Reproducibility of the time to peak torque and the joint angle at peak torque on knee of young sportsmen on the isokinetic dynamometer




Abstract


Background


Although peak torque has shown acceptable reproducibility, this may not be the case with two other often used parameters: time to peak torque (TPT) and the angle of peak torque (APT). Those two parameters should be used for the characterization of muscular adaptations in athletes.


Methods


The isokinetic performance of the knee extensors and flexors in both limbs was measured in 29 male athletes. The experimental protocol consisted of three consecutive identical paradigms separated by 45 min breaks. Each test consisted of four maximal concentric efforts performed at 60 and 180°/s. Reproducibility was quantified by the standard error measurement (SEM), the coefficient of variation (CV) and by means of intra-class correlation coefficients (ICCs) with the calculation of 6 forms of ICCs.


Results


Using ICC as the indicator of reproducibility, the correlations for TPT of both limbs showed a range of 0.51–0.65 in extension and 0.50–0.63 in flexion. For APT, the values were 0.46–0.60 and 0.51–0.81, respectively. In addition, the calculated standard error of measurement (SEM) and CV scores confirmed the low level of absolute reproducibility.


Conclusions


Due to their low reproducibility, neither TPT nor APT can serve as independent isokinetic parameters of knee flexor and extensor performance. So, given its reproducibility level, TPT and APT should not be used for the characterization of muscular adaptations in athletes.


Résumé


Position


Alors que le paramètre de force maximale a montré un bon niveau de reproductibilité, il n’en est pas de même pour le temps de développement de la force maximale (TDFM) et l’angle d’efficacité maximale (AEM) qui demeurent controversés. Ces deux paramètres pourraient participer à la caractérisation des adaptations musculaires de sujets sportifs.


Méthode


Les performances isocinétiques des fléchisseurs et extenseurs du genou ont été mesurées chez 29 sportifs masculins. Le protocole comprenait trois séries de tests séparées de 45 minutes avec au sein de chaque test quatre contractions maximales réalisées aux vitesses de 60 et 180°/seconde. La reproductibilité a été quantifiée par la mesure de l’erreur standard (SEM), du coefficient de variation (CV) et des coefficients de corrélation intra-classe (CCI) selon six méthodes de calcul.


Résultats


Sur la base des CCI, les corrélations du TDFM sont situées entre 0,51–0,65 en extension et entre 0,50–0,63 en flexion. Pour l’AEM, les valeurs étaient respectivement de 0,46–0,60 et de 0,51–0,81. De plus, les calculs du SEM et du CV confirmaient les faibles niveaux de reproductibilité absolue.


Conclusion


Au regard de leurs trop faibles niveaux de reproductibilité, les deux paramètres de TDFM et d’AEM ne peuvent servir fiablement la caractérisation des adaptations des muscles fléchisseurs et extenseurs du genou de sportifs.


1


English version


1.1


Introduction


Most muscular function studies have shown good inter-test reproducibility of three closely inter-related isokinetic parameters: peak torque, work and mean power . Several parameters are generally used to characterize muscular adaptations, but all must first meet the validation criteria that ensure methodological value and clinical interest .


Since many years, the relations between muscular composition and isokinetic strength were studied . More, a critical approach existed about the relation between the isokinetic strength characterised by the peak torque and muscle fiber type .


For many years, the value of the time to peak torque (TPT) and the angle of peak torque (APT) have remained controversial . TPT characterizes “muscular explosiveness” , and some studies have reported a relationship between high velocities of joint rotation and a certain number of anatomical and physiological disorders . APT is the joint angle when peak torque is reached. Given the contradictory reports in the literature , our objective was to test the reproducibility of TPT and APT. We did so by analyzing the reproducibility of TPT and APT values in 29 athletes using knee muscle flexors and extensors at 60 and 180°/s on both the dominant and opposite sides.


