Effect of linear and weekly undulating resistance training on muscle mass and running performance of project athlete

Introduction: Resistance training is a specialized conditioning method that uses progressively increasing loads and varied training modalities to improve health, fitness, and athletic perfor- mance. Periodized RT adjusts training volume and intensity to enhance performance, yet the most effective model remains uncertain. Limited evidence compares linear and weekly undu- lating periodization, particularly in athletes. Objective: To compare the effects of 12 weeks of linear and weekly undulating resistance train- ing on muscle mass and running performance, as measured by 800 m and 1500 m time trials, in male project athletes. Methodology: A quasi-experimental study design was employed to conduct the study. Thirty- six male runners were randomly assigned to a linear group (n=18) and an undulating group (n=18). Statistical analyses were performed using SPSS V. 26 with a significance level set at P <0.05. Paired and independent samples t-tests were analyzed within- and between-group dif- ferences. Levene’s test assessed variance homogeneity, Shapiro-Wilk tested normality, and par- tial eta squared (η²) indicated effect size. Results and Discussion: The results showed no significant differences between the linear re- sistance training and weekly undulating resistance training groups in muscle mass (t (34) = – 0.36, p = 0.73, η² = 0.01), 800 m time trial performance (t (34) = 0.87, p = 0.39, η² = 0.02), and 1500 m time trial performance (t (34) = 1.50, p = 0.14, η² = 0.06). Conclusion: Both linear and weekly undulating resistance training produced improvements in muscle mass and middle-distance running performance; however the differences between

– 0.36, p = 0.73, η² = 0.01), 800 m time trial performance (t (34) = 0.87, p = 0.39, η² = 0.02), and 1500 m time trial performance (t (34) = 1.50, p = 0.14, η² = 0.06). Conclusion: Both linear and weekly undulating resistance training produced improvements in muscle mass and middle-distance running performance; however the differences between groups were not statistically significant. Keywords Muscle hypertrophy; performance; periodization. Resumen Introducción: El entrenamiento de resistencia es un método de acondicionamiento especiali- zado que utiliza cargas progresivamente crecientes y diversas modalidades de entrenamiento para mejorar la salud, la condición física y el rendimiento deportivo. El entrenamiento de resis- tencia periodizado ajusta el volumen y la intensidad del entrenamiento para optimizar el ren- dimiento; sin embargo, el modelo más eficaz aún no está claro. Existe evidencia limitada que compare la periodización lineal con la ondulante semanal, especialmente en atletas. Objetivo: Comparar los efectos de 12 semanas de entrenamiento de resistencia lineal y ondu- lante semanal sobre la masa muscular y el rendimiento en carrera, medido mediante pruebas de 800 m y 1500 m, en atletas masculinos participantes en el proyecto. Metodología: Se empleó un diseño de estudio cuasiexperimental. Treinta y seis corredores mas- culinos fueron asignados aleatoriamente a un grupo lineal (n=18) y a un grupo ondulante (n=18). Los análisis estadísticos se realizaron con SPSS versión 26, con un nivel de significancia de p < 0.05. Se analizaron las diferencias intra e intergrupales mediante pruebas t de Student para muestras pareadas e independientes. La prueba de Levene evaluó la homogeneidad de la varianza, la prueba de Shapiro-Wilk evaluó la normalidad y el eta cuadrado parcial (η²) indicó el tamaño del efecto. Resultados y discusión: Los resultados no mostraron diferencias significativas entre los grupos de entrenamiento de resistencia lineal y entrenamiento de resistencia ondulante semanal en masa muscular (t (34) = –0.36, p = 0.73, η² = 0.01), rendimiento en la prueba contrarreloj de 800 m (t (34) = 0.87, p = 0.39, η² = 0.02) ni rendimiento en la prueba contrarreloj de 1500 m (t (34) = 1.50, p = 0.14,

