Examining the Efficiency of Electric-Assisted Mountain Biking across Different Types of Terrain

Abstract

Mountain bikes with electric assistance (e-bikes) have gained popularity recently by allowing riders to increase their pedaling power through an electric motor. This innovation has raised questions about how e-bikes compare to traditional mountain bikes regarding physical effort, speed, and physiological demands. By examining these factors, the study aims to compare and characterize differences in performance-related parameters when using an electric-assisted mountain bike compared to a conventional mountain bike on different types of terrain (uphill, downhill, flat section, technically demanding terrain) concerning power output, velocity, cardiorespiratory parameters, and energy expenditure. Six experienced mountain bikers (mean age: 44.6 ± 6.4 years, mean body height: 173.3 ± 5.6 cm, mean body weight: 70.6 ± 4.9 kg) cycled 4.5 km on varying off-road terrain at their own race pace, once with and once without electrical assistance, in randomized order. The results of the study indicate significantly faster (24.3 ± 1.85 to 17.2 ± 1.22 km/h (p < 0.001)) cycling on an electric-assisted mountain bike, which reduces cardiorespiratory parameters and metabolic effort as well as results in less demanding workload (138.5 ± 31.8 W) during the cycling with an electric-assisted mountain bike in comparison to a conventional mountain bike (217.5 ± 24.3 W (p < 0.001)). The results indicate significant differences especially when riding uphill. The performance advantage of an electrically assisted mountain bike diminishes compared to a conventional mountain bike on downhill, flat, or technically challenging terrain. The highlighted advantages of electric-assisted mountain bikes could represent a novel strategy for cycling in different terrains to optimize efficiency.

1. Introduction

Electrically assisted bicycles (E-bikes) require the rider to pedal for assistance to be provided [1]. Unlike a motor-bike, the battery driven e-bike is equipped with a torque or velocity sensor that signals the production of supporting power only when the cyclist exerts force onto the pedals. Depending on local regulations, as well as on the motor size and variations in design, these bicycles may be used at speeds of up to 25 km/h. Higher speeds can also be attained, but this requires enhanced effort by the cyclist since no additional support is provided by the electrical unit [2].

In recent years, different new technologies have become increasingly popular [3]. During the past decade, E-bikes have become a popular alternative to traditional bicycles [4]. Electric-assisted bicycles (E-bikes) represent one of the fastest-growing segments of the transport market. Among the new technologies, e-bikes have a huge potential for a different use among amateur or professional cyclists [5]. Over 31 million e-bikes were sold in 2012, and sales forecasts indicate a promising upward trend [6,7]. Recent research shows that e-bike sales increased for 145% between 2019 and 2020, outpacing the growth rate of conventional bicycles, which is less than half of this remarkable increase [8]. There are several reasons for this rise in popularity. Some models compensate for physical impairments and have the potential to reach farther destinations more easily. A range of factors helped to raise the popularity, including improvements in battery and motor technology, coupled with innovative industrial design, which contributed to the greater range and enhanced performance of E-bikes [6,7,9,10]. E-bike users have reported advantages such as higher speed with less effort and reduced travel time compared to conventional bicycles [5,6]. The combination of higher average speed and lower power output indicates that electric-assisted bikes can provide cyclists with a more efficient and less strenuous experience [11].

Some studies have compared cycling with or without electric assistance and found that e-biking was faster and less intensive than conventional bicycling especially on the hilly route [9,12]. Simons et al. [13] investigated the effects of three different power assistant modes on physiology. They found that all three power settings contributed to meeting minimum physical activity requirements. Even with electrical assistance, riders achieved the necessary physical activity intensity of 3–6 METs. The MET concept represents a simple, practical, and easily understood procedure for expressing the energy cost of physical activities as a multiple of the resting metabolic rate [14]. Sperlich et al. [2] found that E-bikes provide moderate physical activity (MET > 3) on flat segments and downhill segments and vigorous physical activity (MET > 6) on uphill segments.

