Abstract
curved treadmill offers a practical method of assessing an- aerobic power by enabling unrestricted running motion and greater sport specificity. The purpose of this research was to determine reliability of a curved treadmill (cTM) sprint test and to compare performance measures to the traditional Wingate anaerobic power test (WAnT) performed on a cycle ergometer. Thirty-two recreationally active men and women (22.4 ± 2.8 yrs; 1.73 ± 0.08 m; 74.2 ± 13.2 kg) performed four familiarization trials on cTM, followed by two randomly assigned experimental trials consisting of one 30-second maximum effort on either cTM or WAnT. Each trial was separated by at least 48 hours. Repeated measures analysis of variance (ANOVA), interclass correlations (ICC), standard error of measurement (SEM), and minimal differences (MD) were used to determine reliability of familiarization trials on cTM, and Pearson product moment correlations were calculated to compare cTM and WAnT. ANOVA results showed significant differences (p < 0.05) dur- ing the four familiarization trials. Post hoc analysis showed significant differences (p < 0.05) between the first two trials. Familiarization trials 3 and 4 showed a high reliability for each performance variable (distance: ICC 2,1 = 0.969, %SEM = 2.645, p = 0.157; mean velocity: ICC 2,1 = 0.969, %SEM = 2.622, p = 0.173; peak velocity: ICC 2,1 = 0.966, %SEM = 3.142, p = 0.033; mean power: ICC 2,1 = 0.940, %SEM = 4.140, p = 0.093; and peak power: ICC 2,1 = 0.887, %SEM = 11.244, p = 0.669). Par- ticipants elicited an average peak power of 1050.4±338.5 Watts on cTM and 1031.4±349.8 Watts on
0.969, %SEM = 2.622, p = 0.173; peak velocity: ICC 2,1 = 0.966, %SEM = 3.142, p = 0.033; mean power: ICC 2,1 = 0.940, %SEM = 4.140, p = 0.093; and peak power: ICC 2,1 = 0.887, %SEM = 11.244, p = 0.669). Par- ticipants elicited an average peak power of 1050.4±338.5 Watts on cTM and 1031.4±349.8 Watts on WAnT. Pearson product moment coefficients indicated high correlations between peak power, mean power, and peak velocity (r = 0.75, p < 0.001; r = 0.84, p < 0.001; and r = 0.76, p < 0.001, respectively) derived from cTM and WAnT. In conclusion, results suggest that after two familiarization trials, cTM is a reliable sprint test for recrea- tionally active men and women. In addition, there are strong relationships between cTM and WAnT in assessing anaerobic performance. Key words: Anaerobic capacity, power, Wingate anaerobic power test, sprint speed. Introduction Assessment of anaerobic power performance is an inte- gral part of the monitoring and evaluation of strength and power athletes. Several laboratory and field assessments have been suggested as valid and reliable measures of anaerobic power performance (Hoffman, 2006). Labora- tory measures have the advantage over field assessments by providing greater sensitivity and reliability in the eval- uation of athletes. To date, the gold standard for anaerobic power assessment in the laboratory remains the Wingate anaerobic power test (WAnT) (Bar-Or, 1987, 1996; Bar- Or et al., 1977). Considering the test is performed on a cycle ergometer, the specificity for most competitive strength and power athletes is questionable. Several in- vestigations have used jump tests to provide a greater specificity of power measurement, especially for basket- ball or volleyball athletes (Hertogh et al., 2002; Hoffman et al., 2000; Ostojic et al., 2010; Sayers et al., 1999). Although these assessments are able to assess peak or mean power performance in single or repetitive jumps, they are unable to provide any feedback regarding fatigue rate or anaerobic conditioning levels. The development of non-motorized treadmills has created the ability for athletes to generate maximal sprint speeds in a laboratory setting. Many of these treadmills are
