When Has Your Horse Had Enough?

Posted by Nancy S. Loving, DVM on 06/08/2020


As your horse gets fitter, it is tempting to keep asking for more in his daily workouts. But, when is it enough, or when have you passed a safe threshold? Perhaps everything seemed to be going just fine, but suddenly your horse isn’t putting out as much as usual and he seems irritable and less cooperative when asked to perform his normal tasks under saddle. Not only is he not as interested in food, he also isn’t much stimulated by things happening around him. He just doesn’t seem himself.

These signs reflect that your horse is being asked to do too much work relative to his ability to cope with the exercise stress. Terminology for this syndrome has specific meanings. Many might refer to this as overtraining when, in fact, most horses engaged in performance and sport horse activities are more likely to experience a less severe syndrome called “overreaching.” Horses that train in high-intensity exercise like racing and high-speed sports are the ones that more commonly experience “overtraining.” This type of performance shutdown can happen to horses that aren’t yet adequately prepared and even to those that are well prepared for the exercise demands. 

Let’s look at the differences in these two conditions and discuss ways to keep your horse mentally sharp and in peak fitness without overdoing the exercise demands.

Overreaching versus Overtraining

In any equine sport, accumulated stress of training and competition can lead to fatigue if overdone; horses display standard responses to chronic fatigue. No matter if your horse is trained in racing, barrels, gymkhana, reining, roping, Eventing, dressage, competitive trail, endurance, polo, or other Western equestrian sports, the variety of signs of chronic fatigue will be similar.

The key difference between these two syndromes is that a horse that is overreached recovers within days or at most a two-week period when given time to rest. In contrast, the chronically over-trained racehorse, for example, is one that may not recover for months or even years due to extreme stresses on his physiology; in some cases, the consequences could be career ending. 

What possible signs might tip you off to a fatigue problem? You might notice:

  • Decreased performance or lack of improvement in performance despite on-going training.
  • Decreased body weight by as much as 10%. Usually, weight loss is around 3% but this requires accurate scales to evaluate. Muscle glycogen (an energy source) normally adds to body weight by increasing water content in the muscles. Body weight reductions have more to do with diminished muscle glycogen stores rather than resulting from reduced feed consumption. 
  • Elevated heart rates during exercise. This is detected using a heart rate monitor.
  • Delayed heart rate recovery, i.e. the time to return toward resting heart rate following exercise.
  • Behavioral changes: head tossing, tail wringing, unwillingness to perform tasks, irritability, grumpy or nervous behavior – in humans, emotional changes are referred to as profiles of mood state (POMS) and are sensitive indicators of overtraining. Similar behaviors occur in horses if you just know to look.
  • Less interest in interacting with other horses, including introduction of a new herd member. 

These changes can be characteristic of many other issues. It is essential that a thorough physical exam and laboratory workup be performed on a horse demonstrating poor performance in order to rule out an underlying disease. If nothing is found, then a diagnosis of overreaching or overtraining may be suggested. Blood work run in the lab enables your veterinarian to identify specific indices of overreaching/overtraining:

  • Elevated muscle enzymes such as creatinine kinase (CK) and aspartate amino transferase (AST).
  • Elevated gamma glutamyl transferase (GGT) concentrations, which is typically a liver-associated enzyme but may increase when glycogen stores are consistently depleted and replaced during intense training.
  • Lower plasma cortisol response test at rest or with exercise. Cortisol, among many other hormones (testosterone, ACTH, prolactin, leptin, thyroxin, insulin-like factor 1, and insulin), is significantly influenced by an increasingly heavy workload. These hormones could prove to be useful biomarkers in future to detect that a horse is overworked. 
  • Irregular overnight growth hormone pulsatile release following six weeks of high intensity training. This hormone – important for controlling recovery from stressful events – tends to release in pulses at night, with the pattern of the pulses more critical than overall blood concentration levels. Testing this is expensive and not a normal procedure, but this phenomenon has been identified in over-trained horses.
  • Adverse effects on immune function. 

