BioMed Research International

Volume 2015 (2015), Article ID 954780, 12 pages

http://dx.doi.org/10.1155/2015/954780

## Reliability of Force-Velocity Tests in Cycling and Cranking Exercises in Men and Women

^{1}Laboratoire CeRSM (EA 2931), Equipe de Physiologie, Biomécanique et Imagerie du Mouvement, UFR STAPS, Université Paris Ouest Nanterre La Défense, 200 avenue de la République, 92000 Nanterre, France^{2}Laboratoire de Physiologie, UFR de Santé, Médecine et Biologie Humaine, Université Paris XIII, 74 rue Marcel Cachin, 93017 Bobigny, France

Received 16 December 2014; Accepted 2 March 2015

Academic Editor: Paulo R. Lucareli

Copyright © 2015 Hamdi Jaafar et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

#### Abstract

The present study examined the reliability of the force-velocity relationship during cycling and arm cranking exercises in active males and females. Twenty male and seventeen female physical education students performed three-session tests with legs and three-session tests with arms on a friction-loaded ergometer on six different sessions in a randomized order. The reliability of maximal power , maximal pedal rate , and maximal force were studied using the coefficient of variation (CV), the intraclass correlation coefficient (ICC) and the test-retest correlation coefficient . Reliability indices were better for men (1.74 ≤ CV ≤ 4.36, 0.82 ≤ ICC ≤ 0.97, and 0.81 ≤ ≤ 0.97) compared with women (2.34 ≤ CV ≤ 7.04, 0.44 ≤ ICC ≤ 0.98, and 0.44 ≤ ≤ 0.98) and in cycling exercise (1.74 ≤ CV ≤ 3.85, 0.88 ≤ ICC ≤ 0.98, and 0.90 ≤ ≤ 0.98) compared with arm exercise (2.37 ≤ CV ≤ 7.04, 0.44 ≤ ICC ≤ 0.95, and 0.44 ≤ ≤ 0.95). Furthermore, the reliability indices were high for and whatever the expression of the results (raw data or data related to body dimensions). and could be used in longitudinal physical fitness investigations. However, further studies are needed to judge reliability.

#### 1. Introduction

Maximal anaerobic power can be measured on friction-loaded cycle ergometers or isokinetic ergometers. Many protocols have been proposed for maximal power measurement: all-out tests against a single load (e.g., the Wingate test) [1, 2], relationship between torque and pedal rate on an isokinetic ergometer [3, 4], relationship between load and peak velocity [5], and force-velocity relationship during a single all-out test against a pure inertial load [6] or inertial + braking load [7–9].

On friction-loaded ergometer, maximal power corresponds to power at peak velocity or is computed during the acceleration phase taking into account the power necessary to increase the flywheel kinetic energy [10]. The relationship between pedal rate () and braking force () or torque () can be described by a linear relationship [3, 5–9, 11]. Linear force-velocity relationships have been described for all-out exercises performed on a cycle ergometer not only with the legs (i.e., cycling exercise) but also with the arms (i.e., cranking exercise). The individual characteristics of the force-velocity or torque-velocity relationship can be defined by two parameters: (the intercept with the pedal rate axis which has the dimension of a maximal pedal rate) and or (the intercepts with the force or torque axis, which have the dimension of a maximal force or a maximal torque). Maximal power () corresponds to an optimal pedal rate () equal to and an optimal load or torque equal to or .

Previous studies reported that [8] or peak power during a Wingate test [12–15] are significantly correlated with the percentage of the fast muscle fibers in the vastus lateralis. Furthermore, a significant positive correlation was observed between and triceps surae musculotendinous stiffness at relative peak torque corresponding to the optimal cycling rate [16]. On the other hand, the value of during sprint cycling was significantly correlated with vastus lateralis myosin heavy chain II composition in a study comparing old and young participants [17]. The proportion of fast twitch fibres expressed in terms of cross-sectional area was highly correlated with (, ) [18], and the authors of this latter study suggested that would be the most accurate parameter to explore the fibre composition of the knee extensor muscle from cycling tests. The value of in cycling depends on the strength and the rate of force development of muscle knee extensors [19]. The Wingate optimal braking force can also be determined from the result of a cycling force-velocity test as this braking force is close to [5, 20].

