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[RC] Understanding Saddle Tissue Physiology - Robert FerrandTruman, You are quite right about the real saddle fitting issue is FORCE. For that reason the Mk I pressure system was called a “Force Management System”. Now, your focus on tissue physiology is right on the mark, and we do have some peer review clinical research on mammalian tissue to better understand the saddle tissue interface. Skin and muscle tissue require a constant intermittent flow of blood to remain healthy. In strenuous exercise the muscles require significantly more blood flow to maintain a healthy metabolism. This exchange of oxygen and waste products occurs in the capillary bed. The saddle fitting problems occur when the saddle causes continuous excessive pressure on the capillaries that exceeds the blood pressure and structural strength of those vessels and the capillary vessels collapse. This collapse leads to the deprivation of oxygen and nutrients brought by fresh blood and the removal of waste products. CAPILLARY CLOSING PRESSURE IS THE CRITICAL ISSUE IN PREVENTING SADDLE-RELATED TRAUMA AND IMPROVING THE PERFORMANCE OF THE HORSE'S MUSCLES UNDER SADDLE. The following experiment was made to determine the relationship of external pressure on blood flow by using a radioactive isotope 133Xe. The amount of radioactivity was measured as external pressure was applied. One can observe that as external pressure increases the blood flow reduces. What is most notable is that pressures as low as .25 P.S.I. or 4 ounces can reduce flow by as much as 60%. This is a significant point when related to saddle fit, especially with a bridging saddle that does significantly increase pressures. Serious saddle fitting problems develop particularly on "bridging" saddles in a relatively short amount of time because pressures can easily reach 4 P.S.I or 64 ounces. This excessive pressure not only cuts off the blood supply but can additionally traumatize the muscle tissue itself. In all cases pressure release is followed by reactive hyperemia and the parts originally starved of arterial blood are instantly flooded with oxygen. The extent and duration of the blood in flow is proportional to the needs of the tissues. Below is a study performed at University of Georgia on a horse using a compression bandage. One can observe that the blood flow decreases significantly with the application of pressure, however, when released the blood flow increases beyond the original base flow. This is a clinical verification of reactive hyperemia and reveals what happens to the tissue when the saddle is removed i.e. heat bump. For a given pressure applied to the surface of the skin (interface pressure) capillary closure pressure will vary from horse to horse, as well as location to location on the horse, depending on the amount of fat, location of adjacent bone, status of the vascular system, systemic blood pressure and general health of the animal. As the animal ages its physiology also changes, compounding this significant Issue. A critical discovery in tissue research was that in a given location, pressure is not even throughout the tissue. Clinical studies have established that the internal pressure close to bones is three to five times higher than on the surface This principle is easily demonstrated with a simple sponge as illustrated above. One can observe that when two different size areas are pressed towards each other, the smaller area will create higher pressures. Weight divided by surface area equals interface pressure. This is an important issue for horses because the longissimus dorsi muscle, one of the major muscles used in locomotion, lies adjacent to the spinal column and is directly affected by saddle pressure. Each vertebrae of the spinal column has bony prominances with small surfaces that concentrate points of pressure down the length of the longissimus dorsi muscle. It is critically important to understand that muscles are far more susceptible to the effects of pressure than skin. The internal damage to the tissue caused by the surface pressure only becomes obvious at the surface over an extended time. Many serious pressure sores first occur internally adjacent to the bone and then radiate to the surface. This fact makes it very difficult to use apparent trauma to the horse's back as an indicator of saddle fit, because during the time interval that the horse is not being ridden, the horse begins to heal the internal trauma. This makes it virtually impossible to develop a cause and effect relationship between saddle fit using observable external trauma to the horse as the standard. Therefore, just because we do not see obvious damage to the skin of the horse does not mean that damage has not occurred internally. The most important issue to remember with tissue trauma is that higher pressures do damage in shorter periods of time, however, even low pressure for long periods of time can do damage. This is significant to saddle fit because the fit of the saddle relates to how much time one can ride before causing trauma to the horse. Obviously if the saddle fits one can ride the horse longer without sustaining damage than a