• Korean Journal of Applied Biomechanics
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• v.22 no.3
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• pp.357-363
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• 2012

The purpose of this study was to investigate the effects of different saddle heights on lower-limb joint angle and muscle activity. Six elite cyclists(age: $32.2{\pm}5.2years$, height: $171.0{\pm}3.5cm$, weight: $79.7{\pm}5.6kg$, cycle career: $13{\pm}6.2years$) participated in three min. submaximal(90 rpm) pedaling tests with the same load and cadence based on saddle heights where subject's saddle height was determined by his knee flexion angle when the pedal crank was at the 6 o'clock position. Joint angles(hip, knee, ankle joints) and the activity of lower limb muscles(biceps femoris(BF), vastus lateralis(VL), tibialis anterior(TA) and gastrocnemius medial(GM)) were compared by measuring 3D motion and electromyography(EMG) data. Results showed that there were significant differences in minimum hip & knee joint angle and range of motion of hip and knee joint between saddle heights. Onset timing and integrated EMG of only BF among 4 muscles were significantly different between saddle heights. Especially there was a negative relationship between minimum hip joint angle and onset timing of BF in most subject, which means that onset timing of BF became fast as the degree of bending of the hip joint became larger by saddle height. Optimal pedaling will be possible through increased amount of muscle activation due to the appropriate burst onset timing by proper pedaling posture with adjusted saddle height.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2012.05a
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• pp.1165-1166
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• 2012

• The korean journal of orthodontics
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• v.37 no.3 s.122
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• pp.192-203
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• 2007

Objective: The aim of this study was assessment of the relationship between airway space and facial morphology in Class III children with nasal obstruction. Methods: For this study, 100 Class III children (50 boys and 50 girls) were chosen. All subjects were refered to ENT, due to nasal obstruction. Airway space measurements and facial morphology measurements were measured on lateral cephalometric radiograph. Pearson correlation analysis was used to assess the relationship between airway space and facial morphology Results: Ramal height, SNA, SNB, PFH, FHR and facial plane angle were positively related to upper PAS, and sum of saddle angle, articular angle, and genial angle, SN-GoGn, Y-axis to SN and FMA negatively related to upper PAS. Genial angle, FMA were positively related to lower PAS, and articular angle, facial depth, PFH and FHR negatively related to lower PAS. PCBL, ramal height, Mn. body length, Mn. body length to ACBL, facial depth, facial length, PFH and AFH were positively related to tonsil size. Sum of saddle angle, articular angle, genial angle, facial length, AFH, FMA and LFH were positively related to tongue gap, and IMPA and overbite was negatively related to tongue gap. Upper PAS, related to size of adenoid tissue, was mainly related to posterior facial dimension following a vertical growth pattern of face and mandibular rotation. Lower PAS and tonsil size, related to anterior-posterior tongue base position, were significantly related to each other. Lower PAS was related to growth pattern of mandible, and tonsil size was related to size of mandible and horizontal growth pattern of face. Tongue gap was related to anterior facial dimension following a vertical growth pattern of face. Conclusion: Significant relationship exists between airway space and facial morphology.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2012.05a
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• pp.1139-1140
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• 2012

• Korean Journal of Applied Biomechanics
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• v.24 no.4
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• pp.417-423
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• 2014

The purpose of this study was to compare two saddle height determination methods by the effectiveness of pedal reaction force. Ten male subjects (age: $24.0{\pm}2.4years$, height: $175.1{\pm}5.4cm$, weight: $69.3{\pm}11.1kg$, inseam: $77.8{\pm}4.5cm$) participated in three minutes, 60 rpm cycle pedaling tests with the same load and cadence. Subject's saddle height was determined by $25^{\circ}$ knee flexion angle (K25) when the pedal crank was at the 6 o'clock position (knee angle method) and 97% (T97), 100% (T100), 103% (T103) of trochanter height (trochanteric method). The RF (resultant force), EF (effective force), and IE (index of effectiveness) were compared by measuring 3D motion and 3-axis pedal reaction force data during 4 pedaling phases (phase1: $330^{\circ}-30^{\circ}$, phase2: $30^{\circ}-150^{\circ}$, phase3: $150^{\circ}-210$, phase4: $210^{\circ}-330^{\circ}$). Results showed that there were significant differences in EF at phase1 between T97 and K25, in EF at phase4 between T100 and T103, in IE at total phase between T97 and K25, between T100 and T103, in IE at phase1 & phase2 between T97 and K25. There was higher IE in the K25 than any other saddle heights, which means that K25 was better pedaling effectiveness than the trochanteric method. Therefore it was suggested the saddle height as 103.7% of trochanter height that converted from K25.

