Utility of Infrared Thermography for Monitoring of Surface Temperature Changes During Horses' Work on Water Treadmill with an Artificial River System

Abstract

Water treadmill (WT) exercise is used for horses' rehabilitation and training. Given that each training needs to be individualized for each horse, the goal is to assess whether infrared thermography (IRT) can serve as a non-invasive tool for daily monitoring of individual training and rehabilitation progress in horses undergoing WT exercise. Fifteen Polish Warmblood school horses were subjected to five WT sessions: dry treadmill, fetlock-depth water, fetlock-depth water with artificial river (AR), carpal-depth water, and carpal-depth water with AR. IRT images, collected pre- and post-exercise, were analyzed for the mean temperature (Tmean) and maximal temperature (Tmax) across 14 regions of interest (ROIs) representing the body surface overlying specific superficial muscles. While on a dry treadmill, Tmean and Tmax increased post-exercise in all ROIs; wetting of the hair coat limited surface temperature analysis in ROIs annotated on limbs. Tmax over the m. brachiocephalicus, m. trapezius pars cervicalis, m. triceps brachii, and m. semitendinosus increased during walking in carpal-depth water, which therefore may be suggested as an indirect indicator of increased activity related to forelimb protraction and flexion-extension of the limb joints. Tmax over the m. latissimus dorsi and m. longissimus increased during carpal-depth WT exercise with active AR mode, which may be suggested as an indicator of increased workload including vertical displacement of the trunk.

Keywords: equine; hydrotherapy; infrared thermography; water counterflow; water treadmill.

Figure 1

Thermographic images of the lateral surface of the same horse (A) with annotated landmarks and lines; (B) with annotated regions of interest (ROIs). Landmarks: a—wing of atlas, b—half the length of the neck, c—one third the length of the scapula, d—two thirds the length of the scapula, e—major tuberosity of humerus, f—lateral epicondyle of humerus, g—radiocarpal joint, h—tuber coxae, i—third trochanter of femur, j—patella, k—cut edge of deep crural fascia, l—tibiotarsal joint; Lines: 1—dorsal edge of the jugular groove, 2—cranial edge of the scapular muscles, 3—spine of the scapula, 4—horizontal level of one third of the scapula, 5—horizontal level of two thirds of the scapula, 6—horizontal level of the third trochanter of femur, 7—horizontal level of the major tuberosity of humerus, 8—horizontal level of the patella, 9—horizontal level of the lateral epicondyle of humerus and the cut edge of deep crural fascia, 10—horizontal level of the tibiotarsal joint, 11—horizontal level of the radiocarpal joint, 12—lateral midline of the forearm region, 13—vertical level of the tuber coxae, 14—vertical level of the third trochanter of femur, 15—the intermuscular groove (poverty line), 16—lateral midline of the leg region. The crosshair represents the lowest temperature on the image.

Figure 2

Thermographic images of the lateral surface of the same horse (A) before an exercise session; (B) after dry treadmill (DT) session; (C) after fetlock-depth water treadmill (WT) session; (D) after fetlock-depth WT session with artificial river (AR) mode; (E) after carpal-depth WT session; (F) after carpal-depth WT session with artificial river (AR) mode. Arrows indicate the upper level of wet hair coat after exercise. The crosshair represents the lowest temperature on the image.

Figure 3

Training type effect on (A,B) the mean temperature (Tmean) and (C,D) the maximal temperature (Tmax) obtained from regions of interest (ROIs), representing body surface areas overlying specific superficial muscles responsible for forelimb protraction. The Tmean and Tmax were obtained after five sessions: dry treadmill (DT) session, water treadmill (WT) session in fetlock-depth water (FD WT), WT session in fetlock-depth water with artificial river (AR) mode (FD WT + AR), WT session in carpal-depth water (CD WT), and WT session in carpal-depth water with AR mode (CD WT + AR). Boxes represent median and lower and upper quartiles, while whiskers represent minimum and maximum values. Superscripts letters (a–c) indicate training-type-related differences. Statistical significance was set at p < 0.05.

Figure 4

Training type effect on (A–C) the mean temperature (Tmean) and (D–F) the maximal temperature (Tmax) obtained from regions of interest (ROIs), representing body surface areas overlying specific superficial muscles responsible for forelimb retraction. The Tmean and Tmax were obtained after five sessions: dry treadmill (DT) session, water treadmill (WT) session in fetlock-depth water (FD WT), WT session in fetlock-depth water with artificial river (AR) mode (FD WT + AR), WT session in carpal-depth water (CD WT), and WT session in carpal-depth water with AR mode (CD WT + AR). Boxes represent median and lower and upper quartiles, while whiskers represent minimum and maximum values. Superscripts letters (a–c) indicate training-type-related differences. Statistical significance was set at p < 0.05.

Figure 5

Training type effect on (A,B) the mean temperature (Tmean) and (C,D) the maximal temperature (Tmax) obtained from regions of interest (ROIs), representing body surface areas overlying specific superficial muscles responsible for (A,C) hindlimb protraction and (B,D) dorsoventral displacement of the trunk. The Tmean and Tmax were obtained after five sessions: dry treadmill (DT) session, water treadmill (WT) session in fetlock-depth water (FD WT), WT session in fetlock-depth water with artificial river (AR) mode (FD WT + AR), WT session in carpal-depth water (CD WT), and WT session in carpal-depth water with AR mode (CD WT + AR). Boxes represent median and lower and upper quartiles, while whiskers represent minimum and maximum values. Superscripts letters (a–c) indicate training-type-related differences. Statistical significance was set at p < 0.05.

Figure 6

Training type effect on (A–C) the mean temperature (Tmean) and (D–F) the maximal temperature (Tmax) obtained from regions of interest (ROIs), representing body surface areas overlying specific superficial muscles responsible for hindlimb retraction. The Tmean and Tmax were obtained after five sessions: dry treadmill (DT) session, water treadmill (WT) session in fetlock-depth water (FD WT), WT session in fetlock-depth water with artificial river (AR) mode (FD WT + AR), WT session in carpal-depth water (CD WT), and WT session in carpal-depth water with AR mode (CD WT + AR). Boxes represent median and lower and upper quartiles, while whiskers represent minimum and maximum values. Superscripts letters (a–c) indicate training-type-related differences. Statistical significance was set at p < 0.05.