1.2


Method


1.2.1


Subjects


The study cohort consisted of 29 male athletes, soccer players (Soccer), gymnasts (Gymnast), or swimmers (Swimmer), which practice at national level of competition. For soccer and gymnast sportsmen, they trained two hours by day in elite federal structure. For reason of homogeneity of population, we only selected men’s gender. They were separated by sport into three groups which did not differ significantly regarding anthropometric characteristics or the number of years of training ( Table 1 ). All participants were selected on the basis of the following criteria: involvement in their respective sport for a minimum of 3 years and training for at least twice weekly; age range was defined between 18-30, inclusive. We excluded any athlete presenting with serious injury to the quadriceps, hamstring or knee within 12 months preceding the tests. We also excluded athletes who had an isokinetic assessment of the knee within the last 12 months for familiarisation reason.



Table 1

Characteristics of the participants.































































Age Height Weight
Population
m 21.91 177.93 73.48
sd 2.29 6.69 6.58
Soccer n = 15
m 21.33 178.40 73.13
sd 2.01 5.88 4.39
Gymnast n = 7
m 22.36 174.43 70.14
sd 2.11 7.11 6.28
Swimmer n = 7
m 22.71 180.43 77.57
sd 2.96 7.46 9.20


1.2.2


Experimental protocol


Tests were performed bilaterally in the seated position (hip flexion angle at 110°) with Velcro straps to stabilize the trunk, waist and the thigh of the tested leg. The contralateral limb was not strapped. The resistance pad was placed 3 cm above the ankle joint and the dynamometer’s axis of rotation was aligned with that of the knee joint. During testing, the hands were crossed over the trunk. The dominant limb was assumed to be the one spontaneously used to kick a ball. The peak torque was not corrected with respect to the effects of gravity.


Each subject warmed up with 10 min of cycling and 5 min of quadriceps and hamstring stretching exercises. For all subjects, motion ranged from 0° (full extension) to 90° of knee flexion. The warm-up was followed by four submaximal exercises of the knee extensors and flexors before each isokinetic velocity test (60 and 180°/s). The experimental protocol consisted of three repetitions of an isokinetic test at 60 and 180°/s with 45 min of rest between the three tests (1: 60 and 180°/s, 45-min rest; 2: 60 and 180°/s, 45-min rest; 3: 60 and 180°/s). Each test consisted of four maximal concentric efforts of the knee extensors and flexors of the dominant limb at 60°.s −1 and then of the non-dominant limb after 3 min of rest. The participants then rested for 5 min before the second part of the test. The second part consisted of four maximal concentric efforts of the knee extensors and flexors of the dominant limb at 180°/s and then of the non-dominant limb after 3 min of rest. After both the first and second isokinetic tests, 45 min of rest were given. We thus analyzed TPT and APT in eight test conditions: quadriceps dominant 60°/s, quadriceps non-dominant 60°/s, quadriceps dominant 180°/s, quadriceps non-dominant 180°/s, hamstring dominant 60°/s, hamstring non-dominant 60°/s, hamstring dominant 180°/s and hamstring non-dominant 180°/s. The subjects were instructed to work as hard as possible in the entire range of motion (0–90°) of the movement.


1.2.3


Instrument


We used the Cybex Orthotron KT ® isokinetic dynamometer of the Helio Marin Medical Centre in Vallauris, France. Humac Médimex ® Windows software was used to record the parameters.


1.2.4


Statistical analysis


The normality of the subjects’ characteristics and values was verified with the Kolmogorov-Smirnov test. Absolute reproducibility, defined as the degree to which repeated measurements vary for a given individual (i.e., trial-to-trial noise), was expressed by the standard error of measurement (SEM). SEM is presented as the percentage of the mean value (SEM(%) = SEM(Nm)/mean value of two sessions). The 95% limits of agreement for the determination of the minimum detectable change (MDC) was calculated as ±1.96 × √2 × SEM. The level of significance was set at P < 0.05. These analyses were performed with Statview ® software (Version 5.0, SAS Institute, Inc., Cary, NC).


For both TPT and ATP, reproducibility was quantified by means of intra-class correlation coefficients (ICCs). ICCs are relative measures of reproducibility . Technically, these coefficients are the ratios of variances computed by repeated measures ANOVA. The value of an ICC ranges from 0 to 1, 0 indicating no reproducibility and 1 corresponding to maximal reproducibility. ICCs were considered excellent if greater than 0.9 and at good level between 0.7–0.9.


