there are many more in the same vein. Suffice to say that science is heavily in favor of weightlifting, although the type of training may be dictated by your own personal health.
Lifting is still important to people later on in life as it provides the strength required to support the body as is becomes increasingly fragile. Not all weightlifting is beneficial however. As a more senior lifter with a potential heart-risk, definitely do not train for strength (heavy 1rp or similar exercises). Instead, focus on low weight with an emphasis on technique and repetition. This will ensure the muscles are doing the required movements without the stress on your body involved with heavier more compound lifts. Heart risk is significantly reduced in these less-strenuous, but still beneficial exercises.
Since I do not know the details of your family history of heart disease I answer with general recommendations. You should consult with your your doctor to make sure they are appropriate for you.
According to the WHO heart disease and stroke are (by far) the biggest cause of death.
In the book on brain health "The Brain Always Wins" Dr. John Sullivan states that "anything that is good for your heart is great for your brain.
Recent research seems to indicate that strength training is better for the heart than cardio, but the best is a combination.
The HUNT Fitness Study concluded that waist circumference or body mass index (BMI), leisure-time physical activity and resting heart rate are the most important factors for longevity. They also found that the risk of dying from cardiovascular disease was 21 % lower for each increase of 3.5 mL/kg/min.
BMI is much simpler to measure than body fat. However this study concluded that percent body fat is a better predictor of cardiovascular risk factors than body mass index.
Another study concluded that muscle mass is a better predictor of longevity than BMI.
So for longevity you want to have a low percent body fat, high muscle mass and a high VO2 max.
Endurance training can ensure a low percent body fat but at the cost of muscle mass. A combination of endurance training and strength training can both ensure a low percent body fat and a high muscle mass.
Also long distance running may cause low testosterone, which in turn have negative health effects, whereas weight training increases testosterone and growth hormone levels.
I think it is little known that skeletal muscle has been identified as a secretory organ. This may have wide ranging implications. I am guessing that the healthiest in this regard is to have medium amount of musclemass.
The Cooper test was devised in 1968 by MD Kenneth H. Cooper as a simpler way for the US army to measure VO2 max of its members. It consist of running as long as possible for only 12 minutes. This tells us that the focus of the cardio training should be to be able to run very fast for 12 minutes, not how long you can run.
Science is great. I think it is a good idea to also use common sense and caution. The golden mean dictates that you should do a bit of both cardio and strength training, but not too much of either.
Finally the Physical Activity Guidelines for Americans specifically states that adults should do strength training.
There is no way you can get this answered correctly on these forums. See your doctor and if appropriate ask for a referral to a physical therapist (not to be confused with a personal trainer).
They'd be able to assess your situation, answer your questions and give you an exercise program to help get you on track and mitigate your risks.
Both strength and endurance are absolutely essential for survival. Every species of animal requires both strength and endurance to survive. Of course, in the unnatural environment in which we currently live, modern humans can survive without either strength or endurance. But there is no reason to believe that things will always be this way.
I wouldn't consider quitting either strength training or endurance training any more than I would consider quitting eating or drinking water.
