In the pursuit of optimal performance, athletes typically participate in a variety of training methods designed to reduce injury and enhance athletic outcomes. Backward running (BR), which has been used to prepare athletes for competition demands (5,32) and as a return to play protocol for injured athletes (24), is one such method. Although a formal definition of BR has yet to be adopted in the scientific community, Uthoff, Oliver, Cronin, Harrison, and Winwood (58) defined BR as “any form of locomotion in a reverse direction where movement is accomplished through a single leg of support throughout foot-ground contact and both feet simultaneously in the air between contralateral foot strikes.” Backward running is different than other forms of backward locomotion such as backward pedalling—the crouched technique often used by defensive backs in American football. Figure 1 provides an example of different backward running gaits. Backward running, for the purpose of this article, more closely emulates forward running (FR) with an upright running posture and contralateral arm swing (60). Figure 2 highlights the technical models adopted over the gait cycle during maximum velocity BR and FR.
A recent review examining the acute and trained responses to BR found that running in reverse had a unique energetic and biomechanical profile useful for enhancing a range of athletic performance measures from running economy to change of direction ability (58). Given the recent developments in literature pertaining to the use of BR for athletic enhancement in both youth and adult populations (56,58–60), this article aims to examine why BR has made a resurgence in the literature and provides practical recommendations for how to integrate BR into athlete training programs.
THE WHY: THE ROLE OF BACKWARD RUNNING IN SPORTS AND TRAINING
Backward running is a form of locomotion which, like FR, is used by athletes in most overground sports (6,37). Running itself is defined as a form of gait that is characterized by a single support phase and double flight phase (8). Although both directions of locomotion are believed to be generated by the same neural pathways (25), BR is unique in that visual feedback is altered and greater demands are placed on alternative sensory systems to maintain positional awareness (25,34). The ability to run backward with an altered visual orientation may give athletes a tactical advantage. For example, being able to run backward at high speeds while maintaining a view of the ball or opposition will allow athletes to make more informed decisions (4). This is particularly important when you consider rugby league players BR an average of 3.6–5.4 m after each tackle (48), BR comprises of 3.4% of total distance covered by professional handball athletes during competition (36), and that elite soccer players cover 3–4% of the entire match distance running backward (3,37).
Outside of game play, BR is commonly included in injury prevention and rehabilitation programs (20,24,27). Backward running is also part of many warm-up protocols that prepare the body for specific movements encountered during the sport and enhance athletic performance (39,46,49,65). In addition, BR has been used as a training tool by coaches to increase qualities of aerobic and anaerobic fitness (40,55), vertical jump height (60), change of direction performance (53,56), and sprinting speed (60). It is important that strength and conditioning professionals understand the body's immediate response to BR and the efficacy of training using this modality, so they can better integrate BR in their practice.
ACUTE RESPONSES TO BACKWARD RUNNING
The immediate physiological or biomechanical adaptations to a stimulus provide a snapshot of the potential long-term effects of an exercise. A number of researchers have studied the energetic, kinematic, and kinetic responses to BR, and compared these with FR. Table 1 provides an overview of the acute responses of BR versus FR at similar relative intensities (i.e., BR at ∼70% of FR speed).
As identified in Table 1, researchers have shown that, at the same relative, or matched, intensity (e.g., maximal velocity or BR at 70% of FR velocity), BR is characterized by greater energetic expenditure (15,17,63), lower running speed (4,59) and overall joint ROM (4,18), unique step kinematic interactions (12,18,62), decreased lower-limb compliance (9,10), reliance on isometric and concentric muscle actions (9,10), greater leg muscle activation (18,51), reduced knee joint stress (19,45), modified ratios of braking and propulsive forces (9,10), and greater rates of force development (63) compared with FR. The unique physiological and biomechanical responses to BR indicate that it may provide a different training stimulus to FR, which may serve to reduce injury risk, enhance metabolic functions, and improve muscular capabilities. Furthermore, including BR into a program while following the principles of variability, specificity, and overload may serve as a conjugate method to combat training monotony.
