Determine the Occurrence of Latent Myofascial Trigger Points Through Binary Logistic Regression Model in Sportsmen

This study aimed to ascertain the prevalence of latent myofascial trigger points (L-MTrPs) among male athletes. Ninety participants were randomly included in the study. The presence of L-MTrPs was identified based on Simon’s criteria, leading to the categorization of participants into two groups: L-MTrPs (n=45) and non-myofascial trigger points (N-MTrPs) (n=45). Pain pressure thresholds (PPT) of muscles were quantified using a pressure algom-eter, while force production was measured with HUMAC NORM isokinetic. The range of motion (ROM) for knee flexors and extensors was determined using Kinovea software. These parameters were treated as independent variables, whereas L-MTrPs and N-TrPs were considered dependent variables. Binary Logistic Regression (Enter Method) was employed for data analysis. Model fitness was evaluated through standard error computation, Wald’s χ2, and odds ratios with a 95% confidence interval. Model adequacy was assessed via the likelihood ratio, Cox & Snell (R2), Nagelkerke (R2), and Hosmer and Lemeshow tests. The results effectively predicted L-MTrPs and N-MTrPs, revealing that force production, PPT, and ROM were the most significant predictive variables for L-MTrPs. In conclusion, reduced force production, lower PPT, and restricted ROM were indicative of L-MTrPs. Consequently, regular evaluation of muscular strength, PPT, and ROM are recommended for athletes to prevent the development of L-MTrPs.


Introduction
Myofascial Pain Syndrome (MPS) is a musculoskeletal ailment responsible for the sensation of pain (Duarte et al., 2021).This type of pain is characterised by the presence of hyperirritable regions known as trigger points (TrPs).These hyperirritable regions, specifically termed myofascial trigger points (MTrPs), are located within taut groupings of skeletal muscle fibers (Bethers et al., 2021;Das & Jhajharia, 2022b).These are tender, firm nodules measuring 3-6 mm in diameter (Donnelly & Simons, 2019).The research findings indicate that there is a notable difference in the occurrence of myofascial pain between males (37%) and females (65%) (Xia et al., 2017;Sabeh et al., 2020).Moreover, clinically, MTrPs are categorized into two types, namely active and latent MTrPs (L-MTrPs) (Jiménez-Sánchez et al., 2021).MTrPs that do not elicit pain are commonly referred to as L-MTrPs (Ge & Arendt-Nielsen 2011;Cygańska et al., 2022), whereas constant discomfort is a result of active-MTrPs (A-MTrPs) (Ibrahim et al., 2021).Musculoskeletal injuries are very common, and research in the fields of sports and exercise has shown that these are the most frequent kinds of injuries (Haser et al., 2017;Lee et al., 2020).Moreover, scientific investigation indicates that myofascial pain constitutes a substantial percentage (approximate-DETERMINE THE OCCURRENCE OF LATENT MYOFASCIAL TRIGGER POINTS | R. DAS ET AL. ly 85%) of musculoskeletal pain from injuries (Wheeler, 2004), As a consequence, scholars have recommended that MPS be taken into consideration as a possible cause of musculoskeletal pain (San-Antolín et al., 2020).Research indicates that athletes are susceptible to developing MTrPs over time (Fousekis & Kounavi, 2016;Kisilewicz et al., 2018;Das et al., 2022).Long-term or inconsistent training, low-load repetitive muscular activity, chronic and acute mechanical and electrical damage, persistent stress, and prolonged ischemia can all damage myofibrils and promote the formation of L-MTrPs (Ge & Arendt-Nielsen, 2011), It requires a thorough evaluation and a customised treatment plan (Barbero et al., 2019).The presence of MTrPs in the myofascial system is linked with reduced flexibility and strength of the affected muscles, as well as an increased sensation of muscle tightness (Fousekis & Kounavi, 2016;Haser et al., 2017).Athletes who are injured experience a decline in physical performance (San-Antolín et al., 2020;San-Antolín-Gil et al., 2022).Therefore, it becomes very important to identify MTrPs and take proper action.A correct diagnosis is the first step to treatment, and diagnostic accuracy depends on test reliability.Reliability pertains to the level of agreement among examiners when conducting the same test on the same patients (Das & Jhajharia, 2022a).There are a number of technologies that have been utilised to detect MTrPs, including microdialysis, biopsies (Do et al., 2018), imaging techniques by ultrasonography (Elbarbary et al., 2023), electromyography (Chattrattrai et al., 2023), and a digital pressure algometer (Karpuz et al., 2023).Among them, the most cost-friendly tool is the pressure algometer.This device is used by various researchers and they confirm that it has high reliability (Escalona-Marfil et al., 2020).This instrument measures the pain pressure threshold (PPT) of muscles.From the review of literature, it was observed that L-MTrPs reduced range of motion (ROM), muscular strength (Walsh et al., 2019), andPPT (Rodríguez-Jiménez et al., 2022).Therefore, these factors are believed to be crucial to determining the existence of L-MTrPs.Despite the fact that a great number of studies on MPS and MTrP have been published, only a few have been published regarding the symptoms of L-MTrPs.In addition, L-MTrPs can have a negative impact on daily life and sports performance (Shah et al., 2015;Das & Jhajharia, 2022b;Das et al., 2023), therefore, L-MTrPs is perceived as a serious health problem by researchers (Ribeiro et al., 2018).A review of related literature suggests that MTrPs reduce muscular strength (Das & Jhajharia, 2022b) and flexibility (Das et al., 2023) which affect the daily activity of sports person as well as sedentary people.Therefore, the purpose of this study was to identify that losing muscular strength, flexibility, and low PPT can be the symptoms of L-MTrPs.From the past research evidence, it was found that most of the studies were conducted on A-MTrPs, and very few studies are available on L-MTrPs (Duarte et al., 2023).Li and his colleagues reported in their systematic review article that a number of studies failed to properly report the MTrP diagnostic criteria (Li et al., 2020).Therefore, the objective of the study was to find out the symptoms of L-MTrPs.To fulfil the purpose of this study, a binary logistical regression approach was used.The findings of the present study will help the athletes detect the early symptoms of L-MTrPs, and that will help them prevent and take proper care of myofascial layer.

