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Are you sitting comfortably?
How sound ergonomic principles impact cognition

INSIGHTS / Guide 02 / Ergonomics

James Clarke, Education Consultant - March 2026

Understanding how we design for the human body is essential, yet much of today’s classroom furniture still reflects outdated ideas about posture and ergonomics. Modern research paints a very different picture—showing why the traditional 90‑degree sitting position is problematic, why movement supports cognition, and what students’ instinctive behaviours reveal about their physical needs. The sections below explore how these insights have evolved and why more supportive, dynamic seating can make a meaningful difference to comfort, focus, and wellbeing.

The Measure of Man and Early Anthropometrics

Back in the 1950s, American industrial designer Henry Dreyfuss published a book illustrated by Alvin Tilley called The Measure of Man. It contained anthropometric data sourced from over a decade of research, consolidating information from a wide range of scientific, academic, and military sources. It quickly became a bible for designers concerned with anything the human body needs to interrelate with. However, the majority of illustrations in The Measure of Man showed mannequins with their upper legs horizontal and their back vertical, creating a 90° angle between the two. Sixty‑odd years later, we now know that while a vertical back is appropriate (your head is the heaviest part of your upper body and should sit directly above your pelvis to avoid strain), the angle between your thigh and thorax should be closer to 110°–120°, dipping the legs from the horizontal.

The Measure of Man & Woman

Why the 90° Sitting Posture Is Problematic

This shift in understanding is due to the fact that the majority of your vital organs are located in the lower part of your torso. Bending your legs to create the right angle shown in Tilley’s illustrations constricts the arteries that run through these organs—arteries that in turn take oxygenated blood to the brain. Think of it like putting a kink in a garden hose: the liquid inside, whether blood or water, does not flow as freely. At the same time, care must be taken not to put pressure on another key artery—the popliteal artery—which runs down the back of the knee. This is why most chairs have a “waterfall edge” at the front of the seat pan.

Bodies in Motion StudyCognitive Control & Academic Achievement

Movement, Cognition, and the Myth of Sitting Still

One oxymoron is the old mantra—common among teachers in the sixties—to “sit still and concentrate”. We now know that movement actually boosts cognition. Two studies support this finding: one by Dieter Breithecker in research supported by German furniture manufacturer VS, and another by Professor Chuck Hillman at the Neurocognitive Kinesiology Laboratory at the University of Illinois. So if your school, college, or university still has plastic chairs throughout, one simple way to help students is to tolerate (or even integrate into lessons) an element of movement. That’s often what students are instinctively doing when they lean back in their chairs.

Leaning Back, Posture, and Better Seating for Students

When children lean back on their chairs, they’re not doing so because they’re naughty or inattentive. They’re responding to a natural reflex that alleviates the pressure inherent in a “legs forward, back straight” posture. That’s not to say such behaviour should be ignored, but rather recognised as a sign that the student’s body has been static for too long. There are chairs that genuinely support healthy posture in students, but because students come in all shapes and sizes, the adjustability required tends to make these chairs more expensive than the plastic versions commonly found in classrooms. The boy on the left, just approaching his fourth birthday when the photograph was taken, demonstrates this well: he sits upright with his head over his pelvis (the part of his body evolved to take his weight), his legs drop below the horizontal, the backs of his knees are not constricted thanks to the saddle-shaped seat, and even without casters he can swing from side to side. It also neatly illustrates another myth—just like on his bicycle or a horse, he can manage perfectly well without a backrest.