Inertial stresses of national and international motorcycle circuit racing riders

Abstract

The forces on the human body associated with motorcycle racing are currently unpublished, and this study aimed at quantifying the negative and positive accelerations that circuit racers experience during real competitions via direct measurements in different classes of racing. Kinematical measurements of braking actions and corner exits during competitive laps were identified via GPS signal in 23 riders competing in 13 different circuits and categories (i.e. European Junior Cup 2016, national and world level 600 cc SuperSport). Fully equipped body mass of riders was measured and individual inertial forces were calculated. Riders in an entry-level class championship experienced 87 ± 11 brakes per race, while national and world SS600 class championships were found to have on average 144 ± 14 and 171 ± 28 brakes per race, respectively. For each braking action, the calculated inertial mean force acting on the rider centre of gravity was from 476 to 513 N on average, and peak forces doubling these values. Moreover, the mean inertial forces generated while accelerating to exit the corners were from 300 to 384 N on average, with the WSS class recording 33% larger accelerations compared to the entry category EJC. The findings of this study: suggest that international level riders experience positive and negative inertial loads considerable in volume, frequency and intensity; provide novel information enhancing the knowledge on the performance model for motorcycle circuit racing; and, offer a profile useful for the design of training programmes aiming at preparing riders for competition.

Keywords

Acceleration,braking,global positioning system,kinematics,motor sport

Introduction

Motorcycle racing exposes riders to considerable mechanical loading during circuit competitions.^1,2 Indeed, to minimise lap-time, riders aim to increase their mean speed throughout the lap, therefore late braking, high mid-cornering speed and early and intense corner exits are strategies employed by skilled competitive riders.^2–4 These maneuvers expose the rider to abrupt postero-anterior decelerations and antero-posterior accelerations, as well as centrifugal forces balanced by leaning the motorcycle into corners.^1,2,4–6 Profiling these inertial stresses would help understand the physical load and muscular demands in this population of athletes.

Recently, researchers have quantified the physical actions of top-level riders, measuring the volume and frequency of brakes and corners per race, as well as calculating the intensity of the braking actions by using the kinematic variables from race reports. At professional level, in a single race, riders brake on average more than 170 times, and over 40% of those postero-anterior negative accelerations experienced by the system bike-rider are initiated at a speed higher than 260 km/h.² Using top-level carbon disk brakes, circuit racers experience a mean negative acceleration ranging from 2.7 to 16.5 m/s²; despite 25% of those braking actions generating a mean inertial stress greater than 1 g, there is no published research describing the forces that riders are required to counteract whilst racing.²

According to the level-proportioned number of laps per race, the load induced by the repetitive cycle of technical actions (i.e. accelerating, braking, cornering) might be considered of lower magnitude at lower categories. However, even though this sport is highly supported by forefront technology, direct measurements of these mechanical stresses experienced by racers remain unpublished. Indeed, currently there are no available studies that have instrumented the motorcycle or the rider with the intent of directly measuring the physical stresses of competitions with the objective of estimating the relative muscular strength requirements of racing. With this in mind, and based on previous findings,² it is hypothesised that the inertial stress from the braking and corner exiting actions is substantial during racing, and perhaps different across categories. Therefore, the aims of this study were to: 1) directly measure and quantify the negative and positive accelerations that riders experience during changes of speed (i.e. braking actions and corner exits), to estimate the sagittal forces experienced on their centre of gravity while riding in dry conditions during competitions; 2) investigate potential differences between categories of racing (i.e. entry-level and mid class); and, 3) determine potential relationships between estimated inertial loads and ranking level or experience of riders.

Methods

Design and methodological approach

A cross-sectional descriptive design was implemented, where circuit racing motorcycles were equipped with a 10 Hz GPS unit to measure and record positions on track and changes of velocity while racing. Measurements were collected from racers competing in different categories and on different tracks during dry sessions (i.e. free practice, qualifying or race) of official competitive events.

