Publication ahead of print
Journal
Mov Sport Sci/Sci Mot
DOI https://doi.org/10.1051/sm/2022001
Published online 04 February 2022

© ACAPS, 2022

1 Introduction

The origin of air bike dates back to the 1970s, but it grew more popular only in the 21st century. In past years, it became a very widespread cardio machine that can be often found in gyms and fitness centres. It tends to be associated with HIIT and endurance training and is used to develop cardiorespiratory fitness or for weight management (Kim et al., 2017). It is a non-specific tool for developing strength and endurance parameters. One exception is CrossFit where it is used in a similar way as rowing or cross-country skiing machine for athletic performance.

Air bike is a type of stationary bike equipped with two handles allowing upper-body activity. The movement consists of two parts: 1st pedalling (same as cycling), 2nd handles work allowing both pulling and pushing motions. The pedals are mechanically connected to the handles, which implies equal frequency. Both the handles and the pedals can be used separately, or in other words, the power can be distributed at will. The resistance is created by a flywheel and the load increases with speed (frequency). Another way of load regulation is usually not available. The seat position can be adapted; the handles are constructed in a fixed way. As opposed to a stationary bike, the movement is more strength-based; the pedalling frequency is usually in the range of 40 to 80 rpm (revolutions per minute), compared to a stationary bike (70 to 110 rpm). The movement is less technically demanding, and thus suitable for specific groups (Pitetti, Climstein, Campbell, Barrett, & Jackson, 1992).

Stress testing has a long history and it is still an essential part of sports training or assessing the adaptation of organism in various population samples. The best practice is ramp test using a treadmill or stationary bike (Joyner & Coyle, 2008). Both variants work mostly the lower body and the movement has a higher frequency and lower resistance. That is why they are specific movements and they might not be ideal for each individual or sports discipline. Martial arts, judo, rugby, ice hockey, etc. are disciplines typical for their strength and low-frequency nature and also for a significant role of the upper body (James, Haff, Kelly, & Beckman, 2016; Tavares, Smith, & Driller, 2017). Not only athletes but also firefighters or soldiers do complex movements using many muscle groups (Peterson, 2015). For these individuals, it would be good to find an alternative that significantly engages upper body muscles too.

Spiroergometry is a tool for qualitative and quantitative assessment of cardiovascular, respiratory and metabolic reactions to exercise. Measuring oxygen consumption, carbon dioxide, minute ventilation, and heart rate provides significant diagnostic and prognostic information in a wide range of fields (Wonisch et al., 2003). The most important variable in spiroergometry is maximal oxygen consumption (VO2peak), which determines the capacity of the cardiopulmonary system and muscle tissue. It also provides information on overall cardiorespiratory fitness. The base of the spiroergometric test is an analysis of the composition of inhaled and exhaled air and it helps assess the functional response of the organism to stress (Corrà et al., 2018).

In older studies, in stress testing, air bike was compared to stationary bike (Eston & Brodie, 1986), running on a treadmill or other cardio machines (Zeni, Hoffman & Clifford, 1996). Unfortunately, there is only a small number of studies that use air bike as a tool for testing. The authors do not know of any study that would consider the relation between using an air bike and strength or endurance parameters.

Using air bikes for spiroergometry is not yet common practice and thus it is necessary to precisely determine the benefits and limitations of the whole process. To interpret testing and draw detailed feedback, it is important to know the variables that play a significant role in the performance on air bike. The study aimed to assess the functionality of ramp stress test to failure using air bike and to discover the relation with selected strength, endurance, and anthropometric parameters. Due to the nature of air biking, a more dominant influence of strength parameters and weight can be expected.

2 Methods

The experimental group comprised 20 healthy, physically active individuals (average age: 22.1; weight: 70.6 kg; height: 172.5 cm). The tested subjects (14 women, 6 men) were introduced to the testing and research process. They were supposed to not change their eating habits neither before nor during the research. A rest day was prescribed one day before the testing. The whole group was tested within 10 days. The anthropometrics parameters were measured using bioimpedance scales (Tanita® RD-545), specifically weight, fat-free mass (FFM), body fat percentage, body mass index (BMI). Participants, who had no experience with air biking, were given the opportunity to get acquainted with it before testing under the supervision of examiners.

2.1 Laboratory testing

The testing was done using an air bike (Echo bike, Rogue®). It was preceded by a very light warm-up. The testing protocol was a ramp test to failure, the load was increased every 3 minutes with no break (Lamont, Rupert, Director, Alexander, & Goldberg, 1992). The test was ended when the subject was not able to maintain the required speed (W). The spiroergometry was done using METAMAX® 3B, CORTEX Biophysik GmbH. For the purpose of the study, the following parameters were chosen: VO2peak, respiratory equivalent ratio (RER), heart rate (HR), minute ventilation (V’E) and total test time that corresponds to absolute endurance performance. In our case, we used our practical experience and research by Hoffman, Kassay, Zeni, & Clifford (1996) and Lamont et al. (1992). Individual levels increased based on RPM to make maintaining the prescribed requirement simpler. The base value was 40 RPM (85 W) for men and 35 RPM (65 W) for women. Maximum effort was required for both laboratory and field-testing.