Sayers et al., 1999). Although these assessments are able to assess peak or mean power performance in single or repetitive jumps, they are unable to provide any feedback regarding fatigue rate or anaerobic conditioning levels. The development of non-motorized treadmills has created the ability for athletes to generate maximal sprint speeds in a laboratory setting. Many of these treadmills are fitted with force transducers into the running platform that can assess force, velocity, and power performance. As such, these new treadmills may provide a more sport specific assess- ment of anaerobic power for field, court, and track ath- letes. There have been several investigations examining the reliability and efficacy of flat non-motorized tread- mills and their ability to assess power and anaerobic ca- pacity (Highton et al., 2012; Hopker et al., 2009; Hughes et al., 2005; Lakomy, 1987; Lim and Chia,, 2007; Ross et al., 2009; Sirotic, et al., 2008; Tong et al., 2001). Previous research has shown high reliability similar to that seen with the WAnT (Lim and Chia, 2007); however the de- sign of many non-motorized treadmills impedes natural running stride dynamics due to the use of bulky harnesses and instrumentation. In addition, some treadmills require subjects to overcome a resistance to start the sprint that demands a different running strategy than seen in a track- based sprint (Ross et al., 2009). Although training on a flat non-motorized treadmill has been shown to enhance power performance and improve sprint time (Ross et al., 2009), these benefits may only be realized during the initial acceleration phase (Hrysomallis et al., 2012). Recently, a new treadmill (Woodway Curve 3.0 TM , Woodway, Inc., Waukesha, WI) was designed that allows unrestricted sprinting. The treadmill is designed with a curved platform to permit the runner to reach full velocity using running techniques that are similar to running on a track or field. Before tests of anaerobic power can be meaningful to sports training and assessment, reliability testing is necessary. Thus, the purpose of this study was to examine the reliability of this newly designed non- Research article
the runner to reach full velocity using running techniques that are similar to running on a track or field. Before tests of anaerobic power can be meaningful to sports training and assessment, reliability testing is necessary. Thus, the purpose of this study was to examine the reliability of this newly designed non- Research article
Gonzalez et al. 105 motorized treadmill on anaerobic power performance, and compare to values generated from the WAnT. Methods Participants Twenty-four men and eight women (n=32; 22.4 ± 2.8 yrs; 1.73 ± 0.08 m; 74.2 ± 13.2 kg) volunteered to participate in the study. The research protocol was approved by the University’s Institutional Review Board. Following an explanation of all procedures, risks, and benefits associ- ated with the experimental protocol, each participant gave his or her written informed consent to participate in this study. All participants were recreationally active and were familiar with sprinting and cycling activities. None of the participants had any physiological or orthopedic limita- tions that could have affected performance as determined by completion of a health history questionnaire before participation. Participants were instructed to refrain from eating or drinking one hour prior to each trial. Experimental design Participants reported to the Human Performance Labora- tory on six separate occasions. During the first four visits, participants performed familiarization sessions which provided detailed verbal instructions on the testing proto- col and allowed acclimation to the device with lower intensity jogging. During each familiarization session, each participant completed one 30-s sprint test on the Woodway Curve 3.0 TM non-motorized treadmill (cTM) (see Figure 1). There was at least 48 hours between each session. Following the four familiarization visits, the participants reported to the lab on two additional occa- sions and were randomly assigned to perform either a 30- s sprint on the cTM or a 30-s WAnT. Figure 1. Woodway Curve 3.0 TM Non-Motorized Treadmill (cTM) Maximal treadmill sprint testing Each familiarization trial and the 30-s treadmill sprint test were performed with identical protocols and were sepa- rated by at least 48 hours. Prior to the sprint, participants performed a 10-min warm-up consisting of 5-min on a cycle ergometer, followed by a 5-min walk on the cTM interspersed with two maximal sprints lasting 5-s. Follow- ing a 2-min rest, participants began one 30-s maximum effort sprint on the cTM. Prior to the onset of the sprint, participants walked at a pace of approximately 1.8 m·s -1 and were not
