Exploring the stride-to-stride variability and fluctuations during maximal lactate steady-state running in horses

• Grant number: 25/05372-0
• Support Opportunities: Regular Research Grants
• Start date: August 01, 2025
• End date: July 31, 2028
• Field of knowledge: Agronomical Sciences - Veterinary Medicine - Animal Clinics and Surgery
• Principal Investigator: Guilherme de Camargo Ferraz
• Grantee: Guilherme de Camargo Ferraz
• Host Institution: Faculdade de Ciências Agrárias e Veterinárias (FCAV). Universidade Estadual Paulista (UNESP). Campus de Jaboticabal. Jaboticabal , SP, Brazil
• Associated researchers: Filipe Manuel Serra Braganca ; Jeanne Isabelle Monette Parmentier

Abstract

The welfare of horses in competitive equestrian sports is under growing public scrutiny. Musculoskeletal injuries induced by fatigue are common reasons for high-level athletic horses to be withdrawn from the sport. Ensuring the safety of both horse and rider is crucial, and fatigue management using non-invasive devices is vital. Exercise workload can induce neuromuscular fatigue (NMF) and impair exercise performance. It is unknown whether small changes in speed below and above the maximal lactate steady state (MLSS) induce NMF. MLSS is a well-known performance indicator for endurance fitness, representing the highest intensity at which plasma L-lactate concentration ([La-]) remains constant, and the energy demand is adequately met by oxidative phosphorylation. Gait variability (GV) has been extensively studied in relation to fatigue and injury in humans, while only a few studies have examined the relationship of GV with MLSS in horses. This study aims to examine the relationship between GV, lactate threshold, and MLSS in horses during exercise, and to identify relevant gait features that can indicate fatigue, enabling noninvasive monitoring of fatigue state. This project will compare, through a new-generation wireless inertial measurement unit (IMU), the GV in horses in response to exercises performed at MLSS, 10% below (MLSS-10%) and above (MLSS+10%). The project also aims to identify gait features that indicate fatigue, allowing for noninvasive monitoring of fatigue states in horses. Fifteen Arabian horses will undergo an incremental exercise test (IET) to determine their lactate threshold. This information will be used to predict their MLSS. Following this, the horses will undergo 30-min constant-velocity exercise bouts every other day using standardized exercise tests (SETs) on a treadmill to estimate the horses' MLSS. Heart rate (HR) and [La-] will be measured. In addition, gait variables such as stance duration, swing duration, and limb range of motion will be recorded using a movement analysis system (Equi-Pro Equine Gait Analysis®). The study will also calculate the standard deviation (SD), coefficient of variation (CV), and the long-range correlations (¿) for each gait variable. The relative intensity for SD, CV, and ¿ during the IET and SET will be evaluated over time using a two-way repeated measures analysis of variance (ANOVA) within-horse factors defined as exercise velocity (LT and MLSS-10%-MLSS- MLSS+10%) x time (3 min for LT stages, and 10min-20min-30min during MLSS protocols). (AU)