The need for strength and power training within endurance running

Thomas Stringwell reflects on the increase in running-related injuries and the need for a greater level of physical preparation to ensure runners are better equipped for the physical demands of endurance running.

The popularity of endurance-based running continues to grow year upon year, with more and more individuals hitting the road and entering road races worldwide¹. The easy accessibility and positive health benefits associated with increased running activity make running an effective form of exercise, with significant reductions in cardiovascular and cancer-related mortality being demonstrated within runners vs non-runners^2-5. However, such an increase in road-running activity has resulted in an increase in reported running-related injuries, with 86% of injured runners continuing to run despite suffering with a current performance- and training-limiting injury^6,7. Furthermore, runners using a self-devised training programme have been shown to be at a higher risk of injury occurrence when compared with runners who follow a structured programme⁷.

These findings demonstrate the need for a greater level of physical preparation in runners, ensuring individuals are better prepared for the physical demands of endurance running. This can be achieved with the successful implementation of an evidence-based, running-specific strength and conditioning programme, which aims to improve the physical qualities needed for optimal running performance while reducing the occurrence of injury. Therefore, the aim of this article is to highlight some of the physical qualities required for running performance and how these qualities can be improved through strength- and power-based training, allowing coaches to better prepare recreational and competitive runners for the physical demands of running performance, while increasing overall robustness to injury.

The need for muscular strength

Whenever an individual walks, runs, jumps or performs any form of locomotion, that individual is applying a force into the floor. The greater the speed at which we are travelling, the greater the force being applied (in conjunction with Newton’s second law of motion: force = mass x acceleration). Likewise, if we rearrange this equation (acceleration = force / mass) it demonstrates that, to improve an individual’s running speed (acceleration), we can either reduce their mass or increase how much force they can apply into the floor when running. Such ground reaction forces are many multiple times bodyweight, with the forces being experienced directly within the Achilles’ tendon reaching up to 12.5 x bodyweight⁸. Therefore, if we can improve a runner’s ability to apply larger ground reaction forces per foot contact, we will not only improve their ability to run quicker, but also to better tolerate the forces being transmitted throughout the body per foot contact. Likewise, the muscles that make locomotion possible have to apply a repeated pulling force on the bones to which they attach (via a tendon) at a distance from the joint centre, allowing the bones to rotate at their relative joints. This turning force or ‘torque’ is what makes locomotion possible. Therefore, if we can improve an individual’s ability to generate greater torque at the ankle plantar flexors (gastrocnemius and soleus), knee extensors (quadriceps) and hip extensors (gluteus maximus and hamstrings) during the propulsion phase of a running cycle, that individual will run at a greater running speed.

Such ground reaction force and torque-generation capabilities are improved via strength training. Previous research investigating the effects of concurrent strength training and endurance running have demonstrated improvements in ankle plantar flexor, quadriceps, hamstrings and gluteal force-generating capabilities⁹. Furthermore, endurance running programmes supplemented with additional strength training have been shown to improve running economy within endurance runners¹⁰. An improvement in running economy means an individual is able to perform a greater amount of mechanical work (e.g., running speed, stride length, stride frequency) with an equal or reduced amount of muscular chemical expenditure (e.g., ATP production, glycolytic energy stores). Such a reduction in bioenergetic demand allows a runner to perform a greater amount of work while staying within their aerobic capacity and, therefore, increase their minute mile/km running speeds. The positive effects of strength training on running economy have even been reported after only a 10-week strength-training intervention¹¹. Based on the research findings presented, it is evident that lower-body strength training improves muscular force-generating capabilities and running economy within endurance runners and should, therefore, be programmed accordingly.

When selecting strength-based training modes within endurance runners, it is imperative that the concept of ‘strength training’ isn’t lost in translation and replaced with bodyweight/light load endurance circuit-based training¹². If we wish to improve an individual’s ability to generate ankle, knee and hip extensor torque and apply larger ground reaction forces, heavy loaded (relative to an individual’s 1RM) lower-body strength-based movements need to be programmed (e.g., bilateral squat and unilateral squat variations). Furthermore, such applied strength training needs to be programmed for an optimal transfer of training effects by using a combination of bilateral movements (e.g., back squats, front squats, overhead squats), unilateral movements (e.g., split squats, Bulgarian split squats, lunges) and running-specific movements that closely replicate the mechanics of running (e.g., loaded step-ups with contra-lateral hip extension/hip flexion). As with any form of strength-based training, coaches need to ensure such lower-body-dominant training modes are well coached, performed correctly with appropriate loads and periodised with progressive overload.

The need for muscular power and rate of force development

Endurance runners are required to repeatedly produce mechanical work per foot contact. This ‘repeated power production’ quality is vital within endurance running, allowing runners to perform a greater amount of mechanical work (e.g., greater stride length, frequency and running speed) within the same foot contact time duration¹³. Another closely related key performance quality when looking to optimise running ground contact time is rate of force development (RFD). RFD can be defined as the ability to produce high force within a limited timeframe, or mathematically defined as:

RFD = ΔF ÷ Δt

Where RFD represents an athlete’s rate of force development, ΔF represents the change in force from the initiation of the concentric action to the peak force achieved during the concentric action, and Δt represents the change in time from the same corresponding force measures. An increase in RFD has previously been associated with an improvement in running economy within endurance runners¹⁴. Both muscular power output and RFD can be significantly improved using training methods that require rapid explosive movements with load, including the classic Olympic lifts (snatch, clean and jerk) and their derivatives (hangs, powers and pulls)^15,16. However, it must also be noted that gaining competency at performing the Olympic lifts takes time and commitment (from both the coach’s and runner’s perspective) due to their complexity and, therefore, requires correct coaching guidance.

