The muscle strain injury(MSI) is one of the most common from of occupational or sports related muscle injuries. Heat has been used to prevent the MSI for a long time. However, it has been little known about the pathophys iology of the MSI and heat action on it. To clarify the effect of intramuscular temperature elevation on active(eccentric) strain injury, we stretched the muscle by the speed of 10cm per second to produce strain injury on tibialis anterior (TA) and extensor digitorum longus(EDL) in seventeen rabbits with their neurovascular supplies preserved. During the stretch, the peroneal nerves were electrically stimulated simultaneously to evoke muscle contraction with and without infrared ray irradiation on muscles. Also, to specify the location of lengthening during active strain, we attached markers on the muscles and did the motion analysis. Following results were obtained. The length increments of stretch in heated TA and EDL at the time of total disruption were 40.3+/-3.76% and 43.6+/-6.62%, respectively. But those of non heated TA and EDL were 35.5+/-2.13% and 34.4+/-5.83%, respectively, which were significantly lower than those of heated TA and EDL(p<0.05). The absorbed energy in heated TA and EDL until the time of total disruption were 175+/-9.8N.% and 248+/-7.0 N.%, respectively. But those of non heated TA and EDL were 134+/-6.1N . % and 184+/-3.2N. % , respectively, which were signficantly lower than those of heated TA and EDL(p<0.05, P<0.01). But there was no difference in peak force on the time of total disruption between two groups. The distal muscle segments including distal musculotendinous junction were the most lengthened parts in both muscle groups but the distal muscle segments of heated muscle groups showed more length increment than that of non heated muscle groups statistically. The most frequent site of total disruption by active strain injury was the distal musculotendinous junction in both groups. In conclusion, the result that the heated muscles showed larger musculotendinous length at the time of total disruption than non heated muscles supports that intramuscular temperature elevation has preventive effect on muscle strain injury, not by increasing contractile ability but by improving extensibility of musculotendinous units. And it is the distal muscle segment including distal musculotendinous junction that lengthens and absorbs the energy mostly.
Equipment and Supplies ; Hot Temperature ; Infrared Rays ; Muscle Contraction ; Muscles ; Peroneal Nerve ; Rabbits ; Sports

Skin diseases associated with athletic activities can be classified as skin infections, inflammatory reactions, trauma, and abnormal proliferation, depending on the cause of the condition. Athlete's nodule is a generic term for reactive nodules that occur in athletes. It is particularly common in the foot due to tight sneakers, repetitive pressure or friction, and inappropriate choice of shoes or other sports equipment. The diagnosis of black heel (calcaneal petechiae) should be considered when numerous black spots occur on the soles in patients who frequently engage in abrupt movements, such as starts, stops, or leaps. Palmoplantar eccrine hidradenitis may occur in athletes who play baseball, dance, and climb, activities in which repetitive and strong stimuli are applied to the floor of the hands and feet. Painful fat herniation should be suspected in cases of painful skin-colored firm nodules on the feet of athletes who place a large amount of weight on their feet when moving. Itching, urticaria, angioedema, chest tightness, and syncope occurring within 5 minutes after starting exercise should be suspected to be exercise-induced angioedema/anaphylaxis. Excessive force can cause deformation of nails, as in tennis toe and jogger's toenail. For the diagnosis and treatment of sports-related skin diseases, it is essential to pay attention to patients' hobbies and exercise habits, including sports, and to consider the relationship of those habits with the presumed mechanisms of the skin disease. In addition, thorough pre-exercise warm-ups, increasing strength gradually, and wearing proper equipment will help prevent the occurrence of sports-related skin diseases.
Angioedema ; Athletes ; Baseball ; Dancing ; Diagnosis ; Foot ; Friction ; Hand ; Heel ; Hidradenitis ; Hobbies ; Humans ; Nails ; Pruritus ; Shoes ; Skin Diseases ; Skin ; Sports ; Sports Equipment ; Syncope ; Tennis ; Thorax ; Toes ; Urticaria