chair or gym ball at the office?

Gym balls (so-called Swiss Ball) are in fashion, but are they healthy to sit at work and at home? Let's go back to the basics...

A healthy sitting posture revolves around a stable pelvis. The first posture below (on the sit bones or ischial bones, and against the lumbar support) is the healthiest to sit for prolonged periods of time. Conversely, 

• a hollow back will contract the lower back muscles and let your weight rest on the intervertebral cartilage,
• a round back will overload the intervertebral discs (increased risk of hernia) and push your head and shoulders forward (i.e. the neck cannot relax).

What happens when sitting on a gym ball? Firstly, the flexible and round shape of the seat create pelvic instability. Hence, the spine is also unstable. Secondly, the lack of lumbar support makes that your pelvis is free to rotate backwards, i.e. your spine tends to slouch unless you mobilize your muscles: your weight remains on your tissues instead of being transferred onto the chair. If you try and "sit straight", you will hollow your back, sometimes helped by keeping your feet back.

how to sit on a swiss ball?

To sit well on a gym ball, you should have your heels under the knees and sit with a flat back, i.e. on your sit bones. As when you sit on an office chair, your torso should be slightly forward.

To hold the pelvis in this neutral posture, you should engage the lower transverse abs (under the navel): if you bring them slightly inwards, you increase the pressure around the lower spine, which stabilizes it. This muscle effort explains why you can't sit for too long on a gym ball.

To make your job easier, the ball pushes your feet and knee outwards. As a result, the femur bones tighten the sacro-illiac joint, and therefore participate in stabilizing the pelvis. This posture is particularly advised for pregnant women to compensate for the softening of the ligaments that occurs after 3 months. However, nothing prevents you from assuming the same posture on a standard office chair...

Some advocate in favor of the gym ball because it allows for a "dynamic sitting posture". Of course, you need to move, but not anyhow and anytime! A well adjusted office seat does not make you a rigid statue; rather, it allows for micro-movement which supplies oxygen to the deep muscles whilst distributing your weight on the tissues. After 25-30 min, it is indeed time to decompress the lumbar spine, but the best solution is to stand up and consequently adapt the task: make it a habit to stand for informal chats and phone calls, and you will move whilst always keeping a posture that is adapted to your activity.

a swiss ball for all?

A gym ball is therefore a training tool... but nobody should train 8hr per day, a certainly not while focusing on something else (esp. work!). The gym ball is therefore meant

• for short periods of time: as soon as you can't hold your pelvis or abs anymore, change seat and opt for a lumbar support;
• for intellectually light activities, so that you can focus on your posture.

Hence, I do not recommend that companies invest in Swiss balls as an alternative to ergonomic office chairs that are individually adjusted. As a private person, you may however want to give it a try, provided that you remain within the above-described framework.

Personally, I prefer however to invest in things only when I am in full control of what Mother Nature gave me, i.e. my muscles and gravity. These two are always available, and mastering them makes me free: my health does not need to depend on anything but me.

For more information on office ergonomics, DSE and homeworking, visit the course summary on Erg'OH Conseil website.