Abstract Bermingham MA, Mahajan D, Neaverson MA. Blood lipids of cardiac patients after acute exercise on land and in water. Arch Phys Med Rehabil 2004;85:509–11. Objective To compare the effect on lipids of a single bout of high-intensity interval training performed on land and in water in a group of cardiac patients involved in an intensive cardiac rehabilitation program. Design Single-group, quasiexperimental, crossover design. Setting Swimming pool at a cardiac rehabilitation hospital in Australia. Participants Ten men, ages 55 to 77 years, with ischemic heart disease. Intervention Subjects performed 15 minutes of interval arm ergometer work at 65% to 75% of attained heart rate, as determined by treadmill testing on land and in water on the same day. Each patient had his own exercise prescription. Main outcome measures At each endurance phase, the number of revolutions and rate-pressure product (RPP) during the final minute of work were taken. Fasting bloods were taken at baseline and after maximum exercise, and lipid profiles were determined; differences were analyzed by paired t test. Results No significant differences in revolutions or RPP were observed, which indicates that workload and heart work were similar in all experiments. There were no significant changes in total, low-density lipoprotein cholesterol, triglyceride, or apolipoproteins A-I or B after exercise (paired t test). High-density lipoprotein cholesterol (HDL-C) was increased significantly by exercise on land. In 6 patients with low baseline HDL-C (<0.9mmol/L), HDL-C was increased only on land. Conclusions A single bout of high-intensity interval training was more effective in improving HDL-C when performed on land than in water.