Therefore, it could be interesting to determine the parameters of the force-velocity relationships (, , or ) in addition to on a cycle ergometer. Furthermore, the study of the changes in power-velocity relationship during an annual training cycle has been proposed in volleyball players [21], which assumes that the results of the force-velocity tests on cycle ergometers are reliable. The reliability of the cycling all-out tests has mainly been investigated by studying either the test-retest correlation coefficients () or the intraclass correlation coefficient (ICC) or the standard errors of estimations (SEE) or the coefficients of variation (CV) for the indices of maximal power (Wingate peak power or ) with the different protocols [1–4, 6, 9, 22–27]. In contrast, the reliability of the parameters of the force-velocity relationship (slope, , , and ) has been investigated in a few studies, only [4, 6, 26]. Moreover, the validity of the statistical tests in these studies on reliability was probably questionable [28].

In a review on the reliability of power in physical performance tests, Hopkins et al. [29] suggested that nonathletic females might be less reliable than nonathletic males, probably because the nonathletic females may be less physically active than the nonathletic males. Similarly, cranking exercises are probably less familiar than cycling exercises and the effect of familiarisation sessions might be more important for force-velocity tests with the arms.

Thus, the aim of the present study was to examine the reliability of , , and during force-velocity tests. In light of the literature observations, we hypothesized that reliability is lower in women than in men and for cranking force-velocity tests than for cycling tests.

#### 2. Materials and Methods

##### 2.1. Participants

Twenty healthy males ( years, m, and kg) and seventeen healthy females ( years, m, and kg) volunteered to participate in this study. The participants were all active physical education students but none of them were familiarized with sprint cycling or arm cranking before participation in the study. Before any data collection, all participants were fully informed of the possible risk and discomfort associated with the experimental procedures and gave written informed consent. The experimental protocol was approved by the Institutional Review Board of the University and carried out according to the guidelines of the Declaration of Helsinki.

##### 2.2. Procedures

The participants performed three session tests with the legs and three session tests with the arms on six different sessions in random order. All the tests were performed within a period of four weeks with at least 48 hours between the sessions. Participants were instructed to avoid any strenuous activity between sessions and to follow their usual diet throughout the experimental period. All tests were performed at the same time of day to minimize the effects of circadian rhythms [30] and with similar standard environmental conditions for all participants (mean temperature and humidity: °C and %, resp.). Body mass and height measures of all subjects were examined before each testing session.

The participants performed a standard warm-up consisting of 5 min cycling (80 W and 50 W for men and women, resp.) before the leg tests or arm cranking (50 W and 20 W for men and women, resp.) for the arm tests, with two short accelerations (3-s) at the end of the third min and the fifth min. After 5 minutes of passive recovery, participants performed the force-velocity test which consisted of repetitive short maximal sprints of 6-s against increasing braking forces. The braking forces administrated at the beginning of the sprints cycling were 2 kg and 1.5 kg for men and women, respectively, while during arm cranking the loads were equal to 1.5 kg and 1 kg for men and women, respectively. Then, the braking force was increased after 5 min of passive recovery (sprints cycling: 2 and 1.5 kg for men and women, resp.; arm cranking: 1.5 and 1 kg for men and women, resp.) until the participant was unable to reach a peak velocity higher than 100 rpm. The same order of braking force application was respected across session tests.