The use of hexagonal bar jumps and loaded squat jumps as a form of speed strength training, and as an effective alternative to Olympic weightlifting training methods, has recently been highlighted within research literature¹⁷. A recent study by Oranchuk et al¹⁸ demonstrated that vertical jump, RFD and isometric force performance improved in equal amounts after the completion of a high hang clean pull and hexagonal bar jump training intervention. These findings suggest that the use of loaded jumps as a means of increasing RFD within runners is warranted and can be applied as an equally effective alternative to the Olympic lifts. However, in conjunction with the law of training variation and the need to apply different training stressors within athletes to force training adaptations, it is apparent that both loaded jumps and Olympic lifts should be used together within strength and conditioning programmes aimed at improving power and RFD performance within endurance runners.

The need for musculotendon stiffness 

Tendon stiffness is the ability to produce rapid RFD within the shortest ground contact time possible, with little change in ankle, knee and hip flexion occurring during the ground contact phase of a running cycle. Such little change in joint angle requires a greater amount of mechanical work within the tendon rather than the muscle itself, therefore costing less chemical energy due to the Achilles’ tendon’s reduced blood supply requirements. This means that, while the muscles are being held isometrically within the same position (before being eccentrically lengthened under load), the tendon can undergo a rapid stretch-recoil action. The greater the tendon stiffness, the greater the RFD and energy economy of the movement¹⁹.

Previous research investigating the effect of plyometric training on running performance, musculotendon stiffness and various performance measures has demonstrated significant improvements within 3km and 2.4km running performance, running economy, vertical jump performance, drop jump performance and five bound distance tests^20,21. These findings clearly demonstrate the link between an improvement in running performance and running economy due to an increase in power production via musculotendon stiffness adaptations. It is therefore evident that power output and musculotendon stiffness are important performance qualities within endurance-based runners and should be trained accordingly in conjunction with other running-based training.

The need for greater robustness

The frequent occurrence of lower-extremity injuries within recreational runners is well documented, with Achilles’ tendinopathy, patellofemoral pain, plantar fasciitis and other running-associated injuries often being reported^22-25. The causes of such injuries are multifaceted. However, research suggests that with increased force-absorption/generation and torque capabilities (achieved via increased strength and musculotendon stiffness), runners are at a reduced risk of such injuries^24,26,27. Lorimer and Hume²⁶ previously highlighted the multi-Achilles’ injury mechanisms within sport, including excessive ground reaction forces, insufficient muscle activity or lack of muscle engagement timing immediately prior to or post ground contact, a lack of joint range of motion and joint stiffness and neuromuscular control of the lower limb. Therefore, Achilles’ tendinopathy preventative injury measures should include increasing force tolerances within the lower limb (via strength training), in addition to enhancing motor unit recruitment timing and co-ordination (via the coaching of correct landing mechanics and neuromuscular challenging unilateral-based training, such as multiplanar hops, etc.) and increasing dorsiflexion range of motion.

Likewise, at the point of ground contact, the huge forces being experienced within the Achilles’ tendon are transmitted directly via the plantar fascia located under the foot. Such repeated forces, in conjunction with non-optimal foot mechanics (hyper pronation, lack of dorsiflexion, excessive medial longitudinal arch), can lead to plantar fasciitis, characterised as heel pain, increased plantar fascia thickening and degeneration^28-32. A limitation in plantar flexor strength results in a decreased efficiency of force absorption and propulsion capabilities, increasing the risk of plantar fascia degeneration²⁷. Therefore, an increase in plantar flexion strength could reduce the occurrence of plantar fasciitis within endurance runners, while increasing overall robustness to injury.

During a running cycle, the patella tendon undergoes a rapid shear force as the patella tendon stretches under load over the patella bone, before rapidly shortening during the propulsion phase due to the applied pulling force on the tibia via the knee extensor torque moments generated by the large quadricep muscles. This repeated shear force and knee extensor torque demand places the patella tendon under considerable biomechanical demand. Messier et al²⁴ previously reported reduced knee extension torque capabilities as a significant discriminator between runners with and without existing patellofemoral pain. These findings demonstrate the need for increasing knee extensor strength in runners via lower-body strength-based training modes, therefore increasing a runner’s robustness to the common occurrence of patellofemoral pain or ‘runner’s knee’.

Conclusion

It is evident that the supplementation of basic strength and power training can not only have a positive effect on endurance-running performance, but also help to prevent against many common running-based injuries. Coaches should therefore programme lower-body strength training modes with the aim of increasing force absorption and production capabilities (e.g., bilateral and unilateral squat variations, loaded step-ups), running-based plyometrics with the aim of increasing musculotendon stiffness (e.g., pogo jumps, broad jumps, single leg hops) and power training methods with the aim of increasing power output and RFD (e.g., loaded jumps, Olympic weightlifting variations), allowing endurance runners to perform to the best of their ability, while reducing the chance of injury.

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