Manitoba Horse Council Prevention Recovery 1 Brandon MB

Manitoba Horse Council Prevention & Recovery 1 Brandon, MB March 25 2019

Outline Ø Prevention and recovery : • Horses: adaptation to exercise • New techniques in equine imaging • 10 most common treatments

Introduction • Diversity of the horse as an athlete

Diversity of physical abilities • Racing TB: 65 km/h (18 m/s) for one minute, stride length 7. 5 m • Endurance: 100 mile races • QH ¼ mile acceleration (0 -70 km/hr): 21 seconds • Roping: rest to 30 km/h to reverse in < 6 sec • AUDI R 8 V 10 :

Diversity of physical and mental abilities Racing Jumping Reining Pleasure Dressage, paradr Hunting Endurance Poneys …….

Introduction • What makes horses great athletes ?

Horses: great athletes • Cardio-respiratory power& energy metabolism • Mental : – Adaptability – Responsiveness • Limbs: efficient, strength ð Intelligence of movement

Adaptation to exercise Horses have one of the highest athletic ability of all species Extremely high aerobic power: è Horses VO 2 max: up to 160 ml. O 2/kg/min è Human VO 2 max: 69 -85 ml. O 2/kg/min

HIGH AEROBIC POWER Pump maximum amount of blood per time unit Ø Increase heart rate Ø Increase amount of blood pumped

Cardiovascular Adaptations • Heart rate (horse) – Rest: 28 -36 bpm – Maximal: 250 bpm Greyhound (100 -300 bpm) Man (40 -190 bpm) è Very high range è Extremely fast rate of increase

Cardiovascular adaptations CARDIAC OUTPUT Amount of blood pumped in one minute • Cardiac output = heart rate X stroke volume – Stroke Volume: amount of blood pumped by each heart beat – (Stroke index = stroke volume/body weight)

Cardiac output increase Increase: heart rate and stroke volume Horse: 25 lt(rest) 300 lt max (0. 7 lt/min/kg) Human athlete: 5 lt(rest 30 lt (max) (0. 35 lt/min/kg)

Cardiovascular adaptations Maximal exercise Ten fold(+) increase in heart rate 28 -32 to 240 bpm One to two fold increase in stroke index 1. 0 ml/kg to 2. 5 ml/kg è Most of the increased cardiac output is due to increased heart rate

Cardiovascular adaptations Heart rate regulation • Two opposed systems regulate: – Sympathetic (Fight or flight): stress – Parasympathetic: relaxation – Horses have fast sympathetic responses • Exercise « anticipation » response: HR increase in preparation to exercise: – Ex: increase to 80/bpm when in paddock

Cardiovascular adaptations 1. 2. 3. 4. 5. Heart rate during exercise Anticipatory increase Rapid increase (30 -35 sec) at onset Peak Plateau Decrease: 1 – 2 min after end of exercise Depends on workload, exercise capacity of horse, environmental factors • HR is linear with workload above 160 bpm

Cardiovascular adaptations: Blood 10 % of the horse’s body weight Ø Appx 50 Lt Composition: – Red blood cells – White blood cells – Plasma: – water (92 %), – proteins (6%) – dissolved substances (hormones, vitamins, electrolytes, etc)

Cardiovascular system adaptations Packed cell volume – Rest: • 32 -46% vs 40 -50% (hu) – Maximal exercise: • 60 -70% vs 40 -55% (hu) – Horses have an inherent « blood doping » system Increase packed cell volume through spleenic contraction (Spleen red blood cell reservoir at rest)

Cardiovascular system adaptations Great oxygen transport capacity of the horse èGreat ability to increase cardiac output through increased heart rate èGreat ability to carry oxygen in blood through increased PCV at exercise

Respiratory adaptations • Tidal volume (amount of air per breath, 470 kg, TB on threadmill): – – – Rest: 5. 6 lt Walk: 5. 8 lt Trot: 6. 2 lt Canter: 9. 2 lt Gallop: 12 -13. 2 lt • Tidal volume X respiratory frequency = Expired minute ventilation

Respiratory adaptations Respiratory frequency – Rest: 12 -16 bpm – Exercise: • Trotters: up to 133 (avge 80) bpm • Gallopers: 110 - 130 bpm Locomotion coupling: 1 stride = 1 breath • Coupling observed at gallop not canter • (Longer stride = larger tidal volume ? ? ) • Piston-pendulum theory of the abdominal organs

Respiratory adaptations Increased expired minute ventilation (Ve) – Rest: 50 -60 lt/min – Gallop: 1600 lt/min< – (Respiratory frequency X tidal volume) – Increase in tidal volume and respiratory frequency

