Contributing factors to postural stability in Prader-Willi syndrome

BACKGROUND

Prader-Willi Syndrome (PWS) is a rare neurodevelopmental disorder affecting multiple functional parameters. This study examined postural stability and associated gait and neuromuscular factors in young adults with PWS.

METHODS

Participants included 10 adults with PWS [7 M/3F; Body Fat % 40.61 ± 7.79]; ten normal weight (NW) adults [7 M/3F; Body Fat % 23.42 ± 7.0]; ten obese (OB) adults [7 M/3F; Body Fat % 42.40 ± 5.62]. Participants completed the Sensory Organization Test (SOT)®. Condition (C) specific and a composite equilibrium score (CES) were calculated (maximum = 100). Quadriceps strength was assessed using an isokinetic dynamometer. Three-dimensional gait analyses were completed along a 10 m walkway using a motion capture system and two force plates. A gait stability ratio (GSR) was computed from gait speed and step length (steps/m).

RESULTS

The PWS group had lower scores for C1, C3, C4 and CES compared to the NW (p < .039 for all) and lower scores for C4 and CES than the OB (p < .019 for both) groups, respectively. In C5 (eyes closed, sway-referenced support) and C6 (sway-referenced vision and support), 33.3% of participants with PWS fell during the first trial in both conditions (X2 [2] 7.436, p = .024) and (X2 [2] 7.436, p = .024) but no participant in the other groups fell. Those with PWS showed higher GSR than participants with NW (p = .005) and those with obesity (p = .045).

CONCLUSION

Individuals with PWS had more difficulty maintaining standing balance when relying on information from the somatosensory (C3), visual-vestibular (C4) and vestibular systems (C5, C6). A more stable walk was related to shorter steps, slower velocity and reduced peak quadriceps torque. Participation in multisensory activities that require appropriate prioritization of sensory system(s) input for controlling balance in altered sensory environments should be routinely included. In addition, exercises targeting muscular force and power should be included as part of exercise programming in PWS.

The control of respiratory pressures and neuromuscular activation to increase force production in trained martial arts practitioners

PURPOSE

The mechanisms that explain the ability of trained martial arts practitioners to produce and resist greater forces than untrained individuals to aid combat performance are not fully understood. We investigated whether the greater ability of trained martial arts practitioners to produce and resist forces was associated with an enhanced control of respiratory pressures and neuromuscular activation of the respiratory, abdominal, and pelvic floor musculature.

METHODS

Nine trained martial arts practitioners and nine untrained controls were instrumented with skin-surface electromyography (EMG) on the sternocleidomastoid, rectus abdominis, and the group formed by the transverse abdominal and internal oblique muscles (EMG_tra/io). A multipair oesophageal EMG electrode catheter measured gastric (P_g), transdiaphragmatic (P_di), and oesophageal (P_e) pressures and EMG of the crural diaphragm (EMG_di). Participants performed Standing Isometric Unilateral Chest Press (1) and Standing Posture Control (2) tasks.

RESULTS

The trained group produced higher forces normalised to body mass^2/3 (0.033 ± 0.01 vs. 0.025 ± 0.007 N/kg^2/3 mean force in Task 1), lower P_e, and higher P_di in both tasks. Additionally, they produced higher P_g (73 ± 42 vs. 49 ± 19 cmH₂O mean P_g) and EMG_tra/io in Task 1 and higher EMG_di in Task 2. The onset of P_g with respect to the onset of force production was earlier, and the relative contributions of P_g/P_e and P_di/P_e were higher in the trained group in both tasks.

CONCLUSION

Our findings demonstrate that trained martial arts practitioners utilised a greater contribution of abdominal and diaphragm musculature to chest wall recruitment and higher P_di to produce and resist higher forces.

Lean, fast and strong: Determinants of functional performance in the elderly

BACKGROUND

The current literature indicates that functional capacity is associated with physical performance and body composition measurements in older adults. However, it is not clear which tests can best explain the functional capacity in this population. This study aimed to investigate the physical performance and body composition determinants of functional capacity in older adults.

METHOD

Twenty-four older adults (66.4 ± 4.7y) undertook body composition (body fat and muscle), rate of torque development (0-50 and 0-200 ms); countermovement jump (height, power and impulse); leg-press and seated-leg-curl 5-repetition maximum; and functional-performance tests (Timed-up-and-go, stair ascent and stair descent).

FINDINGS

Timed-up-and-go correlated with countermovement jump (height, R² = 0.303; power, R² = 0.198; and impulse, R² = 0.224) and 5-repetition maximum (seated-leg-curl, R² = 0.172). Stair ascent correlated with body fat (R² = 0.213), rate of torque development (0-50 ms/body fat, R² = 0.301; 0-200 ms_, R² = 0.197; 0-200 ms/body fat, R² = 0.340), countermovement jump (height, R² = 0.325; power/body fat, R² = 0.413; impulse/body fat, R² = 0.422) and 5-repetiton maximum (leg-press/body fat, R² = 0.384; seated-leg-curl/body fat, R² = 0.341). Stair descent correlated with rate of torque development (0-50 ms/body fat, R² = 0.164; 0-200 ms, R² = 0.203; 0-200 ms/body fat, R² = 0.213), countermovement jump (height, R² = 0.458; power, R² = 0.212; power/body fat, R² = 0.358; impulse, R² = 0.218; impulse/body fat, R² = 0.369) and 5-repetition maximum (leg-press/body fat, R² = -0.227; seated-leg-curl/body fat, R² = 0.209; seated-leg-curl, R² = 0.181).

INTERPRETATION

Higher body fat is associated with weaker stair ascent performance. An increase in the correlation coefficient was observed for the countermovement jump, rate of torque development, and 5-repetition maximum tests when normalized by body fat compared to the absolute values. Countermovement jump height presented the highest correlation to timed-up-and-go and stair descent, while impulse/body fat for stair ascent.

Aggravated neuromuscular symptoms of mercury exposure from dental amalgam fillings

Dental amalgam fillings are widely used all over the world. However, their mercury content can lead to various side effects and clinical problems. Acute or chronic mercury exposure can cause several side effects on the central nerve system, renal and hepatic functions, immune system, fetal development and it can play a role on exacerbation of neuromuscular diseases. In this case, we will present a patient with vacuolar myopathy whose symptoms were started and aggravated with her dental amalgam fillings.