McLean et al. 2013, Year-to-year variability in haemoglobin-mass response to altitude camps

Twelve elite team-sport athletes completed two moderate-altitude (~2,100 m) training camps of about 18 days each, twelve months apart (British Journal of Sports Medicine 47(Suppl 1):i51–i58). Haemoglobin mass rose on average after each camp, but an individual’s change from one camp to the next barely correlated (r ≈ 0.21), so the group response was reproducible while the personal “responder” status was not. Moderate (small sample, observational).