Each ICC has its statistical advantages and limitations . In order to obtain a complete description of the reproducibility of the TPT and APT parameters, we calculated the six forms of ICCs proposed by Shrout and Fleiss . These forms are derived from different ANOVA models. First, there are three general models denoted 1, 2 and 3, depending on the sampling of the raters (or trials) assumed to be used to assess the subjects. For each of these models, two ICCs can be defined according to the way the scores are considered in the analysis. If single scores are used, the associated ICC is designated by the number 1. If the score of each subject is obtained by an average across trials, the letter k is attributed to the corresponding ICC. Hence, we obtained six ICCs, respectively denoted by: 1,1; 1,k; 2,1; 2,k; 3,1 and 3,k. These analyses were performed with Matlab ® software.


1.3


Results


1.3.1


For time to peak torque in extension


For TPT in extension on the dominant side at 60°/s, the six forms of ICCs delivered values between 0.65 and 0.85. These values were lower and ranged 0.51–0.76 at 180°/s ( Table 3 ). At 60 and 180°/s, the values of CV were respectively 9.8 and 11.1%, with respective SEMs of 0.12 and 0.15 ( Table 2 ). On the non-dominant side, the values of ICC ranked 0.57–0.86 at 60°/s and 0.57–0.81 at 180°/s ( Table 3 ). For these test speeds, the values of CV were respectively 8.1 and 10.3%, with respective SEMs of 0.08 and 0.13 ( Table 2 ). For the isokinetic data, we observed values of between 0.38 and 0.41-s at 60°/s and between 0.18 and 0.19-s at 180°/s during the three dominant side tests. On the non-dominant side, the values were ranked between 0.38 and 0.43-s at 60°/s and 0.19–0.20-s at 180°/s ( Fig. 1 ).



Table 2

Values of the standard error of measurement (SEM) and coefficient of variation (CV) of the time to peak torque (TPT) and the joint angle at peak torque (APT) measured during flexion and extension movements on the dominant and non-dominant sides at 60°/s and 180°/s.














































































% SEM % CV
TPT
Dom Ext 60 0.12 9.8
Dom Ext 180 0.15 11.1
Ndom Ext 60 0.08 8.1
Ndom Ext 180 0.13 10.3
Dom Fl 60 0.18 16.1
Dom Fl 180 0.16 14
Ndom Fl 60 0.15 13
Ndom Fl 180 0.15 14.7
ATP
Dom Ext 60 0.05 4.5
Dom Ext 180 0.08 7.4
Ndom Ext 60 0.04 3.3
Ndom Ext 180 0.07 5.7
Dom Fl 60 0.15 11.7
Dom Fl 180 0.13 10.8
Ndom Fl 60 0.14 10.3
Ndom Fl 180 0.12 10.7


Table 3

Values of intra-class correlation coefficients (ICC) for the time to peak torque (TPT) and the joint angle at peak torque (APT) measured during flexion and extension movements on the dominant and non-dominant sides at 60°/s and 180°/s.















































EXT TPT dom 60 TPT nd 60 TPT dom 180 TPT nd 180
1,1 0.65 0.57 0.51 0.57
1,k 0.85 0.80 0.76 0.80
2,1 0.65 0.59 0.51 0.58
2,k 0.85 0.81 0.76 0.80
3,1 0.66 0.68 0.51 0.59
3,k 0.86 0.86 0.75 0.81















































FL TPT dom 60 TPT nd 60 TPT dom 180 TPT nd 180
1,1 0.50 0.62 0.63 0.63
1,k 0.75 0.83 0.83 0.84
2,1 0.51 0.62 0.63 0.64
2,k 0.76 0.83 0.83 0.84
3,1 0.55 0.62 0.62 0.67
3,k 0.78 0.83 0.83 0.86















