Respiratory frequency: decoupling Decoupling: uncouple stride and respiratory frequency Occurs • Post exercise • During change of leads, acceleration, jumping, etc • With upper airway disturbances: laryngeal hemiplegia (roaring)

Respiratory Adaptations Thermoregulation • Horses cannot breath through mouth • Air movement through upper airways and the highly vascularized lungs is an important cooling mecanism Limited effect during exercise because of the respiratory coupling Becomes factor post exercise

Respiratory adaptations Dead Space • Gas exchange occurs only in the alveoli (in the lungs) • All the air in the airways (nasal cavity, larynx, trachea and bronchii) is not used for gas exchange • As respiratory frequency increases , the effect of dead space becomes more important

Respiratory adaptations Conclusion • Training has very little effect on the respiratory system – Horses « blow » less after training because of improved oxygen intake and better muscle metabolism • Normal respiratory system is rarely a performance limiting factor • Respiratory problems (upper airway problems, IAD and COPD) can affect exercise ability

Musculoskeletal adaptations • Horses have a large muscle mass (45 -55 % body mass/40 - 45 % other species) • Horses: muscles located on trunk with long tendons (efficiency of longer lever arcs) • Postural muscles: smaller, on the inside • Locomotor muscles: larger, on the outside

Muscle types Skeletal muscle Cardiac muscle Involuntary muscle

Muscle fiber types Classification systems • • Appearance: color, diameter Speed of contraction and relaxation: slow, fast Oxydative power: ability to use oxygen Type: I, IIa, IIb, IIc

Type 1, red endurance fibers • Slow twitch: slow contraction and relaxation • Small diameter: low strength and power • High endurance: high oxydative (aerobic) power (very efficient use of oxygen) • Low glycogen content • Most common type for postural and fine movements

Type 2, white sprint fibers �IIa: middle level of power and anaerobic/aerobic metabolism �IIb: highest power, lowest endurance, highest glycolytic and lowest oxydative metabolism With training switch from IIb to IIa fibers

Muscle contraction • Electrical signal (nerves) produces release of calcium which releases a phosphate from ATP to move the actin on the myosin èNeed ATP (energy) to produce the muscle contraction èNeed ATP to pump calcium back in the SR

ATP production • ATP = ADP + P • Small ATP reserve in the muscle ( 1 -2 contraction) • Glucose and fatty acids are used to regenerate ATP – Glucose is stored as glycogen in liver and muscle – Fatty acids as triglycerides in adipose tissue(fat) around muscles, crest, loins, etc • 4 ATP production pathways – – Anaerobic phosporilation Aerobic glycolysis Aerobic fat Anaerobic carbohydrate metabolism

ATP production: energy pathways Anaerobic phosphorylation: – CP +ADP= C+ATP – CP reserves are small – Used for explosive short power(jumping) – Fast ATP regeneration without use of Oxygen or other energy stores(glucose or fat) – CP replenishement limiting factor

ATP production: energy pathways Aerobic phosphorylation of ADP – Uses carbohydrate stores through glycolysis and Krebs cycle One glucose H 2 O and CO 2 + 39 ATP è Oxygen is required for Krebs cycle

Aerobic glycolysis

ATP production: energy pathways Aerobic phosphorylation of ADP using fatty acids �Fat stores (triglycerides) produces free fatty acids(bloodstream) which are broken down to acetyl Co. A which goes to Krebs cycle èProduces 139 ATP from one fat unit (vs 39 for CHO unit)

ATP production: energy pathways Anaerobic phosphorylation using carbohydrate – Transforms glycogen or glucose to lactic acid – Produces 3 ATP (glycogen) or 2 ATP (glucose) and transformation of NAD to NADH • Breakdown of fat anaerobically is impossible Energy partitioning

ATP production: energy pathways Power(ATP/kg) Time(to power) O 2 Fatigue Anaerobic ATP 11. 2 1 sec no seconds PCr 8. 6 1 sec no seconds CHO to lactate 5. 2 5 sec no minutes Aerobic CHO to CO 2+H 2 O 2. 7 FFA to CO 2+H 2 1. 4 2 -3 min 30 min yes+ yes hours days

Energy partitioning • Up to HR 160 bpm: – aerobic pathways • Over HR 160 bpm, 5 -600 m/min: – ATP production starts to rely on anaerobic pathways – Limit is not O 2 availability but need for more ATP ØAerobic production is at maximum and anaerobic mecanisms are needed to supplement

