An Analysis of Marathon Racing
- 29 Apr, 2023
For those who know, my name is Samantha (or, Sam!) and I'm the creator of 10W2S: Strength for Running. I'm physiotherapist with a background in research & sports science. In Australia, to be recognised a specialist sports physio you have to take additional training (in the form of another masters degree, this will be my second!). So, I'm currently in the middle of completing mine. It's an extra busy time managing FT study alongside FT physio and running all things 10W2S!
Naturally, I chose marathon running for one of my units assessments. For those who are interested, I thought I'd share the essay as it contains up to date relevant research. I hope it's an interesting read for you!
An Analysis of Marathon Racing
Running is one of the most accessible and popular sporting activities worldwide. Marathon racing, viewed as one of the true tests of endurance, is the longest race in the Olympic games. The marathon spans over 42.2km with the fastest men’s and women’s times at the 2020 Tokyo Olympics being 2:08:38 and 2:27:20, respectively.
Marathon performance is determined by an athlete’s velocity over the race distance. This is influenced by metabolic power as well as the energy cost of running (Thompson, 2017). Compared to shorter distances, the metabolic demands of marathon racing are significantly higher (Rapoport, 2010).
Biomechanics can also influence the energy cost of running and relies on an athlete performing an efficient running gait while avoiding non-productive patterns (Thompson, 2017). Running biomechanics also influences the distribution of load through the musculoskeletal system and can therefore influence how an athlete adapts or maladapts to their training load.
The requirements of distance running also heavily rely on following correct training principles. This is not only to improve running performance but also to mitigate injury risk, as up to 85% of runners may experience an injury each year (van Gent et al., 2007). This can significantly limit and halt training.
The interplay between a marathon athlete's physiology, biomechanics and application of training principles all influence race performance. Here it is analysed how each can contribute to marathon race success.
Analysis of the sport and movement components
How a runner moves through their gait cycle affects the distribution of force through their musculoskeletal system. The running gait cycle, as previously described, is broken down into two phases; stance and swing. During initial swing, the iliopsoas and rectus femoris flex the hip (Hanley, 2021). The knee moves from near extension at toe-off to a flexed position at mid-swing (55-60°) and then straightens to ~20° in preparation for the landing at terminal swing (Hanley, 2021). The eccentric activity of the hamstrings controls knee flexion throughout the swing phase with the activity of the quadriceps straightening the knee in preparation for landing. The tibialis anterior dorsiflexes the ankle in preparation for landing, with the additional activity of the plantar flexors increasing joint stiffness before and after ground contact (Hanon et al., 2005).
The stance phase initiates when the foot is in contact with the ground. The runner will land on the outside of the foot, where the ankle will dorsiflex and pronate to absorb shock, facilitated by activation of tibialis anterior (Hanley, 2021). The hip is flexed at ~30° so the thigh is ahead of the body (Hanley, 2021). The hip extensors contract concentrically to facilitate the drive forwards to extend the hip at toe-off (Hanley, 2021). During midstance, the knee reaches maximal flexion (~45°), where the body’s CM moves over the foot (Novacheck, 1998). The pelvis moves obliquely with the action of gluteus medius required to stabilise the pelvis (Powers, 2010). The ankle at midstance dorsiflexes more and then supinates as the plantar flexors contract concentrically to push off (~25°) (Hanley, 2021; Novacheck, 1998). At the upper body, arm swing acts in opposition and counterbalances the motion of the opposite leg (Hanley, 2021). Trunk rotation also pairs with this movement and improves running efficiency (Bramble & Lieberman, 2004).
Foot strike pattern varies amongst marathon runners. Neither a rearfoot strike (RFS) or a forefoot strike (FFS) will have a greater impact on injury rates (Anderson et al., 2020). Rather, it changes the loading profile from the knee to the ankle plantar flexors, respectively (Anderson et al., 2020). The vast majority of distance runners rearfoot strike early (76%), with prevalence rising to 86% with increased distance (Bovalino & Kingsley, 2021). This change to a RFS throughout the race may be beneficial as it has been shown to elicit a lower rate of carbohydrate (CHO) oxidation than a FFS (Gruber et al., 2013). As a marathon has the potential to deplete muscle glycogen stores this may be a limiting factor (Smyth, 2021).
