Koryagina Yu.V., Kushnareva Yu.V., Nopin S.V., Abutalimova S.M. Functional status of the musculoskeletal system and physical working capacity of astronauts compared to healthy volunteers

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Publication date: 15.06.2025
DOI: 10.24412/2782-6570-2025_04_02_4
UDC 612

FUNCTIONAL STATUS OF THE MUSCULOSKELETAL SYSTEM AND PHYSICAL WORKING CAPACITY OF ASTRONAUTS COMPARED TO HEALTHY VOLUNTEERS

Yu.V. Koryagina, Yu.V. Kushnareva, S.V. Nopin, S.M. Abutalimova

North-Caucasian Federal Research-Clinical Center of Federal Medical and Biological Agency, Essentuki, Russia

Abstract. Microgravity in conditions of spaceflight has its own effects on almost all physiological systems of a human. The most vulnerable ones, which are of key importance, are the musculoskeletal, vestibular and nervous systems. Currently, there are many programs of sanatorium-resort treatment and health-improvement of these systems for different population groups. Thus, an issue occurs on how applicable the already existing restorative and therapeutic procedures and methods are in the post-flight rehabilitation of astronauts. Therefore, the aim of this work is a comparative analysis of functional features of the musculoskeletal system and physical working capacity of astronauts compared to healthy male volunteers. The study involved 7 male astronauts and 10 healthy male volunteers. The observation included densitometry, bioimpedance analysis, dynamometry of knee joint flexor and extensor muscles, and registration of physical working capacity on a bicycle ergometer. The results have shown that the mineral density of skeletal structures in the astronauts corresponds to the age norm. According to the bioimpedance analysis data, the fat component of body mass is slightly higher than the norm, and the muscle component of body mass is significantly lower than the norm, the strength indices of the right hand are lower than the norm as well. Low indices of maximum strength and power of the knee joint flexor and extensor muscles in the astronauts match with sufficient indices of strength endurance. The astronauts also had a high level of physical work capacity. The obtained data will be implemented in the development of the 2nd stage post-flight rehabilitation program for astronauts.

Keywords: astronauts, functional status, musculoskeletal system, muscle strength, physical working capacity.

Introduction. Zero gravity is a specific integral irritator affecting an astronaut’s body during the whole orbital flight. It causes changes in a number of vital functions, including musculoskeletal, central nervous systems and receptors of many analyzing systems (vestibular and musculo-articular systems) [1-3]. At present, the general patterns of readjustment shifts in astronauts during the post-flight period are well known. They mainly center around a decrease in tolerance to physical activity and orthostatic effects, a significant muscle mass loss, and a complex of sensory and motor disorders [3-5].

The aforementioned defines significance and need to develop an effective program of the 2^nd stage of post-flight rehabilitation (PR) of astronauts in sanatorium-resort conditions, the basis of which will include a creation of maximally favorable conditions contributing to a faster and more fulfilling restoration of the musculoskeletal system function, muscle strength and physical working capacity of astronauts [6-8]. At present, a large number of programs of sanatorium-resort treatment and recovery for various population groups have already been developed [9-10]. The question arises about the applicability of already existing developed restorative and therapeutic procedures and methods in the astronauts’ PR program. In this regard, the aim of the work was a comparative analysis of functional features of the musculoskeletal apparatus and physical working capacity of astronauts compared to healthy male volunteers.

Methods and organization. The study was carried out in the North-Caucasian Federal Research-Clinical Center of Federal Medical and Biological Agency, the S.M. Kirov Sanatorium and the Orion Center for Athlete Recovery and Rehabilitation. The study included seven male astronauts (Me [Q1; Q3]): age – 55 [52; 57] years, height – 176 [172; 178] cm, weight – 89 [82; 102] kg, they were included in the main group (MG). The control group (CG) included ten male volunteers leading an active lifestyle (coaches in different sports), age – 44.5 [42; 48] years.

All the participants gave an informed consent in accordance with the WMA Declaration of Helsinki – Ethical Principles for Medical Research Involving Human Subjects (2013), as well as a permission for personal data processing. The study was approved by the Local Ethical Committee for Biomedical Research Expertise of the North-Caucasian Federal Research-Clinical Center of Federal Medical and Biological Agency.

