TABLE 3.

Recommendations for ¹H MRS of intramyocellular lipids (IMCL)

Acquisition	Whenever the study aim allows, fusiform muscles with an orientation along the static magnetic field are recommended to increase EMCL/IMCL separation.
	Extended high‐resolution imaging series are mandatory to find an optimal voxel position; in particular, preintervention and postintervention studies require careful repositioning.
	Positioning of the small, anisotropic voxel (eg, 10 mm x 10 mm x 18 mm along muscle) must, whenever possible, avoid visible EMCL along fasciae.
	Manufacturer‐provided shimming routines might be optimized for brain and fail in muscle. Shimming volume, localization and algorithms need to be adapted.
	Single‐voxel MRS is inappropriate for a determination of EMCL levels, which requires fat‐selective imaging techniques
Processing and /Quantitation	Clearly visible spectral separation of EMCL/IMCL methylene signals is a prerequisite for a robust fitting procedure, either with commercially available or self‐tailored fitting routines.
	Self‐tailored fitting routines (e.g., jMRUI) require relatively strong prior knowledge boundaries to be sufficiently robust.
Physiology and Preconditioning	IMCL levels are highly dynamic (exercise, diet) and also influenced by long‐term effects (eg, lifestyle, insulin sensitivity) and thus, careful preconditioning of subjects is crucial.
	Comparison of resting IMCL levels in groups with different lifestyle easily introduces biases between groups; an adapted instruction and supervision regrading diet and physical activity of the groups is mandatory.
	Large variations in macronutrient composition should be avoided for 2 weeks and feeding to maintain energy balance should be ensured in the last 3 days prior to IMCL investigation. Ideally, the diet should be provided, alternatively, a diary can help to follow the dietary habits of the subjects.
	Exercise‐induced variation of IMCL levels are influenced by intensity (40%‐60% of VO2max), duration (≥60 min), muscle involved and fed/fasting state.
	Combination of light‐to‐moderate exercise and caloric restriction over several days might help to deplete IMCL in patient groups with limited exercise capacity.
	Replenishment of IMCL levels takes several hours to days and depends on the type of diet and the observed muscle group.