目的：一、探討不同強度單次網球「米」字型步法間歇訓練後血尿素氮(blood ureanitrogen, BUN)、肌酸激酶(creatine kinase, CK)、乳酸脫氫酶(lactate dehydrogenase, LDH)的影響，以考驗本研究所擬的間歇訓練負荷強度是否有效。二、探討該三項代謝指標恢復所需的時間，以確定下一次間歇訓練應有的間隔時間。方法：本研究以大專網球運動社團的24名健康男學生為受試者，將其隨機分成高強度組、低強度組與對照組。所有受試者分別在運動前、運動後1小時、3小時、6小時、24小時做血液樣本的採集與BUN、CK、LDH等代謝指標的測量。以重複量數二因子變異數分析考驗三組在不同時間恢復期的變化，若達顯著水準則以杜凱式法進行事後比較。結果：對照組運動前後BUN、CK、LDH等代謝指標無明顯變化。高強度組BUN運動後1小時和3小時與對照組相比有顯著性增高；CK與LDH運動後1小時、3小時和6小時與對照組相比有顯著性增高。低強度組BUN運動後1小時和3小時與對照組相比有顯著性增高；CK與LDH運動後1小時、3小時和6小時與對照組相比有顯著性增高。高強度組BUN運動後1小時與低強度組相比有顯著性增高；CK運動後1小時和3小時與低強度組相比有顯著性增高；LDH運動後1小時與低強度組相比有顯著性增高。高強度組與低強度組運動後BUN、CK、LDH的變化，在24小時恢復或接近安靜值。結論：本研究所擬的二種不同間歇訓練負荷強度可作為一般喜愛網球運動的大專學生，從事「米」字型步法間歇訓練負荷強度參考之用。而兩種不同的間歇訓練負荷應有24小時的間隔時間以利代謝機能恢復。

This study explored the effects on human metabolic indicators, i.e., BUN, CK, and LDH, when subject undergoes different intensities of a six-point criss-cross intermittent tennis running exercise. This study explored also proper duration time for recovery in metabolism after a six-point criss-cross tennis running exercise. This study tested 24 healthy college student subjects who were members of a college tennis club. The subjects were randomly divided to High Intensity Group, Low Intensity Group, and the Control Group. All subjects had blood samples taken for testing at: before exercise, 1 hour after exercise, 3 hours after exercise, 6 hours after exercise and 24 hours after exercise. The blood samples were tested for the metabolic indicators, i.e., BUN, CK, and LDH. The data were analyzed using the two-way ANOVA method and tested for the changes at different periods of recovery in the three groups. If the results were statistically significant, then the Tukey's-HSD method was used to conduct the post-hoc comparison. As a result, the control Group's BUN, CK, and LDH levels showed no change before and after exercise. The High Intensity Group's BUN levels 1 hour and 3 hours after exercise were significantly higher than those of the Control Group; the CK and LDH levels 1 hour, 3 hours, and 6 hours after exercise were significantly higher than those of the Control Group. The Low Intensity Group's BUN levels 1 hour and 3 hours after exercise were significantly higher than those of the Control Group; the CK and LDH levels 1 hour, 3 hours, and 6 hours after exercise were significantly higher than those of the Control Group. The High Intensity Group's BUN level 1 hour after exercise was significantly higher than that of the Low Intensity Group; High Intensity Group's CK levels 1 hour and 3 hours after exercise were significantly higher than those of the Low Intensity Group; High Intensity Group's LDH 1 hour after exercise was significantly higher than that of the Low Intensity Group. The changes in BUN, CK, and LDH levels all returned to resting values in both the High Intensity Group and the Low Intensity Group after 24 hours. To conclude, the two different intensities of six-point criss-cross intermittent tennis running exercises will cause the levels of metabolic indicators to significantly increase, and the level of increase is affected by the level of exercise intensity. The BUN, CK, and LDH levels were suitable biomarkers for tennis players to monitor training intensity of the six-point criss-cross intermittent running. In accordance with the recovery of BUN, CK, and LDH levels 24 hours after exercise, we suggest the duration with 24 hours for recovery in metabolism between six-point criss-cross tennis running exercises.