The effects of mountain bike suspension systems on energy expenditure, physical exertion, and time trial performance during mountain bicycling

Current Perspectives of Cross-Country Mountain Biking: Physiological and Mechanical Aspects, Evolution of Bikes, Accidents and Injuries

Mountain biking (MTB) is a cycling modality performed on a variety of unpaved terrain. Although the cross-country Olympic race is the most popular cross-country (XC) format, other XC events have gained increased attention. XC-MTB has repeatedly modified its rules and race format. Moreover, bikes have been modified throughout the years in order to improve riding performance. Therefore, the aim of this review was to present the most relevant studies and discuss the main results on the XC-MTB. Limited evidence on the topic suggests that the XC-MTB events present a variation in exercise intensity, demanding cardiovascular fitness and high power output. Nonetheless, these responses and demands seem to change according to each event. The characteristics of the cyclists differ according to the performance level, suggesting that these parameters may be important to achieve superior performance in XC-MTB. Moreover, factors such as pacing and ability to perform technical sections of the circuit might influence general performance. Bicycles equipped with front and rear suspension (i.e., full suspension) and 29″ wheels have been shown to be effective on the XC circuit. Lastly, strategies such as protective equipment, bike fit, resistance training and accident prevention measures can reduce the severity and the number of injuries.

Olympic Sports Science-Bibliometric Analysis of All Summer and Winter Olympic Sports Research

Introduction: The body of scientific literature on sports and exercise continues to expand. The summer and winter Olympic games will be held over a 7-month period in 2021-2022. Objectives: We took this rare opportunity to quantify and analyze the main bibliometric parameters (i.e., the number of articles and citations) across all Olympic sports to weigh and compare their importance and to assess the structure of the "sport sciences" field. The present review aims to perform a bibliometric analysis of Olympic sports research. We quantified the following topics: (1) the most investigated sports; (2) the main journals in which the studies are published; (3) the main factors explaining sport-specific scientific attractiveness; (4) the influence of being in the Olympic programme, economic weight, and local influences on research output; and (5) which research topic is the most investigated across sports. Methods: We searched 116 sport/exercise journals on PubMed for the 40 summer and 10 winter Olympic sports. A total of 34,038 articles were filtered for a final selection of 25,003 articles (23,334 articles on summer sports and 1,669 on winter sports) and a total of 599,820 citations. Results and Discussion: Nine sports [football (soccer), cycling, athletics, swimming, distance & marathon running, basketball, baseball, tennis, and rowing] were involved in 69% of the articles and 75% of the citations. Football was the most cited sport, with 19.7 and 26.3% of the total number of articles and citations, respectively. All sports yielded some scientific output, but 11 sports (biathlon, mountain biking, archery, diving, trampoline, skateboarding, skeleton, modern pentathlon, luge, bobsleigh, and curling) accumulated a total of fewer than 50 publications. While ice hockey is the most prominently represented winter sport in the scientific literature, winter sports overall have produced minor scientific output. Further analyses show a large scientific literature on team sports, particularly American professional sports (i.e., baseball, basketball, and ice hockey) and the importance of inclusion in the Olympic programme to increasing scientific interest in "recent" sports (i.e., triathlon and rugby sevens). We also found local/cultural influence on the occurrence of a sport in a particular "sport sciences" journal. Finally, the relative distribution of six main research topics (i.e., physiology, performance, training and testing, injuries and medicine, biomechanics, and psychology) was large across sports and reflected the specific performance factors of each sport.

The impact of uphill cycling and bicycle suspension on downhill performance during cross-country mountain biking

Non-propulsive work demand has been linked to reduced energetic economy of cross-country mountain biking. The purpose of this study was to determine mechanical, physiological and performance differences and observe economy while riding a downhill section of a cross-country course prior to and following the metabolic "load" of a climb at race pace under two conditions (hardtail and full suspension) expected to alter vibration damping mechanics. Participants completed 1 lap of the track incorporating the same downhill section twice, under two conditions (hardtail and full suspension). Performance was determined by time to complete overall lap and specific terrain sections. Power, cadence, heart rate and oxygen consumption were sampled and logged every second while triaxial accelerometers recorded accelerations (128 Hz) to quantify vibration. No differences between performance times (P = 0.65) or power outputs (P = 0.61) were observed while physiological demand of loaded downhill riding was significantly greater (P < 0.0001) than unloaded. Full suspension decreased total vibrations experienced (P < 0.01) but had no effect on performance (P = 0.97) or physiological (P > 0.05) measures. This study showed minimal advantage of a full suspension bike in our trial, with further investigations over a full race distance warranted.

