A Discussion of the Deadlock Confronted by Chinese Writers of English Academic Articles

As a consequence of receiving frequent complaints from students and colleagues about their difficulties in writing papers in English, I have to reconsider the deadlock confronted by Chinese writers of English academic articles. Obviously, these writers have similar difficulties in approaching academic writing, not because lack of professional knowledge, but because the ability of processing language is not handy enough, though the majority of them demonstrate good lexical and grammatical knowledge, or even discourse knowledge of the target language. Therefore, summary and exploitation of the deadlock confronted by them facilitates the improvements of language efficiency in expressing ideas. If they can build certain cultural awareness before constructing ideas, writing in English may not be so problematic as they anticipate. In this article, the deadlock confronted by Chinese writers based on a theoretical research about EAL or EFL academic writing and interview with carefully selected writers is concluded as three major difficulties: text borrowing, critical writing, as well as structural and ideological diversity between L1 and L2. They should be highlighted as the most conspicuous problems for Chinese writers. However, most of the difficulties originate from cultural difference and language obstacles posed by it, which needs to be realized by Chinese EFL writers. To solve the problems, I recommend teachers and learners to adopt comparative approach and text-based approach which emphasize cultural awareness in training writing skills.

Introduction
Writing for an academic community like a college or university is not as easy as many people expect. It poses considerable difficulties for writers using English as an additional language (EAL), or a foreign language (EFL) than for native speakers to write the disciplinary discourses on numerous subjects. For advanced EFL students at graduate and post-graduate level, writing can be even more complicated since a relatively high standard and often specialized language is required. The purpose of this essay is to describe the deadlock faced by writers from China based on the generalization of relevant literature in this field, as well as interview with some of my students and colleagues, by whom the deadlock is reported. Then, a critical evaluation will be given in order to sort out the crucial attributions to the hardness of achieving a satisfactory goal in English academic writing. The largest influential factor is, as I perceive, cultural and language obstacle. The discussion over the deadlock and its attributions may indicate feasible solutions to the problem.
First of all, many students have the problem of textual borrowing, or incorporating other people's work naturally and intelligently into their own writing. 'Many of the genres commonly found in graduate-level writing require sophisticated weaving of prior texts into a larger piece of written discourse' (Barks and Watts 2001: 247), and this can be extremely difficult for EAL or EFL students. Barks and Watts (2001) has summarized three contributing factors to the 'issues surrounding textual borrowing' as 'the problematic and dynamic concepts of authorship and originality', 'different culture and educational practices', and 'the complex nature of language learning itself'. They argue that there is lack of consistency of the concepts of authorship and originality within and without western culture. They also point out that people from different cultural background may have different perspective towards the conventions of textual borrowing. For example, some cultural and educational practices like that in China tend to be more tolerant of 'plagiarism' because Chinese value memorization as a standard and effective learning style. Barks and Watts (2001: 249) state that 'achieving the level of language proficiency necessary not just to survive but to thrive in the English-speaking academic context is clearly a complex task for a nonnative speaker.' They point out that as one aspect of language proficiency, the ability to integrate others' work into their own work requires sophisticated knowledge and skills, such as reading comprehension ability, the skills of processing and synthesizing reading materials, linguistic knowledge and the necessary background knowledge of one's subject matter. Non-native writers are doubly challenged by the emerging difficulties around text borrowing because they are unfamiliar with the writing culture of English and have limited linguistic proficiency. The situation gets worse if they apply the mistakenly interpreted reading materials into their written work.
Second, quite a lot of students find it difficult to write critically, though they are expected to write like 'experts in training' rather than 'receivers and demonstrators of knowledge' (Belcher 1995: 137). In other words, most Anglophone educators encourage college students from various disciplinary areas to read and write critically on their way of becoming specialized scholars. However, some students and especially EFL students are reluctant to challenge established authority. One reason for this reluctance simply lies in the lack of confidence. Once they have accumulated enough specialized knowledge and become familiar with the critical and analytical way of learning, they begin to write critically. While another reason is culturally dominated, to which difficulties relate usually take extra time and effort to overcome. For example, teachers in the university of Auckland have noticed the relative unwillingness of Chinese writers to criticize other people's work. They design a lot of group work tasks in teaching academic writing, preparing students from China and other Asian countries with necessary skills of thinking, discussion and writing critically. Every student who joins the group must accomplish equal amount of work in order to get a pass score. This is because Chinese students are perhaps too cautious to critique other people's work for the sake of so-called 'social harmony'. Their cultural background does not encourage them to do so, which creates for them either the difficulty of referring to the source and its authors, or the difficulty of writing critically by themselves.
Finally, some EFL students, even if at or above graduate level, have the difficulties of organizing rhetorical structure and communicating ideas with their readers, owing to the strong influence of their first languages. Hamp-Lyons and Zhang (2001) in their research report compare different attitudes towards rhetorical diversity between Chinese-speaking and native English teachers who participated in an experiment on assessing two problematic compositions of Chinese students. They conclude that this diversity has two levels: the level of structure and that of ideology. The former has to do with the way of structural organization within and between paragraphs, whilst the latter focuses on the way of forming ideas and perspectives. The authors' purpose of introducing the diversity is to provide useful hints for assessing students' written work. Meanwhile, it suggests how strong the influence of the first language over English might be in terms of structure and ideology, so that it can pose considerable difficulty for EFL students when they strive to write successfully for academic purposes. Jin and Cortazzi (1993: 91-92) also illustrates the structural and ideological difference between Chinese and English writing systems in their paper Cultural Orientation and Academic Language Use, which affects the production of writing of even post-graduate EFL students. On one hand, as they state, the contrasted views of the two languages on the discourse patterns may be contributors. On the other hand, the different ways of thinking lead to occurrence of additional difficulties, from constructing ideas to seeking help from tutors. For example, Chinese students, out of the collective way of thinking, may get used to do the research according to the need of the authority instead of personal interests, thus they are passive about choosing a research topic. Generally speaking, the difficulties for advanced EFL students with rhetorical structure and ideology often originate from a potent influence of one's native language and culture.
There are implicit problems that hamper students from writing successfully in academic English. Schneider and Fujishima (1995) point out in their account of one foreign student's struggle to make his academic achievements that the difficulties challenging this student's writing can be divided into several categories: 'English language proficiency', 'sensitivity to sociolinguistic norms', 'motivation for learning', 'learner strategies' and 'other personal factors'. Nevertheless, if the problems of language use and typical personal factors are excluded, writing academic papers is still difficult. At a higher English proficiency level, the deadlock of Chinese writers lies in text borrowing, critical writing, as well as structural and ideological diversity between L1 and L2.
In order to check the authenticity of the concluded difficulties, I interviewed two groups of Chinese writers: group one are senior students of English major who were busy preparing thesis for their graduation; group two are my colleagues -teachers from different departments who have experience in writing papers in English. Each group involved 10 people. All the interviewees are from a local university in China. They have proved English language proficiency for high intermediate or advanced level, and are competent writers of L1, for I need to sort out the dominant difficulties other than language use from a rather academic point of view. The result of the interview is summarized in the list below.  All interviewees agreed that text borrowing, critical thinking, and structural and ideological diversity between L1 and L2 were 3 most difficult areas to adapt to.  10 out of 20 reported that text borrowing was the most difficult part of writing, even if they had already been familiar with APA referencing style.  The difficulty of text borrowing mainly arose from processing reading materials. On one hand, they needed more reading time; on the other hand, sometimes it was hard to decide whether citation of the source text is necessary or not.  6 of 20 reflected that critical thinking was the leading difficulty because they were seldom trained to challenge the established authority.  4 of 20 thought writing in English was difficult owing to L1 influence. They could not get used to constructing ideas in English, and would rather think in Chinese firstly and translate their view later.  All interviewees agreed that if they were given more time and appropriate tutoring the difficulties could be overcome.

