Factors Affecting Training and Physical Performance in Recreational Endurance Runners

nce running has become an immensely popular sporting activity, with millions of recreational runners around the world. Despite the great popularity of endurance running as a recreational activity during leisure time, there is no consensus on the best practice for recreational runners to e ectively train to reach their individual objectives and improve physical performance in a healthy manner. Moreover, there are lots of anecdotal data without scienti c support, while most scienti c evidence on endurance running was developed from studies observing both recreational and professional athletes of di erent levels. Further, the transference of all this information to only recreational runners is di cult due to di erences in the genetic predisposition for endurance running, the time available for training, and physical, psychological, and physiological characteristics. Therefore, the aim of this review is to present a selection of scienti c evidence regarding endurance running to provide training guidelines to be used by recreational runners and their coaches. The review will focus on some key aspects of the training process, such as periodization, training methods and monitoring, performance prediction, running technique, and prevention and management of injuries associated with endurance running. Keywords: endurance exercise; sports performance; sports training; running technique; exercise intensity; amateur runner

running to provide training guidelines to be used by recreational runners and their coaches. The review will focus on some key aspects of the training process, such as periodization, training methods and monitoring, performance prediction, running technique, and prevention and management of injuries associated with endurance running. Keywords: endurance exercise; sports performance; sports training; running technique; exercise intensity; amateur runner 1. Introduction Endurance running has been suggested to be a biological trait associated with the survival of our species [1,2]. In fact, our species could be considered one of the best examples of natural endurance athletes, with neurobiological mechanisms reinforcing the search for habitual aerobic exercise, particularly running [3]. Therefore, it is easy to understand why millions of people compete every weekend in road endurance running races of variable distances, from 5 km to marathon races, around the world [4,5]. Currently, a great number of recreational runners train every day in di erent places. The success of this recreational sport might be attributed to its simplicity and accessibility while favoring health development [6], and the social interactions and leisure experiences that it lends to most people, regardless of level or age. Despite its great popularity, there is no consensus on the best practice when looking for sustained or improved endurance running performance in recreational running while maintaining or enhancing Sports2020,8, 35; doi:10.3390 /sports8030035 /journal/sports

Sports2020,8, 35 2 of 20 health status. However, there are a plethora of anecdotal guidelines without robust scienti c support, including the use of nonvalidated algorithms (e.g., Trainingpeaks—) for training monitoring, the “10% rule” for weekly training load increments, or the use of di erent types of shoes to reduce injury rates. In fact, it is common to see recreational runners imitating training practices similar to those of professional athletes, including completion of high weekly mileage (e.g.,>70 km), which may be behind the high prevalence of some health-related problems [7]. Further, as current scienti c evidence on endurance running was developed from studies observing recreational and professional athletes of very di erent levels (from untrained to elite), it is unclear how recreational runners can e ectively use all the available information. Furthermore, the de nition of a recreational runner is very wide, since we could include in this category any runner who trains and competes regularly during leisure time independently of the performance level (from novice to well-trained athletes) and speci c objectives (e.g., enjoyment, health, competition, etc.). However, in contrast to professional athletes, recreational runners have limited schedules to train, which often are adapted to other daily living activities and duties. Moreover, although some ex-professional athletes exist in the recreational runner category, it is expected that most recreational runners do not possess the genetic advantages and the physical, physiological, and psychological traits of professional endurance runners. Therefore, the aim of this review is to present a selection of scienti c evidence regarding recreational runners to identify best practices and to present a starting point for further studies regarding this population. This narrative review will focus, based on our practical experience, on some key aspects, such as periodization, training methods and monitoring, performance prediction, running technique, and prevention and management of injuries associated with endurance running. The information provided here may be useful for recreational runners and their coaches to optimize the process of endurance running training in order to look for better performances in a healthy manner. However, adapting all of this information should be performed on an individual

