This single-center randomized controlled trial (RCT; Multimedia Appendix 1) was conducted at the Peking Union Medical College Hospital, affiliated with the Chinese Academy of Medical Sciences. The study is registered with the Chinese Clinical Trial Registry (registration number: ChiCTR 2300071648).

This study was approved by the Ethics Committee of the Peking Union Medical College Hospital (approval number: JS-2648). All participants provided written informed consent prior to enrollment, ensuring their voluntary participation with a full understanding of the study’s objectives, procedures, and potential risks. All personal data collected were anonymized and stored in encrypted electronic databases accessible only to the research team members. Neither the manuscript nor the supplementary materials include any identifiable information or photographs of individual participants. Additionally, no form of financial compensation was provided to participants; participation was entirely voluntary and would not influence their routine medical services.

All participants in this study were recruited offline from the Peking Union Medical College Hospital, a large comprehensive hospital. The specific process was as follows: First, the researchers posted recruitment advertisements in the hospital’s outpatient hall. Second, potential participants contacted the recruitment team (2 geriatricians and a rehabilitation physician with extensive experience in sarcopenia) over the phone, and the recruitment team conducted an initial telephone screening. Third, potential participants who passed the initial telephone screening were invited to the hospital for a face-to-face detailed assessment, including medical history taking, physical examination, and necessary laboratory tests. Finally, if the conditions of the potential participants met all the eligibility criteria, they were formally included in the study after obtaining written informed consent. During the informed consent process, participants were not informed whether they were in the intervention group or the control group in order to avoid bias. The inclusion and exclusion criteria are outlined in Textbox 1.

The sample size was calculated using PASS 15 software (NCSS, LLC). Based on the principle of noninferiority RCTs and previous clinical studies [21], the mean difference in the grip strength between the home-based exercise group and the therapist supervision–based exercise group was 3, the SD was estimated to be 4 for both groups, and the noninferiority margin for the grip was 1. A sample size of 46 was required based on a 1-sided α=.025 and β=.1, and a sample size of 58 was required to account for a 20% dropout rate. The formula used is the following:

A total of 58 participants were randomly assigned to either the telerehabilitation group (TRG, n=29, 50%) or the in-person rehabilitation group (IRG, n=29, 50%) using a randomization platform. Based on the platform’s results (eg, C, T, C, T, T, C), slips of paper labeled “T” and “C” were placed into sealed, opaque, and uniformly sized envelopes. After completing baseline measurements, the envelopes were opened in sequence to reveal group assignments. The allocation sequence was generated using a blocked randomization model by 2 researchers who were not involved in the study.

The training program for patients with sarcopenia in both the TRG and the IRG was identical. The program consisted of 6 resistance exercises targeting specific muscle groups, including back extensors, biceps brachii, gluteus maximus, gluteus medius, the deltoid, and quadriceps femoris. The specific exercises included glute bridges, resisted elbow flexion, hip extension, hip abduction, shoulder abduction, and knee extension (Figure 1). Participants performed resistance training 3 times a week, with each exercise performed in 3 sets of 10 repetitions per set, over a 4-week period (Multimedia Appendix 2). Effective training intensity was ensured through the use of the Borg rating of perceived exertion (RPE), with a target RPE of 12-14 at the end of each exercise session. Each session included approximately 10 minutes of warm-up, 40 minutes of resistance training, and 10 minutes of stretching, totaling around 1 hour.

All assessments were conducted by a dedicated blinded physical therapist with professional certification. This individual conducted all tests within 3 days in the hospital before and after the 4-week intervention for every participant.

Data analysis was performed using IBM SPSS version 26.0. Categorical variables were expressed as numbers, while continuous variables were presented as the mean (SD). Categorical variables were compared using the chi-square test. Paired t tests were used for within-group comparisons before and after the intervention, while independent-sample t tests were applied for comparisons between groups. P<.05 was considered statistically significant.

Between May 30, 2023, and July 1, 2024, 106 patients were assessed for eligibility. Of these, 43 (40%) patients were excluded based on the criteria, while 5 (5%) declined participation after the initial screening. As a result, 58 (55%) patients were included in the final study. As shown in Figure 3, participants were randomly assigned to 1 of 2 groups: the TRG (n=29, 50%) or the IRG (n=29, 50%).

