(If you’re still doing ab crunches and triceps kickbacks, you need to read this. Although I wrote this article way back when I did more “body part” training, the science still applies.)
It’s not your fault. The vast majority of people – including lots of personal fitness trainers – get this all wrong.
The truth is that just a couple of physiology (yikes!) tips can help you get maximal results from your training program.
One vital concept you need to understand for fast results is Slow-twitch versus Fast-twitch muscle fibers.
Hold on! It’s not as complicated as it might sound.
And this is crucial if you want to get maximal results in minimal time.
Human muscles follow what’s called a ramp-like recruitment pattern.
Here’s why that should matter to you …
Different muscles respond best to different stimuli. If you don’t understand this, you’re probably wasting a lot of your time and effort in the gym.
Each muscle has two (at least for the scope of this article) types of fibers – slow-twitch and fast-twitch. (Beware, the “slow” and “fast” labels have absolutely nothing to do with your speed of lifting in the weight room.)
What this graph shows us is that when you lift a weight that’s fairly light, you’ll use ONLY your smaller, slow twitch muscle fibers – and just a few of those. The bigger, fast-twitch fibers are “held in reserve.”
With heavier, more challenging weights, however, you move toward the right of the graph and start to use your fast-twitch fibers AND more of your slow-twitch fibers.
And it’s the recruitment of more fibers that burns more fat and changes your body!
Even more important to us Baby Boomers …
It’s the fast-twitch fibers that we tend to lose as we get older
– UNLESS we make sure we’re working them in our exercise program.
Although there are obvious exceptions – Olympic sprinters tend to be fast-twitch dominant while Olympic marathoners tend to be slow-twitch dominant – the average muscle in the average person is about 50/50 slow-twitch-vs-fast-twitch.
But certain muscles tend to be either fast- or slow-twitch dominant.
Fast-twitch dominant muscles (for most people) include your triceps (the back of your upper arms), rectus abdominis (the “six-pack” muscle), hamstrings and gastrocnemius (the most prominent calf muscle).
Slow-twitch dominant muscles include the soleus (a calf muscle largely involved in walking), and shoulder girdle stabilizers like the middle and lower trapezius in your mid-back.
If you’re doing “body part” training, you need to work fast-twitch and slow-twitch dominant muscles differently.
Specifically …
If you’re training your rectus abdominis and your triceps like they’re slow-twitch dominant with low weights and high reps (e.g. dozens of ab crunches or kickbacks with pretty pink, lavender or teal dumbbells), you’ll never get the results you’re looking for.
You can’t. The science just showed us.
If you’re using a weight that’s so light you can do more than 20 or so reps (or worse yet, you could do 50 but some magazine told you to do 20), you’re using ONLY your slow-twitch muscle fibers …
You’re missing out on over half your available muscle fibers!
And you certainly can’t expect to see results if you over half your muscle fibers are sitting there dormant.
So, here’s what you need to do …
To get the quickest, most effective results from any triceps, rectus abdominis, hamstring, or gastrocnemius exercise, you need to use a weight that’s heavy enough for you to do a maximum of about 10 reps.
Don’t focus on some magic number of reps then stop once you reach that number. Focus on selecting a challenging weight first, then doing as many safe repetitions as you can. If you’ve picked the right weight, you’ll end up somewhere around the target number of reps.
For slow-twitch dominant muscles, the traditional 15 reps or so – with the appropriate weight, of course – should put you in the right range. (Of course, your mileage may vary.)
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