Electromyographic activity of the rectus femoris muscles following the knee joint cooling with different cooling agents

Introduction: Local cryotherapy (LC) is a common physical treatment often used in the area of joints. However, it has not been assessed whether the procedure performed within the joint may significantly affect the function of the muscles in its close vicinity. The aim of the present study was to assess the impact of the most commonly used clinical cooling agents – liquid nitrogen (LN), cold air (CA), and an ice bag (IB) – applied to the knee joint on the bioelectrical activity of the rectus femoris muscle, as assessed by surface electromyography (sEMG).Materials and methods: The study population consisted of 12 healthy women (mean age: 25.33 years) and 11 healthy men (mean age: 28 years). Each participant reported to the study center 3 times. Study procedures included a one-time body composition analysis, measurement of skinfold thickness above the knee, completion of the International Physical Activity Questionnaire (IPAQ), and 3 LC sessions. Each visit began with sEMG recordings of the right and left rectus femoris muscles in a free-standing position. One of the 3 cooling agents was then applied to the right knee joint only (for 3 min), and sEMG was repeated after 20 min. The rectus femoris muscle of both the exposed and unexposed lower limbs was evaluated.Results: There was no significant effect of the LC procedure on the root mean square amplitude (ARMS) of the sEMG signal after LN (p = 0.887), CA (p = 0.559), or IB (p = 0.999) stimulation. There was also no significant change in the ARMS value of the rectus femoris muscle in the unstimulated limb.Conclusion: Regardless of the cooling agent used, cooling the knee joint does not significantly affect the spontaneous bioelectric activity of the rectus femoris muscle in either the treated or the contralateral limb.