Running speed is determined by a runner's step length and cadence. Step length is determined by how far the foot lands in front of the CM, the distance of the foot behind the athlete in toe-off, and how far the athlete travels during flight (Hanley, 2021). A long stride is best determined from large amounts of hip extension, rather than landing with the foot in front of the CM (known as overstriding). This movement pattern leads to higher impact loading and breaking forces, which can both slow an athlete down and may contribute to an increased injury risk (Moore, 2016; Napier et al., 2018).
Cadence refers to how many steps a runner completes in a minute. For distance runners, this typically varies between 165 and 195 steps per minute (Hanley, 2021). A lower cadence has been associated with an increased injury risk, such as bone stress injury (BSI) (Kliethermes et al., 2021). However, a recent systematic review has suggested the impact of changes in cadence on injury and performance in the long term remains inconclusive (Anderson et al., 2022). Trained runners are likely to select an optimal cadence (in regard to RE) compared to novice runners (de Ruiter et al., 2014). A trained runner's optimal cadence or stride length is on average 3% faster and 3% shorter respectively, than their preferred frequency or length (Barnes & Kilding, 2015). For novice runners, this may be as great as 8% (Barnes & Kilding, 2015). This suggests that trained runners can self-optimise their running biomechanics in response to their physiological state (Moore, 2016).
To optimise the biomechanics of running to improve running economy (RE) and thus performance, there are a few modalities available. Most are related to running biomechanics during the stance phase, particularly at toe-off (Moore, 2016). This includes improving musculotendinous (MT) stiffness by utilising the spring-like capability of the stretch-shortening cycle (Moore et al., 2012). MT stiffness can be improved with strength and plyometric training, facilitating reduced ground-contact time (Spurrs et al., 2003; Støren et al., 2008). Lesser MT stiffness is associated with greater muscular activity of the lower limbs and is detrimental to RE as it increases oxygen consumption (VO2) demands (Kyrolainen et al., 2001).
Analysis of other requirements for optimal movement performance
Physiologically, the mean pace a distance runner can maintain during a marathon is determined by three factors; RE, velocity at lactate threshold (vLT) and maximum oxygen uptake (VO2max). RE, the VO2 at submaximal speed is considered one of the most important determinants of distance running performance (Daniels & Daniels, 1992; Roecker et al., 1998). RE is a complex physiological process that is influenced by variables such as metabolic and biomechanical, neuromuscular factors as well as VO2max and ventilation (Barnes & Kilding, 2015). Distance runners with a high RE use less oxygen than athletes with a poor RE at the same steady-state pace, thus contributing significantly to marathon performance (Barnes & Kilding, 2015).
vLT is also a superior predictor of marathon running performance. The lactate threshold is the differentiation point between aerobic and anaerobic contributions to glycolysis in the muscles. It is the point immediately below where lactate starts to accumulate in the body, and coincides with an increase in ventilation relative to VO2. An improvement in vLT allows for greater VO2 before this threshold is met, where thereafter fatigue occurs rapidly (Ghosh, 2004).
VO2Max is considered one of the most important parameters to determine aerobic endurance, representing the maximum rate at which oxygen can be consumed. Elite distance runners have similar and very high VO2max values (70-80 mL/kg/min), with therefore only very small variations between athletes (Nevill et al., 2003). Because of this, there is only a low to moderate correlation with VO2max within this subpopulation (Mooses et al., 2015; Shaw et al., 2015). Previous research has shown for elite distance runners with a similar VO2max, RE can vary as greatly as 30% (Mooses et al., 2015). As both vLAT and RE are better representors of submaximal running speed, they are more strongly related to elite distance running performance (Farrell et al., 1993; Franch et al., 1998).
A marathon runner’s physical characteristics also impact race performance. Elite marathon runners have lower body fat percentages, skinfold thickness and flexibility (Nikolaidis et al., 2021; Saunders et al., 2004). Reduced flexibility is beneficial as decreased range of motion (ROM) in the transverse and frontal physiological planes leads to better stabilisation of the pelvis as the foot hits the ground in the early stance phase (Baxter et al., 2017). Distance runners also exhibit increased MT stiffness, assisting elastic storage and reducing the oxygen demand of running (Blagrove et al., 2018).
