Control Strategy for a Hand Balance

Abstract

The goal of this study was to investigate the control strategy employed by gymnasts in maintaining a hand balance. It was hypothesized that a "wrist strategy" was used in which perturbations in the sagittal plane were corrected using variations in wrist flexor torque with synergistic shoulder and hip torques acting to preserve a fixed body configuration. A theoretical model of wrist strategy indicated that control could be effected using wrist torque that was a linear function of mass center displacement and velocity. Four male gymnasts executed hand balances and 2-dimensional inverse dynamics was used to determine net joint torque time histories at the wrist, shoulder, and hip joints in the sagittal plane. Wrist torque was regressed against mass center position and velocity values at progressively earlier times. It was found that all gymnasts used the wrist strategy, with time delays ranging from 160 to 240 ms. The net joint torques at the shoulder and hip joints were regressed against the torques required to maintain a fixed configuration. This fixed configuration strategy accounted for 86% of the variance in the shoulder torque and 86% of the variance in the hip torque although the actual torques exceeded the predicted torques by 7% and 30%, respectively. The estimated time delays are consistent with the use of long latency reflexes, whereas the role of vestibular and visual information in maintaining a hand balance is less certain.

The level of technical efficiency of youngest-category gymnasts based on the phase structure of elementary floor exercises

“…This study has shown that its participants still lack the skill needed to perform a correct handstand. Such a skill involves appropriate wrists strategy and arms control, through which one's fingers apply the correct pressure to the floor [26]. The movements performed during the handstand are difficult to even notice with the human eye, let alone evaluate; for this reason, we did not assess such movements.…”

A suggested model of handstand teaching method

“…Ова истражи-вања указују на потребу развоја стварања осећаја за одржавање равотежног положаја тела. Такође се указује да при извођењу става у упору постављање дланова на подлогу представља базу при одржава-њу тежине тела (Yedon, & Trewartha, 2003). Оне се постављају у ослонац целом својом површином при чему се тежина тела у равнотежном положа-ју упора одржава на завршним фалангама прстију шака.…”

“…Своју посебност и значајност став у упору проналази специфично у спортској гимнастици. Познате су многе варијан-те извођења, али у свим техникама, извођач мора имати одговарајућу равнотежу и снагу горњег дела тела (Yedon, & Trewartha, 2003;Uzunov, 2008).…”

“…Шта је потребно да би се квалитетно савладала техинка става у упору? Осим правилне технике, потребна је снага му-скулатуре целог тела, координативна способност контроле појединих делова тела, као и оријента-ција у простору, а свакако се не сме занемарити (што можда на први поглед не изгледа) флекси-билност појединих зглобних система; специ-фично раменог појаса (Yedon, & Trewartha, 2003;Uzunov, 2008;Živčić, 2007).…”

The role of functional variability in a whole body co-ordinated movement – Application to high bar giant circles

“…An increase in movement variability associated with a gymnast making feedback corrections would fall under the definition of functional variability since the adjustments have the function of controlling the pace of the giant circle. Feedback control has been demonstrated in a number of gymnastics activities such as hand balance (Yeadon & Trewartha, 2003) and twisting somersaults (Yeadon & Mikulcik, 1996;Yeadon & Hiley, 2014). In both cases the control strategy was based on detecting an error in the desired state and providing a correction, based on the mechanics of the system, after an appropriate time delay (Latash, 1998;Jagacinski & Flach, 2003).…”