Absolutely, maintaining a certain level of physical activity intensity is important for various aspects of fitness and training, including in the context of sports training. When considering the use of electrical assistance, such as electric bicycles, in sports training, it is important to ensure that the assistance is used in a way that still provides the intended training benefits. E-bikes also have the potential to be used by amateur or professional cyclists. For example, in 2019, electric-assisted mountain bike racing took a sanctioned spot at elite-level events. The first-ever elite World Championship was held during the 2019 UCI Mountain Bike World Championships. This type of race takes place on varied terrain and includes rocky trails, technical singletrack, and open forest trails. It is characterized by frequent obstacles such as jumps and vertical drops coupled with high-intensity, high-performance uphill sectors. Interestingly, physiological variables (heart rate, respiratory frequency…) remain elevated during descents, although the workload is significantly lower in these sections [15,16].

There is a lack of studies to systematically evaluate and compare the physiological aspects of riding electric-assisted and conventional mountain bikes, particularly in relation to different types of off-road terrain, including technically challenging sections, descents, and flat terrain [1]. As part of our research, we will comprehensively examine off-road cycling, with participants riding various types of terrain common to mountain biking at high intensity. In our study, we will conduct an in-depth analysis of off-road cycling. This will involve participants navigating through a variety of terrain types common to mountain biking while exposing themselves to high physiological intensity. The inclusion of a wide range of terrain and high intensity sets our study apart from previous research.

Therefore, the study aimed to compare and characterize performance-related parameters for riding electric-assisted and conventional mountain bikes. The study was designed to test the hypothesis that the use of an electric-assisted mountain bike would result in significant differences in performance over varying terrain. These differences were anticipated to be most noticeable on climbs, while less pronounced differences were expected when navigating technically challenging terrain and descents. The study incorporated several key variables into its analysis, including metrics related to speed, cycling performance, and physiological parameters.

2. Materials and Methods

2.1. Study Design

An off-road riding on a 4.5 km long lap with four sections was monitored. The first “uphill” section was 1.6 km long with 128 m of elevation and consisted of a compact gravel terrain. The second “downhill” section was 1.4 km long, consisting of packed gravel and grass terrain, and was followed by an 800 m “flat” section with mixed open forestry roads and a paved surface. The fourth and last section of the lap was 700 m in length and included a technically demanding single track with frequent obstacles, such as rocks, roots, and many curves. A repeated measures design was employed. The participants cycled on a mountain bike course with different off-road terrains (i.e., uphill, downhill, flat section, technically demanding terrain) at their self-pace (as fast as possible) on electric-assisted and conventional mountain bike. The two testing conditions were separated by two days and were randomly performed. Before each measurement, a 10-min warm-up was performed. Two types of mountain bikes were used for the study: a conventional model (Scott Genius 700 PLUS), which is shown in Figure 1, and an electric-assisted version (Scott e-Genius PLUS 700), which is shown in Figure 2. The electric-assisted bike, which was equipped with a battery, engine, and the necessary controls of the Bosch Performance CX drive system, weighed 7.5 kg more than the conventional bike. The Bosch Performance CX motor (Abstatt, Germany), which remained untuned, retained its original 250 W output and was powered by a 500 Wh battery. The electric motor was configured to provide assistance only up to a speed of 25 km/h.”

During all measures, the altitude, distance, velocity, cadence, and power output (PO) values were recorded at a 1 Hz sampling rate. All the values were sensed with the Garmin Vector pedals and Garmin Edge 820 receivers (Garmin, Olathe, KS, USA). The results are shown as mean power output (MPO), peak power output (PPO), and normalized power output (NPO—a 30 s rolling average of the power data. Heart rate was recorded with a Polar v800 device (Polar, Kempele, Finland). Each participant wore a portable breath-by-breath gas analyzer (Cosmed K4b2, Rome, Italy) during the measurements. Oxygen uptake (VO₂), ventilation (Ve), respiration frequency (Rf), and energy expenditure were recorded. Gross efficiency (GE) was calculated following De Koning et al. [17]. For these parameters, averages for all four sections (uphill, downhill, flat, technical demanding terrain) and the total course were calculated.

