A faster running speed is associated with a greater body weight loss in 100-km ultra-marathoners.
In 219 recreational male runners, we investigated changes in body mass, total body water, haematocrit, plasma sodium concentration ([Na(+)]), and urine specific gravity as well as fluid intake during a 100-km ultra-marathon. The athletes lost 1.9 kg (s = 1.4) of body mass, equal to 2.5% (s = 1.8) of body mass (P < 0.001), 0.7 kg (s = 1.0) of predicted skeletal muscle mass (P < 0.001), 0.2 kg (s = 1.3) of predicted fat mass (P < 0.05), and 0.9 L (s = 1.6) of predicted total body water (P < 0.001). Haematocrit decreased (P < 0.001), urine specific gravity (P < 0.001), plasma volume (P < 0.05), and plasma [Na(+)] (P < 0.05) all increased. Change in body mass was related to running speed (r = -0.16, P < 0.05), change in plasma volume was associated with change in plasma [Na(+)] (r = -0.28, P < 0.0001), and change in body mass was related to both change in plasma [Na(+)] (r = -0.36) and change in plasma volume (r = 0.31) (P < 0.0001). The athletes consumed 0.65 L (s = 0.27) fluid per hour. Fluid intake was related to both running speed (r = 0.42, P < 0.0001) and change in body mass (r = 0.23, P = 0.0006), but not post-race plasma [Na(+)] or change in plasma [Na(+)] (P > 0.05). In conclusion, faster runners lost more body mass, runners lost more body mass when they drank less fluid, and faster runners drank more fluid than slower runners.
Facharzt FMH für Allgemeinmedizin, St. Gallen, Switzerland. beat.knechtle@hispeed.ch
Beat
B
Knechtle
Patrizia
P
Knechtle
Andrea
A
Wirth
Christoph
C
Alexander Rüst
Thomas
T
Rosemann
D000328:Adult; D056352:Athletes; D054874:Athletic Performance / Q000502:physiology*; D001810:Blood Volume / Q000502:physiology; D001834:Body Water / Q000502:physiology; D004326:Drinking / Q000502:physiology; D006400:Hematocrit; D006801:Humans; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000033:anatomy & histology / Q000502:physiology; D009929:Organ Size; D010807:Physical Endurance / Q000502:physiology*; D012420:Running / Q000502:physiology*; D012964:Sodium / Q000097:blood; D013046:Specific Gravity; D014556:Urine / Q000737:chemistry / Q000502:physiology; D015431:Weight Loss / Q000502:physiology*
D012964:Sodium