Crucial Attributions
Writing for academic purposes involves various knowledge and skills. It is not linear but a process that contains several dimensions. For instance, when passing through the stages of planning and revision to compose an essay, we need to do a set of jobs ranging from surveying source materials to editing drafts. At the same time, we must follow the academic conventions and make the structure of our articles clear and ideas communicative to our audience. During the composing process, we apply all kinds of strategies, whether consciously or unconsciously. Comparing with native speakers, the difficulties of writing always double for Chinese students, due to their limited language competence and unfamiliarity with different discourse patterns. Moreover, some ethnic students find it difficult to adapt the western way of thinking and reasoning to their own view. At the stance of an EAL or EFL student, no matter what their specialties are, I feel that cultural diversity is indeed a great challenge to producing academic discourses in English. Many difficulties raised in the writing practice have a cultural origin. Here, 'culture' means 'the total pattern of beliefs, customs, institutions, objects, and techniques that characterize the life of a human community' (Deng and Liu 1989: 3). It certainly affects writing, which is a tool of expressing human thoughts and beliefs. Bark and Watts' exploration of the differences in source text use across cultures, and Belcher's comments on the barriers of critical writing for Chinese students remind me the different attitudes of Chinese towards plagiarism and the existing reluctance to challenge scholarly work. Belcher mentioned the term 'experts in training' to indicate that graduate or post-graduate students are expected to write critically like real experts or scholars, but this contradicts what I was taught in china since my childhood. To some extent, Chinese educators do encourage their students to think and write critically, but they constantly give students such instructions as 'Be modest', 'Do not pretend to be experts'. Actually, some Chinese authors avoid giving the impression that they are experts on their subject matter. For example, Deng and Liu (1989: 110) have noticed that the conventional use of titles in scholarly papers and articles written in Chinese is somewhat strange to English speakers. It is common for a Chinese writer to add some words showing humility about their work in titles. Whereas English authors may think it ridiculous to write a title like 'A Superficial Discussion of …', or 'My Humble Opinions on…'. Furthermore, as Hamp-Lyons and Zhang (2001) indicate in World Englishes: Issues in and from academic writing assessment, the influence of students' L1 and home culture is an explanation to the emergence of some problems, in terms of both rhetorical pattern and ideology.
There are other difficulties evident in some sample academic texts that I have studied or students' papers that are marked by their teachers as 'unclear expression of ideas', one of which is the lack of language proficiency. In a broad sense, to achieve this proficiency, students need to have a good knowledge of vocabulary, grammar and to be familiar with the discourse structure of academic English. In addition, they must be aware of the cultural differences and clearly understand academic conventions. However, this is still insufficient. Reading comprehension ability and the ability to integrate reading into reading are also important. On the difficulties of comprehending texts, Bark and Watts (2001: 250) state that inexperienced writers at graduate level may 'approach reading-to-write tasks with limited or misguided strategies and inadequate task interpretation'. They did not notice in their article that a relatively low speed of reading increases the difficulty of applying reading materials. Comparing with native speakers, foreign students need more time to read through and synthesize materials into their writing. Being impatient to read for a long time before drafting can push students into patchwriting, which is normally considered as a kind of plagiarism. Interestingly, many Chinese scholars challenge the western viewpoint towards it. Instead, they would rather regard it as a natural stage on the way of becoming mature writers and accepts it as an effective teaching strategy to students moving at this stage.
Obviously, cultural and language obstacles are two major attributions to various difficulties faced by Chinese English writers even at higher academic level. It does not mean they are the most conspicuous obstacles to every student. The major difficulties for some students are caused by motivation, learner strategies and other personal factors. But as they approach English academic writing, the deadlock arising from cultural difference may be more thorny and hard to overcome if they are unconscious of the internal cause. Therefore, to build culture awareness is an important solution. Chinese EFL writers and scholars should adopt the comparative approach more often. Before writing academic articles in English, they should understand writing conventions, together with the logic reasoning steps of the target language. Comparison between Chinese and English articles under the same topic is always necessary, since it helps the writer voluntarily switch to the thinking mode of another culture. They may constantly ask themselves some questions like 'Do I need to cite experts' words in this paragraph?', 'Is it important to suggest a different opinion at this step?', 'What will a native speaker do in order to summarize this?', etc.

