Abstract
nt moment arm (MA) may help maintain the necessary muscle force when muscle contractions are repeated. This beneficial effect may contribute to re- ducing the energy cost during running. In this study, we examined the correlation between patellar tendon MA and running performance in endurance runners. The pa- tellar tendon MA and quadriceps femoris muscle volume (MV) in 42 male endurance runners and 14 body size- matched male untrained participants were
when muscle contractions are repeated. This beneficial effect may contribute to re- ducing the energy cost during running. In this study, we examined the correlation between patellar tendon MA and running performance in endurance runners. The pa- tellar tendon MA and quadriceps femoris muscle volume (MV) in 42 male endurance runners and 14 body size- matched male untrained participants were measured using a 1.5-T magnetic resonance system. The patellar tendon MA was significantly shorter in endurance runners than in untrained participants (p = 0.034, d = 0.65). In endur- ance runners, shorter patellar tendon MA correlated significantly with better personal best 5000- m race rime (r = 0.322, p = 0.034). A trend toward such a significant cor- relation was obtained between quadriceps femoris MV and personal best 5000- m race time (r = 0.303, p = 0.051). Although the correlation between patellar tendon MA and personal best 5000- m race time did not remain significant after adjusting for the quadriceps femoris MV (partial r = 0.247, p = 0.120), a stepwise multiple regression analysis (conducted with body height, body mass, patellar tendon MA, and quadri- ceps femoris MV) selected the patellar tendon MA (β = 0.322) as only a predictive variable for the personal best 5000- m race time (adjusted R 2 = 0.081, p = 0.038). These findings suggest that the shorter patellar tendon MA, partially accorded with the smaller quadriceps femoris size, may be a favorable morphological variable for better running performance in endurance runners. KEYWORDS joint torque, magnetic resonance imaging, muscle volume, quadriceps femoris
2 of 9 | UENO eT AL. may be associated with better running performance in en- durance runners (Barnes et al., 2014; Hunter et al., 2011; Scholz et al., 2008; Ueno et al., 2018a, 2018b). Unlike the relationships on the ankle joint torque- related mor- phological variables, the effect of the knee joint torque- related morphological variable(s) on running performance is poorly understood. The knee extensor torque is mainly required to obtaining propulsion force during the contact phase and to swinging the legs rapidly during the swing phase while running (Kenneally- Dabrowski et al., 2019; Novacheck, 1998). Indeed, an increase in the running velocity is partially associated with increasing the knee extensor torque during running (Arampatzis et al., 1999; Belli et al., 2002). Therefore, the morphological variable(s) related to the knee extensor torque production during run- ning may be important in achieving superior running per- formance in endurance runners. The joint torque is generally expressed as the product of the moment arm (MA) and muscle force. Hence, a longer joint MA can potentially increase the joint torque. We and others have previously reported a positive correlation be- tween MA and torque in several joints. (Baxter & Piazza, 2014; Blazevich et al., 2009; Hori et al., 2020; Sugisaki et al., 2010; Tottori et al., 2020). Of these studies, we have demon- strated that the patellar tendon MA (i.e., the distance between the tibio- femoral contact point and the mid- line of the pa- tellar tendon), which is calculated as an alternative to the overall knee extensor muscle MA, is correlated with the knee extensor isometric and isokinetic torques in untrained indi- viduals (Hori et al., 2020; Tottori et al., 2020). Therefore, the longer patellar tendon MA may be a favorable morphological variable for achieving superior performance in athletes who participate in sports that require greater knee extensor torque. The joint MA dimension is potentially determined by ago- nist muscle size (Vigotsky et al., 2015). Our previous studies reported a positive correlation between patellar tendon MA and quadriceps femoris muscle size (i.e., cross- sectional area [CSA] and muscle volume [MV]) in untrained
