The Comparison of Lower Extremity Malalignment during HPF and TRD Approach at Forward Diving Straight

Objectives: The present study is a correlational study that was conducted to obtain complete and accurate information by examining “the relationship between diving score and dynamic malalignment of Hip, Knee and Ankle on a 1 m springboard by elite male divers.”

Methods: The subjects of this study were the 12 top divers of Iranian League Championship. The subjects performed FDS technique in one of two ways either the "Hurdle Pre-Flight" or "Hurdle Flight”, and head coach gave them scores. The x and y coordinates of each marker were estimated using the KINOVEA software. The relationship between the performance score of "FDS" and dynamic malalignment of Ankle, Knee and Hip joints in the frontal plane at each step was determined using “Generalized Estimating Equation” (GEE) with the “Identity Function” and the “Normal Distribution”.

Results: There was a significant inverse relationship between FDS score and “L. There was a significant inverse relationship between FDS score and “R. dynamic ankle malalignment in both “HF” and “HPF” steps had a significant inverse relationship with Coach Score.

Conclusions: There was a significant inverse relationship between FDS score and “Ankle Eversion/ Eversion, Knee and Hip Abduction/ Adduction” in Swing or Stance Leg.

Introduction

Exercise training is based on continual repetition of main movements. These repetitions may lead to imbalances in the musculoskeletal system due to changes in strength, flexibility, balance and coordination of movement, as well as a direct impact on the pattern of bone growth. Such effects may develop individual risk factors for postural changes, which in turn may cause injury. Injuries sustained during diving can either result from catastrophic overloading of joints during a poorly executed dive or, more commonly, from repetitive loading at lower levels of force, such as during a successful dive [1].There are also special challenges regarding diving and diver approach on springboard. To perform diving techniques, high power is required for hip, knee and ankle joint muscle groups. In every sport there are athletes who represent true technical excellence. This technical mastery requires a physical structure that supports the sport's biomechanics, the neuromuscular coordination to correctly sequence the movement, the psychological skills to focus effort without unnecessary tension and the physiology to sustain the movement pattern until the event is completed [2]. In closed skill sports such as swimming, pole vaulting or sprint kayak, performance depends upon an ability to accurately reproduce a movement with minimal variation [3]. including diving. According to studies by Pruett 1981and reported by the university of Texas [4], Grace and balance are largely the result of proper body alignment and kinesthetic awareness. Proper poise is required at the initiation of the approach of a dive. Secondly, "the accurate alignment of the body at the end of the board must be maintained through the flexion of the knees and push-off with the accompanying extension of the ankles". Finally, a kinesthetic awareness of the body in motion in relation to the center of gravity is key to a graceful execution. Studies at the University of Texas show that the proper display of balance and grace can be severely plagued by inadequate strength in postural and stabilizing muscle and if the musculature is inadequate to control the recoil of the springboard, a diver may not achieve maximal dive height or even more detrimental, loose their balance. There has been some evidence of muscular imbalance in divers [5] and postural effects on athletes' performance, as dysfunction affected by knee varus [6], knee vulgus [7], ankle pronation and supination [8]. Therefore, the importance of balance of power in muscle groups and postural alignment in the frontal plane is obvious. Every athlete has a movement objective. Whether it is to move faster, jump higher, or even just lift a heavier weight in training, they will try to find a way to meet that objective. If an athlete has a deficit in strength, flexibility, coordination, balance, stability or perception, they will unconsciously try to find a way to achieve their movement objective even if their method is not biomechanically ideal. This is known as compensating. Compensating will cause deviation from a technical "ideal", and can be dramatically obvious or very subtle. It is an attempt to find a solution to make up for a weakness or control problem. Even high performance athletes compensate, and it is challenging for the coach to evaluate the root cause of the compensation and formulate a strategy to overcome it. Many athletic performance plateaus are associated with compensatory movement strategies that cannot support further development [9]. The judge score is based on the observation and evaluation of diver’s performance on the lateral view or sagittal movement plane, so dive coaches are also looking to improve the performance of their athletes on this movement plane. This is probably why previous studies have sought to improve diver’s performance with the approach of exercise physiology and methodology of training [10]. Also, in studies with [11-14] and sport biomechanics [15,16] approach of diving sport injuries the purpose has been to obtain epidemiology statistics, information about rate of sport injuries incidence and types of injuries occurred [17,18].

"Video analysis", as one of the assessment methods of dynamic postural malalignment has limitations. Athletic performance on multiple plane, has made it difficult to evaluate them. So most studies about dynamic postural assessment is focused on simulated performance patterns such as “squat” [19 the results have been extended to the and then) [20,21] landling” (-) and “ jump [22,23] athletic performance. Whereas there are differences between the biomechanical and physiological properties of each sport technique and similar task in laboratory environment that is mentioned by authors as researches limitations.