The effect of mountain bike wheel size on cross-country performance

The purpose of this study was to determine the influence of different wheel size diameters on indicators of cross-country mountain bike time trial performance. Nine competitive male mountain bikers (age 34.7 ± 10.7 years; stature 177.7 ± 5.6 cm; body mass 73.2 ± 8.6 kg) performed 1 lap of a 3.48 km mountain bike (MTB) course as fast as possible on 26″, 27.5″ and 29″ wheeled MTB. Time (s), mean power (W), cadence (revs · min^-1) and velocity (km · h^-1) were recorded for the whole lap and during ascent and descent sections. One-way repeated measure ANOVA was used to determine significant differences. Results revealed no significant main effects for any variables by wheel size during all trials, with the exception of cadence during the descent (F_{(2, 16)} = 8.96; P = .002; P² = .53). Post hoc comparisons revealed differences lay between the 26″ and 29″ wheels (P = .02). The findings indicate that wheel size does not significantly influence performance during cross-country when ridden by trained mountain bikers, and that wheel choice is likely due to personal choice or sponsorship commitments.

Bike racing, recreational riding, impact sport and bone health

Cycling has been shown to confer considerable benefits in terms of health, leading to reductions in death rates principally due to cardiovascular improvements and adaptation. Given the disparity between the benefits of cycling on cardiovascular fitness and previous research finding that cycling may not be beneficial for bone health, Hugo Olmedillas and colleagues performed a systematic review of the literature. They concluded that road cycling does not appear to confer any significant osteogenic benefit. They postulate that the cause of this is that, particularly at a competitive level, riders spend long periods of time in a weight-supported position on the bike. Training programs may be supplemented with impact loading to preserve bone health; however, the small increased risk of soft tissue injury must also be considered. See related commentary http://www.biomedcentral.com/1741-7015/10/168

Physiological demands of downhill mountain biking

Mountain biking is a popular recreational pursuit and the physiological demands of cross-country style riding have been well documented. However, little is known regarding the growing discipline of gravity-assisted downhill cycling. We characterised the physiological demands of downhill mountain biking under typical riding conditions. Riding oxygen consumption (VO(2)) and heart rate (HR) were measured on 11 male and eight female experienced downhill cyclists and compared with data during a standardised incremental to maximum (VO(2max)) exercise test. The mean VO(2) while riding was 23.1 ± 6.9 ml · kg(-1) · min(-1) or 52 ± 14% of VO(2max) with corresponding heart rates of 146 ± 11 bpm (80 ± 6% HRmax). Over 65% of the ride was in a zone at or above an intensity level associated with improvements in health-related fitness. However, the participants' heart rates and ratings of perceived exertion were artificially inflated in comparison with the actual metabolic demands of the downhill ride. Substantial muscular fatigue was evident in grip strength, which decreased 5.4 ± 9.4 kg (5.5 ± 11.2%, P = 0.03) post-ride. Participation in downhill mountain biking is associated with significant physiological demands, which are in a range associated with beneficial effects on health-related fitness.

Comparison of Physiological Responses and Performance Between Mountain Bicycles With Differing Suspension Systems

Purpose:

This study compared the metabolic and performance effects of riding front-only suspension (FS) and front-and-rear suspension (FRS) mountain bicycles on an off-road course that simulated competitive cross-country race conditions (>105 min in duration, with ∼70% of time spent riding uphill).

Methods:

Seven competitive mountain bikers (73.8 ± 7.6 kg; 61.0 ± 4.3 mL·kg–1·min–1) completed two randomized FS and FRS trials. Bikes were similar, excluding rear wheel suspension on the FRS, which increased bike weight by ∼2 kg. Each trial consisted of four laps of rugged 8 km trail with 154 m of elevation gain per lap. The first three laps were performed at ∼70% of VO2max; VO2, HR, and RPE were collected during the first and third laps. The final lap was performed as a maximal time-trial effort.

Results:

During the first and third laps, VO2, HR, and RPE were similar between FS and FRS. However, FS was significantly faster than FRS during the ascending segment of the course (17.6 ± 2.9 vs 18.9 ± 3.4 min, P = .035), despite similar VO2 (P = .651). Although not statistically significant, FRS tended to be faster than FS during the descending portion of the course (8.1 ± 2.0 vs 9.1 ± 2.1, P = .067) at similar VO2. Performance during the final time-trial lap was significantly faster for FS than FRS (24.9 ± 3.9 min, 27.5 ± 4.9 min, P = .008).