Conclusion
The difficulties of academic writing among Chinese EAL or EFL writers often arise from text borrowing, critical writing and following rhetorical conventions. Although it is not the case to all the students, cultural and language barriers are the major contributors that make their writing problematic. As increasing numbers of students pursuing graduate and post-graduate study need to write their papers in English, these problems have gained growing concern among students, teachers and the academic institutions they enrolled in. One possible solution to the problems relating to culture is to let both students and educators be aware of the difference and then seek 'culture synergy', in which 'adaptation, rather than assimilation' is emphasized (Jin & Cortazzi 1993: 95). To teachers, it is necessary to construct a cultural syllabus, that is, EAL or ESL students should be given opportunities to explicitly learn the rules of Western writing conventions, patterns of cognition, and attitudes to text before brainstorming and constructing ideas. To learners, just as Byram and Fleming (1998) suggest, language learning should follow the cognitive process that insight and increased understanding of the society and culture of both L1 and L2 is promoted. With regard to language problems, experienced teachers may propose the text-based approach as a fast solution to some students' problems. For example, when teaching educated adults who are already competent writers in their first language, a teacher of business or scientific English might focus on the features of commercial or technical texts, asking the students to do necessary discourse analysis before compiling their own piece. That is why I recommend my students to study some standard academic articles in the relevant research field before they come to compile their own piece. Analysis of academic discourse paragraph by paragraph increases writers' confidence in completing a paper that caters for the appetite of native English audience. They may clearly realize that copy of any word of the sample text is forbidden, but imitation of the structure and the writing style -the way of constructing ideas is definitely applicable, especially when the due date is near.
It is worthwhile to combine comparative approach and text-based approach in training writing because both of them emphasize cultural awareness. After all, the choice of teaching method should meet the specific needs of learners from different cultural background. To writers from China, being aware of their common deadlock and its influential factors may assist them in adapting English academic writing within short period.


The Importance of Lean Body Mass for the Rate of Force Development in Taekwondo Athletes and Track and Field Throwers

The rate of force development (RFD) is vital for power athletes. Lean body mass (LBM) is considered to be an essential contributor to RFD, nevertheless high RFD may be achieved by athletes with either high or low LBM. The aim of the study was to describe the relationship between lower-body LBM and RFD, and to compare RFD in taekwondo athletes and track and field (T&F) throwers, the latter having higher LBM when compared to taekwondo athletes. Nine taekwondo athletes and nine T&F throwers were evaluated for countermovement jumping, isometric leg press and leg extension RFD, vastus lateralis (VL), and medial gastrocnemius muscle architecture and body composition. Lower body LBM was correlated with RFD 0–250 ms (r = 0.81, p = 0.016). Taekwondo athletes had lower LBM and jumping power per LBM. RFD was similar between groups at 30–50 ms, but higher for throwers at 80–250 ms. RFD adjusted for VL thickness was higher in taekwondo athletes at 30 ms, but higher in throwers at 200–250 ms. These results suggest that lower body LBM is correlated with RFD in power trained athletes. RFD adjusted for VL thickness might be more relevant to evaluate in power athletes with low LBM, while late RFD might be more relevant to evaluate in athletes with higher LBM.

