Also known as Exertional Rhabdomyolysis, Azoturia, Monday morning sickness, PSSM
Rhabdomyolysis: breakdown of muscle
- Generally affects the back and hindquarter muscles – Semimembranosus, Semitendinosus and gluteal muscles
- Stiff to move, stilted gait which may progress to lying down and unable to get up
- The muscles will feel rock hard, and are dry/dehydrated
- Temperature elevated
- Respiratory rate elevated
- Often occurs 15-20 minutes post aerobic exercise (slow to medium work)
- Myoglobinuria (dark coloured urine due to the breakdown of muscle)
- Stretch out as if to urinate
- Loss of performance
- Not finishing off
- Weight loss
- Pain over an affected muscle
- Subtle gait abnormalities
Horses susceptible to Exertional Myopathies
- Fit – working and performance horses
- Horses that are resting but still maintained on full ration then brought back into hard work
- Mares & Fillies are often over represented
- Day off on full ration
- Increase in duration and intensity of exercise
- Participation in an event with inadequate conditioning
Potential underlying causes
- Thyroid disorders
- Hormonal influences
- Electrolyte and Fluid imbalances
- High grain diet – Carbohydrate overload
- Infections – viral & bacterial
- Abnormal muscle calcium levels
- Free radical damage to muscle
- Electrolyte/ fluid imbalances
- Vitamin E, Selenium, magnesium deficiency
A good supply of ATP and calcium is required to be readily available form skeletal muscle contraction. If the ATP has been utilised the myosin cross bridge to actin is stuck and this can lead to muscle spasm. If oxygen supply to the muscle is restricted due to the muscle becoming congested with waste products then pyruvic acid is used in the place of oxygen to form ATP. Pyruvic acid is very inefficient compared to Oxygen as it only utilises 2 % of the glucose molecule and the rest becomes further waste. The build-up is Lactic acid spreads through intercellular fluids and leads to body/muscle fatigue and muscle congestion.
It used to be thought the the lactic acid build up was the culprit of tying up but the current thinking is It is actually related to calcium getting stuck in the cells of the muscles causing persistant contraction.
Through muscle biopsy it has been identified that It is the fast twitch (Anaerobic) fibres that are damaged in tying up. The unusual aspect is that it is usually aerobic work that leads to tying up (slow & medium work), when theoretically the fast twitch fibres are not in use. The recruitment of fast twitch fibres during exercise depends on diet, fitness, prior training, warm up and rate of increase in speed. Anaerobic supply (fast twitch muscle fibre activity) serves as a top up to aerobic energy production, therefore they may come into play earlier if required.
Excitement and stress cause the release of hormones that stimulate muscular activity and specifically the anaerobic energy system – fast twitch fibres. This leads to increased lactic acid. Because the work being undertaken is slow to medium, the blood flow is only moderately increased and not adequate to remove the excess lactic acid, this leads to increased lactate in cells which reduces the capacity of cells to remove calcium. Calcium is involved in muscular contraction, so its inability to be removed from the cell leads to an inability for the cell & hence muscle to relax.
- Work load – sudden change
- Dietry imbalance – electrolytes, high grain, sodium, potassium ,magnesium, calcium, Vitamin E, omega 3 fatty acids.
- Recurrent Exertional rhambdomyolysis
- fillies, nervous disposition, stress, genetic, diet, temperament, lameness, biomechanical problems
- Polysaccharide Storage Myopathy (PSSM)– Excessive glycogen accumulation and may also be an abnormal polysaccharide in skeletal muscle. The glycogen accumulates in an abnormal structure and prevents the horse from using the normal glycogen stored in the muscles. Quarter horses, standardbred, some thoroughbreds and warmbloods.
- PSSM horses are generally calm and not easily stressed – grazing, turned out
- Malignant hyperthermia – genetic – quarter horses & paints
- Measuring blood
- CK - Creatine Kinase( 6hrs (4-12hrs) post exercise)
- AST - Aspartate Amino Transferase(24hrs post exercise)
- LDH (Lactate Dehydrogenase (12 hours post injury).