Participants

During the 2016 racing season, riders competing in the Italian circuit racing national championship (namely Campionato Italiano Velocitá), European Junior Cup and the World SuperSport championship were randomly invited to take part into this study. Participants were provided with an information sheet, signed a consent form and were allowed to withdraw from the study at any time. Twenty-three riders (22 males and one female) volunteered to take part into this study (mean age: 21 ± 4.4 years; mean body mass with protective equipment: 77.3 ± 6 kg; mean time since start of motorcycle competition: 9.1 ± 4.5 years). The research protocol was approved by the institutional ethics review board (AUTEC reference number 16/109).

Biomechanical model

Due to the novelty of the analysis, a simplified biomechanical model was used for this study. Calculation of estimated forces was based on the horizontal component of the acceleration, excluding the drag. Vertical accelerations were considered negligible (i.e. no jumps involved) and also lateral forces involved in the early and late stage of cornering were omitted from the model in consideration to the restricted goals of this study (Figure 1).

Figure 1.

Biomechanical model simplified, describing static calculation of dynamic forces acting on the centres of gravity of a motorcycle and a fully equipped rider, during a braking action in racing.

Indeed, motorcycle circuit racers combat centrifugal forces by leaning the motorcycle (i.e. rolling) and moving their bodies (i.e. hanging-off) towards the inside of the corner. Moreover, the practicality of this elementary model was supported by the filtering applied in data handling, which aimed at isolating the braking and corner exit actions. Despite the pitching and yawing are critical to manage the directionality of the motorcycle, they are not considered a direct source of mechanical stress for a racer, and they were not accounted here. In this model, the inertial forces acting on the sagittal plane have been considered being absorbed by the rider through the points of contact with the motorcycle (i.e. hands, buttocks, inner thighs and knees, and feet), and the estimation of load was calculated by considering the human element as a single system.

Measurements

The European Junior Cup (EJC) was an entry-level category run with single-manufacturer, stock version motorcycles equipped with a 650 cc four-cylinders engine (approximately 180 kg and 80 bhp at rear wheel); while the Italian National SuperSport (NSS) and the World SuperSport (WSS) were a mid-class category run with competition-prepared 600 cc four-cylinders or 675 cc three-cylinders engine (minimum weight 161 kg and approximately 138 bhp and 145 bhp for NSS and WSS respectively). Those championships were regulated from the same tyre supplier and data were collected in equivalent environmental conditions (i.e. dry asphalt, air temperature 20-28°C) at 13 different circuits homologated from the FIM and FMI (International and Italian Motorcycling Federation, respectively).

Body mass of the participant riders wearing the full protective equipment was measured with a 100 gr-accuracy body weight electronic scale (Paula, Korona, Germany) immediately after the riding sessions. At any time during the 3-day events, racers were also required to complete a one-page athlete-background form to assess years and level of riding experience as well as potential titles.

GPS units Qstarz BT-Q1000eX sampling at 10 Hz (Qstarz International Co. Ltd, Taipei, Taiwan) were positioned on the tank or the tail of the motorcycle facing upward to record speed during riding. Widespread use of the same device in racing environment, and previous pilot testing established the utility and reliability of this experimental setup in relation to the purpose of this study. A Fourier analysis on the isolated deceleration periods was performed to explore the validity of the sampling frequency for capturing events of importance in the speed signal.

Data handling

At the end of each session when GPS measurements were collected, the rider was instructed to select one ideal race-pace lap from the list of his/her recorded dry laps, with the criteria that this selection identified a “realistic-to-maintain competitive pace lap” between the fastest laps measured at that track, and could be selected between his/her laps of any available recorded dry session (i.e. free practice, qualifying or race). This strategy allowed filtering a “representative performance” without bias from the researcher. Therefore, a single lap per circuit was analysed for each rider (i.e. single observation per participant). A ranking value (Top third, Mid third, Low third) was given at each selected pace-lap according to the result of that rider at the chequered flag of that respective competition.