variable for achieving superior performance in athletes who participate in sports that require greater knee extensor torque. The joint MA dimension is potentially determined by ago- nist muscle size (Vigotsky et al., 2015). Our previous studies reported a positive correlation between patellar tendon MA and quadriceps femoris muscle size (i.e., cross- sectional area [CSA] and muscle volume [MV]) in untrained individuals (Hori et al., 2020; Miyake et al., 2017; Tomita et al., 2018; Tottori et al., 2020). However, we found the absence of such a correlation in sprinters. Moreover, we reported that although the quadriceps femoris muscle size did not differ between sprinters and body size- matched untrained participants, the patellar tendon MA was longer in sprinters than in untrained participants (Miyake et al., 2017). Furthermore, we reported that the longer patellar tendon MA is correlated with better sprint performance parameters (i.e., persona best 100- m race time and 50- m sprint velocity) independent of the quadri- ceps femoris size in sprinters (Miyake et al., 2017), which may be potentially due to enhanced knee extensor torque- producing capacity (i.e., the knee extensor torque per the unit of the quadriceps femoris size: Hori et al., 2020; Tottori et al., 2020). Therefore, the longer patellar tendon MA may be an important morphological variable for achieving better sprint performance in sprinters. In contrast to our findings in sprinters, several previous studies have reported that in endurance runners, a shorter Achilles tendon MA (i.e., an alternative to the overall plantar flexor muscle MA) may be associated with better running economy (Barnes et al., 2014; Scholz et al., 2008), which is a well- known important indicator of the running per- formance (Saunders et al., 2004). Generally, change in the muscle length is expressed as the product of the changes in the joint angle and MA dimension (Spoor & van Leeuwen, 1992). Hence, the favorable effect of the shorter joint MA on running performance may be because this morphology can mitigate the degree of muscle length changes during joint rotation, potentially by decreasing the velocities of muscle shortening and lengthening (Lee & Piazza, 2009; Nagano &
product of the changes in the joint angle and MA dimension (Spoor & van Leeuwen, 1992). Hence, the favorable effect of the shorter joint MA on running performance may be because this morphology can mitigate the degree of muscle length changes during joint rotation, potentially by decreasing the velocities of muscle shortening and lengthening (Lee & Piazza, 2009; Nagano & Komura, 2003). Such muscle performances secondary to the shorter joint MA may contribute to maintaining the necessary muscle force during repeated muscle contractions, and thus, this may result in improving running economy due to reduced energy consumption in the working muscles during running (Fletcher & MacIntosh, 2017). Therefore, in addition to the Achilles tendon MA, the patellar tendon MA may be an im- portant morphological variable associated with economical running, thereby contributing to better running performance (i.e., personal best time) in endurance runners. Based on this biomechanical background, we hypothesized that the shorter patellar tendon MA would be correlated with better running performance in endurance runners. Endurance runners are required to having leaner body seg- ments than those of many athletes to reduce the energy cost during running (O'Connor et al., 2007; Pollock et al., 1977; Weyand & Davis, 2005). In particular, the leg muscle mass may affect the energy cost during running, especially during swinging of the legs (Browning et al., 2007; Myers & Steudel, 1985), and thus, the smaller leg muscle size may be useful in achieving superior running performance (Black et al., 2020; Lucia et al., 2006; Scholz et al., 2008), as they provide bet- ter running economy owing to lesser leg moments of inertia (Black et al., 2020). In addition, although our previous study reported the absence of a correlation between patellar tendon MA and quadriceps femoris size in sprinters (Miyake et al., 2017), the quadriceps femoris size may be an important deter- minant for the patellar tendon MA in endurance runners, sim- ilar to untrained participants (Hori et al., 2020; Miyake et al., 2017; Tomita et al., 2018; Tottori et al., 2020). Therefore, we also hypothesized that, if shorter patellar tendon MA is cor- related
femoris size in sprinters (Miyake et al., 2017), the quadriceps femoris size may be an important deter- minant for the patellar tendon MA in endurance runners, sim- ilar to untrained participants (Hori et al., 2020; Miyake et al., 2017; Tomita et al., 2018; Tottori et al., 2020). Therefore, we also hypothesized that, if shorter patellar tendon MA is cor- related with better running performance, it may involve a cor- relation between smaller quadriceps femoris size and better running performance in endurance runners. To test our hypotheses, we first compared the patellar tendon MA and quadriceps femoris MV between endurance runners and untrained participants in order to understand the