• Korean Journal of Applied Biomechanics
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• v.22 no.4
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• pp.413-419
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• 2012

The purpose of this study was to investigate the effects of increased saddle height on the length and activity pattern of vastus lateralis (VL) and biceps femoris (BF) muscle. To compare the effects of increased saddle height, Preferred (self-selected height of subject) and High saddle height (approximately 5% higher saddle height than self-selected) were used. Seven elite cyclists (career: $16.1{\pm}8.5years$) participated in 3 min. sub-maximal pedaling tests under the same cadence (90 RPM) and pedaling power (150 W). Hip and knee joint angles, and the length and activity of VL and BF were compared by measuring 3D motion and electromyography (EMG) data. Results showed that there were significant differences in peak extension timing of the hip joint angle and the range of motion of the hip and knee joint between different saddle heights. Although there were significant differences in muscle length of both muscles with increasing saddle height, the timing and amount of muscle activity differed only at the BF. These findings suggest that the timing and amount of bi-articular muscle activity (i.e. BF) can be altered by changing the saddle height. For practically applying these results, further study is necessary to evaluate the effects of various cadence and the pedaling power with various saddle heights.

• Korean Journal of Applied Biomechanics
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• v.22 no.1
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• pp.65-73
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• 2012

The purpose of this study was to identify the saddle to pedal length contributing to successful performance in kayak using a kayak ergometer. Ten male elite kayak players participated in this study. players were tested on the kayak ergometer which was varied saddle to pedal length by the knee flexion angle(90deg; 120deg; 150deg) to measure stroke frequency, paddling amplitude, joint angle, RoM and angular velocity, foot pressure and force, iEMG using the 3D motion system, foot pressure system and EMG wireless system. At a results, rowing at 120deg on knee flexion angle showed higher stroke frequency and paddling amplitude than other knee flexion angles. RoM at upper extremity showed not significant difference between knee flexion angles. But there were significant differences in thorax and pelvis rotation RoM, knee flexion-extension RoM in each condition. In addition, foot pressure, force and iEMG were significantly different in knee flexion angles. Study showed that changed of saddle to pedal length affected rowing performance kinds of stroke frequency, paddling amplitude. The most important thing, increased range of motion in pelvic and thorax has occurred by force that generated foot-bar to seat. Not only that, but it seems to be attributed to a technical adaptation developed to maximum rowing performance.

• Korean Journal of Applied Biomechanics
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• v.24 no.2
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• pp.181-187
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• 2014

In this study, a real-time evaluation system for quantitative dynamic fitting during pedaling was developed. The system is consisted of LED markers, a digital camera connected to a computer and a marker detecting program. LED markers are attached to hip, knee, ankle joint and fifth metatarsal in the sagittal plane. Playstation3 eye which is selected as a main digital camera in this paper has many merits for using motion capture, such as high FPS (Frame per second) about 180FPS, $320{\times}240$ resolution, and low-cost with easy to use. The maker detecting program was made by using Labview2010 with Vision builder. The program was made up of three parts, image acquisition & processing, marker detection & joint angle calculation, and output section. The digital camera's image was acquired in 95FPS, and the program was set-up to measure the lower-joint angle in real-time, providing the user as a graph, and allowing to save it as a test file. The system was verified by pedalling at three saddle heights (knee angle: 25, 35, $45^{\circ}$) and three cadences (30, 60, 90 rpm) at each saddle heights by using Holmes method, a method of measuring lower limbs angle, to determine the saddle height. The result has shown low average error and strong correlation of the system, respectively, $1.18{\pm}0.44^{\circ}$, $0.99{\pm}0.01^{\circ}$. There was little error due to the changes in the saddle height but absolute error occurred by cadence. Considering the average error is approximately $1^{\circ}$, it is a suitable system for quantitative dynamic fitting evaluation. It is necessary to decrease error by using two digital camera with frontal and sagittal plane in future study.

• The korean journal of orthodontics
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• v.28 no.5 s.70
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• pp.751-761
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• 1998

The purpose of this study was to find the characteristics of lateral crphalogram of skeletal class III malocclusion patients to whom orthognathic surgery was essential. For this study 37 patients with skeletal class III and going to treat or be treated orthognathic surgery(age 7-17) were selected to experimental group and 56 people with normal occlusion (age 8-13) were selected to normal group and the two groups were evaluated and statistically analyzed and the results were as follows 1. In comparison of experimental group and normal group in prepubertal group, there were significant differences in ANS-U1/Me-L1, Mx. Length/Mn. Length, S-N/Go-Me, Wits, ANB, SN-Pog, IMPA, Facial Convexity, APDI (p<0.05) 2. In comparison of experimental group and normal group in pubertal group, there were significant differences in ANS-U1/Me-L1, S-Go/N-Me, Mx.Length/Mn.Length, S-N/Go-Me, Wits, Saddle Angle, SNB, ANB, SN-Pog, IMPA, Interincisal Angle, Facial Convexity, APDI (p<0.05) 3. Among items showing characteristics of skeletal class III malocclusion, there were no significant differences between prepubertal group and pubertal group in other items except Mx. Length/Mn. Length,APDI (p<0.05) 4. The significant correlationship was the highest between Saddle Angle and SNB, SN-Pog and SNB, ANB and Facial Convexity in experimental group

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2010.05a
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• pp.1417-1418
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• 2010