and monitoring, performance prediction, running technique, and prevention and management of injuries associated with endurance running. The information provided here may be useful for recreational runners and their coaches to optimize the process of endurance running training in order to look for better performances in a healthy manner. However, adapting all of this information should be performed on an individual basis while assuming that some speci c topics could be missing. 2. Training Characteristics of Recreational Endurance Runners The raining characteristics of recreational runners comprise several relevant topics. Therefore, this section reviews information regarding running training methods, strength training for endurance running, training intensity distribution, and training periodization. 2.1. Running Training Methods Training sessions that include continuous exercise performed at both low and high intensity levels and interval training, including sessions of variable intensity, represent the training methods most often used to improve performance in endurance competitive events [8]. Evidence suggests that several forms of training with single use and combination of continuous and interval training methods are e ective to improve performance in recreational endurance runners, especially in investigations where study samples were composed of athletes with less comprehensive training backgrounds. Several studies involving the use of high-intensity interval training (HIIT) observed performance improvements after interventions from four to ten weeks [9–19]. Studies combining the use of continuous submaximal running (CT) and HIIT found further improvements in performance [10,14,16,18]. Of note, some previous studies used sprint interval training (SIT, all-out e orts lasting 20–30 s with long resting periods of 3–5 min), which also generated improvements in performance in 3 and 10 km competitions [10,15,18]. In addition, studies investigating aerobic HIIT (2–4 min at an intensity 100% of the velocity associated to maximum oxygen consumption [vVO2max]) also found improvements in performance in running competitions from 1.5 to 10 km [10–16], while short intervals of HIIT (lasting 20–60 s at a higher intensity than the vVO2max) also exhibited improvements in performance from 1.5 to 10 km [9,12,13,17,18]. All of these previous studies suggested that di erent forms of HIIT, such as SIT, aerobic HIIT, or HIIT with short intervals, could

in performance in running competitions from 1.5 to 10 km [10–16], while short intervals of HIIT (lasting 20–60 s at a higher intensity than the vVO2max) also exhibited improvements in performance from 1.5 to 10 km [9,12,13,17,18]. All of these previous studies suggested that di erent forms of HIIT, such as SIT, aerobic HIIT, or HIIT with short intervals, could be implemented in order to improve the performance of recreational

Sports2020,8, 35 3 of 20 runners. However, a combination of several methods might be the best option to improve adaptation to endurance running training. Aerobic HIIT [11,12,14,15,19] and short-interval HIIT [9,11,12,16] were deemed as e ective exercise modalities to VO2max. However, Denadai et al. [13] did not nd improvements in VO2max after aerobic HIIT in well-trained runners, indicating that short-interval HIIT at very high intensity might be necessary to produce any signi cant e ect in well-trained athletes. On the other hand, aerobic HIIT was found to improve the velocity associated with VO2max (vVO2max; [11,14,15]), thereby implicating improvements in running performance even without the presence of higher VO2max values. Running economy (RE), or the energetic cost of running at a given running speed [20], was found to improve after aerobic HIIT [13,15,19] and SIT-based programs [10,17]. The lack of RE improvement after a short HIIT intervention [12] suggests that improvements in RE are not only related to the type of HIIT used but also to the total volume completed. In this regard, RE improvements were related to improvements of muscle oxidative capacity, as suggested by Denadai et al. [13]. Interestingly, studies comparing training programs with HIIT and CT showed greater improvements in VO2max [18] and vVO2max [19] when using HIIT, and in RE when using CT [19]. Well-structured intervention studies utilizing other types of running methods are scarce in literature (e.g., running on sand, fartlek, etc.), therefore comparing these and other methods through examination of both physiological and performance adaptations is recommended in future studies. Therefore, a combination of methods, including one to two HIIT sessions per week plus more sessions with moderate- and low-intensity CT, is generally recommended to improve performance in recreational runners in a healthy manner. 2.2. Strength Training In addition to running, strength training (ST) was found to improve muscular strength and RE in runners of very di erent levels [21–23], and performance in previously trained runners [23]. Thus, RE improvements were observed following di erent types of ST, such as resistance training [24–27] and plyometric training [28]. In addition, ST might be also e ective