los grupos de entrenamiento de resistencia lineal y entrenamiento de resistencia ondulante semanal en masa muscular (t (34) = –0.36, p = 0.73, η² = 0.01), rendimiento en la prueba contrarreloj de 800 m (t (34) = 0.87, p = 0.39, η² = 0.02) ni rendimiento en la prueba contrarreloj de 1500 m (t (34) = 1.50, p = 0.14, η² = 0.06). Conclusión: Tanto el entrenamiento de resistencia lineal como el ondulante semanal produje- ron mejoras en la masa muscular y el rendimiento en carreras de media distancia; sin embargo, las diferencias entre los grupos no fueron estadísticamente significativas. Palabras clave Hipertrofia muscular; rendimiento; periodización. Effect of linear and weekly undulating resistance training on muscle mass and running performance of project athlete Efecto del entrenamiento de resistencia lineal y ondulante semanal sobre la masa muscular y el rendimiento de carrera de los atletas de proyecto

2026 (Mayo), Retos, 78, 1021-1032 ISSN: 1579-1726, eISSN: 1988-2041 https://revistaretos.org/index.php/retos 1022 Introduction Resistance training (RT) also known as strength or weight training, is a key method for enhancing per- formance in most sports (Makaruk et al., 2022). It has become one of the most widely adopted training modalities over the past two decades due to its strong impact on athletic performance. RT increases muscular strength, power, speed, hypertrophy, local muscular endurance, balance, coordination, bone density, and connective tissue function (Chaabene et al., 2025; Zouita et al., 2023). As a cornerstone of performance enhancement across nearly all sports, RT provides a potent stimulus for developing strength and skeletal muscle mass (Lopes et al., 2017). Track and field athletes particularly depend on these qualities, making RT an essential component of their preparation (Dombrowski, 2013). Skeletal muscle is integral to many locomotives and metabolic processes critical for good health. Per- forming regular RT muscle contraction against external resistance improves muscular health; in partic- ular, increases skeletal muscle mass (i.e., hypertrophy), strength, and physical function (McLeod, Cur- rier, Lowisz & Phillips, 2024). Periodized RT systematically manipulating load, volume, frequency, rest, & movement velocity has been widely used since the 1950s to optimize strength, power, and running performance (McLeod et al., 2024; Peixoto et al., 2022). Beyond strength gains, RT is equally effective for promoting skeletal muscle hypertrophy, a critical determinant of force production and athletic per- formance (Stone et al., 2022). Increased muscle mass enhances rate of force development, sprinting speed, jumping performance, and change-of-direction ability (Suchomel et al., 2018). Thus, selecting ap- propriate RT methods is vital for maximizing both hypertrophy and performance outcomes (Schoenfeld, 2021). Promoting hypertrophy is a relevant strategy for elevating sport performance (Bernárdez- vázquez, Raya-gonzález, & Castillo, 2022). RT also contributes significantly to endurance and middle-distance performance. Chronic strength de- velopment improves running economy, lactate threshold, peak power, speed, and overall work capacity (Bagheri et al., 2023; Suchomel et al., 2016). It additionally reduces injury risk and enhances tissue re- silience, cardiovascular function, and lean mass among endurance athletes (Blagrove et al., 2018). High- velocity RT, including plyometric training,