Conclusion:

FS was faster than FRS over a course that simulated competitive cross-country race conditions. The faster times were likely the result of improved cycling economy during ascending, which were at least partially influenced by the lighter weight of the FS.

Aspectos fisiológicos do mountain biking competitivo

A prática do ciclismo off-road (mountain biking - MTB), cresceu muito nas últimas duas décadas, sendo incluído como esporte olímpico, nos Jogos de Atlanta em 1996, na modalidade Cross Country. Na última década, houve um aumento no número de publicações científicas que verificaram a demanda fisiológica durante competições, assim como o estudo de possíveis preditores da performance nesta modalidade. O objetivo deste estudo de revisão foi descrever alguns aspectos fisiológicos específicos do MTB Cross Country (MTB CC) competitivo (intensidade de provas, perfil fisiológico de atletas de elite, uso de suspensões e determinantes da performance em subidas). Observa-se na literatura analisada que as provas de MTB CC parecem impor uma sobrecarga fisiológica maior, quando analisada através da frequência cardíaca, do que provas de ciclismo de estrada com duração semelhante. Entretanto, quando analisada pela potência de pedalada, observa-se claramente a característica intermitente da modalidade, com variações de potência durante a prova entre zero e 500W, e potência média relativamente baixa em comparação aos valores de FC encontrados. Outro fator importante levantado neste estudo são as alterações fisiológicas decorrentes do uso de suspensões nas bicicletas de MTB CC. O uso deste equipamento reduz o estresse muscular provocado pelo terreno acidentado, embora pareça não afetar o gasto energético total, tanto em percurso plano como em subidas. Entretanto, é fato que o desempenho em circuitos acidentados é melhorado com o uso das suspensões. Com base nos estudos abordados nessa revisão, conclui-se que o MTB CC enquanto modalidade competitiva apresenta uma grande variação de intensidade (avaliada através da potência), sendo esta atribuída principalmente ao tipo de terreno (irregular e com muitas aclives e declives acentuados) em que as provas de MTB CC acontecem.

Field and laboratory correlates of performance in competitive cross-country mountain bikers

We designed a laboratory test with variable fixed intensities to simulate cross-country mountain biking and compared this to more commonly used laboratory tests and mountain bike performance. Eight competitive male mountain bikers participated in a cross-country race and subsequently did six performance tests: an individual outdoor time trial on the same course as the race and five laboratory tests. The laboratory tests were as follows: an incremental cycle test to fatigue to determine peak power output; a 26-min variable fixed-intensity protocol using an electronically braked ergometer followed immediately by a 1-km time trial using the cyclist's own bike on an electronically braked roller ergometer; two 52-min variable fixed-intensity protocols each followed by a 1-km time trial; and a 1-km time trial done on its own. Outdoor competition time and outdoor time trial time correlated significantly (r = 0.79, P < 0.05). Both outdoor tests correlated better with peak power output relative to body mass (both r = -0.83, P < 0.05) than absolute peak power output (outdoor competition: r = -0.65; outdoor time trial: r = -0.66; non-significant). Outdoor performance times did not correlate with the laboratory tests. We conclude that cross-country mountain biking is similar to uphill or hilly road cycling. Further research is required to design sport-specific tests to determine the remaining unexplained variance in performance.

The physiology of mountain biking

Mountain biking is a popular outdoor recreational activity and an Olympic sport. Cross-country circuit races have a winning time of approximately equal 120 minutes and are performed at an average heart rate close to 90% of the maximum, corresponding to 84% of maximum oxygen uptake (VO2max). More than 80% of race time is spent above the lactate threshold. This very high exercise intensity is related to the fast starting phase of the race; the several climbs, forcing off-road cyclists to expend most of their effort going against gravity; greater rolling resistance; and the isometric contractions of arm and leg muscles necessary for bike handling and stabilisation. Because of the high power output (up to 500W) required during steep climbing and at the start of the race, anaerobic energy metabolism is also likely to be a factor of off-road cycling and deserves further investigation. Mountain bikers' physiological characteristics indicate that aerobic power (VO2max >70 mL/kg/min) and the ability to sustain high work rates for prolonged periods of time are prerequisites for competing at a high level in off-road cycling events. The anthropometric characteristics of mountain bikers are similar to climbers and all-terrain road cyclists. Various parameters of aerobic fitness are correlated to cross-country performance, suggesting that these tests are valid for the physiological assessment of competitive mountain bikers, especially when normalised to body mass. Factors other than aerobic power and capacity might influence off-road cycling performance and require further investigation. These include off-road cycling economy, anaerobic power and capacity, technical ability and pre-exercise nutritional strategies.