The nutritional strategies for the marathon include incorporating a diet that provides a high calorie intake to facilitate the energy requirements of training. An athlete's diet should be moderate-to-high in CHO intake (~60% of energy intake, 6-10g/kg/day) to limit the effects of training-induced glycogen depletion and protein intake ~1.4g/kg/day to facilitate muscle, tendon and bone recovery (Vitale & Getzin, 2019). When running, CHO should be replaced at 30-60g/hr (<2.5hr event/training), and 60-70g/hr (>2.5hr event/training) (Vitale & Getzin, 2019). Fat intake shouldn’t be restricted beyond <20% of total caloric intake, and an athlete must maintain adequate levels of hydration (~400-600 mL/h) (Vitale & Getzin, 2019).
Analysis of Technical Faults and Injuries
The largest contributing factor to a running-related injury (RRI) is training error (Hreljac, 2005). This is where training load (i.e. volume, intensity, duration, frequency) exceeds tissue capacity (Lopes et al., 2012). The weekly running distance for elite marathon runners in the mid-preparatory period is 160-220km, across 11-14 sessions per week, with 80% of the total running volume performed at low intensity throughout the training year (Haugen et al., 2022). Slight changes in training load, biomechanics, footwear and running surface may be enough to be a catalyst for the development for a RRI (Malisoux et al., 2015). Thus, periodisation and quantification of training load and monitoring of athlete response are essential.
There have been several biomechanical faults identified in the literature (Willwacher et al., 2022). However, there is currently not enough sufficient evidence to support that changing a runner’s biomechanics will create a meaningful change in a RRI as most of the studies are retrospective rather than prospective (Willwacher et al., 2022). Key issues with changing a runner's gait are changing where the load is distributed, and indeed faces the risk of increased injury risk by rapidly loading previously underloaded structures (Anderson et al., 2020). An example is seen with changing foot strike, where the load shifts from the knee to the ankle plantar flexors. Because of this, biomechanical risk factors are best used in the context of injury management rather than prevention (Willwacher et al., 2022). In addition to this, gait retraining does not improve RE or performance, as most runners will adopt the most economical pattern (Doyle et al., 2022).
Common injuries seen in distance runners a mostly related to musculoskeletal overload. A systematic review by Lopes et al. 2014 reported that the most frequently reported RRI were medial tibial stress syndrome (MTSS) (incidence 13.6-20%) Achilles tendinopathy (incidence 9.1%-10%), and plantar fasciitis (incidence 4.5-10%) (Lopes et al., 2012). Amongst all conditions, tendon and bone pathology occur most frequently.
Tendon injuries are frequently seen among distance runners (Lopes et al., 2012). Tendinopathy is best addressed by load management, alongside heavy slow resistance strength training (Beyer et al., 2015). As marathon runners are frequently managing high training loads it is important to consider managing training alongside the presence of tendinopathy, rather than complete rest (Haugen et al., 2022). Complete rest makes it more difficult for an athlete to re-enter their training regime due to deconditioning. Considerations include pain levels (i.e. VAS <5/10), 24hr response, and how the condition is trending over time (Silbernagel et al., 2007).
BSI conversely require complete offloading. The bones ability to withstand failure is affected by genetics, diet and nutrition, endocrine status and hormones, physical activity history, bone diseases and medications (Warden et al., 2014). Warden et al. 2021 recently summarised how bone stress injuries can be prevented with optimal workload (Warden et al., 2021). The following suggestions were included; providing variety in training (i.e. running alone is not a good enough bone-building activity), complimenting training with bone-centric exercises (i.e. plyometrics) 6-8hrs after running, periodising training, loading bones in multiple directions, progressing training duration before intensity, avoiding early sport specialising and substituting treadmill sessions when needing to reduce cumulative load. The authors further discuss that relative energy deficiency in sport is prevalent (ReD-S), where dietary intake is not sufficient to meet the energy requirements of training (Warden et al., 2021).
The art of marathon running requires a fine balance between applying the correct training principles to balance the load, alongside appropriate fuelling to facilitate training and recovery. Marathon runners all possess a high VO2max, whereas the elites are best differentiated by RE and vLT. Strength training plays a pivotal role in both RE and performance and may mitigate injury risk. Finally, running biomechanics play a role in stride efficiency and may play a role in injury prevention, however, care must be taken when altering the uninjured runner's gait. Future research should continue to consider the role of biomechanics in injury prevention, rather than in the context of injury management.
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