Browsing by Author "Hung, Cheng-Ju"
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Item Effects of pelvis-shoulders torsional separation style on kinematic sequence in golf driving(Taylor & Francis, 2019) Han, Ki Hoon; Como, Christopher; Kim, Jemin; Hung, Cheng-Ju; Hasan, Mohammad; Kwon, Young-HooThe golfer’s body (trunk/arms/club) can be modeled as an inclined axle-chain system and the rotations of its parts observed on the functional swing plane (FSP) can represent the actual angular motions closely. The purpose of this study was to investigate the effects of pelvis-shoulders torsional separation style on the kinematic sequences employed by the axle-chain system in golf driving. Seventy-four male skilled golfers (handicap ≤ 3) were assigned to five groups based on their shoulder girdle motion and X-factor stretch characteristics: Late Shoulder Acceleration, Large Downswing Stretch, Large Backswing Stretch, Medium Total Stretch, and Small Total Stretch. Swing trials were captured by an optical system and the hip-line, thorax, shoulder-line, upper-lever, club, and wrist angular positions/velocities were calculated on the FSP. Kinematic sequences were established based on the timings of the peak angular velocities (backswing and downswing sequences) and the backswing-to-downswing transition time points (transition sequence). The backswing and transition sequences were somewhat consistent across the groups, showing full or partial proximal-to-distal sequences with minor variations. The downswing sequence was inconsistent across the groups and the angular velocity peaks of the body segments were not significantly separated. Various swing characteristics associated with the separation styles influenced the motion sequences.Item Linear relationships among the hand and clubhead motion characteristics in golf driving in skilled male golfers(Human Kinetics, 2021) Kwon, Young-Hoo; Tuttle, Noelle J.; Hung, Cheng-Ju; Levine, Nicholas A.; Baek, SeunghoThe purpose of this study was to investigate the linear relationships among the hand/clubhead motion characteristics in golf driving in skilled male golfers (n = 66; handicap ≤ 3). The hand motion plane (HMP) and functional swing plane (FSP) angles, the HMP–FSP angle gaps, the planarity characteristics of the off-plane motion of the clubhead, and the attack angles were computed from the drives captured by an optical motion capture system. The HMP angles were identified as the key variables, as the HMP and FSP angles were intercorrelated, but the plane angle gaps, the planarity bias, and the attack angles showed correlations to the HMP angles primarily. Three main swing pattern clusters were identified. The parallel HMP–FSP alignment pattern with a small direction gap was associated with neutral planarity and planar swing pattern. The inward alignment pattern with a large inward direction gap was characterized by flat planes, follow-through-centric planarity, spiral swing pattern, and inward/downward impact. The outward alignment pattern with a large outward direction gap was associated with steep planes, downswing-centric planarity, reverse spiral swing, and outward/upward impact. The findings suggest that practical drills targeting the hand motion pattern can be effective in holistically reprogramming the swing pattern.Item Perceived effort for reaching is associated with self-reported fatigue(2021-01-19) Goh, Hui-Ting; Stewart, Jill C.; Becker, Kevin; Hung, Cheng-JuPerceived effort for goal-directed reaching may be impacted by the level of self-reported fatigue, however, the relationship between self-reported fatigue and perceived effort has not been examined. We examined how perceived effort changed under varied reach conditions and the relationship between fatigue, perceived effort and reach performance. Twenty-three young adults performed reach actions toward 9 different targets on a digitizing tablet. Perceived effort was measured using the Borg Rate of Perceived Exertion and Paas Mental Effort Rating Scale. Self-reported fatigue was quantified using the Fatigue Scales for Motor and Cognitive Functions. As reach conditions became more difficult, perceived effort increased significantly. Further, individuals who reported greater fatigue also reported greater perceived effort and showed greater endpoint error during reaching.Item The influence of attentional focus on movement variability(5/14/2021) Hung, Cheng-Ju; Becker, Kevin AThe advantage of an external focus (EF) over internal focus (IF) in performance outcomes is consistent in a large body of literature. Based on the Constrained Action Hypothesis, an external focus may promote flexibility and adaptability in the motor system which may result in higher movement variability. Limited previous evidence supports the claim that an EF promotes more functional variability. Moreover, the previous studies also suggested that task difficulty may modulate the effect of attentional focus. The purpose of the current study was to investigate the influences of attentional focus (EF & IF) and the level of task difficulty on movement variability (SD of joint angles, goal-equivalent variability [VUCM], non goal-equivalent variability [VORT]) as well as performance (COP trajectory) during a task involving standing and squatting on inflatable balancing discs. Young healthy adults (N = 36) balanced on inflatable discs while standing (low difficulty) and holding squat (high difficulty). For each level of difficulty, they completed three 10-s trials for each focus condition (baseline [no instruction provided], IF, and EF). The order of task difficulty was counterbalanced and the focus condition order was randomized. Kinematic and COP data were captured by 9 Vicon infrared cameras (250 Hz) and 2 AMTI force plates. Separate factorial MANOVAs assessed differences due to focus and difficulty for COP trajectory (SD of COP in anterior/posterior and medial/lateral directions, COPX & COPY) and movement variability as assessed by SD of joint angles and uncontrolled manifold analysis (UCM, VUCM & VORT). Sidak post-hoc tests were used for pairwise comparisons. Results showed there was a reduction of postural sway in the anterior/posterior direction (COPX) in EF compared to IF and baseline (p = .024, p < .001, respectively). An EF also decreased the SD of the ankle relative to baseline in the easier version of task (p = .003) and lowered the SD of knee and hip with reference to baseline across two level of difficulties (p = .050, p = .003, respectively). UCM measures showed no differences between an EF and IF, but there was a reduction of VUCM in the EF condition compared to baseline (p =.009). While behavioral benefits of an EF are consistent with previous research, the hypothesis that an EF promotes greater functional variability was not supported, requiring further study with an array of motor tasks to determine the veracity of the claim.