Harrison, J. R., Dawson, B. T., Lawrence, S., & Blanksby, B. A. (1992). Non-invasive and invasive determinations of the individual anaerobic threshold in competitive swimmers. Journal of Swimming Research, 8, 11-17.

"Without an accurate determination of swimming pace, HR and HLa at the IAnT for every swimmer, a coach cannot be certain of the relative intensity of any particular training session." (p. 11)

The purpose of this study was to determine if a non-invasive HR protocol is a suitable method of determining the IAnT in swimmers. The two methods (a) Cellini et al. 10-15 x 50 m with successively increasing speeds, and (b) 4-5 300 m swims with each 50 m improving in speed by 1 s each repetition.

The HLa recovery curves were found to recover much faster than in other forms of exercise. They peaked after a minute, a finding which disputes what some other researchers have found with swimmers. The difference in swimming and other exercise recovery rates may due to variations in the amount of active musculature (an arms exercise versus a legs exercise) and the improved venous return facilitated by the hydrostatic pressure of the environment and the horizontal body position that reduced the gravitational resistance.

The non-invasive technique did not produce measures that were associated with the invasive technique.

There were some interesting statements included in the article.

"Without an accurate determination of swimming pace, heart rate (HR) and blood lactate concentration [HLa] at the IAnT for every swimmer, a coach cannot be certain of the relative intensity of any particular training session." (p. 11)

Implication. It is necessary to have the pace of the total swim controlled to replicate exact conditions when using either HR or HLa as indexes of work.

The post-exercise lactate removal curves were much steeper in these swimmers than shown previously in other activities. Swimmers recover from lactate accumulation (peak rates occurred in about 1 minute) faster than cyclists and runners (peak rates at about 3 minutes post-exercise). (p 15) "These differences in the kinetics of the La recovery curves may be due to variations in the amount of active musculature (upper versus lower body) and the improved venous return facilitated by the hydrostatic pressure of the environment." (p. 16)

Serious doubts were raised about using HR/velocity as a determination of IAnT. First, a precise protocol that guaranteed performance speeds was not possible because that was left to each swimmer to interpret instructions. In 4 of the 12 subjects, HR/velocity break points were difficult to determine while 2 had no break point at all. This means that in only one of two swimmers the method may have some utility.

". . . the very low, non-significant correlation found here between the HR and the IAnT as determined invasively and non-invasively . . . . a non-invasive determination of the IAnT by HR/velocity breakpoint measurement would seem to be an unreliable estimate of the IAnT when determined by [HLa] measurements." (p. 16)

Implication. Heart rates cannot be used reliably or accurately to estimate the severity of work loads.

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