# Characteristics of Changes in Contractile Properties of Muscle after Anaerobic Exercise
## 1 Introduction  
Tensionyography (TMG) is a method for assessing muscle mechanical response, relying on the radial displacement of the muscle belly following a single electrical stimulus [1, 2]. TMG does not require the subject to exert physical effort, making it a noninvasive and practical method [3,4]. Recordings of displacement-time curves enable the assessment of muscle contractile properties [5]. The parameters measured by the TMG are: radial muscle displacement (Dm), contraction time (Tc), delay time (Td) (also known as reaction or activation time [6]), sustained contraction time (Ts), and half relaxation time (Tr). Dm represents the absolute spatial transverse deformation of the muscle while Tc is measured as the time on an ascending curve between 10 and 90 percent of Dm. The parameter Td is the time between the delivery of the electrical stimulus and 10% Dm, while Tr is the time between 90% Dm and 50% Dm on a descending curve. The parameter Ts is measured as the time between 50% Dm on each side of the curve [6,7]. The high reliability was confirmed for the parameters Tc, Dm, and Td, while parameters Ts and Tr reported poorer reliability and should be further investigated [2,7]. Within the literature, the Tc parameter has been associated with the rate of force generation [3]; however, some studies [4,8,9] have shown that Tc is also associated with the ratio of slow-twitch fibers. For example, [PERSON] et al. [4] found a significant positive correlation among Td, Tc, and Tr and myosin heavy chain I (%MHC-I) in the vastus lateralis muscle. Futuremore, the Dm parameter is associated with the stiffness of the muscle belly, muscle mass, and muscle architecture [10,11], while the Td parameter is associated with the conduction velocity of muscle fibers [3,12]. In addition, the parameters Ts and Tr provide a theoretical evaluation of the fatigue status of muscle [5,13]. TMG has been succesfuly used in sports environments [2,14,15,16,17,18,19,15,14,19,16,17,18,19,15,16,19,17,19,18,19,19,19,120,121]. Researchers have applied this method in a group of male soccer players [17] and showed that the TMG parameters distinguish the the dominant side from the non-dominant side. Also of interest are the findings of the study by [PERSON] et al. [19], which showed that the TMG has been an effective tool in discerning between elite power and aerobic endurance athletes, with the latter demonstrating elevated Tc and Dm values. Additionally, [PERSON] et al. [22] found that an uphill marathon resulted in a reduction in Tc and an elevation in Dm in the vastus lateralis muscle. Moreover, [PERSON] et al. [23] assessed how the contractile properties of muscles in elite futsal players were affected by a repeated sprint ability (RSA) test. The authors showed that the RSA test generated alterations in the contractile properties of the rectus femoris and biceps femoris. Furthermore, correlations were identified between the decline in performance during the RSA test and certain parameters measured by tensiomyography. On the other hand, a study by [PERSON] et al. [1] examined the predictive ability of TMG parameters on peak power output during the incremental cycling test in elite cyclists. The authors demonstrated that parameters acquired via TMG could be valuable in evaluating cyclist performance throughout the season, augmenting the conventional incremental performance test to exhaustion. The effort analyzed in this study was an anaerobic exercise in the form of a Wingate test. To our knowledge, there are two studies [15,24] that combine TMG with that form of anaerobic effort. Firstly, [PERSON] et al. [15] assessed the relationship between the peak power output (PPO) production capacity in the Wingate test and TMG parameters measured before anaerobic exercise in a women's Olympic Rugby Sevens Team. The athletes were examined during the preseason training and their levels of peak power output were homogeneous.