2.2 Field-testing

Three basic compound exercises and a dynamometer (SH5007, Saehan Dynamometer) were used to assess the level of muscle strength. All the participants had had previous experience with the selected strength tests. In bench press and back squat (90°), the subjects had 20 minutes to find their 1 repetition maximum (1 RM) – the number of sets was not limited. In standing long jump, they had three attempts, and the best one was recorded. The same principle was used with the back dynamometer. The tests were chosen specifically to measure both upper and lower body strength and also both push and pull strength. Then, anaerobic endurance was tested using 30 s all-out test on an air bike. 2 km on rowing machine test (Concept2®) was used to assess the level of aerobic endurance.

2.3 Statistical data processing

A statistical program TIBCO Statistica was used to statistically process the results data. Concerning the quantitative form of the research, all the data intended for the statistical processing had to be evaluated to learn if they are normally distributed (Gauss distribution). To assess data normality, graphical representation and Shapiro–Wilk W-test (n < 30) were used. All the data was normally distributed.

Basic descriptive statistics were used to determine the average, standard deviation, minimal and maximal values. Correlation analysis was applied to find significant relations between the variables. To evaluate statistical significance, the level of statistical significance was set to p = 0.01

3 Results

In the matter of body composition, the set of subjects showed standard values typical for young, physically active population (Tab. 1). BMI and fat percentage parameters were normal. Only one woman was overweight. The average FFM value (55 kg) shows that the individuals regularly (in the long term) engage in physical activities.

During stress testing (see Tab. 2), a maximal effort was confirmed; average HRmax was 189.7 bpm, which is close to theoretical limit values. Similarly, the value of RERmax (1.12) shows that the test subjects relied mostly on the anaerobic energy system. It is important to note that the RER value grew rapidly from the beginning. The efficiency of the aerobic system was assessed using VO2peak, the group had average values typical for common physically active population (43.9 ml/kg/min). The value and form of V’Emax were not fully consistent with this data. The average value of 116 l/min is lower and is a result of greater variance of the measured values. On average, the total test/ride duration was 14 minutes, which was long enough to verify the function of energy systems or the efficiency of the cardiopulmonary system.

As shown in Table 3, the strength tests demonstrated that the absolute value of pulling strength (166 kg) was the highest, followed by back squat (74.5 kg) and bench press (54.7 kg). The group’s performance was standard in regard to the ratio of basic strength parameters. The average time in the 2 km row was above 9 minutes, which can be considered a lower average. However, it corresponds with the fact that none of the test subjects did normally do rowing.

A set of values was selected for the correlation analysis (see Tab. 4), with the statistically significant relation (p = 0.01) marked red. The most important value to determine the relation between the stress testing and the selected values was Total (total time). The most significant relation found was with FFM. The most significant relation among strength tests was with back squat (0.83) and bench press (0.84). The pull strength test has also shown a statistically significant relation (0.75), yet not that significant. Both endurance tests have demonstrated a similarly significant relation (0.82 and −0.85) with Total. On the contrary, the least significant relation found was with BMI and body fat percentage. Relation with the long jump (0.63) and VO2peak (0.68) was also a little significant. Strong relation with both strength and endurance test was found in FFM, while a less significant relation was found for the jump and VO2peak (0.59).

Table 1

Anthropometric values and body composition.

Table 2

Stress testing on air bike.

Table 3

Results of strength and endurance tests.

Table 4

Results of correlation of the selected parameters.

4 Discussion

Stress testing on air bike has proven efficient in reaching very high physiological values. It confirms findings of previous studies where air bike was used in gradual load to failure (Hoffman et al., 1996; Nagle, Richie, & Giese, 1984). No universal protocol with set speed/watts/RPM is available so far – we used RPM converted to watts. As opposed to other machines, there are more types of air bikes that differ in construction and exported data. It is important to take into account that with the increasing speed, the resistance of the flywheel increases as well (Lamont et al., 1992). That is why it is more difficult to find an optimal form of the stress test including specific load increase.

One of the important findings was that the VO2peak parameter was not significantly related (0.68) to air bike performance. That is a difference from running or stationary bike where the relation is more significant (Millet, Vleck, & Bentley, 2009). Although air bike falls into the category of cardio machines that are characterized by high values of aerobic endurance, the findings of this study do not fully confirm this. The reason is probably the nature of air biking, which is more strength based, and both the strength and the total muscle mass play a more significant role. Strong significant correlation (0.86) with FFM confirms this statement. Active muscle mass, related also to absolute strength to external load, is likely the most significant predictor of air bike performance. However, in a homogeneous sample regarding FFM, cardiorespiratory parameters will probably decide. Another proof to this is a less significant correlation (0.63) of air bike performance and the long jump, which depends more on relative strength.

