[Is electrical stimulation with voluntary muscle contraction of physiologic interest in aging women?]. / L'électrostimulation surimposée à la contraction musculaire volontaire présente-t-elle un intérêt physiologique chez les sujets âgés?

OBJECTIVE: To analyze the physiological effects of electrical stimulation with voluntary muscle contraction exercise in postmenopausal women. MATERIALS AND METHODS: Thirty-two females aged 62 to 75 years were randomly assigned to three groups to perform four activity sessions for six weeks: group ME (N =11) climbed up and down stairs, group ES (N =11) practised electrostimulation, and group ME + ES (N = 10) undertook both activities. Physiological adaptations of body composition (lean and fat masses and bone mineral density), muscular strength (isometric and dynamic), vertical jump and posturokinetic activities (balance and gait) were analysed. RESULTS: For the three groups, the isometric strength at angle 100 degrees (average increase right and left legs, ME: 19 N.m; ES: 4.5 N.m; ME + ES: 11.5 N.m), the dynamic strength at speed 60 degrees.s(-1) (average increase right and left leg, ME: 15 N.m; ES: 14 N.m; ME+ES: 18.5 N.m) and the vertical jump (ME: 23 mm; ES: 16 mm; ME + ES: 34 mm) increased contrary in the body composition and posturokinetic activities. Nevertheless, the group ME + ES adapted differently on some parameters of bone mineral density (P < 0.05) and dynamic strength (P < 0.01) in relation to the groups ES and ME. CONCLUSION: Electrostimulation with voluntary muscle contraction exercise could induce different physiologic adaptations compared with electrostimulation or voluntary muscle contraction exercise alone.

Effects of brisk walking on static and dynamic balance, locomotion, body composition, and aerobic capacity in ageing healthy active men.

This work analyses the short-term physiological and neurophysiological effects of a brisk walking programme in ageing, healthy, active men. Twenty-one men 63 to 72 years of age were recruited and separated into 2 groups. One group performed a walking programme (WP) (n = 11) and another served as control (C) group (n = 10). The walking programme lasted for twelve weeks and included five sessions per week. Several parameters were assessed before and after the programme for the WP group. The same tests were performed (separated by twelve weeks) in group C. During each assessment, the subjects were put through static and dynamic balance tests, spatio-temporal gait analysis, body composition measurements and determination of aerobic capacity and bone mineral density. The statistic analysis showed a significant improvement in dynamic balance performance, especially in lateral sway when the subjects kept their eyes open, an increase of VO(2) max and loss of fat mass in the WP group. However, no alterations appeared in spatiotemporal gait characteristics, static balance performance, lean mass or bone mineral density (total body and hip). According to these results, this walking programme may have positive effects on preventing ageing subjects from falling.

Neuromuscular effects of three training methods in ageing women.

AIM: The present study aimed to compare the effects of 3 strength development methods on muscular mass and muscular strength in healthy ageing women. METHODS: Thirty-two healthy women, 62 to 75 years old were randomised into 3 groups. The 3 groups performed 4 sessions a week of strength development for 6 weeks. The 1(st) group (SC) climbed up and down 300 stairs per session. The 2(nd) group (ES) followed an electrostimulation programme on the quadriceps muscles. The 3(rd) group (SC+ES) combined stair climbing with electrostimulation. Before and after the 3 programmes, the muscular mass of the leg was assessed using a biphotonic absorptiometry machine. Isometric (angle 20 degrees and 100 degrees ) and isokinetic (60 degrees /s and 240 degrees /s) knee extension torque was measured using an isokinetic dynamometer. RESULTS: None of the programmes changed the muscular mass. All 3 groups increased isometric (angle 20 degrees, p<0.001; angle 100 degrees, p<0.003) and isokinetic (60 degrees /s, p<0.0001; 240 degrees /s, p<0.0001) knee extension torque. None of the programmes appeared more efficient than the others for muscular mass or muscular strength. CONCLUSION: Six weeks of activity (SC, ES or SC+ES) improved the isometric and dynamic muscular strength in ageing healthy women. However, this period was too short to change the muscular mass. None of the activities presented a real advantage over the others in ageing women.

Comparison between three strength development methods on body composition in healthy elderly women.

The effects of three strength development methods (during 6 weeks) were assessed on the body composition in 32 women, 62 to 75 years old and randomised in 3 groups. The first group (SC) has climbed and come down 300 stairs per session. The second group (ES) followed an electrostimulation programme on quadriceps muscles. The third group (SC+ES) has combined the stairs climbing with electrostimulation. Body composition and bone mineral density (BMD) was assessed using Absorptiometry machine before and after the programmes. None of the programmes has increased significantly BMD. Nevertheless, the SC+ES group BMD enhanced more on the trochanter (p<0,05) and the two legs (p<0,05) than the SC and ES groups BMD (interaction group/time). The combined activity (SC+ES) would deserve to be tested on a longer period.

Cholesterol reduction and increased cardiovascular fitness following a 12 weeks brisk walking.

The effects of a walking training programme were assesed on 10 healthy, active men aged 63-69 years. Serum lipids, pulse and blood pressure, maximum oxygen consumption (VO2 max) and anthropometric parameters, were measured before and after this programme. There was a significant fall in LDL (p<0.02) and mean diastolic BP (p<0.005). In spite of the subjects's initial good level of fitness there was still an 8% rise in the mean VO2 max of the group. There was also a significant loss of body fat (P<0.01). These positive physiological effects suggest that brisk walking can be considered as a a useful activity for improving the fitness and general health in this age-range.

