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Comparison of effective body water and body mass changes at three ground speeds during a 164‐km cycling event (707.9)
Author(s) -
Armstrong Lawrence,
Johnson Evan,
Ganio Matthew,
Judelson Daniel,
Vingren Jakob,
Kupchak Brian,
Kunces Laura,
Muñoz Colleen,
McKenzie Amy,
Williamson Keith
Publication year - 2014
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.28.1_supplement.707.9
Subject(s) - chemistry , zoology , body water , dehydration , cycling , fat mass , weight loss , medicine , body weight , biology , biochemistry , obesity , history , archaeology
Although body mass change (ΔM b ) before and after exercise often is measured to assess dehydration, ΔM b does not represent all water losses and gains. The present field investigation was designed to determine if (a) ΔM b equaled net effective body water change during ultra‐endurance exercise, and (b) ground speed and exercise duration influenced these variables. Thirty‐two experienced male cyclists (35 ‐ 52y) completed a 164‐km event in a hot environment (35ºC), were retrospectively triplet‐matched, and were placed into one of three participant groups (C4.8, C6.3, C9.6; named to match their mean exercise duration, h). Net effective body water loss was computed from measurements (body mass, total fluid intake, urine excreted) and calculations (water evolved and mass loss due to substrate oxidation, solid food mass, respiratory water loss, and sweat loss), including and excluding water bound to glycogen (ΔEBW gly and ΔEBW, respectively). With all cyclists combined, the mean ΔM b (i.e., loss) was greater than that of ΔEBW gly by 1194 ± 213 g ( P <.001), was similar to ΔEBW (difference, 0 ± 200 g; P = .21), and was strongly and linearly correlated with both (r 2 = .98). Analysis of variance detected no effect of group between C4.8, C6.3 and C9.6 for ΔM b , ΔEBW gly , and ΔEBW. Due to complexity of calculations, we conclude (a) athletes likely will not utilize ΔEBW gly and ΔEBW routinely during training due to their complexity, and (b) ΔM b remains a field‐expedient estimate of net effective body water change. Grant Funding Source : University and Department Internal Funds