1. Hardware
a. Field strength [T]	7 T
b. Manufacturer	Siemens Healthineers, Erlangen, Germany
c. Model (software version if available)	Magnetom 7 T (VB17)
d. RF coils: nuclei (transmit/receive), number of channels, type, body part	Custom‐built three channel 31P (d = 15 cm, l = 10 cm), two channel 1H (d = 17 cm, l = 12.5 cm) transceiver coil, shaped to the human calf (Goluch et al. Magn Reson Med. 2015;73(6):1190‐1195)
e. Additional hardware	Custom‐built pedal ergometer with pneumatic piston and MR‐compatible sensors for pedal angle and force

2. Acquisition
a. Pulse sequence	Semi‐LASER
b. Volume of interest and VOI locations	Single voxel placed obliquely in gastrocnemius muscle, avoiding subcutaneous fat, fasciae and adjacent muscles
c. Nominal VOI size [cm3, mm3]	Anatomy matched, 27 ± 6 cm3 (ca. 2 × 3.5 × 4 cm 3 )
d. Repetition time (T R), echo time (T E) [ms, s]	T R = 6 s, T E = 29 ms
e. Total number of excitations or acquisitions per spectrum (NA) In time series for kinetic studies i. Number of averaged spectra) per time point (NA) ii. Averaging method (eg block‐wise or moving average) Total number of spectra (acquired/in time series)	1 acquisition per spectrum (NA = 1), except for pH quantification 90 s after exercise, where NA = 4, with block‐wise averaging Total number of spectra in time series was 140, at NA = 1 (or series of 35 spectra at NA = 4)
f. Additional sequence parameters (spectral width in Hz, number of spectral points, frequency offsets) i. If STEAM: mixing time (T M) ii. If MRSI: 2D or 3D, FOV in all directions, matrix size, acceleration factors, sampling method	5 kHz, 2048 complex points after removing oversampling
g. Water suppression method	N/A
h. Shimming method, reference peak, and thresholds for “acceptance of shim” chosen	1st and 2nd order, vendor standard method (DESS sequence in “advanced shim” mode until convergence), line‐width of PCr peak was evaluated post hoc
i. Triggering or motion correction method (respiratory, peripheral, cardiac triggering, incl. device used and delays)	Subjects were instructed to push the pedal only during times without RF excitation or signal reception, cued by gradient noise. Adherence to the protocol was inspected via data from the force sensors.

3. Data analysis methods and outputs
a. Analysis software	31P MR spectroscopy data were processed from raw data exported from the scanner using in‐house developed Python scripts (http://www.python.org) for phasing and channel combination. Signals were phased to the highest peak magnitude of PCr in the frequency domain after 7 Hz Lorentzian apodization and 4 × zero‐filling. The channel combination was then performed by weighted averaging of the raw data (that is, without apodization and zero‐filling). Weights were calculated as proportional to signal, averaged over four resting spectra (excluding the fully relaxed spectrum). Spectra were then fitted in AMARES, as implemented in jMRUI, version 5.0
b. Processing steps deviating from quoted reference or product analysis software (vendor, version)	Gaussian line shapes, soft constraints for frequencies
c. Output measure (eg absolute concentration, institutional units, ratio) Processing steps deviating from quoted reference or product	Concentrations in institutional units and pH values
d. Quantification references and assumptions, fitting model assumptions	Quantification relative to total 31 P signal, which was assumed to be constant. End‐exercise PCr depletion relative to post‐exercise asymptotic value of mono‐exponential fit of recovery

5. Data quality
a. Reported variables (SNR, linewidth (with reference peaks))	SNR was calculated using the partially saturated resting spectra of each time series by dividing the PCr peak amplitude by the SD of the signal in a region containing only noise, 15 ppm off‐center across 1/16 of the total bandwidth. Linewidths were taken from the AMARES fit of the PCr peak.
b. Data exclusion criteria	>10% changes of sum of total 31 P signal Linewidth of PCr peak > 15 Hz Unphysiological pH values (>7.1) Splitting of P i peak
c. Quality measures of postprocessing model fitting (eg CRLB, goodness of fit, SD of residual)	SD of residual
d. Sample spectrum	Figure 2

NAA, N‐acetylaspartate.

The example above used the following paper: Niess F, Schmid AI, Bogner W, et al. Interleaved ³¹P MRS/¹H ASL for analysis of metabolic and functional heterogeneity along human lower leg muscles at 7 T. Magn Reson Med. 2020;83:1909‐1919. https://doi.org/10.1002/mrm.28088.

Items listed in italics are details that were not included in the paper that served as the source for this example.