- CK should return to normal within 2-3 days, AST & LDH should return to normal within 7-14 days if the muscle damage has stopped occurring,
- Electrolyte monitoring – be aware the in chronic tying up serum electrolytes do not actually match body electrolytes
- Muscle Biopsy
- Genetic testing
Aims of treatment: to limit further muscle damage, restore fluid & electrolyte balance, alleviate pain and then promote healing
- Rescue Remedy 4-5 drops onto the gums, under the tongue – can repeat every 10 minutes if needed
- Keep the horse warm and supply with fresh water
- Drench with 200ml Rosehip, & dandelion tea – high in Vitamin C, promotes circulation, liver support
- EMRT as soon as possible
- Pain relief – EMRT can provide fabulous pain relief, use of NSAIDs minimally if required.
- Restore fluid & electrolyte balance- severe cases may require intravenous fluids
- Allow to walk around in a paddock especially if not too severe, if severe, best to keep still & warm
- In Sporadic cases rest is sometimes required
- In chronic cases resting is counterproductive, it is best to keep in work but adjust the work regime, diet and address the underlying cause. Daily turnout and managing stress, anxiety and excitement is also key.
- Reduce STRESS
- Warm up 10-15 minutes steady trot and canter
- Cool down - walking for 10-15 mins after exercise
- Interval training - follow hard work with a slow trot or canter and a 5 minute walk
- EMRT® – regularly to maintain optimal nerve, muscle function, circulation and lymphatic flow – toxin removal. Especially important directly after hard work or a step up in workload. Promoting blood flow directly after work!!
- Minimize days off, mild exercise 15 min walking until enzymes return to normal, interval training to buil dup training levels, wrm up & cool down particularly important, stretchingml rest periods 2-5 mins between periods of collection
- Diagnose the underlying cause i.e. diet, stress, PSSM, workload
- When bringing a PSSM horse back into work – gradual new diet, restrict duration more important than intensity, gradual introductions of consistent exercise, minimize days off even if it is a 15-30 minute walk
- Treatment/ management of underlying lameness, joint management, biomechanical problems
- McDowells Nervous Rehabilitation mix & Nervous tonic - stress
- Afternoon walk out 15-20 minutes especially if kept in a small yard or box
- Replace high carbohydrate/ grain diet with energy from fats/oils.
- No extruded feeds
- On non or reduced work days adjust diet suitably
- Rosehip & dandelion tea – Make up 2 tablespoons of each in 1 L and split over the 2 feeds.
- Supplement with omega 3 fatty acids or use French White millet & linseed – 1 cup twice daily. High in omega 3’s and silica for the health/strength of tendons & bones, reduce inflammation, promote the health of red blood cells.
- Ensuring correct balance of Vitamin E/Selenium/Calcium and Magnesium – consult a nutritionist.
- Selenium and Vitamin E – antioxidant, free radical scavenging properties, protect cell membranes – not the only treatment required & selenium can be overused.
- Magnesium – critical to normal functioning or an estimated 350 enzymes in the body particularly important in skeletal muscle, nervous system & glucose metabolism.
- Symptoms of magnesium deficiency – shying, sensitive to touch jumpy, twitching, muscle tension, anxiety, nervousness, abnormal glucose metabolism
- Ensure correct salt balance – replacing salt lost through sweat adequately. Allow free access to himalayan rock salt
- Increase electrolytes prior to exertion, increased sweat loss
EMRT® is invaluable for horses prone to tying up and I highly recommend it as an important inclusion in their plan. It promotes the release of muscle spasms, relaxation/balance of the nervous system, promotes circulation prevention and removal of toxins and excess acid in the body as well as addressing tight/ restricted fascia leading to compromised muscles and nerve function.
EMRT® is especially valuable when coming back into work after a spell, when workload is being altered and after a race or competition.