PhD O.S. Vasiliev¹
Dr. Biol., Professor S.P. Levushkin^1,2
Dr. Med., Professor I.I. Gaidamaka³
A.A. Stolyarov^3
1Russian State University of Physical Education, Sport, Youth and Tourism (SCOLIPE), Moscow
²Institute of Developmental Physiology of the Russian Academy of Education, Moscow, Russia
³Stavropol State Medical University of the Ministry of Health of Russia, Stavropol

Keywords: rehabilitation service, movement trajectory smoothness, movement harmony, pain syndrome, pain rating scale, injury, musculoskeletal system, athletes, physical workload.

Background. Special efficient post-musculoskeletal system-injury rehabilitation service is in a special priority in the modern athletic rehabilitation systems, with a key role played by the target physical practices. One of the most challenging and still underexplored issues of such rehabilitation systems is how the physical workload on the target musculoskeletal system segment shall be tested and controlled when the movements are still restricted to a degree and the relevant soft tissues (muscles, tendons, ligaments) may suffer from an excessive physical workload.

Objective of the study was to offer movement smoothness rating tests and analyses for the physical workload control in the musculoskeletal system rehabilitation service.

Methods and structure of the study. The study was run in 2015 through 2019 at the Research Sports and Sports Medicine Institute of Russian State University of Physical Education, Sport, Youth and Tourism (SCOLIPE). We sampled for the study the 12-16 (12.5 on average) year old academic gymnasts and choreography school students (n=46, including 27 girls and 19 boys) diagnosed with musculoskeletal system (mostly lower limb) injuries with immobility and functionality disorders need of a rehabilitation service. To develop the kinematic test criteria for the physical workload control, we used an optoelectronic 3D movement capturing Qualisys test system that produces a digital skeleton image for analysis using a set of skin-fixed reflective markers. The test data were analyzed with application of a special mathematical model using the mathematical stat R-language. The Qualisys tests included the following two stages:

1. Movement profiling tests and analyses for the target musculoskeletal system segment, with the subjects executing standard motions in circle, ellipse, Lemniscata Bernoulli, etc.; followed by the actual movement profile analyzed for the movement trajectory smoothness and pain syndrome levels versus the relevant standards on the visual analog pain rating scale. The injured limbs were examined next day after the test to diagnose overstresses if any.

2. Movement smoothness analysis for the subject musculoskeletal system segment used a set of well known movement standards for the choreographic trainings including Demi-plié, Grandplié, Battementdéveloppé, etc.

Every injured limb test was run, when possible, by the other healthy limb, with the injured limb tests limited by at most 1 point on the pain rating scale. Upon completion of every test, the actual movement smoothness and trajectory was rated versus the movement trajectory smoothness standard and pain syndrome rate on the pain rating scale.

Results and discussion. Healthy movements may be rated by certain grace and plasticity (smoothness) tests [5], with the movement harmony known to grow with the nervous system progress and physical trainings to reach certain individual adaptation ranges and stay within them under varying conditions [1]. In kinematic terms, movement harmony may be defined as the movement smoothness based quality regardless of the movement amplitude and duration. Natural healthy movements are perceived, in the kinematic terms, as smooth with the right trajectories [5, 1] – in contrast to the unhealthy intermittent/ unsmooth movements typical of an injured musculoskeletal system segment. In neurophysiologic terms, smooth movements may be interpreted as the physical efforts minimizing ones, i.e. jerk minimizing in the biocybernetics language  for the whole movement trajectory [5, 2, 3]. 

Further studies found the logarithmic dimensionless jerk logs (J_N) having high sensitivity and low intra-group variability and, hence, beneficial for a wide range of the movement smoothness tests [5, 4]. Based on this assumption, we designed the local musculoskeletal system functionality and physical workload control mathematical model for the musculoskeletal system rehabilitation systems geared to minimize the logarithmic dimensionless jerk as follows:

, where  means the average movement speed in  section.  The function was used to rate the movement harmony in the tests. 

