Effects of endurance and strength training of cyclists and triathlon athletes on efficiency, economy and VO₂ kinetics

Effects of endurance and strength training of cyclists and triathlon athletes on efficiency, economy and VO 2 kinetics

Do-Yeon Kim

Dept. of Sports Medicine, Cheongju University

사이클 선수와 철인3종 선수들의 지구력 및 근력 트레이닝이 효율성 및 경제성과 VO

2

효과

김도연

청주대학교 스포츠의학과¹

Abstract The purpose of this study was to evaluate the economy and efficiency of two trained athlete groups of different training status. The subjects were 20 elite athletes composed of the cyclists group (n=10) and triathlon group (n=10). All subjects performed steady state testing at 50, 100, and 150 watts, with ample time to reach resting VO

and ventilation values between stages. The efficiency of two groups appears to be quite different, with triathlon competitors displaying superior efficiency values for the transitions from 0 to 50 and 100 watts. This same principle likely explains the economy of the groups, as triathlon competitor was again more economic at 50 and 100 watts. As though this matching of oxygen consumption and workload they can reduce the amount of oxygen deficit that must be repaid post exercise.

Key Words : VO

kinetics, steady state, economy, efficiency, endurance training

요 약 본 연구의 목적은 훈련된

10

10

.

50, 100, 150 watts

,

3

.

.

주제어 : VO2

kinetics,

,

,

,

* 이 논문은 2012 학년도에 청주대학교 보건의료과학연구소가 지원한 학술연구조성비(특별연구과제)에 의해 연구되었음 Received 28 August 2013, Revised 12 November 2013

Accepted 20 November 2013

Corresponding Author: Do-Yeon Kim(Cheongju University) Email: Kdy4955@cju.ac.kr

Ⓒ The Society of Digital Policy & Management. All rights reserved. This is an open-access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.otg/licenses/by-nc/3.0), which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

ISSN: 1738-1916

1. Introduction

Oxygen uptake kinetics is the study of the rate of

change in oxygen uptake for a given increase in intensity above the gas exchange threshold [1,2,3].

Mechanisms controlling oxygen uptake kinetics are the

subject of heated debate, from which two major camps emerge.

The first camp believes that oxygen uptake kinetics are determined by the “inertia of intramuscular metabolic processes” [4,5]. The second believes that oxygen delivery is the true source of exercise limitations [6]. Although consensus does not exist for the mechanisms controlling oxygen uptake kinetics, the usefulness of this measure is not in question, as through it economy and efficiency can be computed.

Economy is the energy cost of movement, and efficiency is the mechanical energy production of the movement relative to the metabolic energy used to cause the movement [1]. It has been shown that oxygen uptake increases exponentially to a new steady state after an abrupt increase in intensity while still remaining the ventilatory threshold (VT) [4]. This exponential increase in oxygen uptake makes these values integral for endurance athletes, as those who are more economic/efficient then their similarly trained counterparts require less energy input to power exercise, ultimately producing greater performance output.

Efficiency is a measure of effective movement and is referred to the mechanical energy production of the movement relative to the metabolic energy expended used to cause the movement and approximates 30%

during exercise. Cycling efficiency has been reported to be in the range of 10–25% [1].

Although many other key factors exist, those that determine exercise performance of a cycling modality in a controlled laboratory setting include cadence and muscle recruitment [7]. Although it has been shown that untrained subjects perform better at a cadence ≤ 50 RPM [8], trained subjects typically adopt higher cadences (80–100 RPM), as this causes reduced fast twitch fiber recruitment, resulting in increased time to fatigue [9]. Intrinsically this makes sense, as muscle force required per pedal revolution is reduced.

Therefore, those athletes who can sustain higher

cadences for longer periods of time retain a powerful advantage over other competitors. As for muscle recruitment, each muscle has an intrinsic contraction velocity that aligns with peak efficiency for vastus lateralis muscle, with this velocity being 1/3 of maximal contractile speed in type 1 fibers [10,11]. As such, those athletes with greater percentages of type I fibers will prove more efficient, and again, retain a marked advantage.

The primary aim of this study was to evaluate the economy and efficiency of two trained athlete groups of different exercise intensity using cycle ergometer. We hypothesized that triathlon competitors would have characteristically higher economy, efficiency and oxygen uptake kinetics when compared with cyclists.

Moreover, this study was selected that cyclists and triathlon athletes because of their power index of <

40% or > 45% have to their aerobic power [12].

Accordingly, the power index appears useful when recommending training protocols.

2. Methodology

Using a 3L syringe, the flow meter was calibrated.

