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Hindawi Applied Bionics and Biomechanics Volume 2019, Article ID 4505481, 6 pages https://doi.org/10.1155/2019/4505481 Research Article Relationships between Hamstrings-to-Quadriceps Ratio and Variables Describing Countermovement and Drop Jumps 1 2 Artur Struzik and Bogdan Pietraszewski Department of Team Sport Games, University School of Physical Education, Wrocław, Poland Department of Biomechanics, University School of Physical Education, Wrocław, Poland Correspondence should be addressed to Artur Struzik; email@example.com Received 1 December 2018; Revised 27 March 2019; Accepted 19 May 2019; Published 2 June 2019 Academic Editor: Laurence Cheze Copyright © 2019 Artur Struzik and Bogdan Pietraszewski. 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. The impact of the hamstrings-to-quadriceps ratio on sport movement performance has not been suﬃciently described. However, it seems that in movements involving eccentric-concentric muscular contractions, a higher hamstrings-to-quadriceps ratio should have a positive impact on human movement performance. The present study is aimed at identifying relationships between the hamstrings-to-quadriceps ratio and variables describing countermovement and drop jumps. The study was carried out in a group of 14 female soccer players. The tests were conducted using a Kistler force plate, an SG electrogoniometer, and the Biodex System 4 Pro dynamometer. Each player performed three countermovement jumps (CMJ) and three drop jumps (DJ) from heights of 15, 30, 45, and 60 cm. The peak torques of knee extensors and ﬂexors were measured in isometric conditions and in o o o o isokinetic conditions at angular velocities of 30 /s, 60 /s, 90 /s, and 120 /s. Statistically signiﬁcant relationships were found between the variables that describe CMJ, DJ 15, DJ 30, and hamstrings-to-quadriceps ratio at some, though not all, of the angular velocities measured. No signiﬁcant relationships were found between the hamstrings-to-quadriceps ratio and variables that describe DJ 45 and DJ 60. The heights of CMJ, DJ 15, and DJ 30 were increased with higher hamstrings-to-quadriceps ratios. Analogous relationships were found between the hamstrings-to-quadriceps ratio and relative mechanical power during the take-oﬀ phase of the CMJ. Signiﬁcant relationships between the hamstrings-to-quadriceps ratio and variables that describe vertical jump are likely to be observed if adequate angular velocity is used in the measurement of muscle torque. 1. Introduction tively high levels of muscle torque in knee ﬂexors in com- parison with extensors might positively aﬀect sports movement performance. The commonly used conventional hamstrings-to-quadriceps (H/Q) ratio represents the ratio of concentric hamstring peak Maximum values of isometric muscle torque in extensors torque during lower limb ﬂexion to concentric quadricep and ﬂexors of the knee joint have been demonstrated to not peak torque during lower limb extension . The eﬀect of reliably predict the level of jumping ability [7, 8]. Kubo the peak torque ratio of knee ﬂexors and extensors on the risk et al.  reported that isometric training changes the stiﬀness of injury in the lower limbs has been extensively discussed in of the tendon-aponeurosis complex in knee extensors and the literature [2–6]. However, the relationships between the negatively impacts prestretch during the stretch-shortening value of the H/Q ratio and sport movement performance cycle (SSC). It is likely that muscular activation is diﬀerent have not been suﬃciently explored to date. It is generally between static and dynamic actions . However, Trzas- accepted that a value of the ﬂexor-extensor ratio above koma  found positive relationships between maximal 0.6 (for measurements performed under isokinetic condi- power output developed during countermovement jumps tions) might be eﬀective at preventing hamstring strain (CMJ) and the value of the H/Q ratio calculated based and anterior cruciate ligament (ACL) injury risk potential on measurements of muscle torques performed under iso- [2–6]. However, the question arises as to whether rela- metric conditions. 