Thumps: Not As Scary As They Sound by Paulick Report Staff|09.08.202209.08.2022|3:28pm8:32am While not life-threatening or painful, synchronous diaphragmatic flutter (SDF or “thumps”) does affect a horse's respiration. Thumps is caused by an electrolyte imbalance which irritates the nerve that controls the diaphragm, essential for respiration, reports Horse Sport. Calcium is the root cause of thumps, but the imbalance can be caused by either too much calcium or not enough. Thumps can occur if a horse needs calcium while exerting itself and none is able to be mobilized from its bloodstream, but calcium supplementation isn't necessarily the answer. Too much calcium in the horse's body affects its ability to mobilize calcium as well, making the phrenic nerve overly excited and causing it to randomly contract. Though any horse can be affected by thumps, it's often extremely-fit horses like racehorses or eventers that suffer from the condition. Horses which are asked to exert themselves in hot weather can get an electrolyte imbalance when their sodium, calcium, magnesium, phosphorus, or potassium levels get out of whack. Additionally, horses that eat a diet high in calcium – like those fed alfalfa hay – may be more prone to developing thumps during intense exercise. A horse experiencing thumps will look like it is hiccupping; a hiccup-like noise will take place along with a visible abdominal spasm, which is the diaphragm fluttering. This can impact a horse's athletic performance by impeding the way he breathes, because the horse will not be able to take in the oxygen needed to feed their muscles. The best way to rectify thumps in horses is to correct the electrolyte imbalance, either by adding electrolytes to the horse's feed or adjusting the horse's diet so less calcium-rich hay is fed. Some trainers believe that having more liquid in the horse's stomach can prevent thumps as well. Read more at Horse Sport.