Therefore, in the present study, a realistic, rather than simulated study of the technique was performed and we investigated with participation of the elite male divers "the relationship between the score of forward diving straight (FDS) and dynamic malalignment of ankle and knee".

Method

The present study is a correlational study that was conducted to obtain complete and accurate information by examining “the relationship between diving score and dynamic ankle and knee malalignment on a 1 m springboard by elite male divers.” The subjects of this study were the 12 top divers of Iranian League Championship in summer 2016. They have 20±4 years old, 70±9 kg weight, 172±7 cm height, 23±2 BMI, 13±2 skinfold, 1.5±0.3 endomorphy, 5.5±0.7 Mesomorphy and 3±1 ectomorphy. The anthropometric characteristics, static posture, and background of diving sports injuries were assessed, after completing the consent sheet. Subjects had no postural static disorder and no injury at the time of the study. Measurements were taken one day in the pool of Tehran Azadi Sport Complex. The information who needed to participate in the research process was explained to them.

Marker placement

According to the purpose of the present study, the dynamic posture of hip, knee and ankle joints were evaluated in the frontal plane during the "Hurdle and take-off" steps. Therefore, passive or reflective markers were attached to posterior surface of the subjects' bodies Table 1.

The x and y coordinates of each marker were estimated using the KINOVEA software. The joint angles in the frontal plane were obtained by above coordinates and the input formulas in Excel software. The movement angles of the ankle and knee at the frontal plane were defined according to the Figure 1, as follows Table 2:

Figure 1: Marker Placement.

Diving

There are five elements of a dive in this study that head coach considered when evaluation of a dive which as follow respectively: Starting position, Approach, Hurdle, Take-off, Forward Diving (see Figures 2-6). The divers performed the task on 1m springboard. Four divers have performed approach Tradionaly (TRD) (i.e., with one hurdle before take-off), and eight divers with Pre-Flight pattern (PFT) (i.e., with two hurdles before take-off).

Figure 2: Starting position

Figure 3: Approach.

Figure 4: Hurdle Pre-Flight Approach.

Figure 5: Traditional Hurdle.

Figure 6: Forward Diving Straight.

Coach score

The Coach Score Criterion was exactly in line with the Criteria for Judging a Dive that approved by the World Swimming, Diving and Water polo Federation [24]; In the sport of diving, a judge’s award can range from zero (0) to ten (10) points. Awards are given in half point increments according to the following scale. Therefore, “Excellent” performance (10), “Very good” (8.5-9.5), “Good” (7-8), “Satisfactory” (5-6.5), “Deficient” (2.5-4.5), “Unsatisfactory” (0.5-2), “Completely Failed” (0). Therefore, the coach evaluated and rated the diver’s performance since “Start Position" to "Entry”, but video analysis was related to the Start of hurdle to the end of take-off.

Kinematic data collection

The Casio Exilim EX-ZR200 camera was used to record kinematic data and images were captured in 2D at 120 frames per second. The camera was placed at the beginning of longitudinal direction of the springboard to record the technique on the frontal plane. The camera was placed in the posterior view, parallel to the sacrum area, so that diver’s body was seen during the technique performance. The distance between camera and diver was adjusted so that to keep the subject's image at optimum size with minimal perspective. Reflective markers were used to track the organs by the camera.

Kinematic data processing

The recorded videos were examined by the KINOVEA software, which has already been verified and validated [25,26]. The operator showed the exact location of the markers to the software by following each marker in each frame of the image. Then, image calibration was performed. At this point, certain longitudinal values were introduced to the software to calculate the x and y coordinates of all image markers using trigonometric identities. Then the longitudinal and transverse coordinates of all followed markers by the software were determined and data were extracted from the software. Like all motion analysis software, the first output of this software is a set of data based on the x and y of each marker over time that based on the time taken in the technique and the number of markers, this data is very large. All the extracted information was imported into Excel software and then the x and y coordinates of all markers were saved based on time. According to the angles considered in this study, trigonometric formulas were written and all angles were extracted (Figures 7,8).

Figure 7: Determination of movement angles of lower extremity joints during “Hurdle” step.

Figure 8: Determination of movement angles of lower extremity joints during “Take-off” step.

Statistical analysis method

Data were summarized and reported for qualitative variables with frequency and percentage and for quantitative variables with mean (standard deviation). Also, the normality of the quantitative variables used in the analysis was evaluated using descriptive indices such as “Skewness” and “Kurtosis”. The relationship between the performance score of "FDS" and dynamic malalignment of Ankle, Knee and Hip joints in the frontal plane at each step was determined using “Generalized Estimating Equation” (GEE) with the “Identity Function” and the “Normal Distribution”. The dynamic malalignment of knee and ankle joints in the frontal plane at various repetitions and steps were compared using GEE with “Logit Function” and “Bernoulli distribution”. In addition, the qualitative variables are entered as markers in the model. The reason for using these advanced models was the "Repeated Measurements" in elite male divers. This analysis was used to calculate the "correlation of measurements" using a Compound Symmetry Covariance structure. Data analysis was performed using SPSS 25 software at the significant level of 0.05. This analysis and “Compound Symmetry covariance structure” were used to determine the “correlation of measurements”. Data analysis was performed using SPSS 25 software at the significant level of 0.05.

