After the last couple of blog posts which were a lot more free-form I have another university essay for you this week - a needs analysis of BMX racing. I realise that the paragraph discussing how a rider progresses towards the final is more geared towards the Olympic style competitions, but word count limitations meant I didn’t want to discus the different systems. the point was to show that there are multiple races per day. I’ve included the 2020 race schedule although this hasn’t turned out to reflect reality due to the COVID-19 problems, but otherwise I hope it’s interesting for you and as always let me know if you have any comments or questions.
BMX Racing
Bicycle Motocross (BMX) is a sport in which cyclists compete in a series of single lap races over a 300-400m track consisting of a large start ramp, pump sections and jumps along the straights, and banked U-shaped turns linking the straights (Grigg, 2019). It was developed in the 1960s, gained recognition from the Union Cycliste Internationale (UCI) in 1983 and became an Olympic sport at the 2008 Beijing Summer Olympics (Rylands & Roberts, 2014).
A competition starts with an individual time trial which decides the seeding used in the following races. There then follows a series of heats (called motos) where 8 riders per heat race around the track. Qualifiers from these motos compete in a final race to decide the overall winner.
Due to the importance of the start phase and the contrast between it and the following track sections this needs analysis will look at them separately before building an overall picture of the demands placed upon a BMX racer.
Each race starts with 8 riders lined up behind a metal gate at the top of the start ramp. A warning is issued verbally and then the start sequence commences. When the gate drops the riders sprint down the ramp and race around the track. Rylands and Roberts (2014) analysed 175 World Cup races at four different venues during the 2012 season and found a moderately strong correlation between a rider's position 1 second after the start and their finishing position, and a strong correlation between a rider's position 8-9 seconds into the race and their finishing position. These results suggest that the first 8-9 seconds of a race have a significant impact in the final outcome, with the athletes who have the fastest starts having the greatest chance of finishing in the top 3 places. The importance of the start and being in a good position at the first bend has been reported by a number of authors and consequently a lot of emphasis has been placed on it in both research and training (Bertucci, Hourde, Manolova, & Vettoretti, 2007; Cowell, McGuigan, & Cronin, 2012b; Debraux & Bertucci, 2011a, 2011b; Grigg, 2019; Rylands & Roberts, 2014).
As the bike is stationary at the commencement of the first pedal stroke the amount of force that the rider can generate at a relatively low cadence is directly linked to the acceleration that can be achieved by the Newtonian equation of Force = Mass x Acceleration (Bertucci et al., 2007). Debraux, Manolova, Soudain-pineau, Hourde, and Bertucci (2013) took the theoretical model further to include the inertial load of the athlete and bicycle and came to the conclusion that the torque an athlete can generate is significantly correlated to the time taken to cover 20m (r = 0.95). Unfortunately they were testing athletes on a flat track rather than on a start ramp, however the optimum torque they calculated when taking into account gear ratios etc. of 127 ± 24 N.m is very similar to the actual values collected by Gross and Gross (2019) looking at elite athletes on a start ramp (117 ± 15 N.m).
Gross and Gross (2019) reported a very large correlation between the maximum torque generated by riders on a start ramp and the maximum force they generated in a series of squat jump tests. Bertucci et al. (2007) also found significant correlations between squat jump height and starting performance (time to 5.2m r = -0.47 and time to 28.7m r = -0.58). Rylands, Roberts and Hurst (2015) argue that the discrepancies found between laboratory force and power tests and the values measured on a BMX bike may be due to the large contribution to force development from the upper body when riding a BMX bike. A squat jump or a laboratory power test on a static bike will negate this upper body contribution.
During the start the athlete will initially rock slightly backwards on the bike to lift the front wheel over the falling gate mechanism and then rapidly extend the hips to propel the bike forwards (Grigg, 2019), this movement pattern, along with the whole body nature of the activity as discussed above and other components of dynamic correspondence (as developed by Verkhoshansky and Siff (2009)) such as the rate of force development led Cowell et al. (2012) to recommend Olympic weightlifting derivates, for example the hang power snatch, in order to develop the physical capacities required by a rider to make a fast start. Building muscle mass through strength training interventions could be seen as detrimental to a fast start, due to the increased inertial load and the F = ma equation previously described (Cowell et al., 2012b), Bertucci et al. (2007) however argue that this isn't a major handicap due to the fact that the start occurs on a steep ramp (the acceleration due to gravity will convert the athlete's higher potential energy at the top of the ramp to a higher level of kinetic energy going into the first obstacle).
