Research indicates that the proportion of the world’s population aged 60 and above is increasing rapidly. It is projected that by 2050, this proportion will rise by 20%, surpassing the number of children globally. This phenomenon suggests that the population structure of most countries is tending towards aging (Stambler, 2017). Therefore, developing interventions that can slow down the aging process or reduce the incidence of aging-related diseases has become an urgent task, which also holds significant application value in improving the quality of life and reducing medical costs (Chakrabarti and Mohanakumar, 2016; Konar et al., 2016). Studies on human and animal models have shown that various genetic, dietary, exercise, and drug interventions can extend lifespan. Meanwhile, these lifespan - extending methods also contribute to delaying the onset of age - related diseases (Kenyon, 2010; Tacutu et al., 2013). In recent years, research has revealed the importance of telomere length (TL) and its integrity in the aging process, as well as potential interventions to delay aging, such as physical exercise and a healthy diet (Mercken et al., 2012). Since TL plays a crucial role in cellular aging and telomere shortening is associated with a decrease in life expectancy and an increased risk of chronic diseases, telomere attrition has been described as one of the important biological features of aging (López-Otín et al., 2013).

Telomeres are special structures at the ends of linear chromosomes, composed of repetitive G - and C - rich DNA sequences (5’ - TTAGGG - 3’/3’ - CCCTAA - 5′) and bound to a protein complex (shelterin), including telomeric repeat binding factor 1 (TRF1), telomeric repeat binding factor 2 (TRF2), protection of telomeres 1 protein (POT1), TRF1 - and TRF2 - interacting nuclear protein 2 (TIN2), TIN2 and POT1 interacting protein 1 (TPP1), and repressor activator protein 1 (RAP1). These proteins directly recognize telomere sequences and assist in forming T - loop and D - loop structures, thus hiding the telomere ends and suppressing the DNA damage response, preventing the activation of ataxia - telangiectasia mutation (ATM) and RAD3 - related (ATR) kinases (Balan et al., 2018; Blackburn et al., 2015; de Lange, 2005). Telomeres play a key role in stabilizing chromosomes, preventing DNA degradation and end - to - end fusion, and regulating cell growth. Simultaneously, as a mitotic clock, their length gradually shortens with cell division, serving as an indicator of cellular replication potential (Arnoult and Karlseder, 2015; Blackburn, 2010). With aging, telomere shortening leads to functional impairment, triggering genomic instability, cell senescence, and apoptosis (Blackburn et al., 2015). Biological aging is a process independent of chronological aging, which reduces the organism’s viability and increases vulnerability. TL, as a biomarker of biological aging, records both chronological and biological age (Brown et al., 2017). When TL shortens below a threshold, it can trigger chromosome fusion, genomic instability, and DNA damage, resulting in the production of non - functional proteins (Cleal et al., 2018; Hemann et al., 2001). These proteins may induce apoptosis or promote cancer development. Although telomere shortening can suppress tumors, its functional loss accelerates cell aging and tissue degeneration, driving organismal aging (Vakonaki et al., 2018). Therefore, maintaining TL is crucial for delaying aging.

Telomerase is an RNA - dependent DNA polymerase composed of telomerase reverse transcriptase (TERT) and telomerase RNA template (TERC), which can provide cells with unlimited proliferation potential by lengthening telomeric DNA (Blackburn, 2001; Cong et al., 2002). Due to the “end - replication problem”, the telomeres of somatic cells gradually shorten with age, while telomerase can slow down this process (Harley et al., 1990; Beyne-Rauzy et al., 2005). The polymorphism of TERT is associated with a reduced risk of breast cancer (Helbig et al., 2017), and telomerase plays a key role in maintaining genomic stability by synthesizing telomeres and counteracting telomere erosion (Zhang F. et al., 2016). In addition, the regulation of telomerase activity (TA) has potential value in anti - aging and cancer treatment (Cong et al., 2002; Aviv, 2002).

With the change of lifestyle, the lifespan and quality of life of the elderly have improved, especially with regular physical exercise. However, the underlying mechanisms remain unclear, which has, to some extent, promoted research on the relationship between exercise and telomere biology, such as whether exercise can delay aging and improve diseases. This systematic review and meta - analysis aim to integrate existing clinical studies and systematically evaluate the regulatory effects of exercise intervention on TL and TA, providing evidence - based support for formulating precise exercise prescriptions based on telomere protection.

This study was preregistered at PROSPERO (CRD420251006569) and adheres to PRISMA guidelines.