EXT APT dom 60 APT nd 60 APT dom 180 APT nd 180
1,1 0.61 0.60 0.46 0.48
1,k 0.82 0.82 0.72 0.74
2,1 0.62 0.61 0.47 0.50
2,k 0.83 0.83 0.73 0.75
3,1 0.71 0.67 0.51 0.55
3,k 0.88 0.86 0.75 0.79















































FL APT dom 60 APT nd 60 APT dom 180 APT nd 180
1,1 0.51 0.67 0.57 0.54
1,k 0.76 0.86 0.80 0.78
2,1 0.53 0.67 0.57 0.55
2,k 0.77 0.86 0.80 0.78
3,1 0.59 0.68 0.57 0.56
3,k 0.81 0.86 0.80 0.79



Fig. 1


Means and standard deviations of the time to peak torque (TPT) and the joint angle at peak torque (APT) measured during flexion and extension movements on the dominant and non-dominant sides at 60 and 180̊/s.


For TPT in flexion, we observed ICC values between 0.50 and 0.78 at 60°/s on the dominant side. These values ranked 0.63–0.83 at 180°/s ( Table 3 ). At 60 and 180°/s, the values of CV were respectively 16.1 and 14%, with respective SEMs of 0.18 and 0.16 ( Table 2 ). On the non-dominant side, the values of ICC ranked 0.62–0.83 at 60°/s and 0.63–0.86 at 180°/s ( Table 2 ). At these speeds, the values of CV were respectively 13 and 14.7%, with respective SEMs of 0.15 for both measures ( Table 2 ). For the isokinetic data during the three tests on the dominant side, we observed values between 0.30 and 0.36-s at 60°/s and between 0.18 and 0.19 seconds at 180°/s. On the non-dominant side, the isokinetic values ranked 0.33–0.35-s at 60°/s and between 0.17 and 0.19-s at 180°/s ( Fig. 1 ).


1.3.2


For angle of peak torque in extension


For APT in extension, we observed ICCs of between 0.61 and 0.88 at 60°/s and between 0.46 and 0.75 at 180°/s on the dominant side ( Table 3 ). At 60 and 180°/s, the values were respectively 4.5 and 7.4% for CV, with respective SEMs of 0.05 and 0.08 ( Table 2 ). On the non-dominant side, the ICCs ranked between 0.60 and 0.86 at 60°/s and between 0.48 and 0.79 at 180°/s ( Table 2 ). At these speeds, the CV values were respectively 3.3 and 5.7%, with respective SEMs of 0.04 and 0.07 ( Table 2 ). For the isokinetic data, we observed values between 59.9 and 63.6° at 60°/s and between 53.6 and 57.3° at 180°/s during the three tests performed on the dominant side. On the non-dominant side, the values were ranked between 60.6 and 63.1° at 60°/s and between 53.5 and 57.2° at 180°/s ( Fig. 1 ).


For APT in flexion, we observed ICCs between 0.51 and 0.81 at 60°/s on the dominant side. These values ranked between 0.57 and 0.80 at 180°/s ( Table 3 ). At 60 and 180°/s, the values of CV were respectively 11.7 and 10.8%, with respective SEMs of 0.15 and 0.13 ( Table 2 ). On the non-dominant side, the ICC values were between 0.67 and 0.86 at 60°/s and between 0.54 and 0.79 at 180°/s ( Table 2 ). At these speeds, the CV values were respectively 10.3 and 10.7%, with respective SEMs of 0.14 and 0.12 ( Table 2 ). For the isokinetic data, we observed values ranked 25.9–31.1° at 60°/s and 35.6–36.7° at 180°/s during the tests on the dominant side. On the non-dominant side, the values were ranked 27.5–29.2° at 60°/s and 34.6–37.6° at 180°/s ( Fig. 1 ).


1.4


Interpretation


The overall analysis indicates that the reproducibility of TPT and APT, as tested on a sample population of young athletes, was insufficient. The analysis depended on six calculation methods that are more or less rigorous, which therefore generated a range of values. These values were most often positioned between 0.60 and 0.80 for TPT and between 0.50 and 0.80 for APT. An analysis by parameter and by muscular group is now needed. The use of CV and SEM tests completed the analysis.