Strength Training In addition to running, strength training (ST) was found to improve muscular strength and RE in runners of very di erent levels [21–23], and performance in previously trained runners [23]. Thus, RE improvements were observed following di erent types of ST, such as resistance training [24–27] and plyometric training [28]. In addition, ST might be also e ective to improve the VO2max of novice recreational runners after 6 to 14 weeks of training [24,28–30], but this nding was not observed in well-trained runners. One study [31] found that neither physiological nor performance bene ts after the use of ST by recreational marathon runners. In this regard, it was suggested that the lack of improvement in RE may be due to the small sample size used and the short intervention completed [31]. However, the lack of physiological and performance improvements generated by ST may also be explained by the reduction in muscle size that happens after a marathon training period in recreational runners, which may be indicative of an adaptation to reduce oxygen consumption at submaximal intensities [32]. Given that ST is expected to be related to some hypertrophic response [33], ST could impair marathon performance, despite the fact that the hypertrophic e ect is attenuated when both ST and endurance training are concurrently performed [34]. In any case, Blagrove and colleagues [21] suggested the use of free-weight multi-joint exercises to improve running performance. Although there is a lack of knowledge regarding the optimal volume and intensity of ST for endurance running performance [21], the inclusion of ST in the training regime of recreational runners might be recommended, even for marathoners. However, ST should be always performed with caution, while looking for the minimum dose to allow signi cant neuromuscular adaptation. 2.3. Training Intensity Distribution According to Seiler and Kjerland, three intensity zones can be delimited by capillary blood lactate responses to steady state continuous running: Zone 1, the low lactate metabolic phase; Zone 2, the lactate accommodation phase, where blood lactate concentration is higher but production and removal rates are in equilibrium; and Zone 3, the lactate accumulation

neuromuscular adaptation. 2.3. Training Intensity Distribution According to Seiler and Kjerland, three intensity zones can be delimited by capillary blood lactate responses to steady state continuous running: Zone 1, the low lactate metabolic phase; Zone 2, the lactate accommodation phase, where blood lactate concentration is higher but production and removal rates are in equilibrium; and Zone 3, the lactate accumulation uneven phase, where blood lactate production exceeds the maximum clearance rate [35]. Polarized training intensity distribution (TID) [35–37] is conducted with a signi cant percentage of time in Zone 1 (75%–80%) and Zone

Sports2020,8, 35 4 of 20 3 (15%–20%) but with little or no time in Zone 2. TID was suggested to be more e cient than other intensity distributions because it is linked to the physical activity pattern of our ancestors [38]. In contrast, Holmberg proposed the traditional “pyramidal” TID, in which most of the training time is conducted in Zone 1 (70%–80%), with the remaining 20%–30% between Zones 2 and 3 [39]. Nonetheless, the literature regarding TID in recreational runners is scarce, therefore it is di cult to ascertain what models might be more bene cial for these runners. Muñoz et al. found that, despite the reduced volume conducted by recreational runners, a polarized model improved their 10 km performance to a greater extent than a threshold model, in which most of the training volume was conducted in Zone 2 [40]. More recently, it was observed that mesocycles with di erent TIDs (polarized vs. HIIT vs. low intensity) resulted in similar improvements and physiological adaptations [41]. However, the low-intensity group, in which most of the training was conducted in Zone 1, induced improvement in RE, which was not observed in the other groups [41]. Finally, another recent study found that polarized TID improved both RE and performance in ultra-endurance runners [42]. The pyramidal and polarized models might be the most recommended forms of training intensity distribution for recreational runners, with di erent considerations depending on competitive distance, time available to train, and time of the season. Meanwhile, “high volume” or “high intensity” approaches seem to fail to reach optimal results, and only very low tness runners seem to bene t from any training approach in the short-term. 2.4. Training Periodization Periodization refers to subdivision of a training plan into shorter periods by means of manipulating volume and intensity over a season. Overall, periodization may be categorized into two main models, namely, block periodization and traditional periodization [43]. Block periodization refers to the subdivision of an annual plan into shorter periods (blocks) of highly speci c and concentrated workloads, whereas traditional or linear periodization involves di erent cycles in which di