As the athlete accelerates down the start ramp their cadence increases rapidly and peak power is achieved quickly. Bertucci and Hourde (2011) found no significant correlations between power tests and time to 5m on a track, but did find significant correlations to time at 29.7m and 75m (p<0.05). These results again justify looking at the initial start and pedalling sprints separately, and similarly may have implications to an athlete's training (the start is high force, low cadence whereas sprints are performed with a very high cadence, the authors therefore recommend a velocity based training (VBT) approach to ensure the speeds of movement in weight room activities have a high correspondence to the phase being training in order to optimise adaptions).
Measuring peak power during race conditions is complicated by differences in track design, limitations in current technology and, as discussed previously, there are differences in technique when on a BMX bike compared to a laboratory ergometer (Rylands et al., 2015). We can however look at the values collected by researchers in order to see what current high level athletes can achieve in these tests, even if is not a direct needs analysis. Some of these results are summarised in table 1.
Aside from the start riders will also pedal during other short intervals around the track, in order to maintain or increase speed. The opportunities to do so and therefore the contribution of pedalling to the athlete's velocity around the track is dependent upon the track design (Mateo et al., 2011). Cowell, McGuigan, & Cronin (2012a) performed a time-motion analysis of competitors at a UCI World Championship on a supercross track (the type of track with the largest start ramp and largest obstacles, as used by elite riders in World Cups, World Championships and Olympic Games). They found that on average male racers took 39.62 ± 0.78s to complete the track using 30.45 ± 3.2 pedal strokes for a total pedalling time of 11.83 ± 1.11s. Female racers took 40.95 ± .91s to complete the track, using 33.65 pedal strokes and a total pedalling time of 14.40 ± 2.17s.
As the technical difficulty of the track increases the relative contribution of pedalling decreases, Mateo et al. (2011)measured power output of riders over an entire lap using a PowerTap device (CycleOps, Madisson USA) fitted to the rear hub and found that mean power output decreased from 394 ± 39W on a low difficulty track to 360 ± 39W on a medium difficulty track and to 235 ± 39W on a high difficulty track. They argue that the decreasing importance of pedalling power and the increased importance of acyclic speed production (jump technique, manuals, pumping etc.) should influence a rider's fitness program as they progress through competitive ranks.
Along the BMX track's straights are a series of obstacles that have to be cleared by the riders by either jumping or rolling over them. As previously discussed the design of the track plays a major role in determining the demands placed on the rider, with an Olympic supercross track requiring fewer pedalling strokes but much greater aerial technique than a track found on the European circuit, (Mateo-March, Blasco-Lafarga, Doran, Romero-Rodríguez, & Zabala, 2012).
Through video analysis of a World Championships (on a supercross track) Cowell et al. (2012a) found that male riders spent 9.64 ± 1.79s jumping and 17.05 ±1.51s pumping around the track, (female riders 6.28 ± 1.41s and 17.80 ± 1.83s respectively). Similarly Mateo et al. (2011) calculated that of a rider's mean velocity around a track 83.3% was due to acyclic actions (manuals, pumping etc.) and only 16.7% due to pedalling. These results show the importance of improving a rider's skill and capacity in these techniques.
Pumping was described by Cowell et al. (2012b) as the actions the rider takes where he is on the ground and using movements of the body to efficiently overcome the obstacles. The dominant action is flexion and extension at the hips and knees in order to move the thorax (and hence centre of gravity) into advantageous positions and manipulate the bike over the obstacles, with Cowell et al. (2012a) finding this to be performed roughly 30 times per lap. Rylands, Hurst, Roberts, and Graydon (2016) found this action allowed riders to finish a lap 19.5 ± 4.25% faster than when they did not pump. They described the action as being whole body, as force generated through the hip and knee extension is applied through the arms to push the bike down. They therefore conclude that a BMX training program should include an upper body strength element and that this should aim to develop the rider's functional stability to ensure efficient use of the whole kinetic chain. This recommendation is further supported by the previously discussed findings that peak pedalling power is greater when a rider is standing than seated due to the way the upper body manipulates the bike (Bertucci & Hourde, 2011; Rylands et al., 2015). Cowell et al. (2012b) also advocate exercises such as the bench press and rows due to the shoulder actions as the rider manipulates the bike and suggest that free-weight exercises are superior to machine equivalents as body control/stability required to perform them is also a foundation of optimal skill production on a bike and that machines reduce this training stimulus.