Participants
For this study, 90 national-level players were randomly selected on the basis of their sports participation and sports experience from Madhya Pradesh, India, and the research was carried out at the Exercise Physiology Laboratory of Lakshmibai National Institute of Physical Education in Gwalior, India.In this study, a cross-sectional comparative research design was used.The diagnostic criteria proposed by Simons (Donnelly & Simons, 2019) were utilized to identify L-MTrPs.(1) a band of muscle that is physically taut; (2) a spot that is tender and overly sensitive; (3) the compression of MTrP elicits the reproduction of referred pain; (4) and the jump sign when compressed (Zuil-Escobar et al., 2015).The inclusion criteria for the L-MTrPs group were based on three requirements.Firstly, the presence of L-MTrPs in the hamstring and quadriceps muscle groups located in the lower limbs.Secondly, the subjects had to be male athletes who played a sport that involved jumping, sprinting, twisting, turning, acceleration, and deceleration as essential components.Additionally, these athletes had to play their sport competitively, which was defined as participating a minimum of twice per week in an organized training or match situation for a team that competed in an official league or cup.Lastly, all subjects were collegiate athletes who were currently in the competition phase of their sport.On the other hand, the inclusion criteria for the non-L-MTrPs group were the absence of a palpable taut band in the muscles.The exclusion criteria for this study were multifaceted.Firstly, subjects were excluded if they were currently experiencing any injury or illness, including any systemic muscular or neural disease, or any lower limb or lower back injury in the previous three months.Secondly, the study excluded subjects who had recently been diagnosed with or treated for fibromyalgia, suffered from vascular or neural conditions, or received treatment for MTrPs (active or latent).Subjects who met the inclusion criteria were explained the study and were included in the sample only if they agreed to participate.Purposive sampling was used to select the first group, which consisted of 45 subjects diagnosed as positive for L-MTrPs.The second group consisted of subjects who were negative for MTrPs.To ensure an equal sample size and better statistical inference, 45 non-MTrPs subjects were included in this study.A skilled  1).The mean age, height, and weight were found to be statistically same for both the group (p>0.05).All the participants were actively engaged in competitive sports.