periods by means of manipulating volume and intensity over a season. Overall, periodization may be categorized into two main models, namely, block periodization and traditional periodization [43]. Block periodization refers to the subdivision of an annual plan into shorter periods (blocks) of highly speci c and concentrated workloads, whereas traditional or linear periodization involves di erent cycles in which di erent contents are present, but with volume decreasing proportionally to the increase of intensity throughout the season [43]. An alternative traditional periodization is reverse linear periodization, in which the intensity is high and the volume is low in the initial stages of training with the intensity subsequently decreasing and the volume increasing until the end of the training cycle. Research on training periodization in recreational runners is very limited. Bradbury et al. found that linear and reverse linear periodization generated greater improvements in endurance performance, RE, and VO2max in recreational runners than nonperiodized progression of training load [44]. Further, when considering previous studies including the use of HIIT and SIT in recreational runners, it may be suggested that, during the training period, recreational runners should adopt a linear periodization when using HIIT (from high to low volume and from low to high intensity) and a reverse linear periodization when using SIT in order to increase performance [10,14,16,18,45], following the principle of progressive overload. In addition, a general recommendation from our practical experience would be that either block or linear periodization may t better with short or moderate distances (21 km or shorter), while performance in marathons and longer events would probably bene t from reverse periodization. Novice, less experienced runners would also bene t from reverse periodization for 21 km or even 10 km events, in order to be exposed more gradually to peak volume. Further studies are needed to appropriately test the validity of these suggestions. All these ndings suggest that both HIIT and ST should be implemented in the training regime of recreational runners in order to improve performance and its determining factors, such as RE and VO2max. In addition, recreational runners should adopt a polarized TID, although

more gradually to peak volume. Further studies are needed to appropriately test the validity of these suggestions. All these ndings suggest that both HIIT and ST should be implemented in the training regime of recreational runners in order to improve performance and its determining factors, such as RE and VO2max. In addition, recreational runners should adopt a polarized TID, although other models may also be bene cial; however, an important aspect to be considered is that most training time ( 75%) should be completed in Zone 1 for better results. Furthermore, runners should conduct periodized training in order to maximize improvements in performance rather than using nonperiodized training. However, the limited amount of research regarding both TID and training periodization in recreational runners must be acknowledged, therefore, more research regarding these issues would improve the

Sports2020,8, 35 5 of 20 understanding of the underpinning mechanisms involved in the responses of recreational runners to training. In this regard, the time completed in Z1 could be more important than intensity polarization per se, and both testing sessions and competitions should be also included in TID calculations [46]. In addition, the minimum running volume required to improve running performance in recreational runners [47], including the interactions between TID, running, and ST methods [48] and the signi cant in uence of incidental physical activity on running training adaptations [49] still require identi cation. 3. Training Monitoring Recreational runners can monitor their progress through several traditional and modern parameters obtained from training and testing sessions, or competitions. Namely, traditional laboratory evaluations aiming to identify changes in gold standard physiological measures, such as VO2max, anaerobic threshold (AT), and RE, can be monitored in recreational runners alongside professional runners [50]. However, the assessment of these maximal and submaximal variables is not accessible to all runners in terms of cost or availability. Thus, other low-cost and simple evaluations could be used, especially in the eld. From these tests, incremental eld-testing for identi cation of maximum aerobic speed (MAS) could be considered the most practical, as MAS integrates both VO2max and RE into a single parameter and was used regarding endurance running performance from middle- to long-distance races [51]. In addition, incremental-intensity eld-testing could serve to identify the true maximum heart rate (HRmax) [52] and the AT based on HR measures [53], thereby allowing both monitoring of running capacity and training prescription based on these parameters. In this regard, the ve minute running test (T5) could be recommended as a simple and valid alternative for MAS determination in the eld [54], although MAS identi ed using T5 presents greater error and lower reproducibility when compared to MAS recorded using an incremental test [55], probably because of the in uence of pacing strategies in T5. Other eld-testing evaluations include the calculation of critical speed (CS; i.e., the highest sustainable running speed that can be maintained without a continual rise in VO2) from a number of

The review focuses on training methods, performance prediction, and injury management for recreational runners.