Temperature, humidity, and barometric pressure were recorded at the onset of the trial, allowing for proper equipment calibration. The gas analyzers were calibrated against two known gas combinations, employing the Adam software. The Adam Software was used for analysis of breath-by-breath VO

response to exercise. Maximal oxygen consumption was provided by the LabView software, being produced through analysis of ventilation and the expired fractions of oxygen and carbon dioxide.

LabView software was used for data collection, with Prism being used for data analysis.

2.1 Subjects

Ten elite level cyclists competitors (26.4 ± 3.2 yr)

and ten high level triathlon competitors (25.8 ± 6.3 yr) of similar age from the A city area provided an informed written consent to participate in this study.

To qualify for the study, all participants were asymptomatic of any illness or disease and were free of any acute or chronic injury, as established by the American College of Sports Medicine participant activity readiness Par-Q health questionnaire. The study was approved by the Institutional Human Research Committee.

2.2 Design

The nature, purpose, and experimental procedures were outlined verbally to each participant; afterward, each subject signed an informed consent form before participating in the study.

Subjects performed steady state testing at 50, 100, and 150 watts, with ample time to reach resting VO

and ventilation values between 5 minutes at three different stages. Each lasted for 5 minutes and was followed by 10 minutes' rest. Subjects were asked to maintain the load (W) for a period of 5 minutes in an attempt at producing steady state VO

values [1,13].

2.3 Analysis

The group's VO

steady state values from all exercise loads were examined. Prism was used to curve fitting these values, producing a time constant to half decay. The resulting time constant was doubled, producing time to true steady state values. Curves were separated from data and appended. By analyzing mechanical versus caloric energy expenditure efficiency was computed. By examining VO

steady state values economy was deduced.

3. Results

The main characteristics of the cyclists and triathlon training of the athletes are presented in Table 1. No

differences were observed in the total training period between both of two groups before the tests.

<Table 1> Main characteristics of the cyclists and triathlon athletes

Age (yr)

Height (cm)

Weight (kg)

Total training

(yr) Cyclists

(N=10) 26.4 ± 3.2 178.4 ± 5.4 65.1 ± 6.7 6.8 ± 2.7 Triathlon

(N=10) 25.8 ± 6.3 177.3 ± 7.9 67.3 ± 5.9 7.1 ± 1.8

Table 2 shows that oxygen consumption, respiratory exchange ratio (RER), energy expenditure, efficiency, and measured and calculated during the cycle ergometer tests. The triathlon competitors group measured significantly more oxygen consumption (2.3 L/min), energy expenditure (10.78kcal/min), and efficiency (25%) at 150 watts.

Figure 1, 2 shows that the Prism results of cyclists and triathlon competitors's efficiency at 50 (16%: 31%), 100 (23%: 26%), and 150 (21%: 25%). The triathlon group displaying superior efficiency values for the transitions from 50 and 100 watts and more economic at 50 and 100 watts compared with cyclists competitors.

4. Discussion

The purpose of this study was to evaluate the economy and efficiency of two groups of different training status. For this reason this study chose two different athletes groups, as group 1 is an elite cyclists, and group 2 is a moderately high to high level triathlon competitor.

The efficiency of these groups appears to be quite different, with triathlon displaying superior efficiency values for the transitions from 0 to 50 and 100 watts.

This is likely to multiple things, including crank length,

body position, linear and angular displacements,

<Table 2> VO2, RER, energy expenditure, efficiency, and measured and calculated parameters during the cycle ergometer tests. Group 1 (Cyclists)

Watts K * 2

(minutes to steady state) VO2(L/min) RER Kcal/min

0 0 0.4 0.88 4.89

50 2.71 1.33 0.71 4.71

100 2.59 1.63 0.88 4.89

150 1.89 2.09 0.91 4.94

W-kgm conv Kgm-kcal conv Mech Production (kcal) Energy expenditure (kcal/min)

Efficiency (%)

0 0 0 1.96 -

6.118 0.0023 0.7 6.28 0.16

6.118 0.0023 1.41 7.96 0.23

6.118 0.0023 2.11 10.33 0.21

Group 2 (Triathlon competitors)

Watts K * 2

(minutes to steady state) VO2(L/min) RER Kcal/min

0 0 0.48 0.92 4.94

50 2.94 1.1 0.91 4.94

100 2.32 1.63 0.94 4.73

150 1.65 2.3 1.04 4.69

W-kgm conv Kgm-kcal conv Mech Production (kcal) Energy expenditure

(kcal/min) Efficiency (%)

