A young or inexperienced horse needs gradual fitness conditioning as you train him. He may be relatively fit if he's had room to exercise in a big pasture, but he's not accustomed to carrying a rider.
He'll be using different muscles in the work he'll be doing, and needs to develop those muscles more fully.
Every green horse needs a gradually-increasing fitness program to bring heart, lungs, muscles, tendons and joints to optimum strength before you make long rides or rigorous athletic maneuvers.
A mature horse may take fitness conditioning in stride because he's been in good shape before, but a young, still-growing horse should be started carefully and gradually.
Is your horse ready?
Make sure he's ready to start a conditioning program, with everything in his favor for getting in shape. This means deworming, adequate nutrition, taking care of his feet, etc. Check body condition before you start riding.
Ideally, he should be in moderate flesh, with ribs that can be felt but not seen.
Begin slowly. Start with daily short rides at the walk, gradually increasing the length and the work (some trotting, and hill climbing) as he gets to where he can handle it.
If the horse has been at pasture where he's had exercise (especially if he's been with other horses, self-exercising during normal activities) he won't be quite as soft and you can progress a little faster.
Go slow at first
The very soft green horse needs as much as two months to gain fitness, and the safest way is to start slowly, monitoring his response to the work and checking recovery rates during and after a ride.
Muscle is very adaptable and gains strength faster than other body systems; you might be tempted to hurry the conditioning because he's looking good and feeling good, but his bones, tendons and ligaments take longer to get in shape.
If you push him too hard, too fast in a training program he may suffer from pulled muscles or strained tendons. Tired muscles lose their elasticity and ability to help support joints.
If you keep him working after he's tired, joints may overextend and suffer damage. He may also get stiff and sore, and not want to work the next day.
The young, green horse needs a longer and more careful conditioning program than a mature already-trained horse - to adapt and develop the ability to handle more work. Don't burn him out physically or mentally with too much work or repetitive training sessions in an arena.
Keep the horse interested in his work
Riding across the countryside is the best way to condition a horse - especially a young horse. Working in circles soon becomes boring for most horses, and puts twisting force on leg bones and joints, which can cause serious damage.
Just walk for the first rides, gradually adding some trotting and later some galloping as the horse gets farther along in training. Gradually build fitness as he adapts to carrying a rider, and is more surefooted as he learns new balance.
Start in easy terrain, and later add hill-climbing to build muscle and wind, and some side-hill travel to improve agility. You are conditioning his attitude as well as his body.
You want him to mellow out mentally without thinking he needs to go too fast or prance all the way home, yet not overdo him to the point that he resents work.
Monitor fitness level
Evaluate his level of fitness by monitoring how well his pulse and respiration rates recover after a ride, or when you stop to let him catch his breath while climbing a hill.
The easy way is to count breaths (watching flank movements) or heartbeat (with a stethoscope behind the elbow on his left side, or feeling the pulse at the digital artery beneath the fetlock joint or the artery that runs under the jawbone). Count for 15 seconds and multiply by 4 to get rate per minute.
Average heart rate of a resting horse is 30 to 40 beats per minute. A fit horse has a lower resting rate than a soft horse. Resting respiration rate is 8 to 20 breaths per minute (the lower rates in athletic, fit horses).
During a conditioning ride with trotting and hill climbing, heart rate should get no higher than about 160. After the ride, see how long it takes for pulse and respiration to drop back to normal.
In a fit horse, these rates start dropping as soon as he stops moving. Respiration rate should return to normal within 10 minutes, with pulse rate recovering soon after.
If recovery rates are good after a 10-minute rest or cool-down, the horse is handling the work and you can gradually add more speed and/or length to your rides, always monitoring his response to know whether you are pushing him just right or too fast.
Don't push too hard, read the signs
If he has poor recovery rates or any other warning signs of fatigue, back off on the work. Give him a day or two of rest, then start again with work at a lower level before progressing with the conditioning program.
Your horse's sweat can tell you if he's getting in shape. A fit horse has thin, watery sweat that is practically tasteless and odorless.
Thick, smelly, salty sweat that lathers is generally a sign of an unconditioned horse. His muscles are not yet working efficiently; too many waste products are being produced and eliminated via sweat, along with precious electrolytes.
Touch your fingertip to his sweat, then taste it. If the sweat is very salty, he's not yet in shape.
Adequate hydration is crucial for a working horse since he loses fluid through sweating - and he must sweat to keep working muscles cool.
On any ride, let the horse drink whenever he wants. On a hot day he will sweat a lot, and you need to make sure he drinks enough.
Check hydration status with the pinch test, pulling a pinch of skin out from his neck or shoulder. It should snap right back into place.
If it takes a couple seconds to sink back, he is moderately dehydrated, and if it takes 5 to 10 seconds, he is severely dehydrated.
The dehydrated horse has slow capillary refill; when you press his gum with your finger (pressing blood out of that spot) it takes a few seconds for the blood to return. That spot stays pale, with color returning slowly.
To prevent serious effects from dehydration, make sure he gets adequate water and has access to salt, to replace what he loses in sweat.
A horse gives subtle hints that tell you when he's starting to tire. A good trainer can sense how far and how fast to push the horse in a conditioning program.
Early signs of fatigue include less-perky head carriage and ears, and reluctance to continue. He may try to go sideways instead of straight down a hill, trying to spare tired muscles.
Signs of severe fatigue include lack of interest in feed or water, poor response to the rider's cues, dullness and droopiness.
Pulse and respiration rates are high, and stay high even after the horse stops to rest. If pulse stays higher than normal for more than 30 minutes after he stops, this is an indication of fatigue; he's not recovering as he should.
The higher the pulse and the longer it takes to get back to normal, the more serious the fatigue. If you recognize when your horse is a little tired, you can stop the work before you hurt him.