This trial was conducted to compare and investigate the clinical (muscle strength, muscle mass and physical performance) and psychological (kinesiophobia and quality of life) effects of low or moderate intensity aerobic training in community dwelling COVID-19 asymptomatic older adults with Sarcopenia symptoms. The Sarcopenia and physical frailty in older people: multicomponent treatment strategies (SPRINTT) guidelines offered health practitioners to provide proper treatment strategies for older adults with Sarcopenia, which could be followed in COVID-19 scenario.28 Izquierdo M et al noted that older persons with Sarcopenia admitted in hospital or house quarantine for COVID-19 have to undergo regular exercise training for better outcomes.29 The reports of this trial stated that low intensity aerobic training (LAT) had better effects than moderate intensity aerobic training (MAT) in clinical and psychological effects and no or little change in muscle mass between the two groups.
Generally, aerobic exercises are safe physical activities which lead to whole body activation and induce the skeletal muscle properties. It promotes overall energy expenditure; improve physical fitness and pathway for healthy aging.30 In respect to muscle properties, all type of aerobic exercises controls the adverse effects of aging, such as on inflammation process, mitochondrial function, cell apoptosis and insulin activity.31 Among the other types of aerobic training, LAT improves overall endurance by activating skeletal muscle oxidative capacity and improves blood flow to the cell. This is the greatest demand of mitochondria in the cell during physical activity and it becomes enhanced during LAT exercises.32 LAT exercise activates the muscle protein peroxisome proliferator activated receptor gamma coactivator-1 (PGC-1) and facilitates mitochondrial function and increase the energy expenditure.31 Regarding muscle strength (hand grip strength, chair stand test and physical performance test), our reports show significant difference between the two groups. Goto K et al observed that the differences in the muscle strength in LAT and MAT exercise could be due to differences in energy metabolism or differences in training duration.33 The intra group analysis shows both groups have shown significant changes in muscle strength irrespective of exercise intensity. However, low intensity aerobic training group shows MCID (hand grip strength – 3.00, chair stand test – 2.70 and physical performance test – 0.08) than moderate intensity aerobic training group.
At the same time, muscle quantity (arm, thigh and calf) - CSA did not show any statistical difference in LAT and MAT exercises which is in agreement with Pasini E et al, because these exercises did not have any role in altering the number and size of fast twitch muscle fibers.34 Cadore EL et al., stated that the order of performing exercises (aerobic training followed with resistance training) plays an important role in improving the muscle strength and muscle mass,35 but in our study aerobic training was given first and then resistance training was given. This could be the cause for no changes in the muscle mass in both groups and the exact mechanism behind the effects of order of training was not clearly found. Furthermore, it is observed that the little differences in LAT or MAT aerobic training in muscle quantity could be due to either demographic characters or exercise parameters.36
Moreover, inclusion of resistance exercises in the form of PRT would induce and recruit new satellite cells into the weak muscle fibers and increase the number of myonucleus. This process would increases the strength and power of the muscle fibers and it depends upon age of the person, food status, and type of training. During resistance exercises the muscle fibers secrete muscle inflammatory cytokines which stimulate the satellite cells and increase the myonucleus in the muscles.37 Bowen TS noticed that in older adults there is substantial reduction in several muscle inflammatory cytokines and these hormonal and inflammatory changes have helped for the improvement in muscle strength and physical performance after LAT and MAT exercises.38
Improving muscle strength is closely related with the improvement in activities of daily living (ADL), which may decrease kinesiophobia (fear of movement and fall) status. These overall changes improved the quality of life (QOL) of COVID-19 infected older adults with Sarcopenia symptoms as agreed by Rejeski et al,39 and Binder et al40 but against by Holviala et al.41 The reports also suggest that LAT and MAT combined with progressive resistance training improved the psychological effects in older adults with Sarcopenia. Moreover, greater reduction in kinesiophobia status and improvement in quality of life were noted in LAT group than MAT group with MCID score (kinesiophobia – 4.2, quality of life − 5.7) Granacher et al42 have observed that PRE training for the upper/ lower extremities and trunk muscles provide the ability to work and reduce the kinesiophobia status of Sarcopenia patients. Combination of LAT or MAT exercises with PRE training provides both the effects of aerobic and resistance training, which can improve the overall quality of life.
The difference in clinical and psychological variables in low intensity and moderate intensity aerobic training in older adults is due to its variations in parameters such as frequency, intensity, time and mode of execution of exercises. Also, the muscle reaction to different exercise training protocols may be reduced in older adults when compared to younger people, which shows the physiological reserve in different stages of life.43 The combined aerobic and progressive resistance training program may help to overcome this problem in sarcopenia patients as agreed by Cruz Jentoff AJ et al and Deutz NE et al.44,45 Tieland et al46 noticed that combined exercise training with adequate protein intake improve muscle strength, physical performance and quality of life in frail older patients than exercise training alone.
Few limitations have been noticed during the execution of the whole trial. First, the authors felt the sample size of this trial was not sufficient for generalization of the reports, even though the sample size was calculated by previous pilot study. Second, all the participants were undergoing training at same time at same place; hence there is possibility of sharing of study information and masking of participants could be doubtful. Third, the study did not analyze the correlation between the clinical and psychological effects after low and moderate intensity aerobic training exercises. Lastly, there is absence of control group, which may show the real time effects of LAT and MAT exercise. Therefore, future studies should include a control group with more samples and should analyze the correlation between the clinical and psychological effects after low and moderate intensity aerobic exercises in COVID-19 older adults with Sarcopenia symptoms.
Combination of LAT or MAT exercises with PRT provides both the effects of aerobic and resistance training and can improve the clinical and psychological variables in community dwelling COVID-19 asymptomatic older adults with Sarcopenia symptoms. This study reports that low intensity aerobic training exercises improved the clinical (muscle strength and physical performance) and psychological (kinesiophobia and quality of life) aspects than moderate intensity aerobic training in COVID-19 asymptomatic older adults with Sarcopenia symptoms. At the same time, both types of aerobic training exercises have negligible or little role in increasing the muscle quantity - cross sectional area. The reports of the study would be helpful for the health professionals to prevent or postpone the negative consequences of Sarcopenia in older adults. High quality controlled clinical trials can be conducted at multicenter level with the involvement of multicomponent factors that can improve the health status of the COVID-19 infected older adults with Sarcopenia symptoms.