title: Changes in foot volume, body composition, and hydration status in male and female 24-hour ultra-mountain bikers.
abstract: BACKGROUND
  The effects of running and cycling on changes in hydration status and body composition during a 24-hour race have been described previously, but data for 24-hour ultra-mountain bikers are missing. The present study investigated changes in foot volume, body composition, and hydration status in male and female 24-hour ultra-mountain bikers.
  
  
  METHODS
  We compared in 49 (37 men and 12 women) 24-hour ultra-mountain bikers (ultra-MTBers) changes (Δ) in body mass (BM). Fat mass (FM), percent body fat (%BF) and skeletal muscle mass (SM) were estimated using anthropometric methods. Changes in total body water (TBW), extracellular fluid (ECF) and intracellular fluid (ICF) were determined using bioelectrical impedance and changes in foot volume using plethysmography. Haematocrit, plasma [Na+], plasma urea, plasma osmolality, urine urea, urine specific gravity and urine osmolality were measured in a subgroup of 25 ultra-MTBers (16 men and 9 women).
  
  
  RESULTS
  In male 24-hour ultra-MTBers, BM (P < 0.001), FM (P < 0.001), %BF (P < 0.001) and ECF (P < 0.05) decreased whereas SM and TBW did not change (P > 0.05). A significant correlation was found between post-race BM and post-race FM (r = 0.63, P < 0.001). In female ultra-MTBers, BM (P < 0.05), %BF (P < 0.05) and FM (P < 0.001) decreased, whereas SM, ECF and TBW remained stable (P > 0.05). Absolute ranking in the race was related to Δ%BM (P < 0.001) and Δ%FM in men (P < 0.001) and to Δ%BM (P < 0.05) in women. In male ultra-MTBers, increased post-race plasma urea (P < 0.001) was negatively related to absolute ranking in the race, Δ%BM, post-race FM and Δ%ECF (P < 0.05). Foot volume remained stable in both sexes (P > 0.05).
  
  
  CONCLUSIONS
  Male and female 24-hour ultra-MTBers experienced a significant loss in BM and FM, whereas SM remained stable. Body weight changes and increases in plasma urea do not reflect a change in body hydration status. No oedema of the lower limbs occurred.
authors.affiliation: Centre of Sports Activities, Brno University of Technology, Brno, Czech Republic.
authors.forename: Daniela
authors.initials: D
authors.lastname: Chlíbková
authors.affiliation: Institute of General Practise and for Health Services Research, University of Zurich, Zurich, Switzerland.
authors.forename: Beat
authors.initials: B
authors.lastname: Knechtle
authors.affiliation: Institute of General Practise and for Health Services Research, University of Zurich, Zurich, Switzerland.
authors.forename: Thomas
authors.initials: T
authors.lastname: Rosemann
authors.affiliation: Institute of Experimental Biology, Faculty of Science, Masaryk University, Brno, Czech Republic.
authors.forename: Alena
authors.initials: A
authors.lastname: Žákovská
authors.affiliation: Faculty of Forestry and Wood Sciences, Czech University of Life Sciences, Prague, Czech Republic.
authors.forename: Ivana
authors.initials: I
authors.lastname: Tomášková
authors.affiliation: Institute of Technology Tallaght, Dublin, Ireland.
authors.forename: Marcus
authors.initials: M
authors.lastname: Shortall
authors.affiliation: SurGal clinic s.r.o., Center for Sports Medicine, Brno, Czech Republic.
authors.forename: Iva
authors.initials: I
authors.lastname: Tomášková