Impact of strength training in long-distance runners on running performance: a systematic review

complex interaction between physiological, method- ological, mechanical, environmental, and psychological parameters influences its performance. Therefore, this systematic review aimed to evaluate the impact of strength training on long-distance runners on running time. 803 articles were found in the Medline / PubMed Science Direct / Embase / Scielo/ CINAHL/LILACS databases. After applying the exclusion criteria, only five articles were selected for the systematic review. Of the selected studies, the years of publication were between 2014 and 2022, all published in English, 2 in journals with an impact factor. The sample included 166 volunteers, 152 (91.6%) men and 14 (8.4%) women; the average age ranged from 20 to 39. Strength training programs included plyometric, complex, and strength training. The average improvement in running time for the intervention group ranged from 2.5 to 11.6%, and the improvement in time for the control group ranged from 0.07 to 1.3%. The intervention groups that used the plyometric training program obtained the highest average of 11.6% and the lowest average of 1.6% regarding the variation in test time—the results of this systematic review support that a strength training program positively affects long-distance runners’ performance. Keywords: Training, road running, performance, strength training Resumen. El carrera de calle es uno de los deportes más practicados en el mundo, su desempeño está influenciado por una compleja

average of 11.6% and the lowest average of 1.6% regarding the variation in test time—the results of this systematic review support that a strength training program positively affects long-distance runners’ performance. Keywords: Training, road running, performance, strength training Resumen. El carrera de calle es uno de los deportes más practicados en el mundo, su desempeño está influenciado por una compleja interacción entre parámetros fisiológicos, metodológicos y mecánicos, ambientales y psicológicos. Por lo tanto, el objetivo de esta revisión sistemática fue evaluar los impactos del entrenamiento de fuerza aplicado a corredores de larga distancia sobre el tiempo de carrera. Se encontraron 803 artículos en las bases de datos Medline / PubMed Science Direct / Embase / Scielo/ CINAHL/LILACS, luego de aplicar los criterios de exclusión solo se seleccionaron 5 artículos para la revisión sistemática. De los estudios seleccionados, los años de publicación fueron entre 2014 y 2022, todos publicados en inglés, 2 en revistas con factor de impacto. La muestra total estuvo compuesta por 166 voluntarios, 152 (91,6%) hombres y 14 (8,4%) mujeres, la edad promedio osciló entre 20 y 39 años. Los programas de entrenamiento de fuerza incluyeron entrenamiento pliométrico, entrenamiento de fuerza complejo y entrenamiento de fuerza. El porcentaje promedio de mejora en el tiempo de carrera para el grupo de intervención osciló entre el 2,5 y el 11,6% y el porcentaje de mejora en el tiempo para el grupo de control osciló entre el 0,07 y el 1,3%. Los grupos de intervención que utilizaron el programa de entrenamiento pliométrico obtuvieron el promedio más alto de 11,6% y el promedio más bajo de 1,6% en cuanto a la variación del tiempo de prueba. Los resultados de esta revisión sistemática respaldan que un programa de entrenamiento de fuerza genera efectos positivos en el rendimiento de los corredores de larga distância. Palabras-clave: Entrenamiento, carrera de calle, rendimento, entrenamiento de fuerza. Fecha recepción: 14-03-24. Fecha de aceptación: 06-06-24 Alexandre Fernandes Machado xdmachado@gmail.com Introduction Street running is one of the most practiced sports worldwide (de Oliveira & Machado, 2007), both at a rec- reational and competitive level (Martin et al., 2019). VO 2

positivos en el rendimiento de los corredores de larga distância. Palabras-clave: Entrenamiento, carrera de calle, rendimento, entrenamiento de fuerza. Fecha recepción: 14-03-24. Fecha de aceptación: 06-06-24 Alexandre Fernandes Machado xdmachado@gmail.com Introduction Street running is one of the most practiced sports worldwide (de Oliveira & Machado, 2007), both at a rec- reational and competitive level (Martin et al., 2019). VO 2 is the variable that best expresses the functionality of the cardiorespiratory system during physical exercise (Nunes et al., 2019), representing the integration between the respiratory, circulatory, and muscular systems, used as a control, prescription, and performance parameter. run- ning training (Balsalobre-Fernandes et al., 2016). Associated with this variable, running economy, which is characterized as oxygen consumption at a pre-determined