Also, for each participant, an experience index ranging from 0 to 100 was calculated by adding scores in the five areas collected with the athlete-background form. The five areas were: years of competitions (score from 0 to 20 on a scale from 0 to 20 years of motorcycle racing); participation to other competitive motorsports (score from 0 to 5 on a scale from none to regular competitor in a motorsport in addition to motorcycle circuit racing); number of races accumulated (score from 0 to 25 on a 5-point scale from 0 to more than 200 races); level of competition (score from 0 to 20 on a bi-dimensional scale with frequency and level from regional to world championship); titles awarded (score from 0 to 30 on a bi-dimensional scale with quantity of titles - from none to 5 or more - and level - from club/regional to world-).

A MATLAB script (version R2016b, MathWorks, MA, USA) was used to identify the decelerations (i.e. active braking and loss of speed due to engine braking actions) and accelerations (i.e. corner exits) inside each individual pace-lap, by finding local maximum and local minimum speed corresponding with the start and end times of speed changes (Figure 2).

Figure 2.

Example of a selected ideal race-pace single lap in the NSS class with variables brake (B) and corner exit (CE) identified. Illustrated lap-time is 1′52″9 at Imola track, with 9 brakes and 8 corner exits, and unit of measurement reflects data sampling rate (0.1 second).

To accurately isolate the decelerations in each pace-lap, the following criteria were used:

To minimize the effects of GPS error and to exclude passive deceleration before or after the active braking took place (i.e. wind resistance in case riders move from the aerodynamic position a few moments before the brakes are engaged, or mid-corner throttle-off), two algorithms were implemented: a) For passive deceleration prior to braking: the detection of the start of the deceleration period was moved forward to 99.5% of the top speed (within a maximum range of 2 seconds forward); b) For passive deceleration after braking: the detection of the end of the deceleration period was moved backward to 101.5% of the minimum speed (within a maximum range of 2 seconds backward);

To avoid the detection of short loss of acceleration (i.e. gear-shifting or short shut off in a kink of the track layout) a filter of a minimum change in velocity of 5 km/h and 0.5 seconds was applied;

To exclude extended throttle-off portions (i.e. riding through a “change of direction” section or connecting corners in the track), decelerations smaller than 10 km/h were not included in the analysis.

Also, for each brake, three more measurements were collected: the initial speed [km/h] at the start of the braking action, the duration [s] of the individual brake, and a value indicating where the mean deceleration occurred in a percentage scale of the peak deceleration, suggesting the uniformity of braking. Count and duration of braking actions were related to lap-times and race duration, to quantify frequency and size of phenomena.

To accurately isolate the accelerations exiting the corners in each individual pace-lap, the following criteria were used:

To minimize the effects of GPS error and to exclude the transition phase, two algorithms were implemented: a) the detection of the start of the acceleration period was moved forward to 101.5% of the local minimum speed (mirroring the end of the deceleration); and, b) the detection of the end of the acceleration period was moved backward to 99.5% of the maximum speed; and,

To confine the meaningful part of the corner exit (when the motorcycle engine generates the bigger portion of power), the end of the acceleration was detected when 66.7% of the difference between the end and start speeds of the acceleration period determined in previous criteria was achieved.

For each identified brake and corner exit, peak and mean horizontal acceleration [m/s²] were found. Then, the inertial forces [N] acting on the riders' centre of gravity were calculated in each individual case with the formula F = m·a.

Statistical analysis

Descriptive statistics were used to summarise measurements and describe the inertial stress (i.e. calculated forces) riders were exposed to during racing. Differences in the means were explored via magnitude-based analysis,⁷ calculating percent differences, standardized difference between means, and the uncertainty of the true mean (i.e. 95% confidence limits (CI)). Thresholds of 0.2, 0.6, 1.2, 2.0 and 4.0 were used to identify trivial, small, moderate, large and very large standardized difference between means, respectively.⁷ Pearson correlation (r) was used to test potential relationships between variables, and statistical significance was set at p = 0.05. Softwares Open Office 4.1.2 (Apache Software Foundation, MD, USA) and IBM SPSS version 25 (International Business Machines Corp, NY, USA) were used to perform the statistical analysis.

Results

Forty-eight ideal race-pace laps containing 425 braking actions and 397 corner exit accelerations were collected from 23 riders participating during the season (Table 1).