BACKWARD RUNNING AS AN INJURY RESISTANCE TOOL
The primary goal of any strength and conditioning program is to reduce the likelihood of injury and ensure athletes are healthy for competition (29,54). Along these lines, BR is included in programs specifically designed to minimize injury risk in athletes of all ages (14,20,49). In particular, warm-ups such as FIFA 11+ (31), FIFA 11+ kids (46), HarmonKnee (27), Performance Enhancement and Injury Prevention (20), and Dynamic Warm-up (2) provide exercise variation and progression to reduce the likelihood of sustaining an injury to the knee and ankle ligaments and thigh muscle strains. Warm-up programs including BR have been found to be particularly beneficial for reducing the amount of overuse and severe injuries in athletes between 13 and 20 years of age (20,27,49).
One rationale for including BR early into a warm-up protocol or preseason program is that reductions in joint ROM of the lower limbs (15) while concomitantly adopting an increased stride frequency will reduce the load on lower-body joints (19,23,45). Chronic reductions in lower-limb joint loading may lead to fewer impact-related musculoskeletal injuries. Furthermore, functional reversal of the leg muscles during BR may provide a mean to reduce stress on the posterior chain and reduce repetitive strain injuries (24). This is particularly important in adolescent athletes who are undergoing rapid hormonal and anthropometric changes where their training increases (29), and they must be able to withstand greater forces (35). Coaches may use BR to improve neural and musculotendinous properties of the lower limbs, while adding variety into a program, and attenuate stress placed on the lower limbs.
BACKWARD RUNNING TO ENHANCE MUSCULAR FUNCTIONS
The nature of athletic tasks determines the reliance on components of musculotendinous functioning. Forward running is often understood in terms of a spring-mass model by which muscles are stretched, and eccentric energy is absorbed and converted to propulsive energy through the tendons and connective tissue (7). Alternatively, BR more closely reflects a pendulum action whereby the muscle and tendon length remains relatively constant upon foot-ground contact, and propulsion is produced primarily through a contractile movement (9,10). Concentric-dominant exercises offer a potentially useful training tool, which may negate or mitigate muscle damage, soreness, fatigue, and inflammation associated with eccentric movements (26). The specific isometric and concentric nature of BR has led clinicians and coaches to use BR as a tool to return players back from injury (24,33) and increase quadriceps strength (18,53) while concomitantly reducing knee joint stress (19,45).
Training BR leads to preferential adaptations in movements, which are dependent on the concentric muscle functioning of the quadriceps, such as vertical countermovement jumps and early accelerated sprinting (60). Adolescent athletes around the time of their growth spurt seem to respond particularly well to BR, where their vertical jump ability has been found to increase by 9.9% (ES = 0.83) and their sprint performance over 0–10 and 0–20 m improved by 7.5% (ES = 1.56) and 5.0% (ES = 1.04), respectively, following training twice a week for 8 weeks. The dynamic leg extension action produced during BR may provide a method to train the anterior muscles of the thigh and hip to produce concentric force at relatively high velocities. Therefore, if the demands of a sport depend on acceleration ability or an athlete needs to improve their ability to produce concentric force, BR may provide a means to develop this component of athletic performance.
In addition to linear sprinting, BR has also been identified as a method to increase vertical leg stiffness (60) and change of direction ability in athletes (56). Uthoff et al. (60) found that 8 weeks of BR training improved vertical leg stiffness similar to equal volume and intensity FR training in a group of high-school male athletes (10.6 and 12.4%, respectively). In addition, Terblanche and Venter (56) concluded that netball-specific training using BR was more beneficial than equivalent FR training, with 505 agility, Agility T, and ladder tests improving between 3.4 and 10.3% (ES = 0.85–1.44) in a group of highly trained female netball athletes. These findings indicate that BR is not only a contractile stimulus but can promote positive adaptations to fast stretch-shortening cycle tasks (57) and movements which have a large eccentric component (11) for athletes of varying ages and experience levels.