Depending on how successful a rider is in a progressing through the motos and reaching the final each rider could take part in up to 6 races in one day, each lasting 30-40s. Louis et al. (2013) ran a simulated race series with elite riders and found that the energy requirements during a race are not constant, with a very brief requirement for maximum force at the start followed by short bouts of maximal effort pedalling interspersed with the technical sections which were discussed above and which they described as being quasi-isometric. During a race the riders were achieving 94.3 ±1.2% of their VO2max and mean blood lactate levels of 14.5 ± 4.5mmol.L-1 which they suggest as being indicative of very high requirements for both aerobic and anaerobic glycolysis. Unfortunately gas analysis was not possible whilst the riders were on the track, but rather masks were applied within 20 seconds of finishing and then peak values extrapolated from these results. They theorised that the sprint start is the most anaerobically taxing phase of the race, with blood lactate values being maintained by the acyclic actions later on, but this is conjecture as it could not be directly measured. 30 minutes rest were given between races which was sufficient for the riders to repeatedly complete the track at over 97% of their best recorded time, with no differences in perceived exertion over the trials despite some changes in blood markers (base excess and anion gap). Using these findings the researchers concluded that specific training to increase both aerobic and anaerobic energy pathways should be carried out by BMX riders, for example repeated short duration sprints.
BMX races have 8 riders on the track at the same time and occasionally collisions between riders occur. The obstacles also pose challenges to the racers and so there is a significant injury risk associated with racing. In the 2016 Olympics 37.5% of riders suffered an injury and 10% of riders missed more than a week of training or competition due to their injuries, both the highest recorded figures for any sport at the games. The majority of these injuries occurred during competition, (Soligard et al., 2017). Similarly at the 2012 Olympic Games 31.3% of riders suffered an injury, of which 73.3% occurred during competition, (Engebretsen et al., 2013). In order to mitigate these risks Cowell et al. (2012b) recommend hypertrophy training during the general preparation phase, which they suggest will also help with the requirement for producing force during racing. They do however point out that the power to weight ratio of a rider is important and so excessive hypertrophy should be avoided.
As well as the previously discussed requirements for a racer to recover between races there may also be two competitions on consecutive days, further increasing the demands placed on the rider. This irregularity of event scheduling creates a challenge to program design, riders have a long period of time to prepare for one event and then only enough time to travel to the next venue before the next event. Cowell et al. (2012b) recommend that riders aim to peak for certain events and then work backwards to build an undulating periodisation plan based on these events.
In conclusion BMX racing poses interesting physiological challenges as the rider requires a very high maximal power outputs to be delivered in very short bursts, but these need to be repeatable over the course of a race, during multiple races in a day and at back to back events. Both the aerobic and anaerobic energy systems should be trained to meet these requirements, through the use of repeated sprint activities.
A fast start requires a high force output with a high rate of force development, therefore training should focus on hip and knee extension movements with Olympic lifting derivates being recommended (Cowell et al., 2012b). Despite the perception that leg strength is all important in cycling the upper body plays a large role in force production both during cycling and pumping around the track, therefore the upper body should not be neglected in the weights room. A high degree of movement literacy, dynamic stability and efficient use of the kinetic chains are required to manipulate the bike and for aerial skills and so Olympic and other free-weight exercises such as the squat and bench-press are to be prioritised over machine weights.
Elite riders display greater physical capacities than non-elite, but track design places a greater emphasis on technical skill for these riders. Therefore riding time and skill development should not be neglected when building a training plan for riders as they progress through the levels.
The intermittent competition schedule creates a programming challenge with periods where recovery between events is prioritised and other periods where physical and skill development can be targeted. There is a high risk of injury to riders which complicate and disrupt any plans made but these risks can be reduced through skill development to ensure riders are competent over the obstacles found on a track and through hypertrophy training to protect the body in the event of a crash (Cowell et al., 2012b).
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