2 Applied Bionics and Biomechanics Positive relationships between the level of muscle torque and variables that describe vertical jump are, however, signif- icant if the measurement of muscle torque is performed in isokinetic rather than isometric conditions [11–15]. Martel et al.  reported that plyometric training might lead to the improvement of both CMJ height and the values of mus- cle torque in knee ﬂexors and extensors measured at angular o o velocities of 60 /s and 180 /s. Furthermore, Wilkerson et al.  reported that plyometric training results in an increase in the H/Q ratio for measurements taken at an angular veloc- ity of 60 /s. CMJ, drop jump (DJ), and the movements performed during the measurement of knee muscle torque under isoki- netic conditions (especially with high measurement angular velocity) all involve the SSC. The alternating eccentric- concentric muscle work leads to the accumulation of poten- tial elastic energy, consequently allowing for more work to be performed in the concentric phase . It seems that dur- ing movements with eccentric-concentric muscle work, higher values of the H/Q ratio should have a positive eﬀect on human movement performance. Therefore, the aim of the study is to identify the relationships between the value of the H/Q ratio and variables that describe CMJ and DJ ver- tical jumps. Due to the alternate eccentric-concentric muscle work during the countermovement (amortization) and take- oﬀ phases of the vertical jump, it seems that the conven- tional H/Q ratio is more suitable for describing human Figure 1: Drop jump (DJ) laboratory testing set-up. movement performance during SSC compared to the func- tional H/Q ratio, which is a measure of the isokinetic eccen- tric peak torque of the hamstrings relative to the isokinetic (and for each participant). Ground reaction forces were concentric peak torque of the quadriceps during leg exten- recorded by means of the 9281B13 Kistler force plate (Swit- sion at equivalent angular velocities . zerland) with a signal sampling frequency of 250 Hz. The SG Biometrics electrogoniometer in the knee joint was used for recording temporary changes in the angle in this joint. 2. Materials and Methods A comparison of the proﬁle of angle changes in the knee joint with the vertical component of ground reaction forces was The study population consisted of 14 female soccer players from the Polish Women’s Extra League. The study group used to determine the ground contact time (t ), amortization was characterized by the following mean parameters (±SD): time (t ), and take-oﬀ time (t ) [7, 20]. Jump height was cal- a p body height—166 6±5 8cm, body mass—59 3±6 kg, and culated based on the ﬂight phase duration. Relative mechan- age—20 6± 4 1 years. Training experience was 8 8±3 9 ical power (P ) in the take-oﬀ phase was calculated based on rel years. The tests were carried out in the Biomechanical Anal- the equation contained in a study by Pietraszewski and ysis Laboratory (with PN-EN ISO 9001:2009 certiﬁcation). Rutkowska-Kucharska : Prior to the measurements, the participants were familiarized with the purpose of the study and gave written consent for g∙h P = , 1 participating in the experiment. Before the test, the subjects rel were informed of the activities they were supposed to per- form and were motivated to properly perform the task. The where h denotes the jump height, t the take-oﬀ time, and g research project was approved by the Senate’s Research Bio- j p ethics Commission, and the procedure complied with the the acceleration due to gravity. Power calculated using this Declaration of Helsinki regarding human experimentation. equation relates to the vertical displacement of the centre of Prior to the measurements, a 10-minute-long warm-up mass of a jumper from the moment of take-oﬀ to the maxi- was administered, which included jogging, a series of hops, mal location during the ﬂight phase. and rehearsing the drop jumps. Peak muscle torques for extensors and ﬂexors of the knee The participants were asked to perform CMJ (counter- joint were also measured under isometric conditions (for the o o movement jump, which is a vertical jump with an arm swing) angles of 75 and 30 , respectively) and under isokinetic con- o o o o and DJ (drop jump, which is a vertical jump performed ditions (at angular velocities ω 30 /s, 60 /s, 90 /s, and 120 /s immediately after landing) from heights of 15, 30, 45, and in the joint analysed) for each subject. 