Introduction
Explosive strength is of great importance for performance in several power-demanding sports, such as sprints, long and high jumps, athletic throws, and martial arts. Explosive strength may be evaluated with the rate of force development (RFD; i.e., the slope of the tangent line of the force/torque-time curve during an explosive muscle contraction [1,2]), which has been linked with explosive sports performance. Indeed, lower body isometric leg press RFD at 100, 150, 200, and 250 ms from the onset of contraction, is associated with performance in track and field throwers, where the time for the final delivery of the implement is between 150-250 ms [3]. Taekwondo is also considered to be a powerful sport. For example, one of the most effective kicks in taekwondo, the roundhouse kick to the head, is developed between in approximately 250 ms (time from the instant that the striking foot leaves the floor until it reaches the objective and achieves the maximum impact force) [4][5][6]. This kick is characterized as a high velocity unloaded movement, in contrast to track and field throws where a relatively heavy external throwing implement is used. Thus, it might be postulated that RFD might be equally important for taekwondo athletes as for throwers. However, RFD in taekwondo athletes has not been described before.
RFD is influenced by different factors at early (<100 ms) and late phases (>100 ms) from the onset of muscle contraction [2,7,8]. The early phase of RFD is thought to be determined mainly by the neural drive to the muscle, as well as the muscle fiber type composition [2,[7][8][9]. Late phase RFD is largely influenced by maximal strength and most likely muscle mass, as suggested by studies reporting parallel changes in maximal muscle strength and contractile RFD 150-250 ms from the onset of contraction [1,2,7,8,[10][11][12][13]. Nevertheless, little is known about the correlation between muscle mass and RFD in power athletes. Recently, a close relationship was reported between isometric leg press late RFD (>100 ms) and lean body mass in young aged track and field throwers, while early RFD (<100 ms) was not related with their lean body mass [14]. Taekwondo athletes are expected to have lower lean body mass when compared to track and field throwers [15], although direct evidence is lacking on this issue. This may suggest a lower late RFD and lower maximum isometric force (MIF) and/or torque (MIT) in taekwondo athletes as compared to that of throwers, although this remains to be evaluated.
Muscle architectural characteristics, fascicle length, pennation angle, and muscle thickness, may also influence RDF [2,14,16]. Previous studies indicate that pennation angle and muscle thickness seems to affect late RFD [2,14,17,18]. Fascicle length is thought to reflect the number of sarcomeres in series in a muscle and the increase in this number has been suggested to contribute to higher shortening velocity and muscle power [19]. Longer fascicles are typically found in agonist muscles of faster sprinters [20][21][22], while studies in humans have reported longitudinal muscle growth in response to power training [23][24][25][26][27]. Recently, a correlation was found between vastus lateralis fascicle length and late RFD (100-250 ms) in young aged track and field throwers [14]. In addition, previous study indicates that in experienced power trained athletes, vastus lateralis fascicle length have stronger contribution/effect on sprinting, jumping, and throwing performance as compared to pennation angle and muscle thickness [28]. However, the relationship between muscle architecture and early and late RFD in athletes is still debatable, while there is no such information for taekwondo athletes.
The aim of the study was to describe the relationship between lower-body lean mass and RFD and to compare lower-body RFD in taekwondo athletes and track and field throwers, the latter having higher lean body mass when compared to taekwondo athletes. For this purpose, maximal isometric leg press and leg extension RFD curves were recorded from taekwondo athletes and track and field throwers of national and international level. It was hypothesized that (1) lower body lean mass would be associated with RFD in both athletic populations, but also (2) that they would differ in early and late RFD characteristics. Muscle architecture was also evaluated to provide further insight into the muscle morphology origin of the anticipated differences in RFD between the two athletic groups.

Experimental Design
All of the measurements were performed within 20-30 days before the national championship for each athletic group. Athletes visited the laboratory on four different occasions. On day 1, they gave their written consent to participate in the study, and their lower-extremity dominance and anthropometry were evaluated. Familiarization with the countermovement jump (CMJ), isometric leg press and leg extension RFD and maximal isometric force/torque were also performed. On day 2, three days later, athletes visited the laboratory for muscle architecture evaluation and another testing familiarization. On day 3, three days later, they performed the testing session. On day 4, three to four days after the testing session, body composition analysis was performed (see description below). All of the procedures were approved by the local university ethics committee.