also contributes significantly to endurance and middle-distance performance. Chronic strength de- velopment improves running economy, lactate threshold, peak power, speed, and overall work capacity (Bagheri et al., 2023; Suchomel et al., 2016). It additionally reduces injury risk and enhances tissue re- silience, cardiovascular function, and lean mass among endurance athletes (Blagrove et al., 2018). High- velocity RT, including plyometric training, further improves explosive strength and sprinting ability (Ramirez-campillo et al., 2021). Anthropometric factors such as muscle mass distribution also influence running efficiency, with lower limb mass being advantageous in middle-distance events (Mooses et al., 2013). Since both strength and muscle mass are essential for athletic performance and overall health, selecting an appropriate RT program is critical for optimizing these outcomes (Evans, 2019). Among periodization models, linear periodization (LP) and undulating periodization (UP) are the most commonly implemented programs in resistance training scheme (Miller et al., 2015). LP features a grad- ual increase in intensity with a reduction in volume, while UP varies these variables more frequently, either weekly (WUP) or daily (DUP) (Silva et al., 2023). Both models effectively enhance strength, hy- pertrophy, power, and running performance (Abdi et al., 2019; Grgic et al., 2017). LP is often used for endurance-based programs due to its progressive structure, whereas WUP is favored for short- and middle-distance running because of its variability and early anaerobic emphasis (Bradbury et al., 2020). Despite these practical distinctions, research frequently reports minimal performance differences be- tween LP and UP, leaving the choice largely dependent on athlete characteristics and coaching prefer- ence (Antretter et al., 2020; Hassan & Mohamed, 2015). Although strength training is increasingly recognized for improving performance & preventing injuries in runners (Karp, 2024), the role of RT in distance running especially in competitive athletes remains less explored. Evidence on the most effective RT periodization model for enhancing muscle mass & run- ning performance is still inconclusive (Caldas et al., 2016; Rodríguez-Rosell et al., 2021). Comparative studies between LP & WUP are limited, particularly among athletic populations, with most existing re- search conducted on untrained or recreational subjects (Ramalingam, 2019). RT is often overlooked in

remains less explored. Evidence on the most effective RT periodization model for enhancing muscle mass & run- ning performance is still inconclusive (Caldas et al., 2016; Rodríguez-Rosell et al., 2021). Comparative studies between LP & WUP are limited, particularly among athletic populations, with most existing re- search conducted on untrained or recreational subjects (Ramalingam, 2019). RT is often overlooked in favor of technical, tactical, & competition-oriented training, limiting strength development among ath- letes. Moreover, no studies have directly compared the effects of linear & weekly undulating RT on mus- cle-mass and running performance of athletes in the country. Therefore, the present study aimed to compare the effects of a 12-week linear and weekly undulating periodized resistance training program on muscle mass & running performance among male project athletes.

2026 (Mayo), Retos, 78, 1021-1032 ISSN: 1579-1726, eISSN: 1988-2041 https://revistaretos.org/index.php/retos 1023 Method Study Design The current study was employed a quasi-experimental design with a pre- and post-test comparison group approach to assess participants’ performance before and after a resistance training intervention in both experimental groups. One week before the intervention, participants were familiarized with pro- cedures, completed medical questionnaires, and gave informed consent. Researchers then collected base line tests and demographic data. Participants Forty-one male volunteer athletes were included in the study. Based on a priori power analysis using G*Power (version 3.1.9.4, for Windows) with an effect size of 0.85, α =0.05, and power = 0.80, a mini- mum of thirty-six participants were required, which is supported by Uysal, Korkmaz and Aksakall (2024). Only male athletes who had been injury-free for the past six months, had at least two years of training experience, & provided informed consent were included in the study. Following baseline testing & familiarization, participants were randomly assigned to the LRT group (n = 18) & the WURT group (n = 18), and the rest five athletes were excluded based on exclusion criteria, as illustrated in the flow diagram (Figure 1). Figure 1. Participant flow diagram of linear and weekly undulating resistance training groups Procedure Anthropometric test Body mass and height were measured in the morning without shoes using an ELEKTRA digital scale (SEL-3202, China) and a stadiometer (ADIME904-01, China), recorded to the nearest 0.1 kg and 0.1 cm, respectively. Skinfold thickness was assessed at two sites; mid-thigh and calf using a Slim Guide caliper to estimate body muscle mass. Girth circumferences and segment lengths were measured in centimeters using a flexible tape measure. After baseline testing, both groups participated in a 12-week resistance training program (3 days per week) following the protocol of Hassan & Mohamed (2015), with identical training variables but different volume and intensity sequencing. Post-tests were conducted under the same conditions as the pre-tests. Martin formula test Muscle mass was estimated using the formula of Martin et al. (1990), which is based on height, forearm girth, mid-thigh girth, maximal calf girth, and corresponding

days per week) following the protocol of Hassan & Mohamed (2015), with identical training variables but different volume and intensity sequencing. Post-tests were conducted under the same conditions as the pre-tests. Martin formula test Muscle mass was estimated using the formula of Martin et al. (1990), which is based on height, forearm girth, mid-thigh girth, maximal calf girth, and corresponding skinfolds. The researcher used standard anthropometric tools including skinfold caliper, a girth tape, a marker, and a calculator. The calculation requires six measurements: heights, mid-thigh girth, calf girth, forearm girth, mid-thigh skinfold, & calf skinfold. Because girth values include subcutaneous fat, the skinfold measurement was