a 10-min warm-up consisting of 5-min on a cycle ergometer, followed by a 5-min walk on the cTM interspersed with two maximal sprints lasting 5-s. Follow- ing a 2-min rest, participants began one 30-s maximum effort sprint on the cTM. Prior to the onset of the sprint, participants walked at a pace of approximately 1.8 m·s -1 and were not allowed to accelerate until the start of the test. The study investigator provided a “Ready”, “Set” and “Go” command. At “Go”, participants began a maximal effort sprint for 30-s. Participants were verbally encour- aged throughout the sprint. Data (distance, peak power, mean power, peak velocity, and mean velocity) were recorded from transducers built into the treadmill plat- form attached to the manufacturer’s computer software (Pacer Performance System XPV7 2.1.07). Wingate anaerobic power test (WAnT) All participants performed one 30-s WAnT (Lode Excali- bur TM , Groningen, Netherlands). Prior to testing, partici- pants completed a standardized warm-up consisting of 5- min pedaling at 60 rpm interspersed with two maximal sprints lasting 5-s. Prior to the onset of the test, partici- pants pedaled at 60 rpm for 1-min and were not allowed to accelerate until the start of the test. The study investi- gator provided a “Ready”, “Set” and “Go” command. At “Go”, participants pedaled for 30-s at maximal speed against a constant force relative to individual body mass (0.7 Nm·kg -1 ) (Bar-Or, 1987). Peak power, mean power, and peak velocity were determined. Peak power was de- fined as the highest mechanical power output elicited during the test and mean power was defined as the aver- age mechanical power during the 30-s test. The test-retest reliability of the WAnT has consistently exceeded r > 0.90 (Bar-Or, 1987). Statistical analyses Mauchly’s test of sphericity was used to assess homoge- neity of variance, and a Huynh-Feldt adjustment was used if assumptions of homogeneity were violated. A repeated measures analysis of variance (ANOVA) was used to detect differences in the variables calculated during each of the four trials (distance, mean velocity, peak velocity, mean power, peak power, relative mean power, and rela- tive peak
of sphericity was used to assess homoge- neity of variance, and a Huynh-Feldt adjustment was used if assumptions of homogeneity were violated. A repeated measures analysis of variance (ANOVA) was used to detect differences in the variables calculated during each of the four trials (distance, mean velocity, peak velocity, mean power, peak power, relative mean power, and rela- tive peak power). When appropriate, a tukey post hoc comparison was used. As recommended by Weir (2005) for describing the generalized reliability of the cTM pro- cedure, intraclass correlation coefficients (ICC 2,1), stan- dard error of measurement (SEM), standard error of measurement as a percent of the grand mean (%SEM), minimal difference (MD), and minimal difference as a percent of the grand mean (%MD) were calculated. In addition, Pearson product moment correlations were cal- culated between cTM and WAnT measures. For all statis- tical tests, a probability level of p < 0.05 was established to denote statistical significance. All data is presented as mean ± standard deviation. Results Performance data from the familiarization trials on cTM are presented in Table 1. The repeated measures ANOVA showed a significant (p < 0.05) systematic error during the four familiarization trials. Post hoc analysis of the 1 st and 2 nd cTM familiarization trials showed significant differences between trials for distance (p = 0.005), mean velocity (p = 0.003), peak velocity (p = 0.012), and mean