Table 1.

Sample size, ranking and participants characteristics for the three different classes: EJC: European Junior Cup; NSS: National SuperSport; WSS: World SuperSport.

	Riders	Laps	Brake	Corner exit	Circuits	Low rank	Mid rank	Top rank	Body mass fully equipped (kg)	Experience index
EJC	9	16	126	115	5	–	7	9	76.5 ± 7.2	39.7 ± 10.6
NSS	7	10	95	95	4	3	1	6	77.9 ± 6.1	48.3 ± 20.3
WSS	7	22	204	187	10	15	1	6	77.9 ± 5	52.3 ± 15.8

Individual inertial forces generated during the brakes and the corner exits were grouped according to the three classes of competition and measures of central tendency are reported in Table 2. Both the mean deceleration in braking and the mean acceleration in corner exits increased with the higher level of competition and motorcycle power (range from 6% to 28%). Interestingly, the highest peaks were associated with the NSS category, perhaps due to the prevalence of data from the Mugello circuit (Table 3).

Table 2.

Central tendencies of inertial forces and braking uniformity in different classes of motorcycle circuit racing.

Class	Stats	Mean Braking [N]	Peak Braking [N]	Braking uniformity %	Mean Corner Exit [N]	Peak Corner Exit [N]
EJC	mean ± SD median95% CI	476 ± 118478(455–497)	923 ± 294928(871–975)	53.7 ± 11.052.9(51.8–55.6)	300 ± 80.6291(285–315)	551 ± 288483(498–604)
NSS	mean ± SDmedian95% CI	505 ± 124521(479–530)	1026 ± 458933(932–1119)	53.8 ± 13.552.0(51–56.5)	362 ± 120347(337–386)	629 ± 227574(582–675)
WSS	mean ± SDmedian95% CI	513 ± 133523(494–531)	929 ± 350882(880–977)	58.5 ± 12.258.7(56.8–60.1)	384 ± 108392(368–400)	607 ± 218571(576–639)

EJC = European Junior Cup 2016; NSS = National SuperSport 600; WSS = World SuperSport 600.

Table 3.

Selected single ideal race-pace laps collected on different tracks.

	Aragon	Assen	Buriram	Doha	Donington	Imola	Jerez	Lausitzring	Magione	Magny Cours	Misano	Mugello	Vallelunga
EJC	–	1	–	–	8	–	1	–	–	1	5	–	–
NSS	–	–	–	–	–	2	–	–	1	–	–	4	3
WSS	1	2	1	1	4	2	3	2	–	3	3	–	–

Braking actions and forces

Realising the data describes different speeds of racing from different circuits, and the criteria determining inclusion into the analysis, the following observations were made. Riders in EJC performed 7.9 ± 1 brakes per lap, while riders in NSS and WSS recorded 9.5 ± 1.7 and 9.3 ± 1.7 brakes per lap, respectively. Therefore, EJC riders faced 87 ± 11 brakes per race, while riders in NSS braked 144 ± 14 times (+66%) and WSS riders performed 171 ± 28 brakes (+97% compared to EJC) at each race in the sample. In EJC measurements, 29.3% of the lap time was spent braking, and this ratio increased to 32.1% in NSS and 33.8% in WSS. On average, a braking action lasting 3.9 s was initiated every 9.5 s in EJC competitions. More frequent changes of speed were observed in higher classes, riders in NSS braking for 3.6 s every 7.7 s and riders in WSS braking for 3.8 s every 7.5 s.

Obviously, the differences in these profiles are influenced by the acceleration and deceleration capacities of the motorcycles; in fact, in 77% of cases, EJC riders initiated braking below 200 km/h, and they never exceeded the 220 km/h (top speed measured in EJC: 214 km/h). Alternatively, NSS and WSS racers braked above 200 km/h for 42% and 49% of times respectively, and experienced braking above 240 km/h in 8% and 12% of cases, respectively (top speed of both mid-classes: 273 km/h, see Figure 3).

Figure 3.

