Not surprisingly, resistance training increased muscle mass and strength for all subjects. And cardio HIIT (high intensity interval training) improved the age-related decline in mitochondria. This study validates what we’ve known along, that it takes a strategic combination of strength and cardio work to maximize your fitness and age like a fine wine
The big takeaway here is that you need to adequately hit your fast- and slow-twitch muscle fibers to both maximize muscle growth and fight the aging process.
Studies have shown that when it comes to muscle growth, the best results are achieved by using a mix of low, medium, and high reps. And the same things that build muscle also help slow the loss of it.
But don’t get caught in the trap of thinking you can only hit your fast-twitch fibers with heavy strength training and your slow-twitch fibers with cardio. The degree to which you target certain muscle fibers depends on the speed and intensity of the exercise in addition to the rest time between work sets.
Traditionally we’ve been told that fast-twitch fibers get hit with heavy loads or moderately heavy loads moved explosively with longer rest periods between sets, and slow-twitch fibers get hit with lighter loads at slower speeds and with shorter rest periods between sets. In addition, you will recruit your lower threshold slow-twitch fibers first and the higher threshold fast-twitch fibers then kick in later as needed to keep you moving.
Now, heavy lifting can be tough on the body as you get older. Your central nervous system takes more time to recover between sessions from heavier loading and your joints can only take so much wear and tear. Plus, heavy lifting doesn’t adequately stimulate your mitochondria, which will decline with age and are critical for overall health and performance.
That’s why I’m huge believer in what I call “metabolic bodybuilding.” It can hit all of your muscle fibers while simultaneously increasing your mitochondria, all while using much lighter loads than normal. Metabolic bodybuilding involves using longer, higher-rep timed sets to stimulate muscle and mitochondrial growth via metabolic stress, or the accumulation of the acidic waste materials from exercise that causes your muscles to swell and burn. In this way, this revolutionary style of training spares your joints, is easier to recover from, and can be done with minimal equipment setups at home or in a hotel gym.
For example, doing 2-minute time-under-tension sets with resistance training exercises like squats, pushups, or biceps curls using a slow and controlled tempo and with rest periods of 60 seconds or less is one of my favorite ways to boost muscle and mitochondria. Plus, it will get and keep your heart rate up.