Diagnostics of the total bone tissue density and structure, thickness of the superficial bone layer of the musculoskeletal system was carried out by means of densitometry (Hologic Inc., USA) using X-ray radiation. Body composition was determined in accordance with body resistance measurement in tetrapolar mode at a 50 kHz frequency on the ESTECK System Complex (LD Technology, USA).

Strength and static endurance of torso extensor muscles were measured using the DS-200 torso dynamometer (CJSC “Nizhny Tagil Medical Instrument Plant”, Russia), maximal wrist strength – with the EH101 digital dynamometer (China). The study of strength indices of the knee joint flexor and extensor muscles was carried out with the CON-TREX biomechanical complex with biofeedback (MJ modules for muscles and ligaments of the lower limb joints and TP modules for torso muscles) (Physiomed, Germany).

To determine physical working capacity of the astronauts, we used the PWC 170 test on a bicycle ergometer. Calculation of physical working capacity was made with the Karpman’s formula.

The statistical data processing was done in Statistica 13.0. We calculated standard descriptive statistics indicators (median, first and third quartiles). To develop the assessment criteria, we applied the quartile method.

Results and discussion. To identify the features of the functional state of the astronauts’ musculoskeletal system and strength indicators, we measured the mineral density of skeletal structures, body mass composition, and strength characteristics of muscle groups using various specialized dynamometers.

At densitometry the values of t-test in all subjects were within the established norm (not higher than +2,5 SD and not lower than -1 SD) that testifies that the mineral density of skeleton structures corresponds to the age norm and there are no signs of osteoporosis.

The analysis of body composition indices of the astronauts according to the bioimpedance analysis data in comparison with the norms for healthy men revealed that the fat component of body mass was slightly higher than the norm and the muscle component of body mass was significantly lower than the norm (table 1).

The astronauts also had lower than normal (35-50) right hand strength – 28.6 [22.2; 34.5] kg. Left hand strength (38 [28.3; 38.2] kg) and back strength were within the norm (140 [128; 142] kg) for men of this age (the normal values are 30-40 kg and 130-150 kg respectively).

To assess the strength parameters of leg muscles, muscle strength was tested on the CON-TREX isokinetic dynamometer in male volunteers and astronauts. When developing norms in the estimation of indicators of dynamometric research of the knee joint muscular system of men, we registered the indicators of healthy men leading an active lifestyle. These indicators in the form of medians and quartiles are presented in the table 2. According to these data, even in healthy KG men, the performance of flexor and extensor muscles is very different, i.e. muscle performance is not balanced.

Table 1

Body composition of male astronauts according to the data from bioimpedance analysis, Me [Q1; Q3] (n=7))

Indicators	Value	Norm
Fat-free mass, kg	66.2 [65.4; 70.2]	-
Fat mass, kg	21.2 [20.3; 26]	-
Fat component of body mass, %	24.4%	15-24
Total body water, %	57.7 [54.2; 58.4]	52-62.2
Body mass index, c.u.	24.1 [22.6; 24.3]	23-25
Muscle mass, kg	28.4 [27.7; 31.9]	-
Muscle component of body mass, %	32.2%	39-48

Nevertheless, rather high indices of muscular strength were noted, and therefore, according to these indices, norms for assessing the strength of muscles surrounding the right and left knee joints were developed (tables 3 and 4). Comparison of astronauts’ indices with the data of CG men revealed that astronauts lacked muscle strength of the muscles surrounding the knee joints, especially on the right side, as well as even stronger muscle imbalance than CG men. However, low values of maximal muscle strength and power in cosmonauts were combined with good values of power endurance.

Table 2

Dynamometry of the knee joint muscle system in the control group men, Me [Q1; Q3] (n=10)

Muscle groups	Torque max, Nm	Torque max average, Nm	Average power, W	Work – fatigue, J/s	Total work, J
Knee joint extensor muscles on the right	40.6 [30; 106.7]	33.6 [15.9; 58.2]	23.35 [15.2; 50.3]	0.06 [0.03; 0.27]	502.65 [300; 1325]
Knee joint flexor muscles on the right	42.8 [22.4; 67.4]	38.05 [14.3; 63.1]	22.65 [7.6; 41.8]	0.09 [0.02; 0.17]	624.75 [434; 972]
Knee joint extensor muscles on the left	51.9 [26.4; 100.6]	33.55 [10; 88.1]	21.2 [19.2; 50.3]	0.19 [0.13; 0.34]	497.45 [220; 1065]
Knee joint flexor muscles on the left	41.05 [22.7; 50.3]	38.95 [32; 48]	20.4 [14.4; 32.4]	0.11 [0.07; 0.18]	575.5 [421; 840.8]

