Supplementary Materials to Comparative Exercise Physiology: Retrospective study of standardised field exercise test on injury development, blood lactate and recovery time in endurance horses

Abstract

This study investigated the effect of environment, horse and type of different field standardised exercise tests (fSET) on incremental lactate concentration and recovery time in endurance horses. Forty-eight endurance horses underwent one or multiple fSET on a 700-m all-weather racetrack. The fSET comprised phase 1 canter at 19.5-21.5 km/h for 19 km (group N), or 37 km split by 20 minutes of rest (group E1) or 37 km (group E2), followed by phase 2 canter at 26-32.6 km/h and phase 3 at 27.7-42.8 km/h, for 1,400 m each for all groups. Blood lactates were recorded after each phase. Linear mixed models were built with blood lactate value and recovery time as dependent variables and horse and environment data, and type of fSET as fixed effect variables, with horse and horse*fSET group as random effects. Data from a total of 130 fSETs were considered; lactate values were 0.78-7.73 mmol/l (median 1.79 mmol/l) for phase 1, 1.70-10.68 mmol/l (median 3.89 mmol/l) for phase 2, and 3.7-20.86 mmol/l (median 8.74 mmol/l) for phase 3. Blood lactate values after phase 1 and phase 2 were significantly lower in group E1 (median 1.49 mmol/l; median 3.12 mmol/l) compared with group N (median 2.77 mmol/l; median 5.28 mmol/l; P<0.001) and group E2 (median 2.06 mmol/l; median 4.39 mmol/l; P<0.001). Blood lactate after phase 3 did not differ between groups. There were two medical and 19 minor musculoskeletal issues within 2 hours after the fSETs. Weather temperature affected blood lactate values after phase 1 and 2 (R=0.62-0.63). Blood lactate after phase 1 (R=0.93) and 2 (R=0.66) affected values after phase 2 and 3, respectively. There was a considerable variation among horses and horse × fSET group random effects. Moreover, blood lactate values are affected by both weather conditions and by horse individual characteristics.</p