Percentage of occurrence of braking actions and their initial speed across classes. Abbreviations: EJC = European Junior Cup; NSS = National SuperSport 600; WSS = World SuperSport 600.

In the EJC class, the calculated inertial mean force acting on the rider centre of mass for each braking action was 476 ± 118 N, the forces on average 6% and 8% greater in NSS and WSS respectively (see Table 2). However, the standardized difference between means of different classes was small: 0.23 between EJC and NSS, and 0.29 between EJC and WSS.

The brake uniformity was similar between EJC and NSS (i.e. 95% CI: 51.8 – 55.6 and 51 – 56.5, respectively) while the mean braking uniformity of WSS was approximately 9% greater (i.e. 95% CI: 56.8 – 60.1). The standardized difference between means of brake uniformity was also small: 0.36 between NSS and WSS, and 0.41 between EJC and WSS.

Forces of accelerations and associations

The mean inertial forces generated while exiting the corners were found to be 20% and 28% higher in NSS and WSS respectively, compared to 300 ± 80.6 N measured in EJC class. The standardized difference between means was moderate: 0.61 between EJC and NSS, and 0.89 between EJC and WSS. The strongest relationship between variables was found between the mean force in corner exits and the mass-to-power ratio (r = −0.70; p < 0.01). In addition, also the percentage of time spent braking was found having a large negative correlation with the mass-to-power ratio (r = −0.60; p < 0.01), and a moderate correlation with the final ranking value (r = 0.50; p < 0.01).

Interestingly, a moderate positive relationship was observed between the experience index and the braking uniformity (r = 0.46; p < 0.01).

Subgrouping classes

The racing events at different circuits (see Table 3), the limited sample size, and the range of rider's equipped body mass (i.e. 68.5 – 89 kg), necessitated careful consideration of the statistical procedures to be utilised to describe main effects. For the step between the entry class (EJC) and the mid-class (WSS), five couples of observations (n = 10 race-pace laps), that were collected at the same circuits under the same conditions, were isolated for further statistical analysis. When isolating same-circuit data, on average, the lap-time of the EJC sample was 108% ± 1% the lap-time of WSS riders and inertial forces were greater in the faster class from a minimum of 5% to a max of 33% (Table 4). The largest standardized difference between means was in the mean force at corner exits and resulted moderate (0.93).

Table 4.

Magnitude of difference between classes EJC and WSS in five circuits (Assen, Donington, Jerez, Magny-Cours, Misano).

EJC – WSS	Mean braking (N)	Peak braking (N)	Braking uniformity %	Mean corner exit (N)	Peak corner exit (N)
Δ	16%	5%	15%	33%	25%
Standardized difference between means	0.59	0.13	0.63	0.93	0.65

Signal check

The validity of the sampling frequency for capturing events of importance in the speed signal, was quantified using a Fourier analysis on the isolated deceleration periods in the 48 observations (i.e. ideal race-pace laps) used for this study. The results indicated that the signal is dominated by low frequencies and the amplitude of the harmonic components becomes negligible above 2-3 Hz (see Figure 4). Given the duration of such events (mean brake duration 3.76 ± 1.34 seconds; mean full acceleration duration 5.75 ± 3.6 seconds) sampling at 10 Hz (becoming 5 Hz according to the Nyquist-Shannon theorem) was considered ample to reconstruct the signal with confidence to satisfy the purposes of this study.

Figure 4.

Fourier analysis of the signal on the isolated deceleration periods in one observation (i.e. 600 WSS class at Aragon track with lap-time 1′56″9).

Discussion

While racing, the positive and negative accelerations of the reference frame (i.e. the motorcycle) produce pseudo forces acting on the riders. Despite the advanced technology involved in motorcycle circuit racing, direct measurements of mechanical stresses experienced by riders remain unpublished.¹ To our knowledge, this study is the first to have instrumented multiple motorcycles with the intent of directly measuring the inertial forces competitors are required to accommodate, with the objective of estimating the relative muscular requirements of racing.