At each point of observation along the off-road course, the pedaling power (Pp) needed to overcome air drag (Pd), rolling resistance (Pr), and gravity (Pg) as well as the power to produce acceleration (Pa) were calculated, where Pd was defined as Pd = Fd × v, where v is the velocity and Fd is the air drag force based on a previous study Fd = 0.1929 × v^2.0531 [18]. Similarly, Pr was calculated as: Pr = CrFg × v, where Fg is the total weight of the cyclist and the bicycle, and Cr was linearly estimated based on the rolling resistance test results for mounted Schwalbe Racing Ralph TLR tires [19] for a tire pressure of 2 bars. The Pg was calculated as: Pg = Fg × v, and Pa as: Pa = FMa × v, where ‘a’ is acceleration and M is the total mass of the cyclist and the bicycle. Velocity was filtered with the Rauch–Tung–Striebel algorithm [20], which uses two unscented Kalman filters running forward and backward in time and performs fixed-interval offline smoothing of the estimated signals. The Kalman filter has also been used to estimate non-measurable acceleration optimally and was implemented using the Kalman filter toolbox [21] in Matlab 7.9 (Mathworks Inc., Natick, MA, USA).

Finally, the power supplemented by the electric engine (Pe) was calculated as Pe = Pp + Pma − Pr − Pd − Pg.

Note that Pe was calculated for both electric-assisted and conventional mountain bikes, whereas non-zero results for conventional mountain bikes estimate the measure for losses such as the chain, bottom bracket, fork, rear shock, and derailleurs.

2.2. Participants

The study involved six male participants who had a high level of experience in mountain biking and cross-country mountain bike competition. The participants’ data were as follows: age (44.6 ± 6.4 years), height (173.3 ± 5.6 cm), and weight (70.6 ± 4.9 kg). It is important to highlight that all participants met specific inclusion criteria that included cross-country cycling experience, Slovenian Cycling Federation license, and prior experience with electrically assisted mountain biking, as they were all e-bike owners. Identical mountain bikes were used for this study, and due to frame size, participants had to be approximately 175 cm body height. Prior to their participation, all participants were provided with detailed information about the research protocol and voluntarily gave their written informed consent.

2.3. Statistical Analyses

Analyses were conducted using IBM SPSS Statistics (Version 28.0; SPSS Inc., Armonk, NY, USA). The data were presented according to descriptive statistics (Means ± SD). The differences between means of field variables recorded during the different bikes and during uphill, downhill, nearly flat, and technically demanding off-road cycling were evaluated by one-way analysis of variance. The statistical significance was set to p < 0.05.

3. Results

Riding with the electric-assisted mountain bike (24.3 ± 1.85 km/h) on the entire 4.5 km long course (

Table 1. Comparative analysis of performance metrics for electric-assisted (e-MTB) and conventional (MTB) mountain bikes.

	e-MTB	MTB	% Difference
Velocity (km/h)	24.3 ± 1.85 *	17.2 ± 1.22 *	29.2
Cadence (rev/min)	76.5 ± 5.1	72.8 ± 4.1	4.8
MPO (W)	138.5 ± 31.8 *	217.5 ± 24.3 *	36.3
PPO (W)	526.0 ± 150.1	719.7 ± 159.4	26.9
MPO (W/kg)	1.9 ± 0.13 *	3.1 ± 0.28 *	38.7
NPO (W)	186.0 ± 31.6 *	253.5 ± 28.6 *	26.6
HR (bpm)	148.7 ± 14.8	162.5 ± 4.5	8.5
Rf (br/min)	44.8 ± 5.8 *	52.6 ± 6 *	14.8
Ve (L/min)	103.1 ± 26.2 *	130.6 ± 11.7 *	21.1
VO2/Kg (mL/min/kg)	47.5 ± 6.1 *	55.4 ± 3.8 *	14.3
METs	13.6 ± 1.8 *	15.8 ± 1.1 *	13.9

The values presented are means ± standard deviations. MPO—mean power output; PPO—peak power output; MPO—relative mean power output; NPO—normalized power; HR—heart rate frequency; Rf—respiratory rate; Ve—ventilation; VO₂/kg (mL/min/kg)—relative oxygen uptake; METs—metabolic equivalent of tasks; * Indicates statistical differences at p < 0.05 between the electric-assisted and conventional mountain bike.

) was significantly faster than riding the conventional mountain bike (17.2 ± 1.22 km/h). Despite the higher average speed of the electrically assisted mountain bikes, they rode at a significantly lower mean power output (−36.3%) than on the conventional mountain bikes.

In phases where pedaling was not performed (normalized power), there were still significant differences (−26.3%) in normalized power between the electric-assisted mountain bike and conventional mountain bike. There were no significant differences in pedaling cadence between electrically assisted mountain bikes (average cadence of 76.5 ± 5.1 rpm) and conventional mountain bikes (average cadence of 72.8 ± 4.1 rpm).

