Static balance improvement in elderly after dorsiflexors electrostimulation training

The purpose of the present study was to determine the effect of dorsiflexors' ElectroStimulation (ES) training, on postural tasks of increasing difficulty in the elderly. Twenty-one elderly adults were randomly assigned into one of two groups: a Training (TG) and a Control Group (CG). The TG (n = 10) performed (4 weeks, 4 s/week, 40 min/session) superimposed (electrically evoked and voluntary activation) isometric dorsiflexions (ankle 100 degrees ) while seated. Biphasic, rectangular symmetrical pulses (300 ms, 70 Hz, 20-60 mA) were used to provoke maximal muscle activation. Participants performed three static balance tasks (Normal Quiet Stance, Sharpened Romberg, and One-Legged Stance) during which postural sway was quantified using maximum range and standard deviation of Centre of Pressure displacement (Kistler 9281C, 1,000 Hz). Bipolar surface electrodes were used to record the Electromyographic activity (EMG) of Tibialis Anterior, Medial Gastrocnemius, Rectus Femoris and Semi-Tendineous. Two-dimensional kinematic data were collected (60 Hz) and analyzed using the APAS Motion Analysis software. The body was modeled as a five-segment rigid link system. Isometric dorsiflexion moment/angular position relationship was also established using a Cybex dynamometer. ES training resulted in decreased postural sway (P < 0.05), greater ankle muscles EMG activity (P < 0.001), greater stability of the ankle joint (P < 0.05) and significant changes in mean position of all three joints of the lower limb. In addition, dorsiflexion moment significantly (P < 0.001) increased as a result of ES training. It is concluded that dorsiflexors' ES training, could reduce postural sway and the use of ankle muscles, more characteristic of young adults, might appear in the elderly as well.

Glycogen depletion and resynthesis in the rat after downhill running

To study the effect of downhill running on glycogen metabolism, 94 rats were exercised by running for 3 h on the level or down an 18 degrees incline. Muscle and liver glycogen concentrations were measured before exercise and 0, 48 and 52 h postexercise. Rats were not fed during the first 48 h of recovery but ingested a glucose solution 48 h postexercise. Downhill running depleted glycogen in the soleus muscle and liver significantly more than level running (P less than 0.01). The amount of glycogen resynthesized in the soleus muscle and liver in fasting or nonfasting rats was not altered significantly by downhill running (P greater than 0.05). On every day of recovery the rats were injected with dexamethasone, which induced similar increases in glycogen concentration in the soleus muscle and liver after the 52nd h of the postexercise period in the case of downhill and level running. The glycogen depletion and repletion results indicated that, under our experimental conditions, downhill running in the rat, a known model of eccentric exercise, affected muscle glycogen metabolism differently from eccentric cycling in humans.

Splenic immunomodulation with swimming-induced stress in rats

In order to determine the effects of swimming-induced stress, young male Wistar rats swam for a single session of 2 h duration, or for one 2-h session a day for five consecutive days. The absolute number of splenic mononuclear cells and the in vitro proliferation of mitogen-stimulated (PHA) T lymphocytes were studied. A single swimming session did not significantly diminish the number of splenic mononuclear cells, but it did significantly reduce splenic T-lymphocyte proliferation. This effect on T-lymphocyte proliferation was significantly blocked, in part, by subcutaneous injection of naltrexone before a swimming session. It was not significantly blocked by pre-exercise oral administration of aminoglutethimide. Repeated swimming sessions induced no significant changes in immune parameters. In conclusion, these data suggest that immunosuppression seen with a single swimming-induced stress period may partly be due to endogenous opioids, and that repetition of the swimming session reduced swimming-induced immunomodulation.