Effect of suspension systems on the physiological and psychological responses to sub-maximal biking on simulated smoothand bumpy tracks

The aim of this study was to compare the physiological and psychological responses of cyclists riding on a hard tail bicycle and on a full suspension bicycle. Twenty males participated in two series of tests. A test rig held the front axle of the bicycle steady while the rear wheel rotated against a heavy roller with bumps (or no bumps) on its surface. In the first series of tests, eight participants (age 19-27 years, body mass 65-82 kg) were tested on both the full suspension and hard tail bicycles with and without bumps fitted to the roller. The second series of test repeated the bump tests with a further six participants (age 22-31 years, body mass 74-94 kg) and also involved an investigation of familiarization effects with the final six participants (age 21-30 years, body mass 64-80 kg). Heart rate, oxygen consumption (VO(2)), rating of perceived exertion (RPE) and comfort were recorded during 10 min sub-maximal tests. Combined data for the bumps tests show that the full suspension bicycle was significantly different (P < 0.001) from the hard tail bicycle on all four measures. Oxygen consumption, heart rate and RPE were lower on average by 8.7 (s = 3.6) ml . kg(-1) . min(-1), 32.1 (s = 12.1) beats . min(-1) and 2.6 (s = 2.0) units, respectively. Comfort scores were higher (better) on average by 1.9 (s = 0.8) units. For the no bumps tests, the only statistically significant difference (P = 0.008) was in VO(2), which was lower for the hard tail bicycle by 2.2 (s = 1.7) ml . kg(-1) . min(-1). The results indicate that the full suspension bicycle provides a physiological and psychological advantage over the hard tail bicycle during simulated sub-maximal exercise on bumps.

Bicycle shock absorption systems and energy expended by the cyclist

Bicycle suspension systems have been designed to improve bicycle comfort and handling by dissipating terrain-induced energy. However, they may also dissipate the cyclist's energy through small oscillatory movements, often termed 'bobbing', that are generated by the pedalling movements. This phenomenon is a major concern for competitive cyclists engaged in events where most of the time is spent climbing, e.g. off-road cross-country races. An acceptable method to assess the overall efficacy of suspension systems would be to evaluate energy consumed by cyclists using different types of suspension systems. It could be assumed that any system that reduces metabolic expenditure for the cyclist would automatically lead to performance improvement. Unfortunately, only a limited number of studies have been conducted on that subject. Moreover, the conclusions that can be drawn from most of them are limited due to unsatisfactory statistical power, experimental protocols, measuring techniques and equipment. This review presents and discusses the most relevant results of studies that focused on mechanical simulations as well as on energy expenditure in relation to off-road bicycle suspension systems. Evidence in the literature suggests that cyclist-generated power that is dissipated by suspensions is minimal and probably negligible on most terrains. However, the scarce studies on the topic as well as the limitations in the conclusions that can be drawn from most of them indicate that we should remain cautious before supporting the use of dual suspension bicycles on all course types and for all cyclists. For example, it should be kept in mind that most cross-country racers still use front suspension bicycles. This might be explained by excessive cyclist-generated power dissipation at the high mechanical powers developed by elite cross-country cyclists that have not been studied in the literature. Finally, suspended bicycles are more comfortable. Moreover, the fact that suspension systems may significantly reduce physical stress should not be overlooked, especially in very long events and for recreational cyclists.

Self-pacing and cognitive performance while walking

Ten hikers completed a 4 km hike on hilly terrain three times: once self-paced without load, once self-paced with a backpack load of 10% body weight, and once externally paced with a backpack load of 10% body weight. Subjects performed mental arithmetic tasks and provided ratings of perceived exertion while walking. No differences in speed or accuracy of performance of mental arithmetic problems were observed. A battery of cognitive and physical tests was performed prior to walking and after each of the three walks. Significant differences between pre-walk baselines and post-walk tests were found only for the pattern-matching task. Subjects altered their pace in response to the addition of the backpack load, and altered their speed on downhill terrain in response to external pacing. Ratings of perceived exertion were found to correlate relatively well (r = 0.80) with heart rate, but consistently underestimated actual heart rate. Underestimation was much greater for downhill than for uphill terrain. Underestimation of heart rate by rating of perceived exertion was least when subjects carried an external load of 10% body weight.

