Acute Effects of Marathon and Ultramarathon Running on Body Composition in Trained Male Athletes.

Both marathon and ultramarathon groups exhibited significant reductions in body weight and BMI immediately post-race.

• Sixteen male amateur endurance runners were divided into marathon (n = 8, 42.195 km) and ultramarathon (n = 8, 61 km) groups.
• Reductions in BW and BMI were statistically significant (p < 0.05) in both groups.
• More pronounced changes in BW and BMI were observed in the ultramarathon group compared to the marathon group.
• Partial restoration of BW and BMI occurred within 24 hours post-race, attributed primarily to glycogen resynthesis and fluid retention.

Total body water remained stable immediately post-race but increased notably during the 24-hour recovery period, particularly in ultramarathon runners.

• TBW did not show significant change immediately post-race in either group.
• TBW increased notably during the 24-hour recovery phase, with more pronounced increases in ultramarathon runners.
• The authors interpreted the greater TBW increase in ultramarathon runners as suggesting 'more effective hydration responses' following the longer event.
• Body composition was assessed at three time points: pre-race, immediately post-race, and 24 hours post-race using bioelectrical impedance analysis (BIA).

Both total and regional fat percentages declined significantly post-race in both groups, with ultramarathon runners showing greater reductions.

• Regional fat measurements included right arm fat (RAF), left arm fat (LAF), right leg fat (RLF), left leg fat (LLF), and torso fat (TF).
• Reductions in fat percentages were observed across both total body fat (TBF) and all regional fat compartments.
• Ultramarathon runners demonstrated greater fat percentage reductions than marathon runners.
• Fat percentage changes were statistically significant (p < 0.05) in both groups.

Changes in lean body mass and fat-free mass were minimal but more favorable in the ultramarathon group.

• Lean body mass (LBM) changes were described as 'minimal but more favorable in the ultramarathon group.'
• Fat-free mass changes similarly showed small but slightly more positive outcomes in ultramarathon runners.
• The minimal LBM changes suggest muscle mass was largely preserved across both race distances.
• Measurements were taken using bioelectrical impedance analysis at pre-race, immediately post-race, and 24 hours post-race.

Ultramarathon running elicited more pronounced metabolic and fluid balance responses compared to marathon running.

• Greater changes in BW, BMI, TBW, TBF, and regional fat were consistently observed in the ultramarathon (61 km) group versus the marathon (42.195 km) group.
• The authors concluded that 'ultramarathon participation eliciting more pronounced metabolic and fluid balance responses.'
• The findings highlight the importance of 'race-specific nutritional and hydration strategies tailored to event type and duration.'
• The study sample was limited to trained male amateur endurance runners (total n = 16).