0 at the knee joint was 60 cm (Figure 1). Each jump was repeated three times, and considered to be a full extension. The measurements were further analysis was based on the highest jump for each type performed separately for the right and left lower limbs. Applied Bionics and Biomechanics 3 Biodex System 4 Pro was used for the measurements (Figure 2). The measurements under isokinetic conditions (with eccentric-concentric muscle work) were performed o o with a range of motion in the knee joint of 90 (from 90 to 0 ). The hamstrings-to-quadriceps ratio (H/Q ratio) was cal- culated using the following equation: F + F l r H/Q ratio = ∙100%, 2 E + E l r where (F + F ) denotes the sum of the values of peak torque l r Figure 2: Test stand for the measurement of muscle torque. developed in the knee joint ﬂexors in the left and right lower limbs, whereas (E + E ) is the analogous sum for the exten- l r group was characterized on average by about 10% higher sors [10, 21]. This calculation method was used intentionally H/Q ratios. because all types of jumps used in the study were performed with both lower limbs. Therefore, we used the calculation of an index which applies to both lower limbs at the same time. 4. Discussion Furthermore, the research group was divided into two Soccer is a sport involving a predominance of explosive subgroups based on the values obtained for the H/Q ratio. movements that require a substantial level of speed- The subgroup “good” were people (n =7) with higher strength abilities. Although female soccer players do not H/Q ratios compared to the second subgroup (“poor”). jump a lot during a match, they perform other movements The above division was aimed at comparing jump vari- that utilize the SSC, such as strikes, turns, changes in direc- ables between the subgroups. tion, and cuts . Therefore, the jumping ability of soccer Pearson’s r coeﬃcient and Student’s t-test were used to players could still be considered crucial for performance examine the relationships between the selected variables [23, 24]. The adequate strength of the hamstring muscles due to the normality of the distribution of the variables. not only ensures the eﬀective braking of the shank when Additionally, the t-test for independent groups was used to striking a ball but also plays an important role in other move- investigate the diﬀerences between the “good” and “poor” ments, including rapid acceleration/deceleration, cutting, or subgroups. The level of signiﬁcance was set at α =0 05. side-stepping manoeuvres [2, 12, 25, 26]. Fousekis et al.  found a slight increase in the H/Q ratio with greater 3. Results amounts of professional training in soccer players. Cometti Table 1 contains the mean values (±SD) of the variables that et al.  demonstrated that sports skill level in soccer describe the CMJ and DJ. In the group of female soccer players increases with higher H/Q ratios. A similar tendency was not observed regarding the CMJ height . This may be players, the mean value of the H/Q ratio for the torques mea- sured under isometric conditions was 42 ± 3 6%, whereas for the reason why no signiﬁcant diﬀerences in jump variables the measurements performed under isokinetic conditions, were observed between the “good” and “poor” subgroups in the mean values were 48 8±7 4% (for ω =30 /s), 54 1±7 4 this study. Furthermore, Daneshjoo et al.  suggested that o o % (for ω =60 /s), 55 2±7 2% (for ω =90 /s), and 55 1± the physical performance and movement pattern experi- 8 enced when playing soccer should not have a negative eﬀect 3% (for ω = 120 /s). Table 2 contains the values of the correlation coeﬃcients on the H/Q ratio in the knee joint. The values of the H/Q between the variables that describe CMJ and DJ and the ratio were similar across diﬀerent ﬁeld positions for elite col- values of the H/Q ratio. Statistically signiﬁcant positive rela- legiate American football players . tionships (p <0 05) were found between the H/Q ratio and It is diﬃcult to draw unequivocal conclusions concerning o o o the relationships between the H/Q ratio and the variables CMJ height (for isometric and for ω =30 /s, 60 /s, 90 /s, o o o o and 120 /s), DJ 15 (for ω =60 /s, 90 /s, and 120 /s), and DJ describing the vertical jumps studied based on the values of 30 (for ω = 120 /s). The H/Q ratio also showed a statistically the correlation coeﬃcients in Table 2. Statistically signiﬁcant signiﬁcant relationship (p <0 05) with relative mechanical and positive relationships between the H/Q ratio and the power during the take-oﬀ phase of the CMJ (for ω =60 /s, height of CMJ, DJ 15, and DJ 30 allow for the assumption o o that the relatively high level of torque in the knee joint ﬂexors 90 /s, and 120 /s). No statistically signiﬁcant relationships were found between the H/Q ratio and the variables that compared to that in the extensors should positively aﬀect the describe DJ 45 and DJ 60. Statistically signiﬁcant relation- vertical jump height. However, the above relationships for ships (p <0 05) were observed between the H/Q ratio and the DJ 45 and DJ 60 were not statistically signiﬁcant, the duration of amortization, take-oﬀ, and contact phases although the heights obtained for individual types of jumps were nearly identical (Table 1). It should