2026 (Mayo), Retos, 78, 1021-1032 ISSN: 1579-1726, eISSN: 1988-2041 https://revistaretos.org/index.php/retos 1024 used to correct for fat tissue. Height & girths were recorded in centimeters, & skinfolds in millimeters. Each measurement taken three times & the average were used for analysis. Results The equation to use is as follows: Muscle mass (g) = H (0.0553CTG² + 0.0987FG² + 0.0331CCG²) – 2445 CTG = TG – ϖ (mid-thigh skinfold/10) CCG = CG – ϖ (calf skinfold/10) Where: H = height, FG = forearm girth, CG = calf girth, CCG = corrected calf girth, TG = mid-thigh girth, CTG = corrected mid-thigh girth, ϖ = Pi (3.14159). 8oom time-trial test procedures: The 800m run test can be considered an anaerobic capacity test that is a bit long, or an aerobic fitness test that is a bit short. To undertake this test researcher requires oval or 400m running track, stopwatch, recording sheets. To start, all participants line up behind the starting line. On the command ‘go,’ the clock will start, and they will begin running at their own pace. Cheering or calling out the elapsed time is also permitted to encourage the participants to achieve their best time (Wood, 2008). 1500 m Time-Trial test procedures: Testing and measurement are the means of collecting information upon which subsequent performance evaluations and decisions are made (Wood, 2008). The 1500-me- ter Predictor Test calculates an athlete's 1500-meter time. To conduct this test, researcher requires 400 meters’ track, stopwatch and assistant. The athlete is required to complete two sets consisting of: 400 m run 45 s recoveries; 800 m run, 90 s recoveries; and 300 m run, followed by 3 minutes of recovery between sets. Training protocol According to Stricker et al. (2020), beginners should initiate RT with 1–2 sets of 8–12 repetitions at ≤30% RM to develop proper technique with minimal fatigue. As proficiency improves, training can pro- gress to 2–4 sets at ≤60% RM. Programs should prioritize large muscle groups and multi-joint exercises, performed 2–3 times per week on nonconsecutive days for 20–30 minutes. In line with Miller, Cheatham and Patel (2010), each training session has

1–2 sets of 8–12 repetitions at ≤30% RM to develop proper technique with minimal fatigue. As proficiency improves, training can pro- gress to 2–4 sets at ≤60% RM. Programs should prioritize large muscle groups and multi-joint exercises, performed 2–3 times per week on nonconsecutive days for 20–30 minutes. In line with Miller, Cheatham and Patel (2010), each training session has 60-minute session included a 15-minute warm-up (5 minutes of general warm-up followed by 10 minutes of activity-specific preparation) and a 5-minute cool-down with stretching. All sessions were coach-supervised, integrated into regular training, and scheduled at least 48 hours apart to ensure safety and adequate recovery. The LRT program lasted 12 weeks, with three sessions per week. Additional two weeks were dedicated to familiarization with the exercises. At the end of this period, the repetition maximum (RM) for each exercise was assessed, followed by pre-test measurements. Training intensity started at 30% of RM and progressed to 50% by week three (Table 1). At the end of week four, 1RM was reassessed, and the new values guided the remaining weeks, with intensity increasing progressively from 60% to 70% of 1RM. Post-test measurements were taken 48 hours after the final session (Afonso et al., 2021). The WURT program matched LRT in duration, session frequency, exercises, & timing. The primary dif- ference was the variation of volume & intensity each session, producing an undulating progression across the training weeks. Like LRT, RM was reassessed after the familiarization period, and post-test measurements were collected 48 hours after completing the 12-week protocol (Afonso et al., 2021). Table 1. Training Protocol for Linear and Weekly Undulating Resistance Training Groups Week Linear resistance training group Weekly undulating resistance training group Intensity(%RM) Sets/ recovery Reps Intensity (%RM) Sets/ recovery Reps 1–2 30-45% 2-3/ 4-5 min 5-8 40-70% 1-3/ 1-5 min 5-8/12-14 3–4 50-55% 2/ 2-3 min 6-12 60-65% 2/ 1-2 min 10-14 5–6 60-65% 2/ 1-2 min 10-14 50-55% 2/ 2-3 min 6-12 7–8 70-75% 1-2/ 30-60 sec 12-16 45-60% 2-3/ 2-5 min 5-12 9–10 80-85% 1-2/ 30-60 sec 14-16 70-75% 1-2/ 30-60 sec 12-16 11–12 90-95% 1-2/ 30-60