2024, Retos, 58, 76-84 © Copyright: Federación Española de Asociaciones de Docentes de Educación Física (FEADEF) ISSN: Edición impresa: 1579-1726. Edición Web: 1988-2041 (https://recyt.fecyt.es/index.php/retos/index) -77- Retos, número 58, 2024 (septiembre) submaximal speed (Roschel et al., 2015) and aerobic en- durance, explain up to 72% of the performance achieved by athletes (Berryman et al., 2018), which together with bio- mechanical and anthropometric factors, muscle fiber typol- ogy, age, and sex, are responsible for the variability of re- sults in running economy (Balsalobre-Fernandes et al., 2016). Given this scenario, the physiological and metabolic ad- aptations that occur in response to training have been widely investigated by researchers (Martin et al., 2019). The interaction between the neural and muscular sys- tems is fundamental for a better-running economy and per- formance (Saunders et al., 2006; Bonacci et al., 2009 ). The last decades have provided evidence that the development of the neuromuscular system is essential for the develop- ment of muscular strength (Bertuzzi et al., 2013; Roschel et al., 2015), reducing the incidence of injury risk (Abal, Soidán, Giráldez, 2013; Andreu, 2022), increased move- ment economy (Paavolainen et al., 1999; Roschel et al., 2015) and improved running performance (Ramírez- Campillo et al., 2014; Machado et al., 2019; Filipa et al., 2022). The improvement in running economy is a consequence of the intervention of muscular strength training ( Støren et al., 2008; Bertuzzi et al., 2013; Llanos-Lagos et al., 2024), which has been attributed to the increased coordination of the lower limbs and muscle coactivation, reducing contact time with the ground (Paavolainen et al., 1999). However, even with a significant amount of evidence supporting the use of muscular strength training to improve running economy, coaches and athletes explore little of its use in general (Karp, 2007; Filipa et al., 2022), in addition to not carrying out an analysis of the performance variable in the time trial race (Bonacci et al., 2009; Balsalobre-Fer- nandes et al., 2016; Berryman et al., 2018; Llanos-Lagos et al., 2024). Previous systematic review studies (Balsalobre-Fer- nandes et al., 2016; Berryman et al., 2018; Llanos-Lagos et al., 2024) address the description of

2007; Filipa et al., 2022), in addition to not carrying out an analysis of the performance variable in the time trial race (Bonacci et al., 2009; Balsalobre-Fer- nandes et al., 2016; Berryman et al., 2018; Llanos-Lagos et al., 2024). Previous systematic review studies (Balsalobre-Fer- nandes et al., 2016; Berryman et al., 2018; Llanos-Lagos et al., 2024) address the description of training programs and the impact of these programs on the variables analyzed, such as strength, power, running economy and VO2 max, and from this point a conclusion based on that the improvement of the variables will lead to an improvement in the race, that is, that the total race time will be shorter. This opens up a gap as to how much improvement in running strength training programs can provide, as well as which model of strength training program generates the most significant amplitude of improvement in running time, questions that have not yet been answered by previ- ous systematic review research. Based on the previous statements, the objective of the present study was to describe, through a systematic review, muscular strength training programs and their respective impacts on running time in long-distance runners. An analysis of running training programs (training dis- tribution, volume, and intensity) was carried out, as these variables can influence the results. The hypothesis is that athletes who do muscular strength training associated with running training would have better running performance when compared to athletes who only train running. Materials and methods The present systematic review (SR) on muscular strength training in long-distance runners (TFCLD) was prepared following the criteria of the PRISMA methodol- ogy (Moher et al., 2015). The protocol was registered with the National Institute for Health Research – International Prospective Register of Systematic Review PROSPERO (nº CRD42023422332). The PICOT method was used to pre- pare the guiding question. P – Participants (runners); I – intervention (pre-intervention results); C – comparison (post-intervention result); O – outcome (improvement in race time) and T – intervention time (training program equal to or greater than four weeks). The data search was carried out in the following data-

