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Limitations of serum values to estimate glomerular filtration rate during exercise
  1. Jacques R Poortmans1,
  2. Béatrice Gulbis2,
  3. Edward De Bruyn2,
  4. Stéphane Baudry3,
  5. Alain Carpentier1
  1. 1Laboratory for Biometry and Exercise Nutrition, Free University of Brussels, Brussels, Belgium
  2. 2Laboratory of Medical Chemistry, University Erasmus Academic Hospital, Free University of Brussels, Brussels, Belgium
  3. 3Laboratory of Applied Biology, Free University of Brussels, Brussels, Belgium
  1. Correspondence to Jacques R Poortmans, Laboratory for Biometry and Exercise Nutrition, Free University of Belgium, Campus Erasme CP 640, 808 Route de Lennik, B-1070 Brussels, Belgium; jrpoortm{at}


Objective Glomerular filtration rate (GFR) is part of routine medical practice for clinical assessment of kidney function in health and disease conditions, and is determined by measuring the clearance of creatinine (Cl-Crn) or estimated (eGFR) from equations using serum creatinine (Crn) or cystatin C (Cyst C). Crn and Cyst C methods obviate the need for urine collection but their reliability under non-resting conditions is uncertain. This study compared GFR determined by Cl-Crn, Crn and Cyst C methods under the conditions of rest and after exercise.

Methods Twelve young male subjects performed a 30 min treadmill exercise at 80% of the maximal oxygen capacity. Venous blood samples and urine collections were collected before and after exercise and after recovery period. GFR rates were calculated from serum Crn and Cyst C equations, and Cl-Crn measured from serum and urine Crn output. Albumin was also determined for all samples.

Results Under resting conditions, eGFR from Crn and Cyst C did not differ from Cl-Crn (p=0.39). Immediately after exercise, GFR decreased significantly, regardless of the method, but more so for Cl-Crn (−30.0%; p<0.05) compared with Crn (−18.2%) and Cyst C (−19.8%). After the recovery period, GFR determined by Cl-Crn was returned to initial values whereas Crn and Cyst C remained reduced. Although eGFR methods accurately estimate GFR at rest, those methods underestimated the change in GFR after acute exercise.

Conclusions These results indicate that exercise-induced changes in GFR should be determined by Cl-Crn method.

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  • Competing interests None.

  • Patient consent Obtained.

  • Ethics approval Ethical Medical Committee (Academic Hospital).

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Data sharing statement This submission is an unpublished study.

  • ▸ References to this paper are available online at