The principle of air biking is based primarily on push strength of upper and lower limbs. Even though it is possible to use pulling strength on the handles, this variant is usually not used. The analysis has shown higher statistical significance with the performance in back squat and bench press, which confirms this technique. Simultaneous engagement of the upper and lower body leads to faster lactate production and higher demands for lactate metabolism and anaerobic glycolysis (Filipovic, Munten, Herzig, & Gagnon, 2021). Similar load can occur in rowing. That is why the 2 km row test was chosen where a strong negative correlation (−0.85) with air bike performance was found. The rowing machine is used to test cardiorespiratory fitness of not only athletes (Lindberg, Oksa, Gavhed, & Malm, 2013; Peterson, 2015).

HRmax values on air bike were lower than in running, but comparable or higher than on stationary bike (Hoffman et al., 1996; Zeni et al., 1996). VO2peak values obtained have to be related only to air bike. Conversion to other activities might not be accurate – the values in running or rowing can differ significantly (Millet et al., 2009). It is also important to consider the fact that change in FFM or strength abilities can have significant effect on stress testing using air bike and on the resulting VO2peak.

During air biking, a great number of muscle groups of both upper and lower body is engaged and it is also necessary to do more muscle work. This requires great amounts of energy and oxygen, which explains quick RER onset and also high RERmax (1.12 on average). At the same time, cardiac output demand increases – not only because of higher metabolic demand, but also due to vassal compression in peripheries when more motor units are used. The overall physiological response is different – from the beginning, the stress on the cardiopulmonary system is higher which can be observed in the development of minute ventilation, HR, blood lactate level, etc. (Filipovic et al., 2021; Schlegel & Křehký, 2020). Simultaneous engagement of large muscle groups is a typical aspect of many sports (Franchini, Brito, Fukuda, & Artioli, 2014; Tavares et al., 2017). It seems good to use tools with similar attributes in non-specific testing.

One disadvantage of a more strength-based ride can be higher subjective perceived exertion (Kim et al., 2017; Zeni et al., 1996). It was shown that running or stationary bike were perceived as less strenuous with equal HR. Especially for individuals with lower FFM or strength abilities, higher mental demands can be expected (see psychological model) which could lead to earlier stress test end. Unlike other cardio machines, air bike can be individually adjusted only to certain level, which could also play a role. Because there are obvious differences in design of air bike types (handles, seat, and flywheel diameter and construction, etc.) that affect comfort of ride, perceived comfort can play a significant role in its use (Looney & Rimmer, 2003).

Limitation of this study can be seen in the selection of field tests. The strength tests were based on strength against external weight. For a complex picture of the relation between strength parameters and air bike performance, it would be better to also use bodyweight exercises or strength-dynamic exercises. Determining the endurance level could be also more extensive (e.g., add running tests) which could bring some additional useful information. As for the stress testing protocol, a more gradual load increase could have been chosen in order to make the testing longer. However, considering satisfactory length of the testing, this is not exactly a limitation, but rather an impulse for more research.

5 Conclusion

Choosing the right tool for stress testing is an important part of assessing the level of cardiorespiratory fitness. Traditionally used treadmill and stationary bike have their advantages but also limitations given by their specific attributes. By now, air bike is already a widespread tool and it is a part of training programs of various groups and population samples. The results of the study imply that the air bike performance depends mostly on FFM and strength parameters. Strong negative correlation was found with the 2 km row test, which implies similar load. On the contrary, less significant relation was found with VO2peak. Air biking has a more strength-based, low-frequency nature which can be individually preferred for stress testing. For this reason, air bike can be an ideal alternative for more robust and heavier individuals. Air bike also proves to have potential in reaching high physiological values in stress testing together with the results of this study, it can be recommended for cardiorespiratory fitness testing, or in other words, aerobic and anaerobic performance. This is the first study that assesses the relation between stress testing and selected strength and endurance parameters. Thus, the results need to be confirmed in future studies.

Author contribution

P. Schlegel: Conception and design of the study; P. Schlegel, J. Hiblbauer, V. Faltys: Data collection; A. Křehky: Data analysis and interpretation; P. Schlegel, A. Křehký: Final approval.

Conflicts of interest

The authors have no conflicts of interest to declare.

Acknowledgements

We would like to thank all the participants in the research.

References

Cite this article as: Schlegel P, Křehký A, Hiblbauer J, & Faltys V (2022) Air biking as a new way for stress testing. Mov Sport Sci/Sci Mot, https://doi.org/10.1051/sm/2022001

All Tables

Table 1

Anthropometric values and body composition.

Table 2

Stress testing on air bike.

Table 3

Results of strength and endurance tests.

Table 4

Results of correlation of the selected parameters.

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