For TPT of these athletes, the analysis reached 0.86 on the dominant side, whereas the opposite side had a base value of 0.57, which leads to the conclusion that this level of reproducibility is unsatisfactory. At 180°/s, the reproducibility was lower, and this can be explained by the lower resistance to movement at higher speeds, and the shorter duration of isokinetic work . Furthermore, we hypothesize that the typology of slow-twitch fibers of the dominant quadriceps group improved the reproducibility at a lower rate of work. Whatever the supporting evidence, we assume that for this muscular group, better methodological conditions were obtained at a slower evaluation speed.


For the hamstring and knee flexors, the reproducibility appeared to be opposite to that of the quadriceps; that is, slightly better at the fast speed of 180°/s, with similar values on the two contralateral sides and situated between 0.62 and 0.86. Therefore, they were not as good as at slow speeds, ranging from 0.50 at 60°/s on the dominant side using the most rigorous calculation method to 0.83 on the opposite side employing the most tolerant method.


In summary, given its reproducibility level, TPT should not be used for the characterization of muscular adaptations in athletes. So we cannot select TPT parameter to characterize the influence of muscular training or the effects of sport practice. The low level of reproducibility confirms previous research conducted on healthy subjects and a group of 24 young women and contradicts the research showing evidence of satisfactory reproducibility in a group of 18 older women and 178 subjects between 45 and 78 years old .


Clinically, although limited to a methodological point of view, TPT is typically chosen to identify the physical qualities of athletes. It can be linked to explosiveness, one of the components of force. Two validated parameters, maximum force and work, traditionally characterize functional abilities, whereas exercise type, intensity, duration and frequency complete the characterization of training and individual behavior. Given the levels of reproducibility obtained using ICC calculations, one should remain cautious about accepting TPT as an objective parameter of individual muscle qualities. The finding of CV values between 8.1 and 16.1% and greater than 10% in six of the eight test conditions ( Table 2 ), as well as the SEM values generally close to 0.15%, confirms the insufficient methodological value.


Most importantly, TPT should not be taken as a valid means to identify the causes of malfunction regarding the ability to create sudden variations in speed. The acceleration created and sustained at the musculo-articular level requires the integrity of the periarticular structures that ensure physiological work and the nervous control of movement that goes hand in hand with motor efficiency. The concepts of sense of position and direction of movement that mobilize proprioception and the processing of kinesthetic information contribute to this regulation. In certain sports like baseball or tennis, throwing and striking mobilize the upper limbs. Numerous studies have sought to identify the causes of chronic disorders. Explosiveness is a key muscular quality since it is the source of performance all the while controlling development. Given the musculo-articular constraints during repeated movements and the variations in values at heightened speeds, we conclude that TPT is of limited value for understanding and controlling muscular adaptations in the design of training programs that combine optimization and prevention.


A critical approach is necessary about the relations between “explosiveness” and the isokinetic parameter of TPT . We also need for these studies to answer the relation between fiber-type composition and isokinetic strength characterized by peak torque . Moreover, many studies present non-significative relations between isokinetic values of strength and sport performance developed at different speed levels and in anisokinetic movements . So, as regards to these limits and the level of reproducibility observed in our study, we could doubt about the validity of TPT.


The reproducibility of APT, as tested by the ICC calculations, was generally lower than that of TPT. For the quadriceps, it fell below 0.50 at 180°/s under the most rigorous conditions of reproducibility analysis on both tested sides (0.46 and 0.48). At 60°/s, reproducibility was better, positioned between 0.60 and 0.86. This confirms the observation for TPT; that is, the reproducibility for the quadriceps is better at slow speeds. For the hamstrings, the most rigorous calculation conditions showed evidence of low reproducibility, situated between 0.50 and 0.60 in three of the four test conditions and lower than those measured for TPT. However, test speed seemed to have less influence on the ICC value.


The clinical relevance value of ATP is different and therefore complements that of explosiveness. The determination of the joint angle at the occurrence of maximum force is directly dependent on several factors: the assembly of the joint, the muscular group tested, the type of practice (endurance versus maximum strength), and the level of practice. In a more striking manner than that of TPT, the methodological reproducibility of APT was low in a population of young national-level athletes and this confirms the reservations about APT expressed by previous researchers .