BACKWARD RUNNING AS A METABOLIC STIMULUS
From an energetic standpoint, BR places a greater metabolic demand on individuals than FR at similar relative intensities (1,17,63). Essentially, this means that an athlete can perform BR at the same absolute volume and relative intensity as FR yet expect to expend approximately 28% more energy (12). Therefore, when repeatedly exposed to BR training, athletes are able to improve their running economy between 2.5 and 33% (40,55) while also improving their peak oxygen consumption capabilities by 5.3% (55). The exact mechanisms underpinning these adaptations are ambiguous and require further exploration; however, the variability of performing a novel athletic task (34) along with increased demand on the concentric functioning of muscles have been postulated to influence the specific metabolic responses to BR (9,10). Practically, this means that athletes who are either injured, or under a high training load, can include BR into their program to stimulate metabolic responses similar to FR with fewer repetitions.
THE HOW: INTEGRATED PROGRAMMING
Given the highlighted research into why a strength and conditioning coach may wish to implement BR as an acute or chronic training stimulus for athletes, it is important to understand how BR may be integrated as an effective training practice. To minimize the effects of accommodation, subsequent training stagnation, the principle of variation should be applied (64). Appropriate variation is important to stimulate continued adaptations over multiple training phases (28) and is concerned with appropriate manipulation in exercise selection, speed, volume, and intensity (52). Similarly, when an athlete is learning a new skill, there needs to be a sequence of progressions that allow them to become habituated with the movement and master the basics at lower intensities before advancing to higher intensity or more complex movements (40). Therefore, we recommend that coaches use BR as a method to vary exercise selection, and it should be progressed in order of running speed, absolute and relative volume, and finally, by adding external resistance. The following sections provide recommendations for how to progressively integrate different modes of BR into an athlete's training program. Please note that while it is important to consider exercise selection, speed, volume, and appropriate resistance for both purposes of injury rehabilitation and athletic performance, the following program suggestions are focused on healthy, uninjured athletes. However, we recommend any coach wishing to use BR as a return to play protocol to adhere to the principle of variation and confer with their physiotherapist or team physician for programming considerations.
PHASE 1: PROGRESS BACKWARD RUNNING SPEED
Because of the increased coordination demands (34) and modifications to sensory inputs during BR (25,34), running backward at speed should be introduced gradually into an athlete's training program and, where possible, be performed on soft surfaces such as grass. This is especially important if an athlete is young or has limited training history with BR because they may have more variable coordination ability (16,44). The program presented in this section is designed to habituate an athlete to high-speed BR at commonly used speed ranges of 40–55, 60–75, and +90% of maximum BR velocity (59).
An introductory program such as that detailed in Table 2 may be conducted over a microcycle of 2 weeks with training conducted biweekly. As running speed is increased, special attention should be given to the technical running model using ability appropriate cues similar to those found in Table 3 and feedback on running times. As speed is progressed, the amount of feedback on running times may be reduced to allow athletes to autoregulate their speeds. Based on our previous work (59), it takes male athletes between the ages of 15–18 years of age approximately 3 sessions to become accustomed to self-selecting BR and FR speeds consistently between sessions. Overload in this manner serves to both enhance proficiency and confidence in performing high-speed BR and refine autoregulatory capabilities of athletes.
PHASE 2: PROGRESS BACKWARD RUNNING VOLUME
Once an athlete is familiar with BR at high intensities and can accurately self-select running speeds with minimal to no external feedback, the second phase is to overload BR by modifying either relative or total running volume. Respectively, this means a speed or strength coach can either manipulate the distance travelled at each intensity or the sum of all intensities for total session load. Based on current evidence from both youth and adult research, free, or unresisted, sprint programs should be performed 2–3 times a week for >6 weeks and comprise of approximately 16 runs over ∼15–30 m per session (38,47). These programming guidelines have also been found to lead to positive adaptations after BR (60). Therefore, the training program presented in this section is designed to improve performance and lower-body stretch-shorten cycle function by progressively increasing both forms of volume (60).
