The human body is made up of 657 muscles. All day, every day they're working overtime to keep you moving, digesting, breathing, living.
But increasingly people only pay attention to the Instagram-friendly muscles of the abs, buns and guns, overlooking hundreds that are integral to good health.
Just reading this requires 16 muscles in your eyes to focus on the text; a host of other muscles in your neck, back and core to retain your posture; muscles in your arms and hands to hold your drink; and still more muscles to digest your food and keep your heart pumping.
Your muscles are intrinsic to everything you do; not just getting you to the finish line of your park run or making a racket in the gym's weights room.
I came on board to add my weight from years spent working in the health and fitness industry and to help them develop the challenge (that's me in the dubious turtleneck). The goal was that it would be equal parts an effective test of muscle health and a fun, shareable activity that would spread far and wide.
The challenge is a litmus test for how flexible, fit and active each of us are. It's a full-body test of mobility, strength, balance and coordination based on the sitting-rising test that Brazilian physicians used as a scientific checkpoint for life expectancy.
You simply drop from standing into a sitting position and back up, all the while balancing a full cup of liquid on your head. The less you spill, the more impressive.
It's been launched in partnership with the charity The Muscle Help Foundation, helping raise awareness for the genetic muscle-wasting condition muscular dystrophy (MD).
This inherited condition causes muscles to gradually weaken. It's the single biggest genetic killer of children in our world today - more than 70,000 have MD or allied neuromuscular conditions in the UK alone.
Launched earlier this month the #657challenge is gathering momentum on social media as people nominate others to take the test. Some find it easy. While others have been left drenched.
How well have you been looking after your 657 muscles? Take the #657challenge to find out, post it on social media to raise awareness of muscular dystrophy and if you struggle, use this five-move workout to upgrade your muscle health.
How To Upgrade Your Muscle Health
Use these five gym-free moves from muscle expert Mike Aunger of Technique Physiotherapy & Sports Medicine to help master the #657challenge and boost your overall muscle health
1 Seated glute stretch
Sets 1 Time 30sec
Sit on a chair with your right ankle over your left knee to open up your hips. Now hug your knee into your chest to stretch your glutes, then gently press your knee down to open up your hips further. Go for 30 seconds in each direction and on both legs. Repeat daily.
Aunger says "Reverse the damage from hours spent seated in a matter of seconds."
2 Deep squat hold
Sets 1 Time 30-60sec
Lower into as deep a squat as you can manage, keeping your knees wide apart and back as flat as possible (so not hunched over). Hold onto a table for balance and to help you stand up again if needed. For a further stretch, push your elbows into your knees to open them up further. Repeat every other day.
Aunger says "This regular hip stretch will dramatically boost your lower body strength."
3 Chair squat
Sets 3 Reps 5-6
Stand in front of your chair or sofa and lower down until seated, then drive back up using just your legs. Too easy? From standing, slowly lower down until your backside is just touching the seat, then drive back up to stand. Still too easy? Try this with one leg, keeping the other one elevated. As you improve try to use a lower seat or step. Repeat twice a week.
Aunger says "Power up your lower body without leaving your living room."
4 Ankle flex
Sets 3 Reps 10-12
From seated with your heel on the floor and toes elevated, turn your foot outwards to strengthen the peroneal muscles around your ankle and calf. Increase the resistance by using a band wrapped around your foot. Go one step further by doing calf raises while sitting at your desk to strengthen all the muscles in your calves. Repeat every other day.
Aunger says "Keep a band by your sofa and give it a go while watching TV for a painless way to stay stronger on your feet."
Sets 3 Reps 12-15
Lie on your belly with your arms outstretched in front of your head and face down to keep your neck neutral. Now alternate lifting your right leg and left arm off the floor, then your left leg and right arm, pausing for two seconds at the top of each lift. Keep it slow and aim to do it two or three times a week.
Aunger says "Strengthen your core muscles, front and back, with this superhero move."
Sam Rider is editor of the 657Journal, the blog powered by Upbeat Active.