The purpose of this study was to examine the hypothesis that improved prediction of bioenergetics may be achieved when proxies are designed to simulate closely gold standard laboratory protocols. To accomplish this, a modified 'square' variation (SST) of the classical 20m Multistage Shuttle Run Test (MST) was designed aiming to reduce the stopping, turning and side-stepping manoeuvres. Within two weeks, 50 male volunteers (age 21.5+/-1.6, BMI 24.4+/-2.2) randomly underwent three maximal oxygen uptake (VO2max) assessments using a treadmill test (TT), the SST and MST. To assess SST reproducibility, 10 randomly-selected subjects performed the test twice. Validity results showed that mean predicted VO2max from SST was not significantly different compared to TT VO2max (p>0.05). In contrast, the equivalent value from MST was significantly higher (p<0.001) than TT. Furthermore, TT VO2max correlated with SST and MST at r=0.88 (p<0.001) and r=0.61 (p<0.05), respectively. The '95% limits of agreement' analysis (LIM(AG)) for SST and MST indicated a range of error equal to -0.5+/-5.4 and 8.1+/-8.0 (ml.kg(-1).min(-1)) with a coefficient of variation of +/-6 and +/-8.2%, respectively. Test-retest results for SST revealed no mean difference in VO2max (p>0.05) and a correlation coefficient of r=0.98 (p<0.001), while LIM(AG) demonstrated a range of error equal to -0.2+/-2.6 (ml.kg(-1).min(-1)) with a coefficient of variation of +/-5.6%. It is concluded that, compared to MST, the SST had a higher agreement with TT. The latter may well be explained by the closer simulation in bioenergetics between the two protocols (ie, the continuous nature of SST provides a closer proxy of TT).