saddle the bridges and causes high pressures. Tissues do not need a constant flow of blood, but tissues do need a CONSTANT INTERMITTENT FLOW OF BLOOD. This is the reason a healthy individual does not get bedsores. By tossing and turning in our sleep we provide our tissues a constant intermittent flow of blood. It is also important to understand that tissue damage is variable from very slight damage to extremely debilitating damage. As an example, human bedsores are graded in Stages I, II, III, IV, from a slightly red skin to an open sore. The following is a simple scale of increasing severity of trauma caused by an ill-fitting saddle: v Decline in performance v Discomfort - indicated by attitude change in the horse v Inhibited Gait - noted by the horse being a little "off" v Lameness - secondary lameness due to pain or excessive pressure v Swelling - slight swelling under the saddle panels v Bruising - significant inflammation indicating capillary damage v White hair - due to damaged follicles v Hair loss - obvious trauma to the skin and internal muscles v Ulcerous condition - an open, oozing wound with swelling WHAT DO WE "REALLY" KNOW ABOUT PHYSIOLOGY? The clinical research on a variety of mammals has established the following factors to give us a better understanding of the issues relating to saddle fit. v Tissue damage is a function of pressure over time. v Pressure is not distributed evenly throughout tissue. v Pressure on the surface of the skin increases 3 - 5 X close to bones. v Muscle is more susceptible to pressure damage than skin. v Low pressure for long periods of time is more damaging than high pressure for short periods of time. SO WHAT IS GOAL HERE? IN PRACTICE THE GOAL IS TO ACHIEVE THE MOST EVEN PRESSURE THROUGHOUT THE SADDLE CONTACT AREA WITH A RIDER MOUNTED AND TO REMOVE THE SADDLE EVERY FEW HOURS FOR A SHORT PERIOD OF TIME TO PERMIT BLOOD TO FLOW TO THE TISSUES. OH, MY ACHING BACK "Quantifying the degree and precise site of pain in animals always has been difficult. This is complicated further because the major clinical sign in many horses with a back problem is impair performance rather than pain. On the other hand, many horses appear to perform satisfactorily despite some low-grade back pain. To add to the confusion, some horses are naturally sensitive and resent being palpated along the back, which might be wrongly interpreted as a sign of pain." After decades of equine back research, Dr. Leo Jeffcott, BvetMEd, MA, PhD, DVSc, FRCVS, Dean of Cambridge University Veterinary Clinic, notes that 1. Some horses can perform badly without suffering from a back problem 2. Some horses can perform adequately despite having a back problem 3. Spontaneous recovery for many types of back problems is quite common Robert Ferrand Saddle Researcher Husain, Tafazzul, An Experimental Study of Sore Pressure Effects on Tissues, with Reference to the Bed Sore Problem., J. Path. Bact, Vol LXVI, 1953, pg. 354 Allen, Doug, Blood Flow Restriction caused by bandaging and equine in vivo study conducted at the University of Georgia, March 1996, Kimberly-Clark Clinical Study-Flexus 3 Chow, William, et al, Effects and Characteristics of Cushion Covering Membranes Kenedi, R.M. and Cowden, J.M. Bedsore Biomechanics, University Park Press, London, 1975, pg. 96-97 Husain, Tafazzul, An Experimental Study of Sore Pressure Effects on Tissues, with Reference to the Bed Sore Problem., J. Path. Bact, Vol LXVI, 1953, pg. 356 Le, Khanh M., et al, An In-Depth Look at Pressure Sores Using Monolithic Silicon Pressure Sensors Microvascular Research, Vol 17, 1979, PG 753 Husain, Tafazzul, An Experimental Study of Sore Pressure Effects on Tissues, with Reference to the Bed Sore Problem., J. Path. Bact, Vol LXVI, 1953, pg. 356 Guyton, Arthur C., Acute Control of Local Blood Flow, Textbook of Medical Physiology, 1986, pg. 349 Kosiak, Michael, Etiology and Pathology of Ischemic Ulcers, Arch. of Physical Medicine and Rehabilitation, 1959, pg. 62 Le, Khanh M., et al, An In-Depth Look at Pressure Sores Using Monolithic Silicon Pressure Sensors Microvascular Research, Vol 17, 1979, PG 748 Le, Khanh M., et al, An In-Depth Look at Pressure Sores Using Monolithic Silicon Pressure Sensors Microvascular Research, Vol 17, 1979, PG 748 Husain, Tafazzul, An Experimental Study of Sore Pressure Effects on Tissues, with Reference to the Bed Sore Problem., J. Path. Bact, Vol LXVI, 1953, pg. 355 & Groth, K.E. 1942, Acta Chir Scand.,lxxxvii,suppl 76 Husain, Tafazzul, An Experimental Study of Sore Pressure Effects on Tissues, with Reference to the Bed Sore Problem., J. Path. Bact, Vol LXVI, 1953, pg. 356 & Groth, K.E. 1942, Acta Chir Scand.,lxxxvii,suppl 76 Jeffcott, Leo, The Equine Back, the Essential Horse, May 1998, Pg.1 Jeffcott, Leo, The Equine Back, the Essential Horse, May 1998, Pg.10 =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= Ridecamp is a service of Endurance Net, http://www.endurance.net. Information, Policy, Disclaimer: http://www.endurance.net/Ridecamp Subscribe/Unsubscribe http://www.endurance.net/ridecamp/logon.asp Ride Long and Ride Safe!! =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
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