Review PROSPERO (nº CRD42023422332). The PICOT method was used to pre- pare the guiding question. P – Participants (runners); I – intervention (pre-intervention results); C – comparison (post-intervention result); O – outcome (improvement in race time) and T – intervention time (training program equal to or greater than four weeks). The data search was carried out in the following data- bases, Medline / PubMed Science Direct / Embase / Sci- elo/ CINAHL/LILACS, for potentially eligible studies published in English, Spanish, and Portuguese. The follow- ing descriptors were used: The terms “resistance training,” “running,” and “marathon running” were used in the DeCs and MeSh Terms, and the term “Long-distance runners.” The following search terms were used: “resistance training” AND “running,” “marathon running” AND “Long-distance runners,” “resistance training” AND “Long-distance run- ners.” The search was carried out between May 15th and 25th, 2023. For the eligibility criteria of the articles, the following were included as Inclusion criteria: studies published be- tween January 2010 and April 2023, which investigated the influence of muscular strength training on the performance of long-distance runners in at least one variable (running performance), after the intervention period of the training program. Studies should have a control group or at least one outcome group (for example, another intervention pro- gram). As exclusion criteria, studies with an intervention pe- riod of less than four weeks, studies involving animals, course completion works, dissertations, theses, editorials, letters to the editor, case study articles, narrative, system- atic and meta-analysis review articles, or articles that did not have a comparative group or control group in the ex- periment. Two reviewers (AFM and MRN) selected the studies by searching the databases. The search results were imported into Rayyan software (Qatar Computing Research Institute, Qatar Foundation, Doha) by a third reviewer (FRS), who was responsible for managing the program and ensuring an independent review by the two reviewers. The reviewers (AFM and MRN) independently assessed the methodological quality of the selected studies using the Jadad score (Jadad, 1996) and the risk of bias (RoB-2) using the Cochrane tool (Whiting et al., 2016). The two review- ers

Doha) by a third reviewer (FRS), who was responsible for managing the program and ensuring an independent review by the two reviewers. The reviewers (AFM and MRN) independently assessed the methodological quality of the selected studies using the Jadad score (Jadad, 1996) and the risk of bias (RoB-2) using the Cochrane tool (Whiting et al., 2016). The two review- ers discussed disagreements between the reviewers until a

2024, Retos, 58, 76-84 © Copyright: Federación Española de Asociaciones de Docentes de Educación Física (FEADEF) ISSN: Edición impresa: 1579-1726. Edición Web: 1988-2041 (https://recyt.fecyt.es/index.php/retos/index) -78- Retos, número 58, 2024 (septiembre) consensus was reached. When necessary, a fourth reviewer (JSN) was requested to reach a consensus or arbitration agreement between the reviewers. The Jadad score and the final score vary from 0 to 5 points. Scores equal to or less than two are considered low quality, and scores similar to or greater than three are con- sidered high quality (Jadad, 1996). The Risk of Bias Analysis Tool (RoB-2) allows investi- gators to assign a “high,” “low,” or “unclear” risk quality score based on seven factors that may bias the effect of the bias program. Intervention is either overestimated or un- derestimated in individual studies (Whiting et al., 2016). Results After applying the eligibility criteria, five articles were included in the present systematic review (Figure 1). Among the studies selected for the systematic review, in 5 of them, it was identified that the years of publication were between 2014 and 2022, all published in English, 2 of them in journals with an impact factor, and three publica- tions (Li et al., 2019, Machado et al., 2019, Filipa et al., 2022), in a journal without impact factor (Table 1) Figure 1. Phases of the methodology for selecting articles included in the system- atic review. Table 1. General characteristics of the selected studies Authors Language Journal IF Ramírez-Campillo et al., 2014 English Journal of Strength and Conditioning Research 4,415 Damasceno et al., 2015 English Eur J App Physiol 3,346 Li et al., 2019 English PeerJ - Machado et al., 2019 English Journal of Physical Education and Sport - Filipa et al., 2022 English Scand J Med Sct Sports - Table 2 and Figure 2 show the methodological quality using the Jadad scale and the RoB-2 assessment, respec- tively. The average score obtained on the Jadad quality scale (table 2) was 4.2 0.4 points for the five studies considered high quality. Regarding the double blinding item, the eval- uation was not carried out due to

J Med Sct Sports - Table 2 and Figure 2 show the methodological quality using the Jadad scale and the RoB-2 assessment, respec- tively. The average score obtained on the Jadad quality scale (table 2) was 4.2 0.4 points for the five studies considered high quality. Regarding the double blinding item, the eval- uation was not carried out due to the studies being about exercises; therefore, there was no blinding of the volun- teers . Table 2. The methodological quality of the studies according to the Jadad scale. Study Was the study de- scribed as randomized? Was There a Description of Randomization? Were there comparisons and results? Was there a description of the comparisons and results? Was there a description of withdrawals and dropouts? Total Ramírez-Campillo et al., 2014 1 1 1 1 0 4 Damasceno et al., 2015 1 1 1 1 1 5 Li et al., 2019 1 0 1 1 1 4 Machado et al., 2019 1 0 1 1 1 4 Filipa et al., 2022 1 0 1 1 1 4 The studies selected in this systematic review totaled 166 participants (table 3). Among the participants, 152 (91.6%) were men and 14 (8.4%) women. The average age ranged from 20 (Li et al., 2019) to 39 (Machado et al., 2019). The minimum intervention time observed in the se- lected studies was six weeks (Ramírez-Campillo et al., 2014), and the maximum was eight weeks (Damasceno et al., 2015; Li et al., 2019; Machado et al., 2019). The weekly training frequency proposed by the selected studies (table 3) was once a week (Filipa et al., 2022), twice a week (Campillo et al., 2014; Machado et al., 2019), and three times a week (Damasceno et al., 2015; Li et al., 2019).