The physiological parameters during off-road cycling on an electric-assisted mountain bike and a conventional mountain bike over the entire course are shown in Table 1. The effort level during off-road cycling was classified as vigorous intensity (>6 METs). It was also demonstrated during cycling on an electric-assisted mountain bike (13.6 ± 1.8 METs) and a conventional mountain bike (15.8 ± 1.1 METs). The study results suggest that cycling with an electric-assisted mountain bike is more efficient than a conventional one. Gross efficiency (GE), a measure of how effectively mechanical energy is converted into forward motion, was significantly lower when using an electric-assisted mountain bike (14.1 ± 3.3%) than when using a conventional mountain bike (18.7 ± 3.4%). The results also examined various physiological parameters, such as an average heart rate 8.5% higher on the conventional mountain bike than on the electric-assisted mountain bike. The respiratory rate was approximately 14.8% higher on the conventional mountain bike than on the electric-assisted mountain bike. Minute ventilation was 21.1% higher on the conventional mountain bike than on the electric-assisted mountain bike. Relative oxygen uptake was 14.3% higher on the conventional mountain bike than on the electric-assisted mountain bike.

The results in

Table 2. Comparative analysis of power outputs, velocity, and pedaling cadence in different off-road terrains: electric-assisted (e-MTB) vs. conventional (MTB) mountain bikes.

	Uphill		Downhill		Flat		Technical
	e-MTB	MTB	e-MTB	MTB	e-MTB	MTB	e-MTB	MTB
Velocity (km/h)	23.6 ± 0.4 *	11.9 ± 0.9 *	38.5 ± 3.1	35.9 ± 3.1	24.8 ± 0.8	24.2 ± 1.6	18.2 ± 2.1	15.9 ± 1.7
Cadence (rev/min)	82.1 ± 6 *	70.7 ± 7 *	47.3 ± 28	57 ± 17	77.5 ± 8	82.6 ± 5	73.8 ± 9	81.2 ± 5
MPO (W)	225 ± 34	278 ± 31 *	67.8 ± 10 *	114 ± 14 *	158 ± 34 *	245 ± 21 *	156 ± 44 *	242 ± 22 *
NPO (W)	219 * ± 27 *	273± 31 *	16 ± 8	17± 19	152 ± 49	238 ± 27 *	130 ± 39 *	232 ± 26 *
PPO (W)	389 ± 84	397 ± 75	141 ± 39	218 ± 118	456 ± 103	616 ± 191	499 ± 178	593 ± 94

The values presented are means ± standard deviations. MPO—mean power output; PPO—peak power output; MPO—relative mean power output; NPO—normalized power; * Indicates statistical differences at p < 0.05 between the electric-assisted and conventional mountain bike.

compare speed and power output while cycling on different off-road terrains using electric-assisted and conventional mountain bikes. The combination of higher average speed and lower power output indicates that electric-assisted mountain bikes can provide cyclists with a more efficient and less strenuous experience when climbing hills. Specifically, the results showed that cyclists using electric-assisted mountain bikes achieved a significantly higher average speed of 23.6 ± 0.4 km/h when riding uphill. In contrast, cyclists using conventional mountain bikes achieved a significantly lower average speed of 11.9 ± 0.9 km/h under similar conditions. In addition, the study’s results showed that the average power output of riders of mountain bikes with electric assistance was 19.1% lower than that of riders of conventional mountain bikes when riding uphill.

In contrast to uphill cycling, the results presented (Table 2) show no statistically significant differences in cycling speed between an electric and a mountain bike when cycling on flat terrain, downhill, and on technically challenging sections. However, the electric-assisted mountain bike had significantly lower mean power output on downhill, flat, and technically challenging sections. The mean power output while riding an electric-assisted mountain bike was significantly lower than the conventional mountain bike in downhill (−40.5%), flat (−35.5%), and technically demanding (−35.4%) sections.

The results presented in

Table 3. Comparative analysis of physiological parameters in different types of off-road terrains: electric-assisted (e-MTB) vs. conventional (MTB) mountain bikes.