Table 4 exemplifies how an 8-week program can be structured during a transition from the general preparatory phase into the specific preparatory phase with an emphasis on developing speed strength. To standardize the program, lower intensity runs are performed before higher intensities. Volume is progressed first by increasing the number of moderate and fast repetitions over the course of the first 4 weeks while maintaining the same total session volume. Second, using a similar relative loading scheme to the first 4 weeks, running distance is increased by 5 meters for each run, which leads to an increase in total session volume for weeks 5–8. Understanding how BR can be progressed using volume manipulation is useful to strength and conditioning professionals and provides a foundation for adding external load to BR in the form of resisted runs.
PHASE 3: PROGRESS BACKWARD RUNNING USING RESISTANCE
Once an athlete has undergone training phases progressing BR speed and volume, external load can be added in the form of resisted sled towing. Resisted sled towing is a form of unilateral strength training (30), which adheres to the principle of specificity to improve sprinting performance and lower-body power (13,41). Inclusion of unilateral movements is essential given that when athletes perform linear running or change of direction movements, they will predominantly be in a single-leg support during the action (50). Furthermore, variable unilateral multidirectional movements have been shown to improve change of direction ability and multidirectional jumping ability compared with traditional bilateral exercises (21). Therefore, integrating backward sled towing into an athlete's training program is recommended as a means to aid metabolic and neuromuscular functioning (43,61).
The program in Table 5 demonstrates how an 8-week resisted BR program can be structured during the transition from a specific preparatory phase into a precompetition phase with an emphasis on developing strength-speed for accelerated sprinting. The program follows the recommendations that resisted sprint training focused on acceleration performance should be conducted 2–3 times per week for >6 weeks with loads >20% body mass (41). The use of daily undulated loading is used to add novelty and variability to the program (22), whereas the principle of progressive overload is adhered to by increasing resistance each week. The concentric muscle demands of sled towing (43) in combination with BR provide a method to strengthen contractile muscle function.
BACKWARD RUNNING AS PART OF A TOTAL PERFORMANCE PLAN
Although the preceding programs have been recommended for improving running, jumping, and hopping performance in athletes (60), by no means are they the only way to integrate BR into an athlete's training program. By understanding the underpinning mechanisms of BR, an informed coach/clinician can adapt the programs any number of ways to meet the demands of the sport or requirements of the athlete. Similar to any other training method, BR should not be performed in isolation and instead as part of a wider strength and conditioning program that includes a range of training modalities. It is therefore recommended that strength and conditioning coaches include strength, multidirectional running, and ballistic movements because these combinations will provide concurrent training adaptations to muscle force capabilities, stretch-shortening cycle functioning, and metabolic fitness (42). Furthermore, BR may be implemented into regular warm-ups as a time-effective method to reduce injury and enhance performance, or into a traditional FR sprint program on acceleration days as a conjugate method to increase movement variability. Although further research still needs to be performed to identify the optimal application of BR, when it is included as part of a youth athlete development or sport-specific training program, it may reduce injury risk and promote beneficial adaptations across a wide variety of athletic performance tasks dependent on lower-body power, speed, and metabolic fitness (20,40,56,60).
Given the rigors of sport, coaches are constantly looking for effective training strategies to improve their athletes' performance while concomitantly minimizing joint loading. As evidenced previously, BR could be a means of aerobic, anaerobic, and neuromuscular training that does not overload tendons and ligaments as much as FR. Importantly, this article is not intended to understate the importance of training FR nor is BR a panacea for injury prevention or athletic performance, but rather a method in a practitioner's toolkit. Similar to other forms of strength and speed training, BR should be practiced and progressed appropriately. Depending on the competence and goals of the athlete and current training phase, different BR modalities may be used to apply the principles of variation, specificity, and overload. Integrating BR as part of a holistic athlete development program may provide a novel stimulus, which brings physiological and physical adaptations that compliment an athlete's ability, serves to increase training variability, and stave off the monotony of traditional training.
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