| 3 of 9UENO eT AL. characteristics of these knee extensor morphological vari- ables for endurance runners. Thereafter, we examined the correlations of the patellar tendon MA and quadriceps femo- ris MV with running performance in endurance runners. 2 | METHODS 2.1 | Participants Prior to the present study, we calculated a priori sample size using the effect sizes obtained in our previous stud- ies (Miyake et al., 2017; Tottori et al., 2021). To compare the morphological variable (e.g., muscle size) between two groups, the necessary minimum numbers of participants for each group were 9, which was calculated from an effect size of 1.41 (gluteus maximum CSA: Tottori et al., 2021), α- level of 0.05, and β- level of 0.20 (80% power). Additionally, to determine the correlation between morphological variable (e.g., joint MA) and performance in a single athlete group, the necessary minimum number of participants was 18, as calculated from an effect size of 0.61 (patellar tendon MA: Miyake et al., 2017), α- level of 0.05, and β- level of 0.2 (80% power). Forty- two male endurance runners (age: 20 ± 1 years) and 14 untrained participants (age: 22 ± 1 years) participated in this study. The numbers for each group were sufficient for ensuring statistical power and sensitivity based on the pri- ori sample size calculations. The endurance runners were all well- trained, being involved in regular training and com- petition. The official personal best times of a 5000- m race (i.e., personal best 5000- m race time) in the endurance run- ners ranged from 13 min 54 s to 15 min 54 (mean, 14 min 53 ± 25 s). A mean weekly training distance in the endurance runners was 112 ± 28 km. The untrained participants whose physical characteristics (i.e., body height and body mass) were similar to those of the endurance runners were recruited as a control group. All participants were informed of the ex- perimental procedures and provided written consent to par- ticipate in the study. This study was approved by the Ethics Committee of Ritsumeikan University (BKC- IRB-2016-047) and conducted according to the Declaration
physical characteristics (i.e., body height and body mass) were similar to those of the endurance runners were recruited as a control group. All participants were informed of the ex- perimental procedures and provided written consent to par- ticipate in the study. This study was approved by the Ethics Committee of Ritsumeikan University (BKC- IRB-2016-047) and conducted according to the Declaration of Helsinki. 2.2 | Magnetic resonance imaging (MRI) Representative MRI scans for measuring the patellar tendon MA and quadriceps femoris MV are shown in Figure 1. These MRI measurements were performed using a 1.5- T magnetic resonance system (Signa HDxt; GE Medical Systems). To measure the patellar tendon MA and quadriceps femoris MV, participants were placed in a supine position on the scanner bed, with both knees fully extended and both ankles set at the neutral position (i.e., 0°). The participants were also instructed to maintain a relaxed state throughout the MRI measurements. With regard to the patellar tendon MA measurement, three-dimensional isotropic T1- weighted MRI scans of the right knee joint were acquired with an eight channels coil. Sagittal scans were obtained in successive slices with an inter distance of 10 mm with a repetition time of 11.3 ms, echo time of 5.1 ms, slice thickness of 1.2 mm, field of view of 280 mm, and matrix size of 256 × 256 pixels. The patellar tendon MA was calculated as the distance between the tibio- femoral contact point and the mid- line of the patellar ten- don, as in our and other previous studies (Blazevich et al., 2009; Hori et al., 2020; Miyake et al., 2017; Tomita et al., FIGURE 1 Representative magnetic resonance imaging scans for measuring the patellar tendon moment arm (MA) and quadriceps femoris muscle volume (MV). The left scan shows a sagittal image on the knee joint of the right leg. The patellar tendon MA was calculated as the distance between tibio- femoral contact point and mid- line of the patellar tendon. The right scan shows an axial image on the midthigh level of the right thigh. The cross- sectional areas (CSA) of the quadriceps
(MV). The left scan shows a sagittal image on the knee joint of the right leg. The patellar tendon MA was calculated as the distance between tibio- femoral contact point and mid- line of the patellar tendon. The right scan shows an axial image on the midthigh level of the right thigh. The cross- sectional areas (CSA) of the quadriceps femoris included the rectus femoris (RF), vastus intermedius (VI), vastus lateralis (VL), and vastus medialis (VM). The quadriceps femoris MV was calculated by multiplying the sum of the CSAs along their length at intervals of 1 cm