	Uphill		Downhill		Flat		Technical
	e-MTB	MTB	e-MTB	MTB	e-MTB	MTB	e-MTB	MTB
HR (bpm)	156 ± 10	166 ± 4.9	133 ± 18	143 ± 8.0	147 ± 14	159 ± 6.9	152 ± 18.8	164 ± 6.1
Rf (br/min)	46.2 ± 4.5 *	52.4 ± 5.1 *	38.9 ± 8.4	45.6 ± 7.1	43.9 ± 7.5 *	54.3 ± 6.5 *	48.3 ± 7.4	55.7 ± 8.9
Ve (L/min	117 ± 19 *	138 ± 9 *	80 ± 23	92 ± 23.0	98 ± 29.	123 ± 15	104 ± 38	132 ± 24
VO2/Kg (mL/min/kg)	56.4 ± 2.8 *	60.9 ± 3.8 *	31.8 ± 6.5	33.6 ± 9.4	48.8 ± 8.4	50.2 ± 6.4	48.6 ± 11.1	54.1 ± 5
GE	16.5 ± 1.3 *	19.2 ± 1.2 *	9.5 ± 4.3 *	16.5 ± 5.8 *	15.0 ± 1.4 *	20.7 ± 2.6 *	13.7 ± 3.3 *	19.1 ± 2.7 *

The values presented are means ± standard deviations. HR—heart rate frequency; Rf—respiratory rate; Ve—ventilation; VO₂/kg (mL/min/kg)—relative oxygen uptake; GE—gross efficiency; * Indicates statistical differences at p < 0.05 between the electric-assisted and conventional mountain bikes.

compare the physiological demands of off-road cycling on different types of terrain between electric-assisted and conventional mountain bikes. The results highlight several significant differences in physiological parameters between the two types of bikes, particularly during uphill sections. The gross efficiency of the electric-assisted mountain bike was consistently lower than the conventional mountain bike on all off-road sections. This suggests that the electric-assisted mountain bike is not as efficient at converting rider-applied energy into forward motion, which was possibly due to the additional weight of the electric components.

Riding the electric-assisted mountain bike during climbs resulted in a statistically significant 6% decrease in heart rate. This suggests that the rider’s cardiovascular system experienced less stress and exertion when the e-bike was used to negotiate inclines. Oxygen uptake, a measure of the body’s oxygen consumption during exercise, was significantly lower (−7.9%) when riding the electric-bike uphill. The electric-assisted mountain bike resulted in a significant decrease in minute ventilation (−17.9%) and a significant decrease (−13.4%) in respiratory rate during uphill climbs. This indicates that the cyclist’s respiratory rate was lower, suggesting less stress on the respiratory system. The study also shows that the differences in physiological responses between electric-assisted and conventional mountain bikes were less pronounced during the not-uphill sections (downhill, flat, technical demanding terrain).

Based on the results (

Table 4. Mean (±SD) data of power values in varying terrain with electric-assisted (e-MTB) and conventional (MTB) mountain bike.

	Uphill		Downhill		Flat		Technical
	e-MTB	MTB	e-MTB	MTB	e-MTB	MTB	e-MTB	MTB
Pp (W)	220 ± 25 *	274 ± 34 *	14.7 ± 10	20.3± 18	147.6 ± 44 *	219.3 ± 25 *	135.7 ± 47 *	230 ± 26 *
Pr (W)	3.71 ± 0.2 *	1.54 ± 0.3 *	5.89 ± 0.8	5.4 ± 0.7	0.42 ± 0.2	0.49 ±0.2	1.15 ± 0.2 *	0.9 ± 0.2 *
Pg (W)	530 ± 43 *	219 ± 44 *	−839 ± 123	−780 ± 99	−2.7 ± 13	11.5 ± 22	−25.3 ± 34	−4.7 ± 12
Pd (W)	30.8 ± 4.3 *	5.7 ± 3.9 *	137 ± 40	173 ± 29	62.4 ± 25	65.3 ± 31	63 ± 16	50.6 ± 9
Pa (W)	−1.2± 1.6	−0.6 ± 1.1	−0.5 ± 2.5	2.9 ± 4.8	−7.1 ± 3.1	−5.3 ± 4.9	0.2 ± 3.4	0.7 ± 3.4
Pe (W)	346 ± 40 *	−47 ± 17 *	−710 ± 94	−624 ± 87	−66 ± 30 *	−151 ± 36 *	−97 ± 34 *	−184 ± 20 *

The values presented are means ± standard deviations. Pp—pedaling power; Pr—rolling resistance power; Pg—power needed to overcome gravity; Pd—air drag power; Pa—power needed for acceleration; Pe—estimated engine power; * Indicates statistical differences at p < 0.05 between the electric-assisted and conventional mountain bikes.