Participants
Nine male taekwondo athletes (age 21.22 ± 2.90 years, range 19-28 years; body height 174.8 ± 0.05 cm; body mass 67.6 ± 8.3 kg; competition experience = 7.7 ± 4.6 years) and nine male track and field throwers (age 23.66 ± 5.04 years, range 19-34 years; body height 183.3 ± 0.05 cm; body mass 99.3 ± 9.9 kg; competition experience = 7.7 ± 3.9 years) gave their written consent to participate in the study after being informed about the experimental procedures as well as the risks and benefits of this research. Four of the taekwondo athletes were champions in the previous three years within separate weight classes. The rest of the taekwondo athletes placed second or third in the national championship or the national cup competition in the recent years. All of the taekwondo athletes participated in international competitions during the previous two years. The group of track and field throwers included two javelin throwers (mean performance: 79.8 ± 1.8 m), four shot putters (mean performance: 15.6 ± 0.9 m), and three hammer throwers (mean performance: 70.5 ± 4.3 m). The javelin throwers were the national champions in junior and senior categories, respectively, and were also among the best eight throwers of the European championship in the respective age categories, during the previous two years. Two of the shot putters placed first and second of the last years' national outdoor championship while the others ranked 9th and 11th. One of the hammer throwers was among the eight best of the European championship under 23 years, while the other two placed 3rd and 4th at the national championship, during the previous year. After detailed oral and written description of the procedures, they gave their written consent to participate in the study. All of the procedures were approved by the School of Physical Education & Sports Science, National and Kapodistrian University of Athens Ethics Committee (registration number: 1039/14/02/2018).

Training Background
Taekwondo athletes were following a training program that was designed to develop technical skills and increase both their anaerobic and aerobic capacity to face the competition needs as recently described [15]. Resistance training for the athletes in this study was performed 2-3 sessions per week for the previous 4-5 years, including low resistance loads (60-70% of 1RM) with maximum velocity movements using mainly structural exercises (e.g., squat, bench press, leg extension). Body mass explosive exercises were also included in 3-4 sessions per week (e.g., jumps, push ups). On the other hand, throwers performed resistance training 3-4 training sessions per week during the previous 6-8 years using high resistance loads (80-95% of 1RM) with structural exercises (squats, bench press, shoulder press, etc.). Olympic weightlifting exercises performed with high movement velocity were also included [14]. Plyometrics were also performed in 2-3 sessions each week using the body mass as external loading.

Countermovement Jumps
Countermovement jumps were performed on a force platform (Applied Measurements Ltd. Co., Aldermaston, Berkshire, UK, WP 800-1000 kg weighting platform, 80 × 80 cm, sampling frequency 1 kHz) with hands on hips with elbows pointing out. Briefly, after a short warm up on a stationary bicycle, athletes performed three sub-maximal CMJ's with progressively higher intensity. Then, athletes performed three CMJ's with maximum intensity, instructed to jump as high as possible. Two-minute rest was allowed between attempts. Data from the force platform were recorded and analysed (Kyowa sensor interface PCD-320A; Kyowa Electronic Instruments Co., Ltd., Chofu, Tokyo, Japan) to calculate the maximum vertical jump height, the power output, the velocity, and the average rate of force development [ARFD (N·s −1 ) = (Max force − Body weight) × [(Time of maximum force − Time at which force reach the body weight) −1 ]] during the push off phase (Time of maximum force − Time at which force reach the body weight) [29,30]. The highest jump was used for further analysis (Intraclass Correlation Coefficients (ICC) = 0.91, 95% Confidence Intervals (CI; Lower = 0.90, Upper = 0.99, n = 13), coefficient of variation (CV) = 8.1%.

Leg Press Rate of Force Development
Fifteen minutes after the CMJs, leg press maximum isometric force and RFD were evaluated. Throwers were seated on a custom-made completely rigid leg press chair made of steel with rigid plywood boards and placed both their feet on the force platform (Applied Measurements Ltd. Co., Aldermaston, Berkshire, UK, WP800, 1000 kg weighting platform, 80 × 80 cm, sampling frequency 1 kHz), which was positioned perpendicular on a concrete laboratory wall. Knee angle was set at 120 • and hip angle was set at 100 • [7,8,13,30,31]. After three sub-maximal efforts, athletes were instructed to apply their maximum force as fast as possible for 3 s. Three maximum efforts with 3-min rest were performed while athletes were vocally encouraged to perform their maximum. Data from the force platform were recorded and analysed (Kyowa sensor interface PCD-320A; Kyowa Electronic Instruments Co., Ltd., Chofu, Tokyo, Japan) to calculate the maximum isometric force and the RFD from the force time curve. The signal was filtered using a secondary low pass Butterworth filter with a cutoff frequency of 20 Hz, automatically from the analysis software. The best performance according to RFD 100ms was used for statistical analysis. Rate of force development was calculated as the mean tangential slope of the force-time curve in specific time windows of 0-30, 0-50, 0-80, 0-100, 0-150, 0-200, and 0-250 ms, relative to the onset of contraction which was set at 2.5% of the difference between baseline and maximum force; e.g., RFD = DForce/DTime [1,32]. Early RFD includes the previously mentioned time points until the first 100 ms from the onset of a muscle contraction, while late RFD the time points over the first 100 ms from the onset of a muscle contraction [2,7,8,32,33]. Sequential RFD time windows were analyzed, including 30-50 ms, 50-80 ms, 80-100 ms, 100-150 ms, 150-200 ms, and 200-250 ms, while isometric force production expressed per percentage of maximum voluntary contraction (%MVC) in all time windows [(Fms/MVC)·100] was also calculated. MVC was calculated as the highest instantaneous force over the entire force-time curve force. Finally, RFD was expressed per lower body lean mass, per VL muscle thickness, and per maximum isometric force. The ICC for the leg press maximum isometric force, and RFD were calculated during the pilot study: ICC = 0.90 (95% CI: Lower = 0.86, Upper = 0.96), CV = 15%, and ICC = 0.92 (95% CI: Lower = 0.80, Upper = 0.98), CV = 12%, respectively (n = 13).