Exercise maintains TL and enhances TA, potentially contributing to delayed aging. This meta-analysis of 16 RCTs provides evidence for exercise prescriptions targeting telomere protection, aligning with prior meta-analyses like Schellnegger et al. (2022), which found exercise associated with longer TL in leukocytes (SMD = 0.41, P < 0.05) but noted similar heterogeneity challenges (Schellnegger et al., 2022). TL and TA are robust biomarkers of cellular aging, reflecting replication potential more directly than oxidative stress or inflammatory markers (Tacutu et al., 2013). Exercise maintained TL (SMD = 0.60, P = 0.01) and enhanced TA (SMD = 0.35, P < 0.00001). The claim of telomere lengthening is tempered by mechanisms such as selective apoptosis of cells with short telomeres, which may increase the proportion of cells with longer telomeres without actual elongation (Beyne-Rauzy et al., 2005). Thus, exercise primarily maintains TL relative to sedentary controls. TA increases may result from telomerase recruitment to short telomeres (Zou et al., 2004), immune cell proliferation (Simpson et al., 2010), or upregulation of TERT expression (Zhang J. et al., 2016). Mechanistically, exercise reduces oxidative stress via enhanced antioxidant enzyme activity (e.g., superoxide dismutase) (Shin et al., 2008) and suppresses inflammation through reduced pro-inflammatory cytokines (e.g., IL-6, TNF-α) (Werner et al., 2019; von Zglinicki, 2002), both of which protect telomeres from damage (von Zglinicki, 2002).

Subgroup analysis by sex showed a stronger TL maintenance trend in females (SMD = 0.48, P = 0.06) than males (SMD = 0.38, P = 0.40), possibly due to estrogen’s role in telomerase regulation (Konar et al., 2016). AE consistently enhanced TA (SMD = 0.33, P = 0.0001), while HIIT showed promise for TL maintenance (SMD = 0.66, P = 0.01), though this finding is limited by a single study (Werner et al., 2019). RE showed non-significant trends (SMD = 0.16, P = 0.43), likely due to only three studies and high variability in protocols (e.g., intensity, volume) (Zhang F. et al., 2016). Merging AE and RE categories was considered but not implemented, as their distinct physiological mechanisms (e.g., oxidative stress reduction in AE vs muscle hypertrophy in RE) justify separate analyses (Vakonaki et al., 2018).

High heterogeneity (I2 = 92% for TL) was partially explained by measurement methods (e.g., qPCR, Flow-FISH, Southern blot), participant age, and baseline health (Table 2). For example, qPCR is less precise than Southern blot for TL measurement, potentially inflating variability (Chakrabarti and Mohanakumar, 2016). TRAP ELISA for TA is less reliable than gel-based TRAP or droplet digital PCR (Friedenreich et al., 2018). Participant diversity (healthy, cancer, obese, stressed) and age (20–80 years) likely amplify heterogeneity, as disease states or older age may enhance exercise effects (Puterman et al., 2018). Metaregression identified publication year as a significant heterogeneity source, but only 25.2% of variance was explained, suggesting unexamined confounders like diet or genetics (von Zglinicki, 2002). The forest plots (Figures 4,6, ) correctly represent effect sizes favoring exercise, with positive SMD indicating TL/TA increases.

Causal claims about exercise delaying aging are tempered by potential confounders. Diet (e.g., antioxidant intake) and genetic factors (e.g., TERT polymorphisms) may influence TL and TA independently or interact with exercise effects (von Zglinicki, 2002). For instance, high antioxidant diets may synergize with exercise to reduce oxidative stress, while genetic predispositions may modulate telomerase response (de Lange, 2005). These factors were not controlled in most included studies, limiting causal inferences.

Exercise prescriptions include:

• TL maintenance: HIIT, ≥16 weeks, ≥60 min/week, 80%–90% max heart rate, pending further validation.

Limitations include reliance on English literature, limited HIIT/RE studies, measurement variability, and uncontrolled confounders like diet and genetics. Compared to Schellnegger et al. (2022), our study includes more recent RCTs and TA outcomes but faces similar heterogeneity challenges (Schellnegger et al., 2022). Future research should standardize TL/TA measurement methods (e.g., adopt Southern blot or droplet digital PCR), control for confounders, and explore sex- and cell-specific effects.

Exercise maintains TL and enhances TA, potentially contributing to delayed aging. AE shows robust effects on TA, while HIIT and RE require further research due to limited studies and non-significant results for RE. Standardized measurement methods and control for confounders like diet and genetics are needed to strengthen causal inferences.