) for power calculations between the electric-assisted and conventional mountain bikes for each section of the off-road course, the findings reveal distinct differences in power outputs. The most noticeable differences can be observed in the uphill section, where the electric-assisted mountain bike shows significant differences compared to the conventional mountain bike. When riding uphill, it can be seen that the cyclist applies less pedaling power (Pp) with less effort, while the estimated engine power (Pe) generates a significantly higher output power due to the higher speed. At the same time, the power required to overcome gravity (Pg), rolling resistance (Pr) and air drag (Pd) also increases due to the higher speed.

The main objective of this comparison was to evaluate the impact of electric assistance on mountain biking performance requirements on different trail sections. By focusing on the uphill section, this objective was achieved, and the profound impact of electric assist on power demand was highlighted.

4. Discussion

The purpose of the study was to compare and characterize performance-related parameters between electric-assisted and conventional mountain bikes. Highly skilled participants with previous competitive mountain biking experience cycled on a mountain bike course with different off-road terrains (i.e., uphill, downhill, flat section, technically demanding terrain) on electric-assisted and conventional mountain bikes.

Physiological demands and energy expenditure were significantly increased throughout the mountain bike course when participants used conventional mountain bikes versus electrically assisted mountain bikes. There were significant differences in several physiological parameters and speed under different riding conditions. Of note, speed was significantly higher when riding uphill on an electrically assisted mountain bike. Most physiological parameters showed higher efficiency, lower heart rate, and lower oxygen consumption relative to power output while riding an electric-assisted mountain bike. This higher efficiency can be attributed to the electric motor, which assists the cyclist and reduces the physical effort required to ride uphill. As a result, less oxygen is needed to maintain a given speed and cover a given distance, which means improved cycling efficiency.

The results showed that cyclists rode with an electric-assisted mountain bike on technically demanding terrain and ascents with a higher cadence, which can be connected to make it easier to adapt and improve the technique on this terrain, even when replacing an electric-assisted mountain bike with a conventional mountain bike.

Due to the significantly higher speed of riding uphill on an electric-assisted mountain bike, cyclists also had to exert more power to resist air drag. However, there was also a significant difference in the power required to overcome gravity not only at the expense of the weight difference but more importantly at the expense of the difference in riding velocity with the electric-assisted mountain bike when going uphill. E-bikes also have electric motors that assist the rider and make it easier to accelerate and maintain speed.

The motor provides additional power during acceleration, reducing the effort the rider requires. As the results of the study show, when riding uphill, it becomes evident that the cyclist expends reduced pedaling effort. Some physiological and power output differences occur when riding downhill, on a flat section, and on technically demanding terrain. Some explanations might also be that the bike’s weight, where the electric-assisted mountain bike was 7.5 kg heavier than a conventional mountain bike.

Some previous studies investigated the physiological demands of electric-assisted off-road cycling but were mainly focused on health-related issues. The benefits of the physiological demands were similar to our findings, where the intensity was significantly different between riding with electric-assisted power or no electric assistance [2,9,13]. When we compared different types of off-road terrains, we found that riding uphill was the segment where the most benefits of an electric-assisted mountain bike were apparent. Physiological measurements and power output measurements were shown to help provide insights into the physiological profile of off-road cycling in varying terrains with an electric-assisted and conventional mountain bike. During the uphill segment, the oxygen consumption level was significantly larger when riding a conventional mountain bike than an electric-assisted one.