Results

The Results of GEE modeling showed that: There was a significant inverse relationship between FDS score and “L. Ankle Eversion” (6.93±14.73) in “HPF” step (P=0.001, β= -0.010) that was Swing Leg. There was a significant inverse relationship between FDS score and “R. Ankle Inversion” (6.42±11.23) in “HF” (P =0.016, β= -0.009) that was Swing Leg. Also, the results of GEE modeling showed that there is no significant difference between the pattern effect of TRD (5.62±0.609) and HPF (6.81±1.047) approach on "R. Ankle Inversion" (or swing leg) during “Hurdle Flight” step (P=0.326). However, the mean ankle inversion in the HPF approach was higher than the TRD. There was a significant inverse relationship between FDS score and “R. Knee Valgus” (13.31±10.08) in “HPF” step (P=0.044, β= -0.019) that was Stance Leg. There was a significant inverse relationship between FDS score and “R. Knee Varus” (4.01±8.431) in “Take-off” step (P=0.044, = -0.019). Also, the results of GEE modeling showed that there is no significant difference between the pattern effect of TRD (5.91±3.65) and HPF (3.32±0.61) approach on "R. Knee Varus" during “Take-off” step (P=0.485). There was a significant inverse relationship between FDS score and “R. Hip Add.” (11.75±10.01) in “Hurdle Pre-Flight” step (P=0.049, β= -0.017) that was Stance Leg. There was a significant inverse relationship between FDS score and “L. Hip Add.” (5.38±3.43) in “Hurdle Flight” step (P=0.036, β= -0.063) that was Stance Leg. Also, the results of GEE modeling showed that there is no significant difference between the pattern effect of TRD (4.97±0.33) and HPF (5.63±0.75) approach on "L. Hip Add." during “Hurdle Flight” step (P=0.425). The Results of GEE modeling showed that there was a significant difference between mean scores of TRD-FDS (4.39±0.33) and HPF-FDS (5.67±0.33) approach (P=0.000) Tables 3-5.

Discussion

According to the findings of this study, dynamic ankle malalignment in both “HF” and “HPF” steps had a significant inverse relationship with Coach Score. That is, with decreasing coach score, the swing ankle eversion in HPF step and the Swing ankle inversion in HF step increased. The data show that the mean dynamic deviation from the static anatomical alignment is not high in ankle, knee, and hip joints, but it seems that the low malalignment can effect on a simple dive score. It seems like there are critical points for each of these joints as they progress on the springboard, although the mean of Inversion (11.72±18.304) and eversion (9.41±16.537) ankle were higher in the take-off phase than HF and HPF steps, however, there was a significant inverse relationship between FDS score and the malalignments during HF and HPF phases. According to the evidences the attentional demand necessary for regulating postural sway increased as the postural task increased in difficulty but this effect was smaller for the gymnasts during unipedal stance. These findings suggest a decreased dependency on attentional processes for regulating postural sway during unipedal stance in gymnasts with respect to non-gymnasts [27]. Because they, like divers, focus on stability training, and functional performance on an unstable surface such as a springboard may be related to the quality of their physical performance. According to our findings, the HPF step had more effects on FDS scores than the other steps. Also, the mean of effective malalignments on FDS score was higher in HPF step than other steps. Although, it has been said before that dive height is almost exclusively the function of the vertical velocity at take-off [28], But malalignment during the Hurdle can reduce the “Take-off” quality before the flight. The importance of the Hurdle step in diving performance has been mentioned previously in other studies, both in terms of its functionality characteristics [29] and its importance as a risk factor [30]. Given that, there is more Base of Support in take-off than HF and HPF, it seems to maintain of postural stability in take-off is easier than HF and HPF if there is a challenge to postural alignment. Also, the stance leg affected the FDS score more than the swing leg. During HPF step, knee valgus and hip adduction on stance leg (right) had a significant inverse relationship with FDS score. These results suggest that functional movements of pronation may be one of the risk factors on the HPF step and one of the causes of reduce of the FDS score. Despite all postural malalignment, the mean FDS score was significantly higher in the HPF approach than in the TRD. This probably indicates that achieving higher altitude in both Hurdle and Take-off pre-flight is an important factor in enhancing diving quality and gaining success.

Conclusion

It seems that, in addition to evaluating diver performance on the sagittal plane, coaches should be to evaluated diver's dynamic postural alignment in the frontal plane, and as well as evaluation of divers is critical in the lateral view, in both the anterior and posterior view.

Conflict of interest

We disclose any financial and personal relationships with other people or organizations that could inappropriately influence or bias the work

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