Reps 1–2 30-45% 2-3/ 4-5 min 5-8 40-70% 1-3/ 1-5 min 5-8/12-14 3–4 50-55% 2/ 2-3 min 6-12 60-65% 2/ 1-2 min 10-14 5–6 60-65% 2/ 1-2 min 10-14 50-55% 2/ 2-3 min 6-12 7–8 70-75% 1-2/ 30-60 sec 12-16 45-60% 2-3/ 2-5 min 5-12 9–10 80-85% 1-2/ 30-60 sec 14-16 70-75% 1-2/ 30-60 sec 12-16 11–12 90-95% 1-2/ 30-60 sec 2-5 85-90% 1-2/ 30-60 sec 2-5

2026 (Mayo), Retos, 78, 1021-1032 ISSN: 1579-1726, eISSN: 1988-2041 https://revistaretos.org/index.php/retos 1025 Note. Min: minutes; RM: repetition maximum; Reps: repetition; Sec: second; LRT: leaner resistance training; WURT: weekly undulating resistance training. Data analysis All variables were shown to exhibit a normal distribution using Shapiro-Wilk’s test. Levene’s test as- sessed homogeneity of variance. Effect size was measured using partial eta squared (η²), with values of 0.01, 0.06, and 0.14 indicating small, medium, and large effects, respectively, according to Lakens (2013). As eta squared is not provided directly in t-test outputs, it was calculated manually using the t- value and sample sizes. Descriptive values are presented as means ± standard deviations (SD). The dif- ferences between pre- & post-training and between the intervention groups were compared using t-test (student’s t-test and independent samples t-test, respectively) (Sentie, 2025). All of these analyses were performed in IBM SPSS Statistics (Version 26 for Windows; IBM, Armonk, NY, USA) with a threshold significance level set at P <0.05. Results Participants (n=36) had an average age of 19.39 ± 1.52 years, training age of 2.6 ± 0.60 years, weight of 51.07 ± 5.39 kg, height of 1.65 ± 0.08 m, & BMI of 18.75 ± 1.39 kg/m². Baseline test results were analyzed to compare the MD between the LRT and WURT groups. No significant differences were found in mean age (19.44 ± 1.58 vs. 19.33 ± 1.5 years, MD = 0.111, p =0.83), training age (2.56 ± 0.62 vs. 2.67 ± 0.59 years, MD = –0.111, p =0.59), body weight (51.09 ± 5.4 vs. 51.06 ± 5.53 kg, MD = 0.03, p =0.98), height (1.64 ± 0.09 vs. 1.66 ± 0.08 m, MD = –0.02, p=0.57), & BMI (18.94 ± 1.51 vs. 18.56 ± 1.28 kg/m², MD = 0.38, p=0.42) between intervention groups (LRT and WURT). Effect of linear & weekly undulating resistance training on Muscle mass and running per- formance (8oom TT & 15oom TT) Table 2. Pre- & Post-Test Result Comparisons for Linear & Weekly Undulating Resistance Training Group Variables LRT Group (n=18) WURT Group (n=18) Mean ± Std. Deviation Mean ± Std. Deviation Muscle mass

This study compares two resistance training methods on athletic performance.