Reliability of curved non-motorized treadmill 106 Table 1. Performance data from 30-s maximum sprint familiarization trials on cTM (±SD). Trial 1 Trial 2 Trial 3 Trial 4 Distance (m) 155.44 (23.66) 160.98 (23.97) * 165.13 (25.29) * 166.66 (23.23) Mean Velocity (m·s -1 ) 5.16 (.82) 5.36 (.80) * 5.50 (.85) * 5.55 (.78) Peak Velocity (m·s -1 ) 5.96 (.96) 6.19 (1.01) * 6.28 (1.03) 6.38 (.98 * Mean Power (W) 260.53 (44.57) 282.41 (73.14) * 280.81 (45.89) 285.53 (45.61) Peak Power (W) 981.09 (350.97) 992.78 (296.43) 1019.50 (332.58) 1031.88 (343.06) Relative Mean Power (W/kg) 3.55 (.51) 3.86 (1.01) 3.84 (.60) 3.90 (.58) Relative Peak Power (W/kg) 13.11 (3.22) 13.24 (2.57) 13.61 (3.10) 13.80 (3.16) * Significant difference (p < 0.05) from previous trial. power (p = 0.049). Analysis of the 2 nd and 3 rd cTM fa- miliarization trials showed significant differences be- tween trials for distance (p = 0.001) and mean velocity (p < 0.000). Analysis of the 3 rd and 4 th familiarization trials showed a significant difference between trials for only peak velocity (p = 0.033) (Table 1). Reliability data for familiarization trials 3 and 4 are presented in Table 2. The 3 rd and 4 th familiarization trials showed strong intraclass correlations (ICC 2,1) ranging from 0.791-0.969 for all performance measures. Performance data from the cTM and WAnT ex- perimental sessions are presented in Table 3. Significant correlations between performance on the cTM and WAnT were observed for peak power (r 2 = 0.56, p <0.001), rela- tive peak power (r 2 = 0.24, p = 0.005), mean power (r 2 = 0.71, p < 0.001), and peak velocity (r 2 = 0.58, p < 0.001). Relative mean power between the cTM and WAnT was not significantly correlated (r = 0.01, p = 0.508). Discussion This study is the first to show that the cTM is a reliable sprint test for recreationally active men and women (Ta- ble 2). In addition, strong relationships among perform- ance variables (Table 3) were demonstrated between cTM and WAnT. The findings of moderate to high shared variance for
was not significantly correlated (r = 0.01, p = 0.508). Discussion This study is the first to show that the cTM is a reliable sprint test for recreationally active men and women (Ta- ble 2). In addition, strong relationships among perform- ance variables (Table 3) were demonstrated between cTM and WAnT. The findings of moderate to high shared variance for peak power (r 2 = 0.56), mean power (r 2 = 0.71), and peak velocity (r 2 = 0.58) between the methods provides support for the use of the cTM for assessing anaerobic performance capability in recreationally trained men and women. Our data indicate that two familiarization trials, separated by at least 48 hours, are required prior to ex- perimental testing to eliminate systematic error which is likely attributed to a learning effect. It has been suggested that assessing sprint performance on non-motorized treadmills require a familiarization period before reliable results are produced (Lakomy, 1987). Similarly, Hopker et al. (2009) demonstrated the need for familiarization due to the potential learning effects on a non-motorized treadmill. Using a similar group of men and women as recruited for this present study, Hopker et al. (2009) had participants perform four sprints on a flat non-motorized treadmill on separate days. Significant (p < 0.05) in- creases in mean and peak power were observed for the first 2 trials; however no further differences were seen in subsequent trials. Consequently, previous research utiliz- ing flat non-motorized treadmills have employed a famili- arization period prior to testing (Highton et al., 2012; Hughes et al., 2006; Sirotic et al., 2007; Tong et al., 2001). These studies support our findings and are consis- tent with the recommendation that two familiarization sessions should be performed on the cTM, separated by at least 48 hours, prior to experimental testing to improve reliability. A 30-s maximum effort sprint test on the cTM is a reliable assessment of anaerobic power for recreationally active men and women showing strong ICC’s ranging from 0.791-0.969 for performance measures. Previous research has investigated the reliability of flat non- motorized treadmills and yielded similar results. Hopker et al.
