The Science of Horse Racing: Changing Leads

March 27th, 2022

As a biped, when you walk or run, your stride favors either your right or left leg as your leading leg, meaning that, each time you begin to take a step, one of those goes first. With any type of exercise, you might change which leg goes first, especially if you are sprinting. The same goes for horses.

Horses can switch their leading leg, called changing leads, during every type of stride. For a gallop, those changes are especially important because the leading leg is the dominant source of muscular power and also can help a horse navigate turns. Understanding what that means and how it affects performance can help you decide if a horse is worth putting your money on.

For this month’s Science of Racing, I talked to retired Eclipse Award-winning jockey Richard Migliore to learn more about the phenomenon of lead changes, what happens when a horse does or does not initiate those changes on the racetrack, and what you as a handicapper can do with that information the next time you wager.


How It Works

Last month’s edition defined the stride, including how each leg strikes the ground when a horse is at a gallop. Lead changes are an integral part of the stride as well.

“A horse will change their leading leg to give their muscles a break,” Migliore said. “With each change comes a burst of energy as horses will use different muscles, especially when they are galloping at full speed.”

To give fellow bipeds an example of this, think about carrying a bag of groceries to your car. When your arm gets tired, you will shift the bag to the other arm, which will alleviate that feeling of fatigue and give you renewed energy. Now imagine that in a Thoroughbred moving from a straightaway into a turn.

The leading leg also helps steer the horse in the same direction. When horses enter a turn, they will switch to the left lead around those bends. Why? Since American racetracks are counterclockwise, running on the right lead would otherwise tend to cause a horse to bear out around a turn. Going wide causes a horse to cover more ground than necessary and expends energy that would be best saved for a different phase of the race, Migliore explained.

Once in a straightaway, like the backstretch, horses will then shift back to their right lead during that suspension phase of their stride when all four feet are off the ground.

“This change can be subtle,” the retired jockey shared. “Watch when a horse turns for home. You will see a slight hesitation in stride and then a shift in weight as they change leads going from the turn into the stretch.”

Going straight, running on their right lead keeps them away from rivals; running on their left lead in the stretch would mean a horse might lean in on other horses. Changing that leading leg is important at all phases of a race.

This is especially crucial in that last part of the race as horses begin their final sprint for the wire.

“You will see horses that are all out on their right lead then jump to their left lead to find a last gasp of energy,” Migliore said.

Changing leads more than once in a stretch run is often a sign of a tired horse, something to take note of for future races.


Making It Happen

How then do horses know when to make this change? While these are a natural part of each stride for horses, learning when to change in a race is part of the training process.

“Shifting the leading leg going into a turn and then into a straight is something that’s taught in the early training process” Migliore said. “Some horses will take the initiative and do it on their own.”

Though well-schooled horses often will switch leads automatically, others will need help initiating the shift, the jockey cuing his mount to make the change.

Sometimes, regardless of their training and the efforts of the rider on their back, a horse still will not change that leading leg, even if they have done it in past races. Migliore shared a couple of reasons for this.

“Sometimes, it’s just plain stubbornness. A horse might just want to do it his way," he said. "Soundness issues may also be part of it. If a horse will not change or stops changing leads, then it’s up to the trainer to find the underlying issue of why, whether it’s personality or a physical issue.”

A famous example of a horse that would not switch is Calumet Farm’s famed Alydar. Despite this stubborn habit, he was successful, winning the Whitney H. (G1) and the Arlington Classic (G1), and, of course, finishing second to Affirmed in all three Triple Crown races in 1978. However, Alydar’s stubbornness might have played a role in his defeats by Affirmed, a dominant horse who would force his will.

“Alydar might have had more natural talent, but Affirmed dominated him,” Migliore observed. 

It can become a liability when a horse cannot or will not shift that leading leg, especially in a stretch.

“Horses that don’t change leads can get a reputation for hanging in the stretch, not being able to accelerate, and tiring late,” the former jockey said.

Knowing a horse’s tendencies, including their lead habits, can help with handicapping, another piece of information that comes in handy the next time you are crafting your wagers. Migliore recommends looking at not just lead changes, but also paddock behaviors and other habits that can give you a read on a horse’s fitness on race day.

Next Time

For next month’s Science of Racing, let’s look at another phase of a race that can affect its outcome: the start. Getting out of the gate poorly can compromise a horse’s chances, especially in a race as important as the Kentucky Derby (G1). We will examine the starting gate, how it works, and what happens when those doors bang open and the excitement begins.