Instruments
The evaluation of PPT was performed using a digital pressure algometer (FPX 25 Wagner Instruments, Greenwich, CT, USA) in accordance with the methodology reported by Cygańska et al. (2022).It has been reported that this device has high reliability (Castien et al., 2021;Cygańska et al., 2022).The measurement of force production by peak torque (Newton/meter2) in knee tests was performed using the HUMAC NORM isokinetic machine (Computer Sports Medicine, Inc., Stoughton, MA, USA).It has been reported that the reliability of this machine ranges between 0.74-0.89,indicating its consistent and dependable performance in measuring the peak torque (Habets et al., 2018).Kinovea® version 0.9.5 software was used by the researchers to measure the ROM.The software was found to be a valid and reliable tool for measuring accurately at distances up to 5 meters from the object.It is available for free download at (https:// www.kinovea.org/)(Puig-Diví et al., 2019;Fernández-González et al., 2020).

Pain Pressure Threshold Examination
The pain test utilised algometric measurement, with the pain threshold defined in lbs/cm2 and the pressure applied at a constant speed.The PPT was determined as the threshold point at which pressure sensations transitioned to pain (Ortega-Santiago et al., 2020).The measurement of the pain threshold for particular muscles was conducted, and the identification of the locations of the L-MTrPs was established as mentioned by Cygańska et al. (2022).A device at a 90° angle to the skin surface measured the quadriceps and hamstrings in a supine and prone position, respectively (Fig 1 ), consistently beginning at the locations on the right side.When the test point initially hurt, the individual was instructed to say "STOP." Before measuring the actual sites, a trial measurement was taken on the subject's forearm muscles to ascertain their pain threshold.Each measurement was analysed by the same researcher and separated by five minutes.The following sequence was used to test each subject's muscle groups: initially, the right and left quadriceps muscle groups (Vastus lateralis, Rectus femoris, and Vastus Medialis), then the right and left hamstring muscles (Bicep femoris, semitendinosus, and semimembranosus).A physical therapist with over a decade of experience oversaw the measurement process.A 30-second break was provided between each measurement, and the mean of three trials was computed for analysis.This approach to assessing PPT has been proven to demonstrate strong intra-and inter-examiner consistency (Chesterton et al., 2007).

Muscular Strength Measurement
After algometric measurements, the CSMi HUMAC NORM isokinetic dynamometer was used to measure the participants' lower limb force production.Knee flexion and extension muscle strength were measured while participants were positioned on the testing table with stabilisation straps and a horizontal pad over their thighs.The trunk was supported by the backrest of the table.Peak isokinetic concentric knee extension and flexion torque of both legs were evaluated at an angular velocity of 180°/s velocity.The knee extension and flexion contractions were performed through a range of 0-90° (full extension is defined as 0 degree).All participants were instructed to complete three submaximal trials at a given angular velocity for familiarisation and warmup.Peak isokinetic concentric knee extension and flexion torque were measured with the right and left legs at 180°/s extension.All the participants performed five maximal repetitions of knee extension and flexion at a selected angular velocity.A break of at least 3 minutes was given when the machine setting was changed for the opposite leg.The order of testing was randomised for the right and left legs.Verbal encouragement and visual feedback were given by the investigator to all participants to help them concentrate on the quality of their movements.The greatest peak torque (Nm) for knee extension and flexion was calculated automatically by the HUMAC NORM System and served as the outcome measure (Tasmektepligil, 2016).