4 of 9 | UENO eT AL. 2018; Tottori et al., 2020). The measurements of the patellar tendon MA were performed twice, and the mean of the two values was used for the analysis of this study. The coefficient of variations of the two measurements in the patellar tendon MA was 0.5 ± 0.4%. The intraclass correlation coefficient of the two measurements was 0.991. With regard to the quadriceps femoris MV measurement, axial T1- weighted MRI scans of the right thigh were acquired with a standard body coil. Axial scans were obtained in suc- cessive slices with an inter distance of 10 mm from the infe- rior aspect of the greater trochanter to the lower edge of the femur with a repetition time of 600 ms, echo time of 7.6 ms, field of view of 480 mm, and matrix size of 512 × 256 pixels. From these scans, CSAs on each slice were measured. The measured quadriceps femoris CSAs involved the rectus fem- oris, vastus intermedius, vastus lateralis, and vastus medialis. The quadriceps femoris MV was calculated by multiplying the sum of the CSAs along their length at intervals of 1 cm, as in our previous studies (Hori et al., 2020; Tomita et al., 2018; Tottori et al., 2020). The analyses for the patellar tendon MA and quadriceps femoris MV were conducted using image analysis software (OsiriX Version 5.6). The reproducibility of the patellar ten- don MA and quadriceps femoris size on two separate days has been reported in our previous studies (Miyake et al., 2017; Tomita et al., 2018; Tottori et al., 2020). 2.3 | Statistical analysis All data are presented as mean ± standard deviation. Comparisons of physical characteristics (i.e., body height and body mass) and knee extensor morphological variables (i.e., patellar tendon MA and quadriceps femoris MV) be- tween endurance runners and untrained participants were performed using an unpaired t- test. The Cohen's d effect size using the pooled stranded deviation was calculated to deter- mine the magnitude of differences in the variable between the two groups. The effect size was interpreted as small (0.20– 0.49), medium
morphological variables (i.e., patellar tendon MA and quadriceps femoris MV) be- tween endurance runners and untrained participants were performed using an unpaired t- test. The Cohen's d effect size using the pooled stranded deviation was calculated to deter- mine the magnitude of differences in the variable between the two groups. The effect size was interpreted as small (0.20– 0.49), medium (0.50– 0.79), and large (>0.80) (Cohen, 1992). Correlations between knee extensor morphological variables and personal best 5000- m race time in endurance runners were evaluated using the Pearson's product- moment correlation coefficient. The strength of a correlation between two variables was interpreted as trivial (<0.10), small (0.10– 0.29), medium (0.30– 0.49), and large (>0.50) (Cohen, 1992). A partial correlation analysis was used to adjust the effect of the quadriceps femoris MV on a correlation between patellar tendon MA and personal best 5000- m race time in endur- ance runners. A stepwise multiple regression analysis was used to determine the predictive variable for the personal best 5000- m race time in endurance runners. This analysis was conducted with four variables, body height, body mass, patellar tendon MA, and quadriceps femoris MV. The statis- tical significance level was defined at p < 0.05. All statistical analyses were conducted using IBM SPSS software (version 19.0; International Business Machines Corp). 3 | RESULTS Body height and body mass did not differ significantly between endurance runners and untrained participants (170.6 ± 6.3 and 171.5 ± 6.5 cm, respectively, p = 0.653, d = 0.14 for body height: 56.2 ± 5.3 and 58.4 ± 4.5 kg, re- spectively, p = 0.168, d = 0.43 for body mass). Comparisons of the patellar tendon MA and quadriceps femoris MV between endurance runners and untrained par- ticipants are presented in Figure 2. The patellar tendon MA was significantly shorter in endurance runners than in un- trained participants (p = 0.034, d = 0.65). In contrast, the quadriceps MV did not differ significantly between the two groups (p = 0.145, d = 0.45). A correlation between patellar tendon MA and quadriceps femoris MV in endurance runners is presented in Figure
in Figure 2. The patellar tendon MA was significantly shorter in endurance runners than in un- trained participants (p = 0.034, d = 0.65). In contrast, the quadriceps MV did not differ significantly between the two groups (p = 0.145, d = 0.45). A correlation between patellar tendon MA and quadriceps femoris MV in endurance runners is presented in Figure 3. The patellar tendon MA correlated significantly with the quadriceps femoris MV in endurance runners (r = 0.329, R 2 = 0.108, p = 0.034,). A trend toward such a significant correlation was also observed in untrained participants (r = 0.501, R 2 = 0.251, p = 0.068). Correlations of patellar tendon MA and quadriceps fem- oris MV with personal best 5000- m race time in endurance FIGURE 2 Comparisons of the patellar tendon MA and quadriceps femoris MV between endurance runners and untrained participants. Values are presented as mean ± standard deviation
Description
This study examines the correlation between patellar tendon moment arm and running performance in endurance runners.