Energy partitioning • « Anaerobic threshold » is simplistic • At HR 160 -180 bpm, lactates start to accumulate especially if horse has high % of type IIb fibers. – QH races: 40% areobic, 60% anaerobic – TB races(11/2 mi): 80% aero, 20% anaero – Ho races(100 m): 100 % anaero(1 or 2 breaths)

Lactates • Rest: 1 mmol/lt • OBLA 4 (threshold of lactate accumulation): 4 mmol/lt • Horses: – End of 2000 m race: 20 -30 mmol/lt – End of 50 km endurance: < 2 mmol/lt – End of cross country (CCI): 8 mmol/lt Horses have a very high buffer capacity to counter lactate accumulation

Fatigue Inability to maintain optimal performane – Does not occur in all fibers at once but in a selective manner affecting some aspects of the performance. • Depletion of energy substrate: glycogen • Alteration of intracellular milieu which interferes with ATP production: • Lactate accumulation • Changes in neuromuscular irritability: electrolyte distribution • Changes in muscle blood flow and muscle temperature

Fatigue • Glycogen depletion in the muscles and the liver. – Muscle depletion : weakness – Liver depletion: low blood glucose • Glycogen loading: exercise to fatigue then reload (seems to increase storage) – Does not apply to horses: already increased Glycogen stores, danger of tying up. • Glycogen repletion takes 2 days

Skeletal adaptations Limb anatomy • Long tendons and ligaments – Shock absorbtion – Propulsion effects: passive motion and suspension

Musculo-squeletal adaptations • Bone remodeling: Loading Physical maturity changes bone distribution • Respiratory, (shape) of bone. cardiovascular, mental: ? ? – Dorsal cortex of MC 3 in • Bone growth plates racing TBs is much thicker – Head: 3 months to 5 years • Tendons/ligaments: – Spine: 2 to 4 years training/exercise has little – Limbs: tibia, humerus: 3 effect – May decrease size and increase presence of inflammatory mediators. years – Pelvis: 1 yr old • Muscle – fiber type differentiation is present at birth

Thermoregulation Body temperature: ◦ Normal 37. 5 -38 o celsius Heat production during exercise – After cross country, long races • Mild weather 40 -42 o • Hot, humid conditions 45 -46 o

Thermoregulation When body temperatures above 40 o �Cooling down will minimize fluid and electroyte losses trough sweat èWill minimize dehydration

Sweating: evaporative heat loss • Sweat composition – Hypertonic (contains more electrolytes than plasma • Sodium: same as plasma • Chloride: slightly higher • Potassium: 10 to 20 times higher • Sweat losses: up to 10 to 15 liters/hour – 1 mi canter: 5 -7 kg weight loss – 100 mi endurance race: 40 -100 kg weight loss

Respiratory heat loss �Panting: approximately 30% of the heat load ◦ Primary panting: fast, shallow breathing post exercise (up to 180 bpm) ◦ Secondary panting: slower, deeper breathing post exercise (around 50 bpm) (usually reflects higher body temperatures)

Digestive adaptations • Small stomach: 4 -5 liters �Rapid gastric emptying: less than 20 min �Large colon: huge fluid and electrolyte reserve for exercise Adaptation to fight or flight

Fluid recovery • Dehydration becomes problematic when 6 -7% body weight loss (30 -35 kg for 500 kg) • Rehydration: – Fluid redistribution • Large bowel fluid reserve (30 -40 lt) – Oral intake : drinking water • Oral isotonic electrolyte solution – 45 g of salt + 45 gr of lite-salt/ 10 lt of water (+ apple juice for taste) • Electrolytes: drinking reflex based on sodium concentration (without sodium body cannot hold water) – IV Fluids: needed when horses can’t drink enough • Caution: administration rate to avoid diuretic effect

Mental adaptations (Dr R. Miller) Horses are Prey/flight animal Most perceptive Fastest response times Quickly desensitized Infallible memory Categorize stimulii: fear or not Easily dominated Dominates by controlling movement • Body language unique • Very precocial animal • •

Mental adaptations: senses of the horses • Visual: primary danger sensor • Olfactory and auditory: very developed • Tactile: extreme (equals human finger tips) • Gustatory

Summary : horses as athletes • Oustanding aerobic capacity (VO 2 max, Cardiac output, HR range, splenic contraction) • Very high anaerobic tolerance (high type 2 fibers, glycogen reserves, lactate tolerance) • Very high thermoregulatory ability (High To tolerance, high sweat production • Excellent biomechanical adaptations (little vertical movement, structures to biomechanical spring)