The heart rate and blood lactate were studied in field hockey players (25 juniors and 29 seniors) as well as the blood lactate response in training to assess the anaerobic demand of the game and the adaptability of the players to anaerobic metabolism, respectively. The mean VO2 max of the junior and senior players were 3.32 l/min (54.4 ml/kg/min) and 3.28 l/min (53.8 ml/kg/min), respectively. Blood lactate levels after warm up, training and the game were 2.1, 7.4 and 4.2 mM/l, respectively for the juniors and 2.6, 7.7 and 5.6 mM/l, for the seniors. The aerobic capacity (VO2 max) of the juniors did not differ from their senior counterparts, indicating a similar adaptability to aerobic metabolism. However, the Indian players revealed a lower VO2 max than their International counterparts. Similar lactate levels in juniors and seniors after training indicated a similar adaptability to the anaerobic metabolism also. The higher blood lactate level in seniors after the game reflected that they played with greater intensity than the juniors, due to more experience, better motivation and skill.