This study contains many limits. In fact, we have only selected two test speeds and for the population we have selected different profiles of sportsmen. In addition, it would be relevant to analyse the influence of one sport such as swimming or soccer on reproducibility data of strength. So we could make the hypothesis that the swimming practice is in favour of a best control of isokinetic exercise and its repetition in relation with mechanical resistance, which increases with square of speed in water and so is nearer to the characteristics of isokinetic contraction. The application on elderly people or on population being in rehabilitation periods also represents some prospects.


1.5


Conclusion


Our results indicate that TPT values are not sufficiently reproducible for use in the characterization of muscular adaptations in athletes. Given the low reproducibility obtained using ICC calculations, as well as CV and SEM analysis, the reservations about TPT as a means to characterize individual muscle qualities appear to be justified. The reproducibility of APT, as tested by ICC, was generally lower than that of TPT. The low methodological reproducibility value of APT given by ICC, CV and SEM analysis in a population of nationally-ranked young athletes confirms the findings of low APT reproducibility reported by previous researchers.


Disclosure of interest


The authors declare that they have no conflicts of interest concerning this article.


Acknowledgement


The authors wish to thank Dr F. Lemoine and the team of Centre Helio Marin of Vallauris for their participation and the access to the dynamomer.




2


Version française


2.1


Introduction


La majorité des études portant sur la fonction musculaire a montré un bon niveau de reproductibilité des paramètres isocinétiques de force maximale, de travail et de puissance moyenne . Il existe un grand nombre de paramètres de caractérisation des adaptations musculaires mais tous ont initialement dû répondre de leurs critères de validation méthodologique afin de témoigner par la suite de leur intérêt clinique .


Depuis de nombreuses années, les relations entre la composition musculaire et les forces isocinétiques développées sont étudiées . Une approche critique existe au sujet des relations existantes entre les forces isocinétiques caractérisées par le couple de force maximal et la composition typologique . De plus, depuis des années, le temps de développement de la force maximale (TDFM) et l’angle d’efficacité maximale (AEM) demeurent controversés . Le TDFM caractérise « l’explosivité musculaire » et quelques études ont rapporté des relations entre les vitesses angulaires mesurées au niveau articulaire et un certain nombre de dysfonctionnements musculo-articulaires . L’AEM représente l’angle auquel le couple maximal est observé. Considérant les données controversées issues de la littérature , notre objectif était de tester la reproductibilité du TDFM et de l’AEM chez 29 jeunes sportifs lors de mouvements de flexion et d’extension de genou réalisés sur les côtés dominant et non-dominant à 60 et 180°/s.


2.2


Méthode


2.2.1


Sujets


La population étudiée comprenait 29 sportifs masculins pratiquant le football, la gymnastique et la natation à des niveaux de compétitions nationales. Pour le football et la gymnastique, les sportifs s’entraînaient plus de deux heures par jour au sein de structures d’élite de formations fédérales. Pour des raisons d’homogénéité de la population, nous n’avions sélectionné que des hommes. Ils étaient différenciés en trois groupes de sportifs non-significativement différents du point de vue des caractéristiques anthropométriques et des années de pratique ( Tableau 1 ). Tous les participants étaient sélectionnés sur la base des critères suivants : un investissement de plus de trois ans dans leur sport respectif avec un entraînement d’au minimum trois séances hebdomadaires ; un âge compris entre 15 et 30 ans inclus. Nous avons exclu les sportifs ayant des pathologies au niveau des quadriceps, des ischiojambiers ou des genoux dans les 12 mois précédents les tests. Nous avons de plus exclus les sportifs ayant eu une évaluation isocinétique dans les douze mois précédents les tests pour des raisons de risque de familiarisation.


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Apr 23, 2017 | Posted by in PHYSICAL MEDICINE & REHABILITATION | Comments Off on Reproducibility of the time to peak torque and the joint angle at peak torque on knee of young sportsmen on the isokinetic dynamometer

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