My little brother and I grew up on Rollerblades, the terrestrial version of ice skates. We raced on the rumpled streets of New York City, from Greenwich Village north to Central Park, ecstatic not to be circling a small oval of ice. In those days I held two major misconceptions about skating: I imagined that we were pioneering a new form of long-distance transport, and I thought skating was easier than running because of its gliding phase. In neither case was I close to the truth.
As far back as the Bronze Age, 3,000 years ago, skates helped people travel more widely. And it turns out that skating is extremely efficient, taking advantage of biomechanical properties of the muscles throughout the movement cycle—not only during the glide.
To an unmechanized Europe and Russia, ice skates were one of the first useful tools for making winter trips between towns. And since the joys of skating are best appreciated on long stretches of smooth black ice, it comes as little surprise that ice skates made their first appearance on relatively flat, snowless waterways.
Early skates were constructed of trimmed horse or cow bones, pierced at one end and strapped to the foot with leather thongs. Rather than being powered by the classic skating motion, those beauties were used in tandem with a long stick; skaters straddled the stick and poled themselves along. Bone blades gave way to iron ones and then to steel. By the 1800s the idea of a steel blade grafted to a fitted leather boot had firmly taken hold. (Although most skaters still use that design today, the ultimate innovation in the skating world was the "klap" skate; it has a hinge that allows the skater to extend the ankle while pushing, which boosts speeds by 5 percent.)
The advent of thinner blades and a firm attachment to the foot signaled a transition to the longer strides of a modern skater. Those extended strides give skating its advantage over unassisted modes of transport (such as running) because, as it happens, the slower a muscle contracts, the greater the force it develops. To understand how that force difference works on the molecular level, imagine the muscle fiber as a “rope”: slow contractions pull the rope hand-over-hand, as if hauling a bucket from a well; rapid contractions grab and quickly release the rope—delivering a smaller relative force. Since skaters’ leg muscles can contract quite slowly, even at very high speeds, they generate more force during each stride cycle. And that slow contraction can be maintained thanks to the fact that less lateral force—the outward push against the ice—is needed at higher speeds. Thus the strides get longer and the skate tracks become more parallel to the direction of travel. [media:node/1017 full]
[media:node/1018 full caption]Human-locomotion biomechanists Federico Formenti of Oxford University and Alberto Minetti of the University of Milan collaborated to trace the efficiency of ice skates through history. Their aim was to measure the evident increase in efficiency from clunky animal-bone skates (1800 b.c.) to iron skates (a.d. 1200 and 1400) to steel skates (1700) to cutting-edge modern skates, also made with steel blades [the five skates used in the experiment are pictured above]. First the researchers fabricated authentic replicas of the ancient skates, adding only a somewhat safer binding to the oldest models. Then they found five retired professionals—short-track ice skaters—with a sense of adventure. After the skaters had familiarized themselves with the historic skates, they were equipped with a small strap-on apparatus that measured their oxygen intake, heart rate, and (for three of the skates) leg movements. Each skater was then asked to skate both at a slow, comfortable pace and at a faster, more demanding pace with each type of skate. From those data, the researchers derived the energetic demand relative to speed of ice-skating on different kinds of skates.
The oldest bone skates used with the push pole simply would not go very fast; the pros only managed a single speed of about 2.5 miles per hour (mph). Of course, even to achieve a steady, safe walking pace such as that would have been a big advantage to someone on a flat, icy river. The earliest metal-bladed skates that were tested allowed a near doubling of the slow, steady speed, but also permitted a fast gait of about 9 mph. Better bindings and thinner blades further enhanced speeds, culminating in a fast gait of about 15 mph with the modern non-klap skates that were tested.
Not surprisingly, the more modern skates delivered not only on speed but also on distance covered. By far the most impressive increases, though, have to do with efficiency relative to speed. Consider a skater working herself to a point of exhaustion in ten minutes; on the oldest skates or the newest ones, she is putting in the same amount of energy. Yet on the newest blades she could travel considerably farther. Her stride frequency stays the same and her leg muscles continue to operate at high power, independent of forward speed (unlike a runner that squeezes out less force the faster the leg muscles move.)
Runner at the same given speed as a skater might take six steps for every skating "step"—generating less force per leg-muscle contraction. If both athletes exerted the same effort, with heart rates of 120 beats per minute, say, the skater would be almost four times faster.
Formenti and Minetti have gone on to test the bone skates in different locations, and have found that their benefits must have varied with the topography, particularly the number and length of lakes; Finland, with more than 60,000 lakes, seems the ideal locale and the likely place of origin for them. Considering my poor ankles, I might opt for the skates of yore on my next visit to the rink and punt around on horse metacarpals, big stick in hand to fend off any whizzing, would-be Bobby Orrs.