Humans run at the most energy-efficient speed, regardless of distance

As race season approaches, many runners have the same goal: go faster. But researchers now show that speeding up might require defying our natural biology. By combining data from runners monitored in a lab along with 37,000 runs recorded on wearable fitness trackers, scientists have found that humans' natural tendency is to run at a speed that conserves caloric loss -- something that racers seeking to shave time off their miles will have to overcome.