The main findings of this study were: 1) in national and world level SuperSport600 motorcycle circuit racing official competitions, riders experience braking activity which is considerable in volume, frequency and intensity. In a single dry race, braking actions range from 144 to 171 times, they happen every 7-8 seconds, and each one generates an inertial load on average above 500 N, with peaks about double this load. 2) The inertial force experienced when exiting the corners is related to the motorcycle mass-to-power ratio, and in mid-class category is above 70% of the braking force. 3) Despite statistical moderate-to-small differences in inertial forces between the entry-level class (European Junior Cup 2016) and the SuperSport600 class, when riders move up into this faster category, they will be required to control forces 33% more intense when exiting the corners, and 16% greater braking actions, which both occur over a bigger volume of repetitions due to the longer races.

Decelerations

The braking action is a crucial part in the performance of a racer, its intensity and its modulation influencing the lap-time and determining the inertial load acting upon the rider. In this study, the parameters of mean frequency, volume, duration and intensity of the braking actions have been quantified in entry and mid-class categories, suggesting that competitive riding requires specific muscular demands. Considering that riders spent approximately a third of their lap-time (from 29% to 34%) pulling the brake lever to slow their motion, and acknowledging that they experience a rhythmical sequence of inertial forces during the whole race (see Figure 2), reaching peaks of approximately 1000 N during the hardest brakes, it is no surprise that the chronic exertional compartment syndrome of the forearm is the most common muscular overload in this sport.^1,8,9

During the abrupt braking action, the mass of the rider is pushed forward with a force on average above 500 N in the 600 cc class (i.e. anterior pitching phase). While the rider's centre of mass is subject to this mechanical stress, lasting approximately 4 seconds, the racer is required to have full control of the handlebars and body position, in order to modulate the motorcycle yawing and rolling, so as to optimise the racing line and speed for the mid-cornering phase.^4,10,11 Future research might be able to describe the postural strategies adopted by riders to absorb the postero-anterior inertial forces, to quantify the different muscular activations and loads,¹² however, due to the complex mechanical behaviour of the human body during riding, and the accuracy required in inverse dynamics, measuring these movements will be challenging.¹³

In conclusion, the large negative correlation between the percentage of time spent braking and the mass-to-power ratio, confirms that riders aboard faster motorcycles are subject to larger mechanical stresses; nevertheless, when comparing the EJC with the WSS class, despite the 16% gap in inertial force due to braking and the 15% increase in braking uniformity, only moderate standardized differences between means were reported (0.59 and 0.63, respectively). Considering that top-level motorcycle circuit racing (i.e. MotoGP™, SuperBike) is performed at higher speeds with more powerful braking systems,² the demands of the deceleration periods appear to be substantial; however, the muscular strategies to deal with such stresses are still to be clarified.

Accelerations

The data from this study also provide a quantitative description of the mechanical load that competitive national and international racers are required to counteract when exiting corners. In the SuperSport600 class (mass-to-power ratio just above 1.1), every time the riders twist the throttle to rush/accelerate to the next corner, they experience average inertial resistances from 337 to 400 N, with peaks passing 600 N (Table 2). Such effort, sustained by the upper limbs anchored to the handlebars, and by the lower limbs, grasping the tank and loading the foot-pegs to optimise the posterior tyre grip, is 75% of the inertial forces associated with braking in WSS. These postural responses to the accelerations can be considered a substantial contribution to muscular work and are no doubt magnified when racing motorcycles with mass-to-power ratio <1 (i.e. classes with 1000 cc engines), where 300 km/h are often surpassed.^1,2 Moreover, the quantity and duration of such accelerations, the repetitive alternations with braking actions and the postural/muscular demands of cornering, combined with the hormonal responses due to high speed racing – almost half of accelerations terminate over 200 km/h (Figure 3) – may explain the cardiovascular and metabolic demands of motorcycle circuit racing i.e. mechanical demands influences metabolic demands.^1,6,14–18

Progression between categories

The number of laps in a race increases with the higher category and level of competition, therefore both higher volumes of riding actions and mechanical/inertial stresses of higher intensity are expected with bigger motorcycles. Indeed, a potential rider moving from the entry level category to the mid-class of competition (i.e. from EJC to WSS) would be required to manage a 97% increase in quantity of braking actions due to longer races, and each inertial postero-anterior force due to braking would be, on average, more homogenous (+15%) and more intense (+16%) (Table 4).