Leg Extension Rate of Force Development
Fifteen minutes after the isometric leg press test the leg extension test was performed. The athletes were positioned on a custom-made steel chair. Hip angle was set at 110 • and initial knee joint angle was set at 70 • (0 • = full extension), [31,32]. Straps were used to ensure the stable position of the shoulders, hips, non-exercising leg, and the right angle of the exercising knee, as determined during the familiarization session [34]. Measurement was performed using a tension sensor (Applied Measurements Ltd., DBBE-1000 kg, Aldermaston, Berkshire, UK, sampling frequency 1000 Hz), which was positioned between the leg of extension and the immovable back of the chair attached with a metal ring. The distance between the ankle strap, where the tension sensor was attached and the center of the knee, was measured to the nearest mm to calculate the extension torque. Two submaximal efforts were performed with progressively increasing force. Then, three maximal efforts were allowed. Athletes were instructed to apply their maximum force as fast as possible and to sustain it for 3 s. Data from the tension sensor were recorded and analyzed (Kyowa Sensor Interface PCD-320A Kyowa Electronic Instruments Co., Ltd., Chofu, Tokyo, Japan) to calculate the maximum isometric torque and the RFD torque (N·m·s −1 ) from the force-time curve, as described in the previous paragraph, while the torque was corrected for the effect of gravity on the lower leg [32]. The best performance according to RFD 100ms was used for statistical analysis. The ICC for the leg extension maximum isometric force and RFD, were calculated during the pilot study and were: ICC = 0.98, (95% CI: Lower = 0.93, Upper = 0.99), CV = 12%, and ICC = 0.93, (95% CI: Lower = 0.79, Upper = 0.98), CV = 10%, respectively (n = 11).

Muscle Architecture
B-mode ultrasound images were obtained during the morning hours from vastus lateralis (VL) and medial gastrocnemius (GM) of the dominant leg using a 38-mm linear probe (Product model Z5, Shenzhen Mindray Bio-Medical Electronics Co., Ltd., Shenzhen, China). Extended-Field-Of-View mode was used to obtain panoramic images along the fascicle length, according to previous instructions [12,35]. For the assessment of VL architecture, participants laid supine with their knees fully extended and their muscles relaxed. A mark was drawn at 50% of the distance from the central palpable point of the greater trochanter to the lateral condyle of the femur [16]. For the measurement of GM architecture, participants lay prone with their knees fully extended, their feet hanging off the edge of the medical bed, and were asked to leave their feet rested and their muscles relaxed so that ankle angle was in a physiological position. Then the GM was marked at the proximal level of 30% of the distance between the popliteal crease and the center of the lateral malleolus [36]. A water-soluble gel was applied to the transducer to aid acoustic coupling and to reduce the needed pressure from the probe against the muscle. The transducer was placed longitudinal at femur or tibia, oriented in parallel to the muscle fascicles, and perpendicular to the skin. Due to individual differences, the transducer was sometimes aligned slightly diagonally to the longitudinal line of the muscle so that several fascicles could be easily delineated without interruption across the image. Based on this orientation, a dashed line (approximately 10 cm in length) was drawn forwards and backwards to the mark, to identify and capture the largest, continuous fascicle visualization. To obtain the muscle image, a continuous single view was taken by moving the probe along the marked, dashed line. Also, the mediolateral angle of the probe was changed throughout the experiment so that it remained perpendicular to the skin, which ensures the most reliable image acquisition for the measurement of the fascicle length [12]. Images were analysed for muscle thickness, fascicle angle, and fascicle length with image analysis software (Motic Images Plus 2.0, Motic, Hong Kong, China). Muscle thickness was defined as the mean of the distances between the superficial and deep aponeurosis measured at the ends of each panoramic image [26,27]

Body Composition Analysis
Total body scans were obtained with dual X-ray absorptiometry (model DPX-L; LUNAR Radiation, Madison, WI, USA). All of the measurements were analysed using the LUNAR radiation body composition program (LUNAR Radiation Body Composition Program). Analyses included fat mass, bone mineral density (BMD), and lean body mass (LBM) for total body, arms, trunk, and legs, according to manufacturer instructions. The ICC for body composition analysis was determined from two different researchers ICC = 0.98, (95% CI: Lower = 0.95, Upper = 0.99), CV = 9%, n = 13.

Statistics Procedures
All data are represented as mean ± SD. The comparisons between the two groups were also presented as percentage differences between them. One-way ANOVA was used to compare performance and biological variables between taekwondo athletes and track and field throwers. Effect sizes (η 2 ) were also calculated (Palland, 2005). Pearson's (r) product moment correlation coefficient was used to explore the relationships between variables. Standard multiple regression analysis was performed, including both groups of athletes. Because of the relative small sample size (n = 18) adjusted R squared was used for the interpretation of the multiple regression analysis results as the percentage explained variation [37]. Within subject's variation and reliability was determined for all of the variables by calculating the confidence limits (95% CI), intraclass correlation coefficient (ICC), and coefficient of variation (CV), as described before [38]. Significance was accepted at p ≤ 0.05. All statistical analyses were performed using SPSS version 17.0 software (SPSS Inc., Chicago, IL, USA).

