One study found that "untrainable" physical factors, including the Ape Index, were not necessarily predictors of climbing ability, in spite of a general tendency identified in previous studies for elite athletes in the sport to share these characteristics. This was supported by a later study that also found that the Ape Index was not statistically relevant. However, the authors of this second study noted that the findings may have been due to the low variability in the index between the climbers, who all had significantly higher Ape Indices than those found in the control group. Thus they left open the possibility that the Ape Index may be more significant when there is a greater degree of equivalence between the other traits under consideration.