Moreover, racing with a low mass-to-power ratio motorcycle translates in dealing with a powered two-wheeler system build to reach top speed in a short time, therefore considerable inertial forces due to high accelerations are expected to be involved. In fact, when isolating same-circuit data in EJC and WSS categories, riders have been reported to experience 33% larger inertial forces at corner exits, to perform lap-times 8% shorter. Obviously, profiling these mechanical stresses contributes in better understanding performances across classes of motorcycle racing, and could guide specificity of training to better effect, to assist rider's progression up categories of competition.

Limitations

These in-field measurements under real competitive conditions provide valuable and specific data, however, the authors recognise the following limitations in this study: 1) the calculation of forces experienced on riders' centre of mass when braking or accelerating did not take into account the drag forces due to the anatomical areas exposed to frontal air resistance; 2) the calculation of inertial forces acting on the riders did not explain how the riders act to resist them or which muscular regions were activated; 3) even though criteria to isolate the active braking were applied, the identified brakes might include lower magnitude maneuvers where mainly engine braking was used to connect consecutive corners; 4) in each selected race-pace lap, the last acceleration (exiting the last corner before the start-finish line) was not identified from the MATLAB coding due to the lack of detected local maximum (lap-data ends on finish line, see Figure 2); 5) the sample is limited and there is no data from the faster and more powerful categories (i.e. various 1000 cc classes); and, 6) the low acquisition rate may increase the error between the measured velocity changes and the real ones.

Practical applications

The findings of this study provide novel information useful for the design of training programmes aiming at preparing riders for competition. Despite the interpretation and application of these results will vary according to the several classes and levels of competitions, they offer a valuable starting point in quantifying the muscular demands of motorcycle racing, and combined with the findings of D'Artibale et al.,² they enhance the knowledge and understanding of the performance model for circuit racers. To explore preventative strategies to muscular overload (i.e. chronic exertional compartment syndrome of the forearm) and deepen specificity of physical preparation programmes for motorcycle circuit racers, future research is required to describe the postural strategies adopted by riders to absorb those inertial forces, and solve the challenges associated with quantifying the different muscular activations and respective loads during real competitions.

Conclusions

The performance in motorcycle circuit racing exposes riders to mechanical demands due to the positive and negative inertial stresses generated by the alternation of accelerations and decelerations whilst competing. Direct measurements of sagittal accelerations during dry official races in entry and mid-class categories suggest that competitive riding requires specific muscular demands due to the mean frequency, volume, duration and intensity of the braking and corner-exits actions. Riders competing in national and world level SuperSport600 championships experience from 144 to 171 brakes per race, happening every 7-8 seconds of racing. The intensity of the inertial force during braking was estimated on average above 500 N, with peaks about double this load, while exiting the corners generated inertial forces on average greater than 360 N in the mid-class category (i.e. SuperSport600). Despite small to moderate standardized difference between means of entry-level and mid-class inertial forces intensities, and no strong relationships found between inertial loads, ranking levels and riders' experience indexes, this study quantified the mechanical stresses of competitive riders and profiled loads across different categories.

Footnotes

Acknowledgement

The authors express their gratitude to WIL Sport Management and Phil & Cheryl London for their scholarship and assistance with the “Optimising motorcycle circuit racing rider's performance” research project.

Acknowledgements and appreciation to the Engineer Antonino Bonanni for his consultancy and support in running the Fourier analysis.

Declaration of conflicting interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: this article is part of a research project titled “Optimising motorcycle circuit racing rider’s performance” funded with a PhD scholarship from WIL Sport.

ORCID iD

Emanuele D’Artibale

References

D’Artibale

Laursen

Cronin

JB.

Human performance in motorcycle road racing: a review of the literature. Sports Med 2018; 48: 1345–1356.

D’Artibale

Laursen

Cronin

JB.

