Rowing performance, fluid balance, and metabolic function following dehydration and rehydration

Eight international class lightweight rowers were examined to determine the efficacy of rehydrating with water following 24 h of dehydration on body fluid balance, metabolic function, and rowing performance. The rowers performed a maximal rowing trial on a Gjessing rowing ergometer (4200 revs, 3-kg resistance) while euhydrated (ET) and following partial rehydration (RT). Body weight was reduced using exercise together with food and fluid restriction over 24 h and was followed by consumption of 1.5 1 of water over 2 h. Body weight decreased 5.16 ± 0.14% (P < 0.05) and plasma volume decreased 12.5 ± 1.4% (P < 0.05) after dehydration. Rehydration restored plasma volume by 6.02 ± 0.62%. Rowing trial time increased significantly from 7.02 ±0.17 min for the ET to 7.38 ± 0.21 min for the RT (P < 0.05). The net plasma lactate accumulation decreased significantly from 8.77 ± 0.31 mmol • 1-1 for the ET to 6.77 ± 0.24 mmol •1-1 for the RT (P < 0.05). Glycogen content (glycosyl units) of the vastus lateralis decreased by 203.6 ± 18.6 mmol•kg-1 DW during the ET compared with 139.9 ± 13.4 mmol • kg-1 DW during the RT (P < 0.05). These results demonstrate that the dehy-dration/rehydration protocol reduced maximal rowing performance due to lowered plasma volume and decreased muscle glycogen utilization. © 1993 by the American College of Sports Medicine.