title: Impact of repeated prolonged exercise bouts on cardiac function and biomarkers.
abstract: OBJECTIVE
  The present study examined the impact of repeated bouts of prolonged (< 60 min) exercise on left ventricular function and cardiac biomarkers.
  
  
  METHODS
  Ten athletes completed a 15.3-mile hill run on three consecutive days and were assessed before, immediately after, 1 h after, and 20 h after each bout. Six of the athletes completed a fourth bout. Left ventricular (LV) function was examined echocardiographically using two-dimensional M-mode, Doppler, and flow propagation velocity (Vp). Venous blood samples were analyzed for cardiac biomarkers including cardiac troponin T (cTnT).
  
  
  RESULTS
  Ejection fraction (EF) significantly decreased (P = 0.027) after the third exercise bout compared with baseline (mean +/- SD: 56.3 +/- 4.4 vs 51.3 +/- 5.9%), accompanied by a nonsignificant decrease in systolic blood pressure/end systolic volume (SBP/ESV) ratio. A sustained depression in systolic function 20 h after bout 3 also persisted in the subset who completed a fourth bout, yet this did not reach clinical levels. Significant (P < 0.01) reductions in early to late diastolic filling (E:A) ratio pre-to post-bout 1 (mean +/- SD: 1.9 +/- 0.5 vs 1.4 +/- 0.3) and pre- to post-bout 3(2.0 +/- 0.5 vs 1.3 +/- 0.4) normalized after each 20-h recovery period. A similar pattern of change was observed in Vp. Cardiac troponin T was elevated in four individuals 1 h after bout 1 (range: 0.013-0.125 microg.L(-1)) but was undetectable thereafter except in one athlete.
  
  
  CONCLUSIONS
  Repeated bouts of prolonged exercise induce short-term reductions in diastolic filling and a cumulative decrease in systolic function, yet these alterations seem to have minimal clinical or functional impact. Elevated cTnT after the initial bout, but not thereafter, may represent an adaptive response to prolonged exercise.
authors.affiliation: Centre for Sports Medicine and Human Performance, Brunel University, London, United Kingdom.
authors.forename: Natalie
authors.initials: N
authors.lastname: Middleton
authors.forename: Robert
authors.initials: R
authors.lastname: Shave
authors.forename: Keith
authors.initials: K
authors.lastname: George
authors.forename: Gregory
authors.initials: G
authors.lastname: Whyte
authors.forename: Richard
authors.initials: R
authors.lastname: Simpson
authors.forename: Geraint
authors.initials: G
authors.lastname: Florida-James
authors.forename: David
authors.initials: D
authors.lastname: Gaze
mesh_terms: D000328:Adult; D002319:Cardiovascular System; D004562:Electrocardiography; D015444:Exercise / Q000502:physiology*; D006801:Humans; D008297:Male; D020097:Natriuretic Peptide, Brain / Q000032:analysis / Q000378:metabolism; D005082:Physical Exertion / Q000502:physiology; D020107:Troponin T / Q000032:analysis / Q000378:metabolism; D006113:United Kingdom; D016277:Ventricular Function, Left / Q000502:physiology*
chemical_list: D020107:Troponin T; D020097:Natriuretic Peptide, Brain