Profiling the physical load on riders of top-level motorcycle circuit racing. J Sports Sci 2018; 36: 1061–1067.

Corno

Savaresi

Tanelli

, et al. On optimal motorcycle braking. Control Eng Pract 2008; 16: 644–657.

Ibbot

MotoGP performance riding techniques. Sparkford, UK: Haynes, 2013.

Cocco

Motorcycle design and technology. Milano, Italy: Giorgio Nada Editore, 2005.

D’Artibale

Tessitore

Capranica

Heart rate and blood lactate concentration of male road-race motorcyclists. J Sports Sci 2008; 26: 683–689.

Hopkins

Batterham

Marshall

SW.

Progressive statistics, https://www.sportsci.org/2009/prostats.htm (accessed April 2020).

Barrera-Ochoa

Haddad

Correa-Vázquez

, et al. Surgical decompression of exertional compartment syndrome of the forearm in professional motorcycling racers: comparative long-term results of wide-open versus mini-open fasciotomy. Clin J Sport Med 2016; 26: 108–114.

Gondolini

Schiavi

Pogliacomi

, et al. Long-term outcome of mini-open surgical decompression for chronic exertional compartment syndrome of the forearm in professional motorcycling riders. Clin J Sport Med 2019; 29(6): 476–481.

10.

Cossalter

Motorcycle dynamics. North Carolina, USA: lulu.com, 2006.

11.

Evertse

Rider analysis using a fully instrumented motorcycle. Master’s Thesis, Delft University of Technology, The Netherlands, 2010.

12.

Marina

Torrado

Busquets

, et al. Comparison of an intermittent and continuous forearm muscles fatigue protocol with motorcycle riders and control group. J Electromyogr Kinesiol 2013; 23: 84–93.

13.

Gruber

Ruder

Denoth

, et al. A comparative study of impact dynamics: wobbling mass model versus rigid body models. J Biomech 1998; 31: 439–444.

14.

Ascensão

Ferreira

Marques

, et al. Effect of off-road competitive motocross race on plasma oxidative stress and damage markers. Br J Sports Med 2007; 41: 101–105.

15.

D’Artibale

Tessitore

Lupo

, et al. Riding a motorcycle or racing a motorcycle: differences in oxygen consumption, heart rate, blood lactate; a pilot study. In: 18th annual congress of the European College of Sport Science, Barcelona, Spain,26-29 June 2013.

16.

D’Artibale

Tessitore

Tiberi

, et al. Heart rate and blood lactate during official female motorcycling competitions. Int J Sports Med 2007; 28: 662–666.

17.

Filaire

Le Scanff

Salivary cortisol, heart rate and blood lactate during a qualifying trial and a official race in motorcycling competition. J Sports Med Phys Fitness 2007; 47: 413–417.

18.

Tsopanakis

Stress hormonal factors, fatigue, and antioxidant responses to prolonged speed driving. Pharmacol Biochem Behav 1998; 60: 747–751.

	Aragon	Assen	Buriram	Doha	Donington	Imola	Jerez	Lausitzring	Magione	Magny Cours	Misano	Mugello	Vallelunga
EJC	–	1	–	–	8	–	1	–	–	1	5	–	–
NSS	–	–	–	–	–	2	–	–	1	–	–	4	3
WSS	1	2	1	1	4	2	3	2	–	3	3	–	–

	Aragon	Assen	Buriram	Doha	Donington	Imola	Jerez	Lausitzring	Magione	Magny Cours	Misano	Mugello	Vallelunga
EJC	–	1	–	–	8	–	1	–	–	1	5	–	–
NSS	–	–	–	–	–	2	–	–	1	–	–	4	3
WSS	1	2	1	1	4	2	3	2	–	3	3	–	–

	Aragon	Assen	Buriram	Doha	Donington	Imola	Jerez	Lausitzring	Magione	Magny Cours	Misano	Mugello	Vallelunga
EJC	–	1	–	–	8	–	1	–	–	1	5	–	–
NSS	–	–	–	–	–	2	–	–	1	–	–	4	3
WSS	1	2	1	1	4	2	3	2	–	3	3	–	–