Exercise intensity during off-road cycling competitions

PURPOSE

This study was designed to quantify and describe the intensity profile of cross-country mountain-biking races using heart rate (HR) recorded during competitions.

METHODS

Nine mountain bikers participated in four cross-country circuit races of international and national levels. Each cyclist was tested before the competitions to determine lactate threshold (LT), the onset of blood lactate accumulation (OBLA4), and the relationship between percentage of maximum HR and percentage of VO(2max).

RESULTS

To control for intersubject variability, only the five off-road cyclists who completed all four competitions were included in the statistical analysis. The four races' mean absolute and relative time expressed in percentage of race duration (147 +/- 15 min) spent in the EASY(ZONE) (HR below LT) were 27 +/- 16 min and 18 +/- 10%, in the MODERATE(ZONE) (HR between LT and OBLA4) were 75 +/- 19 min and 51 +/- 9%, and in the HARD(ZONE) (HR above OBLA4) were 44 +/- 21 min and 31 +/- 16%. The average HR was 171 +/- 6 beats x min(-1), corresponding to 90 +/- 3% of maximum (84 +/- 3% of VO(2max).

CONCLUSION

This study shows that cross-country events are conducted at very high intensity, especially at the start of the race. Coaches must take into account the distribution of the effort and the high exercise intensity characteristic of mountain-biking cross-country events when prescribing specific training programs.

Voluntary pacing and energy cost of off-road cycling and running

PURPOSE

The purposes of this study were (1) to compare self-chosen speed of off-road cyclists and runners on a hilly course, (2) to compare the energy expenditure of off-road cyclists and runners on the same terrain, and (3) to describe changes in energy expenditure over the course of the exercise period.

METHODS

Runners and cyclists performed three laps on a 2.75 km gravel course in a single exercise bout. The course was divided into 13 segments differing in grade and length. Position on the course and heart rate were recorded every few seconds. Speed was computed for each course segment on each lap; energy expenditure was estimated using recorded heart rates and exercise-specific maximal oxygen uptake measurements made prior to participation in the study.

RESULTS

There were significant relationships between grade and speed for both runners (r = 0.64) and cyclists (r = 0.44). The differences between cyclists and runners were greatest on downhill segments. Energy expenditure rates were not significantly different for runners (71.6% VO2 peak) and cyclists (68.5% VO2 peak).

CONCLUSIONS

Off-road cycling and running are comparable in energy demands. Variation in skill levels may account for the increased variability in speed among cyclists on downhill terrain.

Effects of front and dual suspension mountain bike systems on uphill cycling performance

PURPOSE

The purpose of this study was to evaluate the effects of front suspension (FS) and dual suspension (DS) mountain bike designs on time-trial performance and physiological responses during uphill cycling on a paved- and off-road course.

METHODS

Six trained male cyclists (35.6 +/- 9 yr, 76.9 +/- 8.8 kg, VO2 peak 58.4 +/- 5.6 mL x kg(-1) x min-1)) were timed using both suspension systems on an uphill paved course (1.62 km, 183-m elevation gain) and an uphill off-road course (1.38 km, 123-m elevation gain). During the field trials, VO2 was monitored continuously with a KB1-C portable gas analyzer, and power output with an SRM training system.

RESULTS

On the paved course, total ride time on FS (10.4 +/- 0.7 min) and DS (10.4 +/- 0.8 min) was not different (P > 0.05). Similarly, total ride time on the off-road course was not significantly different on the FS bike (8.3 +/- 0.7 min) versus the DS bike (8.4 +/- 1.1 min). For each of the course conditions, there was no significant difference between FS and DS in average minute-by-minute VO2, whether expressed in absolute (ABS; L x min(-1)) or relative (REL; mL x [kg body wt +/- kg bike wt(-1)] x min(-1) values. Average power output (W) was significantly lower for ABS FS versus DS (266.1 +/- 61.6 W vs 341.9 +/- 61.1 W, P < 0.001) and REL FS versus DS (2.90 +/- 0.55 W x kg(-1) vs 3.65 +/- 0.53 W x kg(-1), P < 0.001) during the off-road trials. Power output on the paved course was also significantly different for ABS FS versus DS (266.6 +/- 52 W vs 345.4 +/- 53.4 W, P < 0.001) and REL FS versus DS (2.99 +/- 0.55 W x kg(-1) vs 3.84 +/- 0.54 W x kg(-1), P < 0.001).

CONCLUSION

We conclude that despite significant differences in power output between FS and DS mountain bike systems during uphill cycling, these differences do not translate into significant differences in oxygen cost or time to complete either a paved- or off-road course.