Mating Center by Frank Belknap Long

Less than thirty feet separated him from the para-guard. He covered two-thirds of the distance without haste, moving stealthily, his muscles tensing in preparation for a leap. Ten feet from the guard he abandoned all caution, not caring if the man heard him and turned. He preferred to grapple with a slightly alerted opponent. It was the surest way of measuring an antagonist, of estimating the quickness of his reflexes with hair-trigger accuracy. It was also the surest way of getting just the right grip on him from the start.

A twig snapped beneath Teleman's no longer cautious tread and the para-guard swung about with a hoarse cry. He was still turning when Teleman flung himself upon him. Teleman's left arm whipped around the guard's waist and tightened. He drew back his right arm and sent his fist crashing against a meaty jaw. He swung the man around and went staggering with him across the forest aisle, hitting him again and again with all his strength, jabbing at his stomach, his nose, landing solid blows on both sides of his face. He had the advantage of surprise and refused to relinquish it, putting a savage fury into each blow, giving the other no chance to regain his breath.