The purposes of this study weie to measure middle power, energy which had been supplied mainly from the lactic acid system, during swimming using an ergometer attachment and to evaluate swimming performance by this middle power To perform these purposes, a middle power measurement test in semi-tethered swimming (STS33) using an ergometer attachment was developed In STS33, the load of the ergometer attachment was set to 7.0kg and the power measurement interval was set at 5.0 seconds The subject was instructed to swim at full strength for 33.0 seconds Power measurements using the ergometer attachment were taken 3 times during the 33.0 seconds at the end of 10s, 20s and 30s respectively The first measurement (1st measured phase) was taken between 5 and 10 seconds from the start of the swim The second measurement (2nd measured phase) was taken between 15 and 20 seconds of the swim, and the third measuiement (3rd measured phase) was taken between 25 and 30 seconds from the start of the swim by the present investigators As in preliminary experiments, the exercise intensity of the STS33 was measured as the average blood lactate concentration produced by the work rate After each STS33, a blood sample was taken by a licensed nurse under supervision of a medical doctor Subjects were 5 junior elite swimmers designated to tram by the N prefecture Swim Association The group mean post exercise blood lactate concentration was 10 5mM/l These concentration of blood lactate was greater than the OBLA measurement of 4mM for lactate accumulation developing in the middle phase of a swim trial This result led to the conclusion that the STS33 test could be used to evaluate the middle power In a main experiment, 21 male elite junior swimmers were measured Middle power in swimming in each subject was measured by the above-mentioned STS33 and the relationship between the group mean middle power and group mean total swim time was analyzed The relationship between the average power (P watt) of the 3 measured phases in STS33 and swimming velocity (V m/sec) in 50m event was P =-134.53 + 87.02 V (r = 0.880, p≦0.001) The relationship between the average power (P) of the 3 phases in STS33 and swimming velocity (V) in 100m event was given by P = - 191.95 + 128.92 V ( r=0 940, p≦O.001) From these results, the middle power in STS33 is appropriate for evaluating swimming performances in 50m and 100m event