During the study, 4 (14%) participants in the TRG and 1 (3%) participant in the IRG did not complete the 4-week follow-up. Additionally, 1 (3%) participant from each group discontinued the training due to worsening pre-existing conditions: hip pain in the TRG and elbow pain in the IRG. After discontinuing the exercise, their hip pain subsided, and the elbow pain returned to baseline levels. Ultimately, 24 (83%) patients in the TRG and 27 (93) patients in the IRG completed both the training program and the 4-week follow-up. Adherence to the exercise intervention was defined as the proportion of completed sessions relative to the total prescribed sessions, with adherence rates of 97% in the TRG and 92% in the IRG. The most commonly reported adverse effect was muscle soreness, and no exercise-related injuries or major adverse events were reported.

The baseline characteristics of the patients in the TRG and IRG were comparable. There were no significant differences between the 2 groups in terms of age, gender, height, weight, the TSM, the BFP, the SMI, grip strength, quadriceps femoris EPT, the BBS score, the 6MWT score, or the IADL score (Table 1).

With the increase in life expectancy and the decline in birth rates worldwide, the proportion of older adults in China has risen sharply over the past few decades. As the aging population grows, national health care expenditures have also surged, prompting the Chinese government to prioritize addressing the health challenges associated with population aging. Sarcopenia, characterized by a significant decline in muscle mass due to factors such as nutritional status, physical activity, genetics, or hormonal changes, along with the deterioration of tendon performance and neural patterns [22], leads to a loss of muscle strength and mobility. Sarcopenia is one of the most critical factors contributing to functional decline and loss of independence in older adults. It not only reduces their quality of life but is also associated with increased morbidity and mortality, as well as elevated public health costs [22]. Supervised exercise is considered an effective strategy for managing sarcopenia and frailty, yet many patients lack access to such resources. This study found that a 4-week remote resistance training program significantly improves the strength and balance of patients with sarcopenia, with outcomes comparable to face-to-face rehabilitation supervised by therapists. These findings highlight the potential of telerehabilitation as a feasible solution for populations with limited access to health care resources and demonstrate how digital health solutions can enhance care for older adults and address the unique needs of an aging society.

Previous studies have reported mixed findings on the effects of resistance training on body composition. Some scholars have observed that 12 weeks of resistance training can increase muscle mass in patients with sarcopenic [23,24]. In another study, women with obesity-related sarcopenia underwent 12 weeks of resistance training, 3 times per week. Although the training group experienced an increase in the lean mass of the lower limbs, the increase in the total body lean mass did not reach statistical significance compared to the control group [25]. Another study found that after 3 months of resistance training in older adults with obesity-related sarcopenia, reductions were observed in the fat mass, total fat mass, and BFP in the upper limbs, but there was no significant increase in lean mass [26]. Two systematic reviews and meta-analyses also yielded conflicting conclusions [9,10]. Mechanistically, the increase in muscle mass in older adults following resistance training may be attributed to enhanced muscle protein synthesis [27], increased satellite cell activity and quantity [28], elevated secretion of anabolic hormones [29], improved mitochondrial quality and function [30], and decreased activity of catabolic cytokines [31]. In our study, we found both groups demonstrated an increase in lean mass and a decrease in the BFP, though these changes did not reach statistical significance. This may be due to the relatively short duration of the 4-week resistance training intervention, which may not have been sufficient to induce significant alterations in body composition. It is also possible that extending the training period could result in more pronounced changes in body composition.

In this study, both the TRG and the IRG showed significant improvements in strength-related indicators, including grip strength, 30SSRT and 30SACT scores, and knee extension torque indices. These findings are consistent with previous systematic reviews and meta-analyses [9,10]. Studies have shown that resistance training can increase muscle fiber volume, particularly type II fast-twitch fibers [32]. Similarly, Ruiz et al [33] and Nunes et al [34] confirmed that resistance training enhances muscle function by improving muscle fiber adaptability and optimizing strength output mechanisms. At the molecular level, Sousa-Victor et al [35] demonstrated that resistance training increases satellite cell activity and muscle protein synthesis, reduces muscle degradation, and improves muscle mass. Coletti et al [36] and Gadelha et al [37] showed that this type of exercise activates the mammalian target of rapamycin (mTOR) signaling pathway, influencing protein synthesis, autophagy, and the expression of peroxisome proliferator–activated receptor-gamma coactivator 1 alpha (PGC-1α), thereby promoting sustained muscle growth and enhancing muscle performance. In this study, these effects were observed after just 4 weeks of resistance training, further demonstrating the significant therapeutic role of resistance training in the treatment of sarcopenia. The lack of significant differences in training outcomes between the 2 groups supports the application of telerehabilitation therapies in older adults with sarcopenia.