Thus we found the reciprocating trajectory in "Beak" test to significantly increase the pain syndrome on the pain rating scale from 3 points in the "Lemniscate" test to 4 points in the "Beak" test. Note that the smooth movement standards were also different for the reason that the movement pattern of every movement is different and implies certain natural discontinuities. Given in Table hereunder are the musculoskeletal system test data with the injury rates, pain syndrome on the pain rating scale, rehabilitation progress rates and movement smoothness rates on a 10-point scale. Note that the rehabilitation progress rates were provisionally classified by the rehabilitation progress periods into the startup, middle, and final ones.

Table 1. Injury rate (diagnoses), pain syndrome on the pain rating scale, rehabilitation progress rate and movement smoothness rate: Grand-plié test

It should be noted that only 5 subjects (11% of the sample) were tested with full rehabilitation by the Grand-plié test in the startup rehabilitation period; and 19 subjects (43%) in the middle rehabilitation period. Furthermore, only 36 subjects (82%) were fully smooth in the Demi-plié test in the middle and 41 subjects (93%) in the final rehabilitation period. It should be emphasized that the Grand-plié effectively tests the lower limb functionality albeit its physical workload may be excessive for some lower limb injuries. Therefore, the Grand-plié test rates may not be recommended as universal rehabilitation rating criteria for the whole injury range.

Conclusion. Multiple foreign studies have acknowledged that the movement smoothness test rates and analyses provide a good insight into an individual motor functionality, with the movement smoothness test rates known to widely vary with neuromotor disorders/ injuries. However, the research community is still in need of special musculoskeletal system injury and rehabilitation service specific movement smoothness tests and analyses. We believe that the idea to rate the movement smoothness for the professional sport motor skills profiling and rehabilitation service progress rating purposes, as offered and analyzed herein, may be rather beneficial for the sport science.

Disclamer

We could find neither direct nor indirect conflicts of interest in the published materials.

Sponsorship: the study was unsupported by sponsors.

References

1. Balasubramanian S., Melendez-Calderon A., Roby-Brami A., Burdet E. On the analysis of movement smoothness. J. NeuroengRehabil. 2015;9(12):112.
2. Flash T., Karklinsky M., Fuchs R., Berthoz A., Bennequin D., Meirovitch Y. Motor Compositionality and Timing: Combined Geometrical and Optimization Approaches. Biomechanics of Anthropomorphic Systems. Springer, Cham. 2019.
3. Flash T., Hogan N. The coordination of arm movements: an experimentally confirmed mathematical model. J. Neurosci. 1985;5(7):1688-703.
4. Gulde P., Hermsdörfer J. Smoothness Metrics in Complex Movement Tasks. FrontNeurol. 2018;12(9):615.
5. Hogan N., Sternad D. Sensitivity of smoothness measures to movement duration, amplitude, and arrests. J. Mot Behav. 2009;41(6):529-34.

Corresponding author: nauka@skfmba.ru

Abstract

Objective of the study was to develop kinematic criteria for assessing local loading on the athletes' locomotor system to further plan rehabilitation activities.

Methods and structure of the study. The study involved the young athletes and dance school students with lower limb injuries and in need of rehabilitation. The study was carried out using the optoelectronic 3D motion capture system "Qualisys". Subsequent data analysis was carried out using a specially designed mathematical model in the statistical computing language R (R programming language) in the RStudio environment.

Results and conclusions. A mathematical model was developed to evaluate the smoothness of the movement trajectory of individual links of the locomotor system, which makes it possible to assess the dynamics and adequacy of local physical load during rehabilitation activities. The kinematic criteria were developed to rate local loading during the rehabilitation of athletes.

The developed concept and mathematical model aimed to analyze the smoothness of the movement trajectory formed the basis of a new perspective tool that enables to rate local loading on the athletes' locomotor system while planning rehabilitation activities.