Running footwear became dramatically lighter over the twentieth century, and the pace of change followed materials science rather than athletic demand. The demand was always there.
Leather set the original limits
The earliest purpose-made running shoes were leather uppers with leather or rubber soles and hand-driven spikes, and they were heavy before they were even worn.
Leather also absorbs water, so a shoe that started heavy became substantially heavier in wet conditions and stretched out of shape as it dried.
Athletes accepted this because there was no alternative material that could be shaped, stitched and made durable enough to survive a season.
Synthetic uppers removed most of the weight
Nylon and similar synthetics allowed uppers that were light, held their shape and did not absorb water, which changed the shoe more than any change to the sole.
They also made shoes cheaper to manufacture, which broadened the market beyond serious competitors to a growing population of recreational runners.
The trade-off was durability and fit, and early synthetic shoes were widely criticised for causing blisters until the internal construction caught up.
Midsole foam was the slower development
Cushioning initially meant more rubber, which meant more weight, so early shoes offered a straight choice between protection and lightness.
Foamed materials broke that link by trapping air within the structure, providing thickness and cushioning at a fraction of solid rubber's mass.
Each subsequent generation of foam has improved the ratio of cushioning to weight, and the recent step change came from compounds that also return more energy.
Spike plates followed the same pattern
Track spikes needed a rigid plate to hold the spikes and provide stiffness, and metal plates were the original solution with an obvious weight cost.
Plastics and later carbon composites provided comparable stiffness at much lower mass, which is why spike weights fell sharply through the later part of the century.
The same composite technology eventually appeared in road shoes, where its function shifted from holding spikes to altering how the foot levers off the ground.
Weight mattered more than it appeared to
Mass carried on the foot costs more energy than mass carried on the trunk, because it must be accelerated and decelerated with every stride.
A modest reduction in shoe weight therefore produces a measurable improvement in the energy cost of running over a long distance.
This is why athletes historically raced in shoes far flimsier than they trained in, accepting reduced protection for a single event, and why racing and training shoes remained separate categories for so long.