Lower limb muscle endurance is critical for dynamic balance. The reduction in the muscle cross-sectional area and neural fibers, particularly fast-twitch fibers, leads to a decline in muscle strength, especially in the lower limbs. This decrease in lower limb strength causes patients to spend extended periods sitting or lying down. Prolonged inactivity and sedentary behavior further exacerbate muscle loss and strength decline [25,35]. Reduced lower limb function impairs the ability to perform daily tasks, such as standing up from a chair, picking up items from the floor, walking, and climbing stairs [38]. In situations of instability, the central nervous system compensates by increasing muscle recruitment. One study [39] found that with aging, there is a loss of up to 75% of type II fibers, which diminishes functional mobility and muscle strength output. Concurrently, the synaptic input to α-motor neurons and the number of cortical neurons forming the corticospinal tract also decrease [40]. Resistance training can activate more motor units and muscle fibers, enhance synaptic input to α-motor neurons, and recruit more cortical neurons within the corticospinal tract, thereby improving coordination, reaction time, and strength to support dynamic balance [41,42]. Studies [43,44] have demonstrated that 3 months of resistance training improves muscle mass, physical fitness, and functional outcomes. In another study [11], participants’ functional fitness, such as the walking time, the chair stand test score, and the 8-foot up-and-go score, improved compared to the control group. In this study, after 4 weeks of training, both groups showed improvements in their BBS scores, which is consistent with previous findings. However, there was no significant improvement in TUGT scores, likely due to the relatively short duration of the training. The effective stimulation of key muscle groups, such as the gluteus maximus, quadriceps, and tibialis anterior, by resistance training may improve lower limb strength and neuromuscular coordination, enhancing stability and balance.

In terms of cardiorespiratory endurance, although resistance training primarily focuses on muscle strengthening rather than endurance, research suggests that resistance training may also improve endurance. For patients with sarcopenia, increased lower limb strength can translate into faster walking speed [25], and training peripheral muscles may improve indices related to respiratory function, thereby providing more substantial support for endurance [45]. One study [46] indicated that resistance training could enhance the 6-minute walking distance in frail older adults, while another systematic review [47] found that resistance training improves cardiorespiratory function in healthy older adults, including the peak oxygen uptake, anaerobic threshold, and 6-minute walking distance. In this study, both groups demonstrated improvements in the 6-minute walking distance, though neither reached statistical significance, possibly due to the short duration of the training program. Regarding the IADL, previous systematic reviews have shown that patients with reduced muscle mass are more likely to experience impairments in activities of daily living (ADL) and IADL, with reduced grip strength also being associated with impairments in ADL and IADL [48]. In this study, both groups showed significant improvements in the IADL after training, with no significant differences observed between the groups.

One of the limitations of this study is that it was a single-center RCT with a relatively small sample size. To address this limitation, the research team plans to conduct follow-up multicenter studies in regions with limited health care resources. Additionally, the follow-up period was relatively short. Future studies will involve a larger cohort over 8 weeks, 12 weeks, or even longer. Lastly, although participants were instructed to maintain consistent dietary habits throughout the study, detailed nutritional data were not adequately recorded. In addition, participants were not blinded, which may have introduced bias. In this study, the TRG received one-time offline instruction from a physiotherapist and were provided with resistance bands of appropriate tension. Furthermore, the pressure of having a follow-up assessment 1 month later may have increased patient compliance compared to routine application settings.

A 4-week mobile app–based telerehabilitation program produced improvements in muscle strength, balance, and the IADL comparable to those achieved by traditional in-person therapy in older adults with sarcopenia. Additionally, this telerehabilitation approach reduced health care resource use and logistical barriers. By offering an accessible, cost-effective, and patient-centered model of care, telerehabilitation shows promise as a viable alternative for patients with sarcopenia lacking convenient access to conventional rehabilitation services.