On the other hand, the smaller differences observed in the downhill and technically demanding sections could be due to several factors. One of these factors could be the effective use of the gear ratio during the ride. It is possible that cyclists more skillfully adjusted their gears on conventional mountain bikes while descending or riding through technically challenging terrain, thus maintaining comparable levels of effort and energy expenditure. In addition, the weight of the bike itself may have an impact. Lighter bikes may offer an advantage on descents because they are easier to ride and adapt more quickly to changes in terrain. There are also some minor changes in bike geometry of both types of mountain bikes, such as frame design and suspension adjustment to a lighter conventional mountain bike, which could help minimize physiological differences between riders. These factors can affect the bike’s performance on rough and technical terrain and potentially level the competition. Another important aspect is the electrical assistance provided by the bike’s battery. The motor stops assisting once the rider exceeds a certain speed, which is usually around 25 km/h. This means that on descents, where the speed may exceed this limit, the importance of the electric assistance decreases. Consequently, the rider with a heavier and less maneuverable bike must rely more on his own pedaling power. Thus, riding a heavy mountain bike with electric assist through technically challenging terrain, such as a rocky single track with numerous roots and rocks, can negate any advantages or even become a disadvantage.

There are also some limitations to this study. Firstly, the small sample size of only six participants and the use of a single cross-country mountain bike course present challenges in terms of generalizing the results despite the variety of terrain of the course. For future research, it is recommended that multiple trials be conducted on different cross-country courses of varying durations. Another limitation of the present study may be the difference in duration of the rides because of the faster cycling with the electric-assisted mountain bike compared to conventional mountain bikes. As riders completed their rides in different time durations, muscular fatigue could influence the physiological response and power output values. A useful strategy might involve conducting studies on different off-road terrains at same speeds both with and without electric assistance. It should be noted, however, that maintaining equal speeds on off-road terrain can be quite challenging due to the unpredictable nature of the terrain. It is also important to acknowledge that mountain bikes with electric assistance tend to be heavier than their conventional counterparts, which means that riding an e-bike with the power off is not directly comparable to riding a conventional bike. For example, it may be assumed that riding with a heavyweight electric-assisted mountain bike through a very technically demanding terrain (e.g., a rocky single track with many roots and stones) would no longer be an advantage or could become a disadvantage. Potentially using the two similar bikes, one could consider that the two bicycles should have had the same weight optimally. This could have been achieved by adding extra weight to the conventional mountain bike, but on the other hand, heavier electrically assisted mountain bikes are still a reality.

5. Conclusions

The current study’s findings have a direct practical application to understanding better the demands and differences between electric-assisted and conventional mountain bikes, particularly for recreational and competitive cyclists, especially while the electric-assisted championship was recently established. Electric-assisted off-road cycling appears to provide extenuating circumstances for riding. Electric-assisted off-road cycling refers to the use of electric motors to assist the rider in navigating difficult terrain. These e-bikes can provide a speed and power boost, which can be beneficial for riders with varying levels of fitness or experience. This assistance can be especially beneficial for mountain biking. By using mountain bikes with electric assistance, people with different abilities, such as trainers, less trained riders, recreational cyclists, and elite athletes, may be able to ride together more harmoniously. The electric assistance can help bridge the gap between physical fitness and technical ability, allowing less experienced riders to keep up with more skilled ones.

In conclusion, the study’s findings illustrate that changes in terrain (uphill, flat, downhill, or technical demanding terrain) influence physiological parameters and mechanical work performed regardless of electrical assistance. The results of the study suggest that physiological and performance measurements help to provide insight into the physiological profile of off-road cycling in different off-road terrain with an electrically assisted and a conventional mountain bike. The results highlight that uphill cycling with an electrically assisted mountain bike can result in more efficient cycling, which is characterized by lower oxygen consumption relative to the power expended. This improvement in efficiency is attributed to the assistance provided by the electric motor, which reduces the physical effort required to ride uphill. In contrast, when riding downhill, on flat trails, and on technically challenging terrain, smaller differences were found between electric-assisted and conventional mountain bikes. When riding downhill and on flat sections, the battery power of the electric bike was decisive in limiting the maximum speed. Below this threshold, electric assistance resulted in a smoother ride and consistent speed. However, once this limit was reached or exceeded, participants had to apply more force to maintain their pace as the electric motor ceased its assistance.

In essence, this study underscores the nuanced impact of electric assistance when cycling off-road, with clear advantages on climbs but more complex interactions on flat sections as well as on descents and technically challenging rides. However, this advantage only applies up to a speed of 25 km/h. Beyond this speed, e-bikes offer no additional support, which can make descents, technically challenging terrain or downhill sections more difficult to ride compared to conventional mountain bikes.

These results provide valuable insights, especially for cyclists and underscore the importance of considering specific terrain when evaluating the effects of electric-assisted mountain bikes on cycling performance.