ROM Examination
A GoPro 9 action camera recorded each participant's knee joint from the sagittal and frontal axis profiles.Markers, both passive and reflective, were placed on the greater trochanter, the external femoral condyle, and the lateral malleolus to measure the angular displacement of the knee joint as seen from the side (Silva et al., 2018;Fernández-González et al., 2020).A tripod-mounted camera was 80 cm high and 1.5 m from participants.To maintain camera-to-participant dis-tance, the tripod was placed on floor tape.Before the tests, everyone did a five-minute warm-up.The knee of each subject was positioned near the edge of the table while they lay prone on it (Fig 3).The individual was instructed to bend their knee as much as possible before extending it to determine the angle of knee flexion.The unfolded leg was measured as knee extension, and a closer to 0° angle was considered a good extension ROM.All videos were imported onto a laptop and analysed using Kinovea software.The greater trochanter, external femoral condyle, and lateral malleolus were marked in the Kinovea.An angle was placed in the external femoral condyle.One line went through the humerus bone and ended at the greater trochanter (stationary arm), while the other went through the tibia bone and ended at the lateral malleolus (movable arm).Angles were used to describe the two lines' intersection (Das et al., 2023).

Statistical Analyses
The statistical analysis was performed using IBM SPSS (version 26.0.0) and involved binary logistic regression (Entre Method) to analyze the relationship between L-MTrPs and N-MTrPs (dependent variables) and PPT, force production, and ROM (independent variables).The analysis included calculation of, β, standard error β, Wald's χ2, odds ratio with a 95% confidence interval.Model evaluation was conducted using the likelihood ratio test, Cox & Snell (R2), and Nagelkerke (R2) tests, and the goodness of fit test was evaluated using the Hosmer & Lemeshow test.Additionally, the observed and predicted frequencies by the regression model were calculated with a cut-off of 0.50.The level of statistical significance was set at p≤0.05.

Result
Table 2 demonstrates the descriptive statistics of average force production, average PPT, and average ROM of keen flexion and extension in the L-MTrPs and non-TrPs groups.And there was a statistically significant difference found as the p-value is <0.05.
Model summary (Table 3) shows that the 82.5% change in the criterion variable can be accounted to the predictor variables in this model.The hosmer and lemeshow test is also a test of model fit.The hosmer-lemeshow statistic indicates a poor fit if the significance value is less than 0.05.Here the model adequately fit the data, as the p-value is .922(>0.05;Table 4).
From the table summary, we found that this model was 82.5% fit, Hosmer and Lemeshow test also confirmed that this model was good as the p-value is >0.05.That means average force production, PPT, and ROM were predicting L-MTrPs.Therefore, if the reduction in force production, lower PPT, and restriction of ROM occur, those are symptoms of L-MTrPs.In this study, it was hypothesised that force production, PPT, and ROM were the significant predictor variables of the L-MTrPs.According to the model this hypothesis was accepted.