at least 48 hours, prior to experimental testing to improve reliability. A 30-s maximum effort sprint test on the cTM is a reliable assessment of anaerobic power for recreationally active men and women showing strong ICC’s ranging from 0.791-0.969 for performance measures. Previous research has investigated the reliability of flat non- motorized treadmills and yielded similar results. Hopker et al. (2009) reported ICC’s ranging from 0.83-0.93 for mean power and 0.54-0.83 for average peak power (Hop- ker et al., 2009). Lim and Chia (2007) also reported sig- nificant intersession correlations (r’s = 0.96 and 0.99) for mean and peak power, respectively, on a flat non- motorized treadmill. Others have reported coefficient of variations (CV) of 8.2 and 9.3 for mean and peak power, respectively (Tong et al., 2001). In agreement, the cTM used in the current study yielded ICC’s of 0.94 and 0.89 and SEM% values of 4.14 and 11.24 for mean and peak power, respectively. Other investigations of flat non- motorized treadmills have also demonstrated strong reli- ability (Highton et al., 2012; Hughes et al., 2005; Sirotic et al., 2008). Despite strong reliability of flat non- motorized treadmills, altered running techniques during their use have raised concern (Ross et al., 2009). An ap- parent benefit of this present cTM is in its curved design Table 2. Reliability data of familiarization trials 3 and 4 for 30-s maximum sprint on cTM. P-Value ICC 2,1 SEM %SEM MD %MD Distance .157 .969 4.387 m 2.645 11.674 m 7.037 Mean Velocity .173 .969 .145 m·s -1 2.622 .388 m·s -1 7.016 Peak Velocity .033 * .966 .199 m·s -1 3.142 .489 m·s -1 7.725 Mean Power .093 .940 11.723 W 4.140 30.214 W 10.670 Peak Power .669 .887 115.326 W 11.244 317.972 W 31.001 Relative Mean Power .133 .926 .167 W·kg -1 4.315 .435 W/kg 11.240 Relative Peak Power .603 .791 1.500 W·kg -1 10.949 4.000 W/kg 29.197 * Significant difference (p < 0.05) between 3 rd and 4 th familiarization trial. ICC2,1 = Intraclass Correlation Coeffi- cient; SEM = Standard Error of Measurement; SEM (%) = Standard Error of Measurement as
W 31.001 Relative Mean Power .133 .926 .167 W·kg -1 4.315 .435 W/kg 11.240 Relative Peak Power .603 .791 1.500 W·kg -1 10.949 4.000 W/kg 29.197 * Significant difference (p < 0.05) between 3 rd and 4 th familiarization trial. ICC2,1 = Intraclass Correlation Coeffi- cient; SEM = Standard Error of Measurement; SEM (%) = Standard Error of Measurement as a Percent of the Grand Mean; MD = Minimal Difference; MD (%) = Minimal Difference as a Percent of the Grand Mean
Gonzalez et al. 107 Table 3. Performance data for 30-s maximum effort on cTM and WAnT (±SD). cTM WAnT r 2 p Peak Power (W) 1050.4 (338.5) 1031.4 (349.8) .56 * .000 Mean Power (W) 293.0 (46.1) 625.7 (166.6) .71 * .000 Relative Peak Power (W·kg -1 ) 14.1 (3.2) 13.7 (3.1) .24 * .005 Relative Mean Power (W·kg -1 ) 4.1 (1.0) 8.3 (1.1) .01 .508 Peak Velocity 6.5 (1.0) m·s -1 133.5 (17.9) RPM .58 * .000 * Significant (p < 0.05) correlation between cTM and WAnT that allows for unrestricted, maximum effort sprint as- sessment. It is also important to note that throughout the study, no participants fell or sustained any injury during familiarization or experimental testing sessions on cTM. Additionally, our results showed that a minimal difference of 31% in peak power needs to be exceeded for an im- provement to be considered real (Weir, 2005). WAnT has been considered the gold standard for assessing anaerobic power in a laboratory setting, and has shown to be reliable with test-retest coefficients between 0.89-0.97 (Bar-Or, 1987; 1996; Bar-Or et al., 1977). The newly designed cTM and WAnT demonstrated strong relationships for peak power, mean power, peak velocity, and relative peak power, however relative mean power did not show a significant relationship (Table 3). Further analysis of performance data indicate that participants elicited a greater peak power output on the cTM, whereas mean power output was greater on the WAnT. This is consistent with previous research illustrating greater peak power outputs on a non-motorized treadmill compared to a cycle ergometer as a result of the larger muscle mass involved in high velocity running (Falk et al., 1996). The cTM requires whole body muscle mass involvement dur- ing sprint performance accounting for the greater peak power, whereas the WAnT primarily activates lower body musculature during cycling allowing a greater mean pow- er output over 30-s. The biomechanical differences be- tween sprinting and cycling assessments account for the different performance values, but the high correlations show that the two assessments are related and reflect the maximal effort employed by participants during
Description
This study examines the reliability of a curved treadmill for assessing anaerobic performance.