2024, Retos, 58, 76-84 © Copyright: Federación Española de Asociaciones de Docentes de Educación Física (FEADEF) ISSN: Edición impresa: 1579-1726. Edición Web: 1988-2041 (https://recyt.fecyt.es/index.php/retos/index) -79- Retos, número 58, 2024 (septiembre) The training programs (table 3) used by the researchers addressed training methods characterized as Plyometric training (Ramírez-Campillo et al., 2014; Machado et al., 2019; Filipa et al., 2022), Muscle strength training (Dama- sceno et al., 2015) and complex strength training and strength training (Li et al., 2019). Figure 2. Cochrane risk of bias for individual studies (Roob-2 evaluation). In- cluded studies falling under low risk (green), unclear risk (yellow), and high risk (red) are shown for each of the seven. Table 3. General characteristics of the studies Reference Sample Groups - Training program Results Conclusion Ramírez- Campillo et al., 2014 n=36 Mean age 22 years Group TG (n=18) Male (n=10) Female (n=8) Group CG (n=18) Male (n=12) Female (n=6) Group Training (TG) – 6 weeks – Twice a week plyometric train- ing plus a session of running training weekly volume of 64.7 km. Program - Twice a week, plyometric training sessions last 30 minutes, with a minimum break of 40 hours between plyometric sessions. Warm-up (5 min submaximal running, 20 submaximal vertical jumps, and ten submaximal longitudinal jumps), the cen- tral part of the session consisted of 60 drop jumps, 2 x 10 jumps (20 cm), 2 x 10 jumps (40 cm) and 2 x 10 jumps (60 cm). Running training, athletes were instructed to maintain their weekly running training routine. Group Control (CG) – 6 weeks –sessions of running training weekly volume of 70 km. Program - Running training: athletes were instructed to maintain their weekly running training routine. There were no significant differences be- tween men and women in the percentage change in any test variables before and af- ter training. Significant reduction in 2.4 km race times (p < 0.01) and CMJA explosive power jumping performance (p < 0.001) in the TG group between the pre and post-intervention moments. There was also a significant difference in the 2.4 km race time (p < 0.05) and the CMJA

in the percentage change in any test variables before and af- ter training. Significant reduction in 2.4 km race times (p < 0.01) and CMJA explosive power jumping performance (p < 0.001) in the TG group between the pre and post-intervention moments. There was also a significant difference in the 2.4 km race time (p < 0.05) and the CMJA explosive power jump perfor- mance (p < 0.01) compared to the group CG. Volunteers achieved sig- nificant adaptations with short-duration, low-vol- ume, moderate-fre- quency plyometric training. The results showed that explosive strength and running endurance training can be performed in the same training session, which can facilitate in- corporating this method into the training pro- gram schedule. Dama- sceno et al., 2015 n=18 Male (n=18) Group STG (n=9) Mean age 34 years Group CG (n=9) Mean age 32 years Group Resistance Training (STG) – 8 weeks – Twice a week, a re- sistance and running training session. Program - Exercises (half squat, leg press, plantar flexion, and knee extension) 3 sets of 8 – 10RM for the first two weeks, three sets of 6-8RM (weeks 3 and 4), three sets of 4-6RM (weeks 5 and 6) and two sets of 3-5RM on the last weeks. The remaining interval between sets was 3 minutes. Group Control (CG) – 8 weeks - Running training. Program - Athletes were instructed to maintain their weekly running training routine. No significant differences (p > 0.05) were observed between pre and post-in- tervention for both groups in the varia- bles: fat percentage, body mass, and vol- ume of weekly running training. There were also no significant differences (p > 0.05) between the groups (STG and CG) for the variables VO2 max and RE. A significant difference (p < 0.05) was observed between the groups for peak treadmill speed (PTS) and 1RM, in which the TSG group showed a more significant percentage variation concerning the CG. In the 10K time trial race, after the train- ing period, the STG improved its execu- tion time by 2.5%, a value significantly higher than that found in the CG (p

The study reviews strength training effects on running performance in long-distance runners.