Discussion
The objective of this research endeavour was to identify pertinent variables directly associated with the prediction of L-MTrPs.To achieve this objective, the study employed binary logistic regression analysis.Force production, PPT, and ROM were considered independent variables, and L-MTrPs and non-TrPs were considered dependent variables.Drawing from an extensive review of related literature, it became evident that L-MTrPs exert a negative influence on muscle force production (Kim et al., 2017;Das & Jhajharia, 2022b).A critical finding from this investigation was the prominence of PPT as a diagnostic marker for L-MTrPs.Research evidence suggests PPT is a reliable source to identify A-MTrPs (Valera-Calero et al., 2023).Notably, several researchers have called for further elucidation on this aspect (Doraisamy & Anshul, 2011).Additionally, L-MTrPs were observed to adversely impact joint ROM, this phenomenon has been consistently underscored by a variety of authors (Charles et al., 2019;Walsh et al., 2019;Öztürk et al., 2022).For instance, a study by Girasol et al. investigated the correlation between L-MTrPs and ROM in the upper trapezius, revealing a reduction in ROM (Girasol et al., 2018).Similarly, other studies highlighted L-MTrPs induced limitations in ankle planter-flexion and dorsi-flexion ROM due to gastrocnemius muscle TrPs (Benito-de-Pedro et al., 2020).Consequently, the evident connection between these variables and L-MTrPs emerges as significant.Consistent with prior research, a lower pain threshold has been linked to muscular abnormalities.Notably, a discrepancy in PPT greater than 2 kg/cm2, in comparison to the identical muscles on the opposing side, is indicative of the presence of L-MTrPs (Park et al., 2011;Cordeiro et al., 2021;Das et al., 2022).This firmly establishes PPT as a robust diagnostic parameter for L-MTrPs, a conclusion bolstered by our own statistical analysis.The precise pathophysiology underpinning myofascial pain remains somewhat enigmatic.Studies indicate that oxidative stress, inflammation, and glial cell activity, particularly astrocytes within the central nervous system, contribute to the persistence of pain signals, culminating in MTrPs (Widyadharma, 2020).Nociceptive chemicals released in response to tissue injury or inflammation are pivotal in perpetuating pain in MTrPs.These chemicals sensitise nerve fibers, inducing pain perception.Biochemical accumulation within MTrPs, localised regions of muscle stiffness and discomfort, includes neurotransmitters, neuropeptides, cytokines, and inflammatory mediators.According to Simons' hypothesis, abnormal endplate activity prompts the release of elevated acetylcholine levels, triggering a cascade.Calcium channels open, and calcium binding to troponin prompts muscle fiber contraction.Inadequate ATP supply sustains contraction near abnormal endplates, leading to an energy crisis, heightened metabolic demands, reduced blood flow, hypoxic conditions, and polarization.This energy crisis may trigger the release of neuroreactive substances and metabolic byproducts (e.g., bradykinin, substance P, and serotonin), sensitising peripheral nociceptors (Shah et al., 2015).Beyond PPT, athletes should not overlook the significance of force production and ROM, as research underscores their pronounced influence by L-MTrPs (Walsh et al., 2019;Cao et al., 2021;Yeste-Fabregat et al., 2021).The exact mechanisms behind these effects remain a subject of exploration.Emerging hypotheses, on the other hand, suggest that L-MTrPs could be a source of muscle dysfunction, causing fatigue, muscle tightness, shortened sarcomeres, and different patterns of activation.These dynamics result in suboptimal muscle contraction, diminished force production, and compromised ROM (Bagcier et al., 2022;Schneider et al., 2022).Consequently, athletes displaying reduced force production and ROM may be predisposed to L-MTrPs.The implications of this study indicate that athletes may unwittingly develop L-MTrPs, potentially impairing performance.It's worth noting that untreated L-MTrPs can even carry greater consequences (Celik & Mutlu, 2013).Therefore, athletes are advised to prioritise proper maintenance of their fascial structures to mitigate such risks.

Strength of the study
This investigation demonstrates novelty and innovation, as the majority of prior research has primarily focused on A-MTrPs and their associated symptoms, with limited inquiry into L-MTrPs within the sports domain.Our study has yielded substantial findings that can serve to aid athletes in averting the transformation of L-MTrPs into A-MTrPs, thus preserving and optimizing their physical performance.

Limitations
The limitations of this study are that it has an exclusive focus on the hamstring and quadriceps muscle groups, as well as its restriction to athletes performing at the national level.

Conclusion
The findings of the study suggest that if an athlete has lower force production, lower PPT in muscles, and restrictions in ROM, that indicates the occurrence of L-MTrPs.Therefore, athletes should take proper care of the muscle fascial structure.Coaches and physical trainers should include routine assessments of the force production, PPT, and ROM of the athletes.Sports scientists and physiotherapists should conduct more studies in this aspect and explore this area.Future studies are recommended for other muscle groups and focus on specific athletic disciplines.

FIGURE 1 .
FIGURE 1. Evaluation of Latent Myofascial Trigger Points

FIGURE 2 .
FIGURE 2. Evaluation of Muscular Strength

Table 1 .
Participants' basic characteristics Written consent was obtained from the participants' parents or legal guardians.The ethics committee of the Lakshmibai National Institute of Physical Education approved this study.It was conducted according to the latest version of the Declaration of Helsinki (approval number: 392/1346/27, 22 February 2023).

Table 2 .
Descriptive Statistics of selected variables reported for L-MTrPs and Non-TrPs Group

Table 3 .
Model Summary a. Estimation terminated at iteration number 8 because parameter estimates changed by less than .001.

Table 4 .
Hosmer and Lemeshow Test

Table 6 .
Variables in the Equation DETERMINE THE OCCURRENCE OF LATENT MYOFASCIAL TRIGGER POINTS | R. DAS ET AL.