All force-velocity tests were performed on a friction-loaded cycle ergometer with weights (Monark 864, Monark Exercise AB, Vansbro, Sweden) adjustable for both leg and arm exercises [31, 32]. During sprint cycling exercises, participants were seated on the cycle ergometer equipped with toe clips and well-fastened straps to avoid losing the pedals. The same riding position was used throughout the study. Participants were instructed to cycle in seated position to avoid the effect of postural changes [33–35]. During arm cranking exercises, the pedals were replaced with handles and the cycle ergometer was fixed on a metal frame. The participants were standing on their feet in front of the ergometer during the exercises. The center of the pedal axis was approximately 20 cm lower than the level of the shoulder axis. All sprints were performed from the same initial pedal position. Participants were encouraged by the same investigator to reach the maximal velocity rate as quickly as possible. Instantaneous pedal rate in cycling or cranking was monitored throughout a PC computer by means of an encoder placed on the cycle ergometer flywheel. Then, the velocity was averaged over 1-s intervals.

The peak velocity () was measured for each braking force () and was used to calculate the linear force-velocity relationship for cycling exercises according to the least squares method:

The above relationship was transformed as follows [33]:

In this equation, and corresponded to the intercepts with the velocity axis and force axis, respectively ( and ). Since a linear relationship between and was assumed, corresponded to an optimal velocity and an optimal braking force equal to and , respectively. Hence, was calculated as follows [5, 33]:

The performance variables were expressed in absolute units and according to dimensional scaling. was expressed in absolute unit (rpm) and relative to body height (). was expressed in absolute unit (kg) and relative to body mass raised to the power of 0.67 (). was expressed in absolute unit (W) and relative to body mass ().

##### 2.3. Relation between the Variabilities of and

The variability of and between the second and first sessions ( and ) and between the third and second sessions ( and ) was calculated according to the following formulas:

##### 2.4. Statistical Analyses

Statistical procedures were carried out using Statistica 7.1 Software (StatSoft, France). Data of , , and are presented as mean and standard deviation (mean ± SD). Before statistical analysis, each performance variable was tested for normality with the Shapiro-Wilk test. With the assumption of normality confirmed, systematic change in performance from trials 1 to 3 was examined using one-way ANOVA with repeated measures and a Tukey’s post hoc test. All significance thresholds were set at .

Absolute reliability, which concerns the consistency of individual’s scores [36], was determined using the standard error of measurement SEM and the coefficient of variation (CV) using the following formulas [37]:where was the standard deviation of the differences between consecutive session tests (i.e., sessions 1 and 2 and sessions 2 and 3).

Relative reliability, which concerns the consistency of individual’s position in the group relative to others [36], was assessed using the intraclass correlation coefficient of two-way random effects model with single measure for each pair of consecutive session tests (i.e., sessions 1 and 2 and sessions 2 and 3) as follows:

In this formula represents the participant mean square, represents the error mean square, is the number of trials, represents the trials mean square, and is the number of participants. The ICC is considered as high for values above 0.90, moderate for values between 0.80 and 0.90, and low for values below 0.80 [38].

In addition, the test-retest correlation coefficient () was calculated for each pair of consecutive session tests in order to compare the results of the present study to the data in the literature [29]. The Bland-Altman plots were used to check for heteroscedasticity [28].

#### 3. Results

##### 3.1. Variations in Body Mass (BM)

For the arm tests, the differences in BM between the sessions were equal to (), (), and kg () in men and (), (), and kg () in women.

For the leg tests, the differences in BM between the sessions were equal to (), (), and kg () in men and (), (), and kg () in women.

##### 3.2. , , and in the Three Sessions

The individual values of and measured in the three sessions are presented in Figure 1. The branches of hyperbolae (i.e., continuous and dashed curves) in Figure 1 correspond to the participants with different combinations of and but the same value of . The means ± SD and ranges of , , , , , , and measured in the different sessions are presented in Tables 1 and 2 and Figures 1 and 2. In Table 1 and Figure 1, BM corresponded to the body mass measured during each session whereas BM was equal to the average of the three measures of BM in Figure 2.