also be noted that for the DJ 30 only. No statistically signiﬁcant diﬀerences in jump variables high H/Q ratios may exist in the presence of relative (for all types of jumps) were found between the “good” weakness in both the hamstring and quadriceps muscle and “poor” subgroups, despite the fact that the “good” groups , which can also explain the lack of the above 4 Applied Bionics and Biomechanics Table 1: Mean values (±SD) of jump height (h ), relative mechanical power during the take-oﬀ phase (P ), contact time (t ), amortization j rel c time (t ), and take-oﬀ time (t ) obtained during CMJ and DJ. a p CMJ DJ 15 DJ 30 DJ 45 DJ 60 0 29 ± 0 04 0 28 ± 0 04 0 28 ± 0 05 0 28 ± 0 05 0 28 ± 0 06 h (m) 10 9±2117 0±3316 8±3917 9± 5317 1±5 7 P (W/kg) rel 0 32 ± 0 05 0 32 ± 0 08 0 3± 0 06 0 31 ± 0 05 t (s) n/a 0 15 ± 0 03 0 16 ± 0 04 0 14 ± 0 03 0 14 ± 0 04 t (s) n/a 0 26 ± 0 04 0 16 ± 0 03 0 16 ± 0 04 0 15 ± 0 03 0 17 ± 0 03 t (s) Table 2: Values of the correlation coeﬃcients between the height of relationships. This may be another reason why no signiﬁcant the vertical jump (h ), relative mechanical power during the take-oﬀ diﬀerences in jump variables were observed between the phase (P ), contact time (t ), amortization time (t ), take-oﬀ time “good” and “poor” subgroups in this study. The female soc- rel c a (t ), and values of the H/Q ratio calculated based on cer players examined in the study showed mean values below o o measurements under isometric and isokinetic conditions. 0.6 for the H/Q ratio (for isometric and for ω =30 /s, 60 /s, o o 90 /s, and 120 /s), which is regarded as a lower limit neces- H/Q ratio sary for the prevention of lower limb injuries [2–6, 30]. o o o o Isometric 30 /s 60 /s 90 /s 120 /s Lehance et al. , despite determining statistically signiﬁ- CMJ cant positive relationships between peak torques of joint ∗ ∗ ∗ ∗ ∗ 0.46 0.49 0.41 0.44 0.62 ﬂexors and extensors (measured under isokinetic conditions) and squat jump (SJ) height, did not ﬁnd similar relationships ∗ ∗ ∗ 0.13 0.24 0.47 0.48 0.42 rel between the H/Q ratio (conventional and functional) and SJ p 0.12 −0.05 −0.3 −0.3 −0.09 height. The SJ, however, does not have an SSC pattern. González-Ravé et al.  did not ﬁnd relationships between DJ 15 ∗ ∗ ∗ knee ﬂexion and extension torque and vertical jump (CMJ 0.44 0.47 0.59 j 0.37 0.37 and SJ) variables. 0.19 0.13 0.31 0.3 0.31 rel The statistically signiﬁcant positive relationship between t 0.15 0.4 0.21 0.16 0.35 the CMJ height and H/Q ratio calculated based on the mea- surements of torques carried out under isometric conditions −0.01 0.29 0.22 0.08 0.17 seems surprising. The relationships between the variables of 0.19 0.35 0.07 0.16 0.25 the vertical jump and isometric torques in the area of the DJ 30 knee joint are insigniﬁcant and occur only in speciﬁc research h groups [7, 8]. The explanation for the widespread occurrence 0.22 0.23 0.28 0.3 0.48 of this phenomenon is likely to be found in the diﬀering −0.01 −0.25 0.01 −0.09 0.08 rel levels of muscular activation between static and dynamic ∗ ∗ ∗ ∗ 0.31 0.67 0.41 0.45 0.51 tasks . ∗ ∗ t 0.57 0.48 0.14 0.34 0.32 The H/Q ratio also showed a statistically signiﬁcant rela- ∗ ∗ tionship with relative mechanical power during the take-oﬀ t 0.6 0.45 0.37 0.32 0.37 phase of the CMJ. The presence of analogous similar rela- DJ 45 tionships has been reported previously by other authors 0.06 0.14 0.37 0.33 0.4 j [10, 11, 13]. The most statistically signiﬁcant relationships between the H/Q ratio and variables of vertical jumps were P −0.2 −0.28 0.07 −0.03 −0.15 rel observed for the CMJ. Therefore, it can be presumed that 0.11 0.26 0.08 0.02 0.28 an adequate ratio of muscle torque between the agonist and −0.04 0.11 −0.1 −0.19 0.13 antagonist muscle groups for this type of jump is the most t critical for performance among all the types of jump ana- 0.14 0.33 0.12 0.17 0.23 lysed. Tansel et al.  reported that training oriented at DJ 60 the development of hamstring strength should positively 0.01 0.02 0.21 0.2 0.26 aﬀect the eccentric knee extension torque and the CMJ 0.02 −0.26 −0.01 −0.04 0.14 height. rel Statistically signiﬁcant positive relationships were also −0.06 0.38 0.15 0.23 0.09 observed between the times of contact, amortization, and t 0.17 0.08 0.06 0.12 0.34 take-oﬀ during the DJ 30 and the values of the H/Q ratio. p −0.18 0.36 0.13 0.17 −0.06 We found no other studies that have described this type of ∗ relationship. 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Applied Bionics and Biomechanics – Hindawi Publishing Corporation
Published: Jun 2, 2019
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