The Felid Purr: a healing mechanism? Part 2

One explanation for the lack of trauma or disease found in cat bone and muscle/ligaments is that cats are more sedentary then dogs, however this is a supposition and is not documented. 

Respiratory

There have been studies that indicate that purring can aid in dyspnoea as Cook in 1972 suggests. Kidd et al. in 2000 found in a study with 11 cats and 17 dogs with acute and subacute myocardial necrosis, none of the cats in the study had dyspnoea, although all the dogs did. The overall incidence of primary lung tumours in the dog is 1.24%, and in the cat, .38% (Miles, 1988)

Tissue

  Free skin grafting is often used for the treatment of large skin defects on the distal limbs of dogs and cats. However while using this technique in dogs, the overlapped skin edges of the graft usually become necrotic by 3 days postoperatively, and need to be debrided. In cats, the grafts are usually viable even after six days.

  Unfortunately, there has been no research that has attempted to explain the extraordinary ability cats have for healing themselves. 

  Just two years ago, Dr. Clinton Rubin and his associates made a fantastic discovery. They found that exposure to frequencies between 20-50 Hz (at low dB) creates the robust striations of increased bone density, Clinton Rubin, (1999), Strain mediated augmentation of bone mass and morphology: Is it possible to harness the anabolic potential of mechanical stimuli without necessarily requiring exercise? Wellcome Trust.  In one study chickens were placed on a vibrating plate every day for 20 minutes, and grew stronger bone, National Geographic, January 2001, p. 11. This discovery of anabolic frequencies between 20- 50 Hz (at low dB), is a tremendous breakthrough. Astronauts in space loose bone density in zero gravity, and this method could help them maintain healthy bones. Dr. Rubin's group has begun research trials with  humans, designed to test whether this non-invasive  method halts osteoporosis and perhaps even renews bone growth in post-metapausal women; J. Zhi, and M. Hadjrargyrou, (1999) The expression of a novel and a known gene, unregulated by disuse is down regulated by anabolic mechanical stimulation, American Society of Bone and Mineral Research. This method is not yet FDA approved, although it is hoped it will be soon. Additionally, Chen et.al  (1994) The effects of frequency of mechanical vibration on experimental fracture healing, Zhonghua Wai Ke Za Zhi, in his work with rabbits, found that frequencies of 25 and 50 hertz promote bone strength by 20%, and stimulate both the healing of fractures, and the speed at which the fractures heal.

  There is also documentation that low frequencies, at low dB are helpful with regard to pain relief, and the healing of tendons and muscles. Vibrational stimulation between 50-150 Hz has been found to relieve suffering in 82% of persons suffering from acute and chronic pain (Lundeberg, 1983). In 1999, M. Falempin and S.F. In-Albon discovered that mechanical vibration at 120 Hz counteracted atrophy in tendons after hind-limb muscle loading.  Biomechanical stimulation, which uses mechanical vibration of standardized frequencies from 18 - 35 Hz, is used in Russian sports medicine. This technique improves the relaxation of strained muscle structures and increases the stretching ability of capsules and tendons.  Lake in 1992, found that biomechanical stimulation prevents a decrease in muscle strength and muscle mass and the oxidative capacity of thigh muscles, following knee immobilization after sports injuries. The use of low frequency therapy also applies to tendon healing. It can increase the mobility of upper ankle joints by 16- 19 %, Klysczt et. al, 1997, Biomechanical stimulation therapy as physical treatment of arthrogenic venous insufficiency, Hautarzt.  Exposure to frequencies between 2-100 Hz results in the reduction of muscle spasms and more pronounced reduction of the spasms occurs the longer the treatment is applied, (D. Ardic, A. Buljina, 2000). After ten days of short periods of biomechanical stimulation, upper mobility of ankle joints improved by 16 and 19 degrees and was accompanied by the healing of venous ulcerations after skin flap transplantation, (Klysch, T. et al., 1997). It is interesting to note that Biomechanical stimulation is also used in public gyms and workout centres to increase muscle mass. A web search will bring up many manufactures of such equipment.

  It has also been found that in- phase chest wall vibration at 100 Hz, is known to decrease dyspnoea in patients with chronic obstructive pulmonary disease while at rest (Cristiano and Schwartzstein 1997; Nakayama, et al., 1998; Sibuya, 1994).

  In Summery: Vibrations between 20-140 Hz are therapeutic for bone growth/fracture healing, pain relief/swelling reduction, wound healing, muscle growth and repair/tendon repair, mobility of joints and the relief of dyspnoea.

  We think that this research could help explain why cats purr, and here is why:   

  Fauna Communications has recorded many cats' purrs, at a  non-profit facility and the Cincinnati Zoo , including the cheetah, puma,  serval, ocelot and the domestic house cat. After analysis of the data, we discovered that cat purrs create frequencies that fall directly in the range that is anabolic for bone growth. 

• The dominant and fundamental frequency for three species of cats' purrs is exactly 25 Hz, or 50 Hz the best frequencies for bone growth and fracture healing.  All of the cats purrs all fall well within the 20 - 50 Hz anabolic range, and extend up to 140 Hz.. All the cats, except the cheetah have a dominant or strong harmonic at 50 Hz.
• The harmonics of three cat species fall exactly on or within 2 points of 120 Hz which has been found to repair tendons. One species within 3 Hz and one within 7 Hz.
• Eighteen to thirty-five Hz is used in therapeutic biomechanical stimulation for joint mobility. Considering the small size of many of these cats, especially the domestic cats, it is interesting to note that that all of the individual cats have dominant frequencies within this range. In fact, some of the cats have 2-3 harmonics in this range.
• The frequencies for therapeutic pain relief are from 50-150 Hz. All of the individual cats have al least 5 sets of strong harmonics in this range.
• Therapeutic frequencies for the generation of muscle strength lie between 2-100 Hz. All of the individual cats have al least 4 sets of strong harmonics in this range.
• Therapy for COPD uses 100 Hz; all of the individual cats have a dominant frequency of exactly 100 Hz. 

  There is another clue found in a study performed by Dr. T. F. Cook, (1973) The relief of dyspnoea in cats by purring, New Zealand Veterinary Journal. A dying cat who could not breathe (they were considering euthanasia), was found to breathe normally once it began purring. The purring opened up the cat's airway, and improvement was "remarkable and the next day commenced to eat....” Three species of cats have a strong harmonic at exactly 100 Hz, the vibrational frequency found to relieve dyspnoea. One species within 2 Hz and one species within 7 Hz of 100 Hz. It could be that the cat's purr decreases the breathlessness by vibratory stimulation. 

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