Part 1- Nutrition
Part 2- Conditioning and fitness
Part 3- Environmental Factors
Part 4- Podiatry
Part 5- Complementary Medicine
Part 2- Conditioning and Fitness
Numerous scientific studies support fitness as a preventative for
musculoskeletal injury. Fitness is a measure of the horse's ability to deliver
oxygen to working tissues under extremes of exercise. Some of this energy is
delivered through aerobic or well-oxygenated conditions.
When that energy is
consumed, the horse must be able to create energy without oxygen, or under
anaerobic conditions. The mechanisms are different and truly fit horses are
able to perform well because they can deliver energy to their tissues
efficiently under both circumstances.
Fitness is also the adaptation of bones
and soft tissues to loads they must carry during competition. A horse is not
truly fit until these adaptive changes are complete.
Cardiopulmonary and muscular fitness precede tendon, ligament, and bone
fitness in early training. Across disciplines, horses in the first few weeks of
intensive exercise are more likely to be injured than those that have been in
training for 60 days or more.
In order for bones, tendons, and ligaments to
adjust to strain and load, they must be pushed gradually to endure the level of
exercise expected in competition. In the past, horses were "spared"
from heavy work and used lightly until show time. That thinking has changed as
we have learned how the musculoskeletal system adapts to work. The trick is to
achieve fitness without adding to repetitive-use injury. Once a horse has
achieved fitness, it takes less work to maintain than what is intuitive and
there is a great need to establish evidence-based best practices for fitness
training within each equestrian discipline.
Exercise induces mild inflammation, which creates increased blood flow
and stimulates musculoskeletal adaptation.
This process often happens in the
recovery or rest phase after work, as does the repletion of glycogen (sugar
reserves) within muscle. Unfit horses tend to injure soft tissue structures
that fatigue when workload exceeds the horse's capacity to deliver oxygen and
sugar to the vital muscular structures supporting the limb, or if their bones
and ligaments are not sufficiently adapted to carry the added load. For
example, a jumper landing on the far side of a fence transmits load to the
structures that support the fetlock joint: the superficial digital flexor
tendon, the deep digital flexor tendon, and the suspensory ligament. The amount
of fetlock drop that occurs in the landing determines the amount of strain to
those structures and thus risk for injury. When horses are fit, they are more
likely to endure movements without their joints exceeding their normal ranges
of motion. However, fit horses can injure bones and joints when they are pushed
outside of the normal physiologic range and are less likely to suffer
soft-tissue injury.
Footing plays a large role in preventing lameness and achieving fitness,
and current thinking suggests that working the horse on multiple surfaces
improves adaptability of the musculoskeletal system. Many horses train on one
surface and then go to a show with different footing and ground surface
characteristics, which affect deceleration of the foot and dispersion of load.
Interestingly, the warm-up ring footing is often different then the show-ring
footing, which adds another variable. Imagine training for a marathon on the
road and then competing in sand. Research is currently underway to identify
qualities of footing that are ideal for the different equestrian disciplines.
The shoe-footing interface is also an important area of future research.
Several parameters can help guide training programs in both human and
equine athletes. Heart rate, during and after work, is one of the most
sensitive indicators of fitness. Horses differ from human athletes in several
regards when it comes to fitness and delivery of oxygen to muscles. Being
flight animals, they are highly adapted for speed to escape predators.
Horses
are able to contract their spleens at the onset of intense exercise and
literally double their oxygen delivery to cells via increased red cell volume.
Horses have a greater muscle mass per kilogram of body weight and have two
times the oxygen delivery system per kilogram of body weight.
Lastly, the
pulmonary function of the horse is compromised in the upper gaits because
respiration is synchronized with stride at the canter and the gallop. This
affects ability to gather oxygen and increases the horse's reliance on internal
mechanisms for enhanced delivery.
In humans, a lower resting heart rate and respiratory rate are
associated with fitness; this is not necessarily the case in horses. As horses
become more fit through base cardiovascular training, they are able to move at
higher speeds with lower heart rates, and their heart rate will come back to
normal more quickly after exercise.
This is known as cardiac recovery.
This
index is used in endurance riding and eventing to ensure that the horses are
fit to proceed and that they are not overloading their capacity. Dehydration,
elevated temperature, lameness, and excitement are all factors that can
influence heart rate and should be considered if the horse's heart rate is
unusually elevated during or after work in a relatively fit horse.
Heart rate
variability, which is the variation of time between heart beats, can be a more
sensitive means of separating excitement from heart rate elevations associated
with decompensation and requires the use of continuous electrical monitoring of
the heart via and electrocardiogram.
Many riders carry heart rate monitors that attach to the tack and
provide feedback to the rider's watch. This is a similar idea as Fitbit, with
biofeedback being used to modify activity levels with an ideal goal in mind.
Although methods of training vary dramatically and no one method is correlated
with success, a common thought is that horses will benefit from initial core
training, followed by interval training that is gradually escalated to the full
work necessary to be successful in the show ring. Base training will often
elevate the horse into the 120-150 beats per minute rate. Maximal heart rate
for a racehorse in full gallop is 240 beats per minute. Racehorses are commonly
timed at the gallop, whereas hunters, jumpers, and dressage horses are not.
Future research in the area
of baseline heart rates of the different disciplines under different gaits
could prove useful to fine-tune conditioning plans. In this day and age of
smart phones and applications, it seems that establishing such a database would
be a reasonable undertaking. The outside factors such as environmental
conditions and the presence or absence of lameness would skew this data, so
inclusion criteria would have to be set.
For horses suffering from injuries that must be rested, auxiliary forms
of exercise such as swimming or underwater treadmill are very appealing because
they offer maintenance of cardiovascular fitness, with decreased loading of the
limbs. These horses will still require a ramping up of load on bones, tendons,
ligaments and muscle once healing has occurred but will not need the additional
time to reestablish cardiovascular fitness.
There is much interest in human and veterinary fields regarding the use
of biomarkers to screen training. Stallside labs to assess excessive bone
remodeling or cartilage repair or tendon or ligament strain are not far on the
horizon. The enzyme lactate is used in laboratory situations to assess fitness
and anaerobic metabolism. MRI tendon mapping, which is currently being
investigated at UC Davis, has shown us that changes start to occur in the
extracellular matrix of soft tissues before any detectable lesion is visible on
MRI. If we could find changes at this level, there would be far less wastage of
horses in the equine industry.
Ideally, a panel test to monitor athletes during the ramping-up phase of
work would be a great tool. Extensive research is currently underway to
identify targets to be measured. These tools could also be used to develop best
practices for the recovery phase of work, which is the essential rest period that
the body needs to repair any damage induced by exercise. The rest period is
vital, and horses that are worked without such breaks will eventually succumb
to overtraining.
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Thank you
Stacey
Hartpury Saddlery Shop
www.hartpurysaddleryshop.co.uk
Maximising enjoyment for you and your horse
Reprinted from The Horse Report (Spring 2014) with permission from the Center for Equine Health, School of Veterinary Medicine, University of California, Davis (UC Davis).
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