Figure 2.
Leg press sequential rate of force development (SRFD) for taekwondo athletes (dark grey) and track and field throwers (light grey). (A) Leg press SRFD in absolute values. Track and field throwers had greater SRFD than taekwondo except during for the 200-259 ms time window where no difference exists. (B) Leg press SRFD relative to lower body lean mass. No significant difference was found between taekwondo and throwers. (C) Leg press SRFD relative to VL muscle thickness. No significant difference was found between taekwondo and throwers (* p < 0.05).
When all athletes were considered as a group, lean mass of the lower extremities was significantly correlated with leg press RFD 250ms (r = 0.89, p = 0.000, Figure 6A) and leg extension RFD 250ms (r = 0.86, p = 0.000, Figure 6B). In taekwondo athletes, lean mass of the lower extremities was significantly correlated with average RFD during the CMJ (r = 0.710, p = 0.041) as well as leg press RFD 100ms (r = 0.680, p = 0.047), RFD 200ms (r = 0.730, p = 0.035), RFD 250ms (r = 0.810, p = 0.016), and leg press maximum isometric force (r = 0.83, p = 0.008). Also, in taekwondo athletes, lean mass of the legs was significantly correlated with leg extension RFD 250ms (r = 0.760, p = 0.026) and leg extension maximum isometric torque (r = 0.800, p = 0.011). In contrast, no significant correlations were observed between lean body mass and performance for the throwers.   Vastus lateralis muscle thickness was significantly correlated with leg extension RFD80ms (r = 0.780, p = 0.018) while GM muscle thickness was correlated with leg press maximum isometric force (r = 0.670, p = 0.049), in taekwondo athletes. VL fascicle length was significantly correlated with leg press RFD250ms (r = 0.67, p = 0.05) in throwers. The linear combination of VL muscle thickness and VL fascicle length could significantly predict the power performance in CMJ and the RFD between 80-250 ms, as well as maximum isometric force/torque for both leg press and leg extension (N = 18, Table  3). Vastus lateralis muscle thickness was significantly correlated with leg extension RFD 80ms (r = 0.780, p = 0.018) while GM muscle thickness was correlated with leg press maximum isometric force (r = 0.670, p = 0.049), in taekwondo athletes. VL fascicle length was significantly correlated with leg press RFD 250ms (r = 0.67, p = 0.05) in throwers. The linear combination of VL muscle thickness and VL fascicle length could significantly predict the power performance in CMJ and the RFD between 80-250 ms, as well as maximum isometric force/torque for both leg press and leg extension (N = 18, Table 3).

