Due to the inconsistency in GXT protocols in cycling research, it is necessary to examine the affect of GXT selection on the determination of Pmax and subsequent affects on the time needed to achieve VO2max. Subjects consisted of 8 trained male cyclists (age: 26 ± 7 yrs, height: 179.1 ± 8.2 cm, weight: 74.4 ± 5.0 kg, VO2max: 63.3 ± 6.5 ml/kg/min) who completed two GXTs. Both tests started at 70 Watts with one increasing 35 Watts/min until volitional fatigue, and the other increasing 50 Watts/3min until volitional fatigue. Pmax was recorded as the lowest power output that coincided with the initial plateau in VO2max, defined as a change of no more than ±2 ml/kg/min from a previous recording. Peak aerobic power (Paerobic) was also determined. Subjects then completed two endurance tests at different Pmax values. During the endurance test, time to achieve VO2max (Tmax), total duration, and the total amount of work were recorded. Pmax as well as Paerobic were significantly lower during the 3 min stage duration GXT (387 ± 27 vs. 342 ± 25 Watts), (424 ± 29 vs. 368 ± 28 Watts)(p<0.05). The percent of Tmax needed to elicit VO2max was not significantly different between endurance tests (61.80 ± 7.00 vs. 62.10 ± 10.50 %). Total work performed was significantly lower when using Pmax values from the 1 min stage duration GXT (5614.95 ± 1509.48 vs. 9625.57 ± 2244.05 kg/m/min)(p<0.05). GXT protocol had a significant influence over the determination of Pmax and Paerobic. Increases in Pmax lead to substantially lower total interval times. Either GXT produced Pmax values that elicit VO2max in 60 % of Tmax.
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