0 0 0 2.37 -

6.118 0.0023 0.7 5.43 0.31

6.118 0.0023 1.41 7.69 0.26

6.118 0.0023 2.11 10.78 0.25

velocities and accelerations of body segments, and forces in joints and muscles [8]. As these variables were not measured and are too cumbersome to be thoroughly analyzed in a manuscript of this length, suffice it to say that the difference in efficiency between the two groups was at first surprising (see Table 2). However, after noting the slight advantage in efficiency of cyclists over triathlon competitors in the 0 to 150 watts transition things became clear, as is likely that cyclists were inept at these lower power outputs due to their non-specificity to his true competition performance. The results of this study and previous

study indicate that endurance training and running economy with no significant influences on the oxygen uptake patterns in incremental exercise [14,15]. A slow component also showed in pre-pubertal children during high intensity exercise, but was not influenced by weight different [16].

This same principle likely explains the economy of

the groups, as triathlon competitors were again more

economic at 50 and 100 watts (see Table 2 and Figure

2).

50 watts for cyclists

0.0 2.5 5.0 7.5 10.0

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0

Time (min)

VO

( L /m in )

100 watts for cyclists

11 12 13 14 15 16 17 18 19 0.0

0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0

Time (min)

VO

( L /m in )

150 watts for cyclists

20.0 22.5 25.0 27.5 30.0

0.00.2 0.40.6 0.81.0 1.21.4 1.61.8 2.02.2 2.42.6 2.83.0

Time (min)

VO

(L /m in )

[Fig. 1] Resulted in cyclists efficiency

[Fig. 2] Resulted in triathlon competitors efficiency

Likewise, the specificity of the higher power output likely explains the significant reduction in VO

seen for cyclists at 150 watts, producing vastly superior economy to triathlon competitors at this output. This significance is astounding, as the 1/3 kcal difference per minute seen between the two groups would quantify to 20 kcal/hour. As such, all other performance variables being equal, triathlon competitors would likely fatigue significantly faster than cyclists. As these power outputs are not as high as would be maintained throughout a traditional even by either subject, it would be interesting to see if this difference in economy remains linear up to each group's race pace.

One final variable of note is the K constant derived through the Prism software. This constant defines the half time to steady state, and, as such, is a valuable marker of the cardiovascular abilities of each of the groups. As stated previously, it is known that an overshoot of oxygen consumption typically results prior to one reaching steady state, with groups of higher cardiorespiratory training typically display a reduced time to steady state values [4]. A reduction of this overshoot displays a superior adaptation of trained subjects, as through this matching of oxygen consumption and work load they can reduce the amount of oxygen deficit that must be repaid post (or in this case once steady state has been reached) exercise. This value was surprising, as cyclists were superior to triathlon competitors at 50 watts, but triathlon competitors were superior to cyclists at 100 and 150 watts. Accordingly, triathlon competitors would reach steady state faster than cyclists at these higher outputs, resulting in decreased oxygen deficit having to be repaid post exercise. As this reflects the training status of the subjects, it is likely that their training status is not significantly different. Also, no changes were reported during the training period in both endurance and strength training [13]. Several researchers have noted that endurance training led to a significant diminution of the amplitude of the slow

component [17,18,19]. However, as trainability can only go so far to overcome genetic factors, there are likely some inherent differences associated with the subjects that we are not able to analyze at this juncture.

Also, although there were widely oscillating values as to VO

for each of the steady state plots, it appears that the subjects reached steady state on each workload, as the K constants do not dictate a time constraint of greater than 5 minutes.

5. Conclusion

The findings of the study demonstrate the effects of endurance and strength training athletes on efficiency and economy and VO

kinetics. Endurance and strength exercise was effective in decreasing oxygen deficit.

Consequently, these heavy exercise may be effective in reaching steady state faster than other exercise training.

On the basis of the results of this study, the following recommendations are made for further studies: crank length, body position, linear and angular displacements, velocities and accelerations of body segments, and forces in joints and muscles; they are also needed to develop effective endurance and strength exercise programs for different age groups or training types.

ACKNOWLEDGMENTS

This work was supported by the research grant of Cheongju University in 2012.

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김 도 연 (Do-Yeon Kim)

․2005년 5월 : U of Utah (미) (체육 학석사)

․2009년 8월 : U of New Mexico (미) (이학박사)

․2011년 3월 ～ 2012년 2월 : 부산대 학교 BK21연구원

․2012년 ～ 현재 : 청주대학교 스포 츠의학과 조교수

․관심분야 : 신진대사, 심폐기능, 열량측정, 비만

․E-Mail : kdy4955@cju.ac.kr