When an Olympic archer readies to shoot, she is staring down a distance of seventy meters — roughly three quarters of a football field — and aiming to hit a circle the size of a CD. An elite archer does not grip her bow tightly, fearing what anxious jitters might do; she attaches it to a string that wraps around her hand, extends her arm forward, and holds the bow in place with the skin between her thumb and index finger. As she draws, more than forty pounds of resistance weighs on her fingers and back, and her bow stores so…