Effectiveness of Percutaneous Microelectrolysis and Stretching Exercises on Agility, Strength, and Knee Joint Range in Hamstring Tightness in Athletes

1. INTRODUCTION

Electrotherapy is a valuable therapeutic resource used by physiotherapists for different purposes, among which are the reduction of pain, control of edema, muscle strengthening, control of the inflammatory process and promotion of tissue repair processes.[1,2] Within the The most widely used electrotherapy modalities are Sensory Transcutaneous Electrical Stimulation (TENS) and Burst Modulated Medium Frequency Alternating Currents (BMAC) commonly applied for analgesic purposes or for neuromuscular electrical stimulation (NMES).[2,3,4] Electromedicine also offers a variety of unidirectional currents such as direct (DC) or galvanic current and other low-frequency variants with a galvanic component such as diadynamic currents, 2-5 (Träbert), or faradic applications. [2,5 ] Direct current, described by Alexander Volta at the end of the 18th century, constitutes one of the first therapeutic currents, and has gained popularity in the last decade due to its use in percutaneous electrical applications that seek to promote tissue repair and decrease pain in musculoskeletal conditions. [5-10] DC is characterized by a unidirectional charge flow, of low voltage (60 to 80 volts) and constant intensity, and is produced from batteries or the rectification of alternating current from the electrical network. DC has particular physiological effects that are not achieved with other types of currents due to their physical characteristics. Its effects are based on the electrolysis process, a chemical decomposition phenomenon of some substances in solution subjected to a direct current and which results in electrophoresis (ion migration) and the formation of acidic or basic substances. [1,11-14] DC favors the accumulation of ions and charged molecules in the biological tissues that underlie the electrodes where it is applied. The deposition of charges occurs as a result of the electric forces of attraction and repulsion that are triggered by molecular dissociation, ionic migration, and accumulation of positive or negative charge depending on the electrode. All unidirectional currents are capable of greater or Less measure of producing electrophoresis and electrolysis under its poles (anode and cathode), triggering a series of physiological effects under the electrodes known as polar effects. These effects occur due to the modification of the local tissue pH and are directly related to the intensity of the current (mA) and its application time (minutes). Acidification of the medium by the production of substances such as hydrochloric acid (HCl) or carbonic acid (H2CO3), in addition to arteriolar vasoconstriction, hyperpolarization of neurons and coagulation, while alkalinization, caustic reactions due to the production of sodium hydroxide (NaOH), vasodilation, facilitation, depolarization and blood liquefaction occur at the cathode. [5,11-15] Due to its electrolytic effects, DC can cause chemical burns if its dosage is inadequate. This is how DC applications use intensities of the order of 0.05 µA/cm2 at 1mA/cm2, and treatment times between 12 to 15 minutes, although for iontophoresis applications, application of drugs loaded with tr Ascutaneous by means of DC, times of up to 30 or 40 minutes can be reached, although with maximum current intensities between 2 to 4mA. This dosage follows the recommendations of the literature to avoid potential adverse effects such as acid or alkaline burns. [5,12,15,19] The stratum corneum of human skin, on the other hand, constitutes an important barrier for bidirectional electric currents, offering a high impedance. although this response is dependent on intensity and time. It is the changes in skin impedance that ensure a depth of 4 to 5 cm for CD, a phenomenon that supports iontophoresis applications or electroporation treatments for drug delivery.[16,20,21]

Percutaneous Microelectrolysis (MEP) In the last decade, different percutaneous procedures have emerged through DC that seek to induce electrolysis in deep musculoskeletal tissues.[6-9,24-26] An example of these percutaneous modalities is percutaneous microelectrolysis (MEP), which consists of the application of a microgalvanic current through acupuncture needles and where high current densities are achieved in the tissues due to the smaller surface area of the needle (2.5 to 3.8 mA/cm2). Unlike other electrolysis treatments, MEP has reported less discomfort in patients because microgalvanic currents (intensities less than 1 mA) are used in it. MEP uses the acupuncture needle (active electrode) as a cathode to induce in the tissues the synthesis of caustic substances such as sodium hydroxide (NaOH) or potassium hydroxide (KOH) resulting from the interaction of sodium (Na+2) and potassium (K+) ions with water (H2O) molecules. This promotes a controlled acute inflammatory response coupled with the release of molecular hydrogen or dihydrogen (H2) that inhibits free radicals that are concentrated in damaged musculoskeletal tissues. The analgesic effects of MEP are explained by the destruction of local free nerve endings as a consequence of the caustic response of the cathode. On the other hand, the needle's own mechanical stimulation promotes tissue micro-rupture that enhances the proinflammatory physiological effects of galvanism. Controlled inflammation induced by MEP promotes collagen genesis and increased circulation, initiating a new repair process Tissue. MEP is currently used as a treatment for acute and chronic tendon injuries, muscle injuries, and in the dermatofunctional area for the management of wrinkles, stretch marks, fibrosis and neuropathic scars. MEP has been proposed as a resource Therapeutic to reduce muscle contractions and shortenings, thus favoring flexibility, although there is a lack of research to support this effect.[24-30]

Muscle flexibility Muscle flexibility is an important component in rehabilitation and training programs. In the lower limb, hamstring muscle shortening is a recurrent condition, a common condition that limits flexibility and affects sedentary, physically active, and athletic people. Hamstring flexibility is frequently evaluated in clinical tests and sports training, and is considered a component Basic physical abilities. Loss of flexibility of the hamstrings is associated with short-run sports and those in which knee flexion is favored, such as skiing, soccer, rugby, basketball, tennis, judo and volleyball.[31,32,33] Loss of hamstring flexibility has been reported for different sports disciplines, showing a decrease in a high percentage except for sports such as rhythmic gymnastics and dance where flexibility is essential for good performance.

Hamstring tightness is characterized by a length-tension alteration compromising the articular range of hip flexion and knee extension, also associated with imbalances of muscular strength of the quadriceps-hamstring complex, which has been reported in soccer players. [31-35] Loss hamstring extensibility has been associated with a higher incidence of muscle tears, patellar tendinopathy, low back pain, and alterations in the lumbar-pelvic rhythm associated with compensatory biomechanical changes such as limb shortening, pelvic retroversion, and increased thoracic kyphosis. In addition, studies in soccer players have documented that a limitation in hamstring flexibility can compromise vertical jump, kick speed, short stroke and agility.