. Author manuscript; available in PMC: 2020 Oct 1.

Published in final edited form as: J Physiol. 2019 May 20;597(19):4943–4957. doi: 10.1113/JP277803

Table 3.

Metabolite levels at rest and at the end of the 24 s isometric MVC

		Young (n= 7)	Old (n= 8)	P value

Rest
[PCr]	(mM)	27.4 ± 3.2	31.6 ± 7.4	0.186
[P_i ]	(mM)	3.7 ± 1.2	4.4 ± 0.8	0.196
pH		6.98 ± 0.04	6.99 ± 0.03	0.832
[H₂PO₄- ]	(mM)	1.4 ± 0.4	1.6 ± 0.3	0.184
End contraction
[PCr]	(mM)	14.5 ± 1.7	18.1 ± 5.1	0.106
[PCr]	(%Rest)	52.2 ± 6.8	56.6 ± 3.7	0.136
[P_i ]	(mM)	17.5 ± 2.8	20.7 ± 4.0	0.106
pH		7.00 ± 0.07	7.00 ± 0.05	0.995
[H₂PO₄- ]	(mM)	6.3 ± 1.4	7.6 ± 1.6	0.143

Millimolar (mM) concentrations of the phosphorus metabolites were calculated assuming a resting [ATP] of 8.2 mM and after correcting for partial signal saturation from using a TR of 2 s. Resting metabolite levels were obtained from the final 64 s (average of eight spectra) of the 10 min recovery period following the 24 s isometric MVC. Values are the mean ± SD.