Volumetric 31P MRSI in the human calf muscle at 7T in principle enables acquisitions with high spatial resolution, but may require signal averaging to improve signal-to-noise ratios of low-concentrated metabolites. To minimize the acquisition duration of volumetric 31P MRSI, in this study we demonstrate that the acquisition of signal averages can be reliably substituted by application of low-rank denoising filters without the introduction of a quantification bias. This allows acquisition of 31P MRSI data with 1 ml voxels in measurement durations of only 14 minutes that have the same quality as if acquired in 56 minutes with signal averaging.