Applications to technicolor models have created an interest in strongly interacting theories with a slowly running coupling and QCD-like behaviour in the large coupling limit. Possible candidates for this kind of walking behaviour lie near the lower end of the conformal window. Non-perturbatice methods are required to establish walking behaviour, since it typically takes place at strong coupling. We present lattice studies of the running coupling of SU(2) gauge theories with fermions in the fundametal and adjoint representations. The studies show that there are large discretisation errors in the measurements. We have minimized these errors using the Sheikholeslami-Wohlert improved action. Repeating one of the studies using the improved actions has produced significantly different results.