Discussion
The aim of the study was to describe the relationship between lower-body lean mass and RFD and to compare lower-body RFD in taekwondo athletes and track and field throwers, the latter having higher lean body mass when compared to taekwondo athletes. The main findings of the present study were that (1) lower body lean mass was significantly correlated with RFD in power-trained athletes having large lean body mass differences, (2) taekwondo athletes had greater early RFD when this was expressed relative to total lean mass or vastus lateralis muscle thickness, as compared to track and field throwers, and (3) throwers performed better in late RFD when compared to taekwondo athletes both in absolute values as well as relative to total lean mass or vastus lateralis thickness. Unfortunately, in the current study neither the neural components nor muscle fiber composition were assessed, therefore the contribution of these components to the early phase of force rise was not explored. However, it is reasonable to assume that longitudinal taekwondo training adaptations induced in response to fast muscle actions performed with relative low external resistance (e.g., body mass, [15]) might have resulted in increased early RFD. Taekwondo is a combat sport that depends on both agility-speed and power production. Anecdotal data from coaches suggests that during competition athletes must use their lower limbs as fast as possible to achieve a successful attack while often earning a point with a reflex-respond kick to the opponent's offence, which is a teaching strategy, an action that it has to be completed instantaneously. According to these, it seems that early RFD might be of significance for these athletes, while their lower legs' lean mass could, at least partly, explain their high early RFD relative to their musculature in comparison to track and field throwers.
Conversely, the delivery phase in track and field throws ranges between 150-250 ms [3,[39][40][41]. Chronic exercise training adaptations may have increased the late RFD ability of these athletes rendering them to perform better relative to their musculature as compared to taekwondo athletes, as found in the present study. Throwers had higher maximum isometric force relative to lean body mass which suggests an improved recruitment of their muscle tissue after the initial milliseconds of a maximum contraction. This might be the result of chronic resistance training adaptations in these athletes as opposed to the taekwondo athletes who do not regularly use high external resistances during training [15]. However, given that both taekwondo athletes and throwers have similar critical time periods to develop their maximum force or power, it would be of interesting, future studies to investigate if a training program, similar to that of the throwers, could increase the performance of Taekwondo athletes.
When RFD was expressed relative to total lean mass and legs lean mass, taekwondo athletes had higher early RFD than throwers in leg press but not in leg extension (no significant difference between groups for the leg extension). Although leg extension is commonly used to assess RFD, it is not regularly performed during training by either taekwondo athletes or track and field throwers. Thus, specific neural adaptations may not have developed for both groups for the leg extension, which might explain these results. In contrast, the multi-articular leg press exercise is a movement regularly performed by athletes either as specific leg press or in a broader sense in jumping, squatting, etc. Neural adaptations may be more applicable in leg press, which might explain the closer link with RFD relative to muscle mass/thickness. When all the athletes were considered together, lean body mass was significantly correlated with late RFD. The close link between muscle mass and late RFD has been predicted in earlier studies where training-induced increases in late RFD correlated with chronic increases in muscle mass [1,10,11,13]. Similar correlations were also found for the taekwondo athletes but not for the throwers in the current study. Significant correlations between lean body mass and late RFD 100-250ms have been recently reported in young well-trained track and field throwers [14]. However, the athletes that participated in that previous study had lower muscle mass (approximately 57.1 ± 13.2 kg, total lean mass) when compared to the athletes that participated in the current study (total lean mass = 75.9 ± 3.4 kg). This may suggest that the impact of muscle mass on late RFD may not be linear when large muscle masses have been accomplished.
The role of muscle architecture in power performance and the RFD has been debated. Some studies have shown a link between fascicle length or fascicle angle and muscle power [14,21,28,42,43], while other studies failed to reveal similar results [28,44,45]. This discrepancy might be due to the differential effect of muscle architecture in the early and late RFD. In a recent study, early RFD during jumping (10-30 ms) has been linked with the gastrocnemius fascicle length [46]. In the present study, neither vastus lateralis nor was gastrocnemius architecture correlated with early RFD. However, vastus lateralis fascicle length was significantly correlated with leg press late RFD in throwers. Moreover, late RFD could be predicted from the linear combination of vastus lateralis thickness and fascicle length when all athletes were considered together. This suggests that in power-trained individuals the combination of muscle hypertrophy (thickness) and the number of sarcomeres in series (fascicle length) might be vital for power production. Similar results were recently reported in a group of young track and field throwers where the linear combination of vastus lateralis muscle thickness and fascicle length could predict 53% of the shot put performance [14]. Future studies should address this intriguing issue more systematically, perhaps in a larger number of power-trained individuals. Finally, in the present study, RFD was evaluated in testing positions that were different to the ultrasound collection position. Recent study report that performing ultrasonography evaluation of vastus lateris architecture with athletes in a lying position or in a different position when compared to those that they have during strength and power evaluations, does not allow for us to have a precise view of muscle configuration that is present during performance evaluations, and this may have some impact on the correlations between strength/power performances and architecture parameters [18]. Unfortunately, the present study performed prior to this report. Thus, the lying position during the architecture evaluation of vastus lateralis, may have some impact on the results of the present study, providing lower or non-significant correlations as compared to those that may be found if the evaluations were performed in a position that is close to those of the performance evaluations [18]. Unfortunately, it was not possible to evaluate the electromyographic activity in this study. This might have provided further insight into the current results, especially about the neural input in the early phase of the RFD curve. Another limitation of this study was the lack of information regarding the muscle fiber composition of the athletes. Previous studies have shown a higher percentage of vastus lateralis area that is covered with type II muscle fibers in track and field throwers [47,48]. Although similar data might be expected for the taekwondo athletes, to our knowledge there are no such experimental data. However, a possible difference between the percentage of the vastus lateralis area that is covered with type II muscle fibers between the two groups of athletes in the current study might explain the differences that are found in early and late RFD relative to lean mass or muscle thickness. Furthermore, the relative small number of athletes in this study as well as the testing procedures (e.g., lack of warm-up activities prior the RFD testing) may pose limitations regarding the generalization of the results.

Conclusions
In conclusion, the current results reveal a significant correlation between lower body lean mass and RFD in power-trained athletes having large inter-individual differences in lean body mass. The track and field throwers are stronger than taekwondo athletes and they have more power in countermovement jumping. When the RFD is expressed relative to lean body mass, taekwondo athletes perform better that the throwers in the initial 30-50 ms after the initiation of an explosive contraction, which might be related to a higher neural input. In contrast, track and field throwers perform better relative to their lean muscle mass in the late part of the RFD curve.
In practice, the current results suggest that taekwondo athletes and coaches should regularly measure the lower body RFD, especially the early part of the force rise (<100 ms), as well as the lean body mass to evaluate the lower body power adaptations induced with training. The importance of the early RFD in taekwondo athletes revealed in this study suggests that these athletes should implement explosive actions with moderate to low external resistance (e.g., drop jumps) in their training. In contrast, in sports demanding explosive movements against higher external loads, such as the track and field throws, training may mainly focus on increasing the later part of the force rise of the force-time curve (>150 ms) and laboratory testing of the RFD may also focus on this part of the curve. For these athletes, development of lean body mass seems to be an important factor for the late RFD.