Effects of cosmonaut vestibular training on vestibular function prior to spaceflight.

The purpose of this study was to quantify the effects of repetitive Coriolis and cross-coupled stimulations, similar to the vestibular training the cosmonauts are exposed to prior to their spaceflight. on vestibular function in control subjects on Earth. Ten volunteers were passively rotated in yaw on a rotating chair while executing standardized pitch head-and-trunk movements. The chair stopped to change direction after 12 head-and-trunk movements were made. The runs were grouped in sessions of ten,which were repeated daily for 10 days. The severity of motion sickness was assessed by subjective judgment and measurements of skin pallor and salivary total protein concentration, and nystagmus was recorded. The severity of motion sickness and nystagmus decreased during cosmonaut vestibular training (CVT). One month after the end of CVT, nystagmus responses were still about 20-30% lower than control values. These results indicate that CVT induces a habituation of vestibular responses. One important implication of this experiment concerns space studies on cosmonauts who are exposed to such vestibular training prior to their spaceflight.

Static and dynamic balance function in spasmodic torticollis.

The consequences of abnormal head posture on static and dynamic balance skill were studied in a group of 10 patients with idiopathic spasmodic torticollis (ST). In static conditions, body sway was assessed using a conventional force platform with eyes open and with eyes closed. Standardized dynamic balance conditions were produced using a rocking platform; lateral and anteroposterior dynamic balance skills were assessed by measuring linear displacement both of the body base and of the head. Dynamic tests were repeated 6 weeks after botulinum toxin treatment in all patients. Patients' results were compared with those obtained from 10 control subjects. In static conditions, ST patients did not differ from control subjects, but in dynamic conditions, balance parameters were greater in the patient group than in the control group. This was true for the lateral direction and for dynamic balance parameters recorded both before and after botulinum toxin treatment. Eye closure significantly increased dynamic balance parameters in both groups. However, the effect of eye closure was greater in the patient group than the control group, especially for lateral sway, suggesting that patients used vision to compensate for the dynamic balance disturbance induced by the spasmodic torticollis. Despite a significant improvement of head posture in all patients after botulinum toxin treatment, no significant changes in dynamic balance parameters were observed between the first and second test. The possible origins of the dynamic balance disturbance observed in ST patients are discussed.

Unusual vestibular and visual input in human dynamic balance as a motion sickness susceptibility test.

BACKGROUND: Motion sickness (MS) is commonly thought to arise from a sensory conflict. However, few quantitative methods based on this theory are available to detect MS susceptibility. HYPOTHESIS: It was asked whether the standardized unusual stimulation of a single sensory channel under quantified dynamic balance conditions in man could elicit a sensory conflict and therefore trigger motion sickness (MS) METHODS: Vestibular and visual channels were stimulated by galvanic current and rotating prismatic glasses, respectively. The moving platform used to create the requirements for dynamic balance conditions was chosen not only to worsen the malaise but also to obtain an objective measurement of the balance consequences of the stimulations. RESULTS: Both vestibular and visual stimulation, applied separately, elicited MS-like symptoms (in 56% and 73% of subjects, respectively) and stereotyped balance reactions. A relationship was found between subjective MS-like symptoms and objective measurements of dynamic balance performance. Subjects sensitive to unusual vestibular messages differed from the others by a greater increase in the parameters indicating a difficulty of balance whereas subjects sensitive to unusual visual messages were recognized by the strategy they used to balance themselves. CONCLUSIONS: These results demonstrated that a sensory conflict can trigger MS-like symptoms. We conclude that the measured parameters of a global somatomotor activity, such as the dynamic balance task proposed here, could be useful for objectively detecting subjects predisposed to MS, for training them and testing the efficiency of anti-MS drugs.

Balance and gait analysis after 30 days -6 degrees bed rest: influence of lower-body negative-pressure sessions.

Five volunteers took part in -6 degrees head-down bed-rest experiments for 30 d. In the first experiment, three subjects underwent several sessions of lower-body negative-pressure (LBNP) per day, with two others serving as controls. In the second, the LBNP group of the first experiment became the control and vice versa. Two experimental protocols analyzed the bed-rest-induced modifications of balance and gait and the efficiency of LBNP in counteracting these modifications. A kymographic method allowed the measurement of walking parameters. Anteroposterior and lateral sways were successively studied with both a force platform (static condition) and a rocking platform (dynamic condition). The tests were performed 2 d before the bed-rest period, and over the 1st, 3rd and 4th days of the recovery period. When the subjects were controls, bed rest decreased step length, walking velocity, and balance stability. LBNP completely counteracted the bed-rest-induced modifications of gait and static balance and of dynamic balance for the lateral sway. As LBNP was ineffective in counteracting the modifications of the anteroposterior sway, dynamic balance deficiency was independent of the beneficial effect of LBNP on the decreased orthostatic tolerance induced by -6 degrees head-down bed rest. The results indicate that head-down bed rest, like spaceflight, induces certain sensorimotor changes involved in the decrease of gait and balance performance.