Another significant finding is that over-trained or overreached horses have no difference in frequency or severity of gastric ulceration compared to horses not suffering from training fatigue. However, a horse experiencing gastric ulcers or musculoskeletal pain has stress overlaid on a demanding work schedule that then can elicit overtraining effects. 

One example of training stress was identified in a study of Luisitano and purebred Spanish horses used in public performances of gallops, sprints, and abrupt stops and starts. The occurrence of infections, musculoskeletal disorders and injury, and behavioral issues increased from 3.5% in the off-season training period to nearly 48% during the high-performance season.

The Fix

Upon recognition that a horse is suffering from fatigue, the first step is to provide plenty of rest for a sufficient time. 

The second effective strategy is to examine all possible stressors in a horse’s life and remove as many as possible. If turnout is not available, then the horse should be rested in as large a paddock as possible and hand walked a couple times a day.

The most important fix for overreaching and overtraining is to prevent it in the first place.


Stress in a horse’s life amplifies the effects of training, especially when engaged in high-intensity work. You may not initially consider the normal ebb and flow of a competitive horse’s life as stressful; it’s easy to take things for granted as long as you see your horse eating and somewhat alert. Part of planning a preventive strategy for your horse’s training relies on knowing what situations and management decisions add stress and have potential to develop overreaching or overtraining.

Think about what it might be like for a horse to experience a monotonous training routine, day by day, with no variation in his workouts. Perhaps he is asked to just gallop in a straight line, or to ride in circles, or repeatedly practice skill sets. How does a horse respond to being stabled with incompatible neighbors or dealing with difficult herd dynamics in pasture? Or, consider a horse living only in confinement without the ability to play in pasture and self-exercise. What about feeding schedules that provide food just twice a day with nothing to forage in between? What about the campaigner that is trailered to and from lessons, clinics, and competitions with all the stresses inherent in transport in addition to ever-changing routines? All these situations contribute to a horse’s anxiety and emotional stress. There may also be an overlay of a low-level disease, like inflammatory airway disease, viral respiratory infection, or gastric ulceration, any of which impact a horse’s steady state.

Another primary issue that creates overreaching or overtraining occurs when a horse is faced with too much work or intensity of work without the appropriate amount of background conditioning and/or training in a specific skill set. These horses are over-faced; this particularly happens to young horses that start with plenty of ambition. A rider or trainer might try to capitalize on this energy and enthusiasm, but ends up asking too much over prolonged periods of weeks and months. While young horses may be more at risk of fatigue, any age horse can experience being asked too much time after time. On-going training demands coupled with a busy travel and competitive season create progressive fatigue. Trauma and inflammation within musculoskeletal tissues may result in soreness and pain that affects how well a horse responds to workouts. 

Ideally, a horse is trained systematically with progressively increasing demands, first in duration and then in intensity. In addition, more intensive training periods are best coupled with alternate days of light work and/or turnout. Before more training loads are asked of the horse, his tissues need time to respond and recover; avoid repeating strenuous efforts on consecutive days. 

After every workout, examine your horse for leg swellings or lameness, and monitor resting heart rate, rectal temperature, appetite, and attitude and general demeanor. Ice boots (or cold water hosing) help limit inflammation in the lower legs when applied for 30-40 minutes after a strenuous work effort. Following cold therapy, support bandages for the legs, with or without poultices, may be useful for horses that tend to develop windpuffs. If limb swelling does develop, then it is likely that the horse is being asked too much for his level of fitness and structural strength.

Tapering down the training effort – a steady reduction in training intensity, but not necessarily a change in training volume – for a few weeks prior to competition is an additional important strategy to bring a horse to a peak physical and mental state on competition day. 

Just as you like days off from work to be able to recoup from the stress of the daily rat race, your horse, too, needs time to relax and just be a horse. At the start of each season, carefully consider your horse’s training regimen and competitive schedule to enable your horse to do well without incurring the effects of fatigue. Attention to even the smallest management details yields dividends in your horse’s health and performance. 

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