Table 3

Dynamometry of the right knee joint muscle system in astronauts compared to volunteers

Indicators	Level (based on the control group)			Main group indicator	Level
	Low	Average	High
Knee joint extensor muscles
Torque max, Nm	<30	30-106.7	>106.7	21.1	low
Torque max average, Nm	<15.9	15.9-58.2	>58.2	5.5	low
Average power, W	<15.2	15,2-50.3	>50.3	7.4	low
Work – fatigue, J/s	<0.03	0.03-0.27	>0.27	0.15	average
Total work, J	<300	300-1325	>1325	171.4	low
Knee joint flexor muscles
Torque max, Nm	<22.4	22.4-67.4	>67.4	24	average
Torque max average, Nm	<14.3	14.3-63.1	>63.1	20.3	average
Average power, W	<7.6	7.6-41.8	>41.8	11.1	average
Work – fatigue, J/s	<0.02	0.02-0.17	>0.17	0.03	average
Total work, J	<434	434-972	>972	284.3	low

Table 4

Dynamometry of the left knee joint muscle system in astronauts compared to volunteers

Indicators	Level (based on the control group)			Main group indicator	Level
	Low	Average	High
Knee joint extensor muscles
Torque max, Nm	<26.4	26.4-100.6	>100.6	104.8	high
Torque max average, Nm	<10	10-88.1	>88.1	34.1	average
Average power, W	<19.2	19.2-50.3	>50.3	16	low
Work – fatigue, J/s	<0.13	0.13-0.34	>0,34	0.38	high
Total work, J	<220	220-1065	>1065	420.7	average
Knee joint flexor muscles
Torque max, Nm	<22.7	22.7-50.3	>50.3	50.2	average
Torque max average, Nm	<32	32-48	>48	24.5	low
Average power, W	<14.4	14.4-32.4	>32.4	13.9	low
Work – fatigue, J/s	<0.07	0.07-0.18	>0.18	0.01	low
Total work, J	<421	421-840.8	>840.8	361.5	low

The initial level of physical working capacity of the astronauts was determined with the PWC 170 test on a bicycle ergometer. The results have shown the value of 1607.5 [1564.5; 1677.0] kgm/min. According to the norms for men of this age this index is estimated as high (>1200), hence the astronauts had a high level of physical working capacity.

Conclusion. Thus, the functional state of the musculoskeletal system of the astronauts is characterized by sufficient bone tissue indices, a high level of physical working capacity, but a small muscular component of body mass and lower maximal strength capabilities, especially in the right limbs, compared to normal men. There is a strong imbalance in muscle development: the muscles of the left limbs are more developed, which indicates the need to apply and develop special recovery and rehabilitation measures to increase the functional capabilities of the astronauts’ musculoskeletal system and optimize the balance of muscles of the left and right halves of the body.

The obtained data will be used in the development of the 2nd stage post-flight rehabilitation program for astronauts.

Conflict of interest. The authors declare no conflict of interest.

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INFORMATION ABOUT THE AUTHORS:
Yulia V. Koryagina – Doctor of Biological Sciences, Professor, Head of the Center of Biomedical Technologies, North-Caucasian Federal Research-Clinical Center of Federal Medical and Biological Agency, Essentuki, e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it..
Yulia V. Kushnareva – Senior Researcher of the Center of Biomedical Technologies, North-Caucasian Federal Research-Clinical Center of Federal Medical and Biological Agency, Essentuki, e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it..
Sergej V. Nopin – Candidate of Technical Sciences, Lead Researcher of the Center of Biomedical Technologies, North-Caucasian Federal Research-Clinical Center of Federal Medical and Biological Agency, Essentuki, e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it..
Sabina M. Abutalimova – Candidate of Medical Sciences, Lead Researcher of the Center of Biomedical Technologies, North-Caucasian Federal Research-Clinical Center of Federal Medical and Biological Agency, Essentuki, e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it..    

For citation: Koryagina Yu.V., Kushnareva Yu.V., Nopin S.V., Abutalimova S.M. Functional status of the musculoskeletal system and physical working capacity of astronauts compared to healthy volunteers. Russian Journal of Sports Science: Medicine, Physiology, Training, 2025, vol. 4, no. 2(14). DOI: 10.24412/2782-6570-2025_04_02_4