Wide-pulse-high-frequency neuromuscular electrical stimulation in cerebral palsy.

OBJECTIVE: The present study assesses whether wide-pulse-high-frequency (WPHF) neuromuscular electrical stimulation (NMES) could result in extra-force production in cerebral palsy (CP) patients as previously observed in healthy individuals. METHODS: Ten CP and 10 age- and sex-matched control participants underwent plantar flexors NMES. Two to three 10-s WPHF (frequency: 100 Hz, pulse duration: 1 ms) and conventional (CONV, frequency 25 Hz, pulse duration: 50 µs) trains as well as two to three burst-like stimulation trains (2s at 25 Hz, 2s at 100 Hz, 2s at 25 Hz; pulse duration: 1 ms) were evoked. Resting soleus and gastrocnemii maximal H-reflex amplitude (Hmax) was normalized by maximal M-wave amplitude (Mmax) to quantify α-motoneuron modulation. RESULTS: Similar Hmax/Mmax ratio was found in CP and control participants. Extra-force generation was observed both in CP (+18 ± 74%) and control individuals (+94 ± 124%) during WPHF (p<0.05). Similar extra-forces were found during burst-like stimulations in both groups (+108 ± 110% in CP and +65 ± 85% in controls, p>0.05). CONCLUSION: Although the mechanisms underlying extra-force production may differ between WPHF and burst-like NMES, similar increases were observed in patients with CP and healthy controls. SIGNIFICANCE: Development of extra-forces in response to WPHF NMES evoked at low stimulation intensity might open new possibilities in neuromuscular rehabilitation.

Ergogenic effect of hyperoxic recovery in elite swimmers performing high-intensity intervals.

This investigation tested the hypothesis that breathing oxygen-enriched air (F(i)O(2) =1.00) during recovery enhances peak (P(peak)) and mean power (P(mean)) output during repeated high-intensity exercise. Twelve elite male swimmers (21 ± 3 years, 192.1 ± 5.9 cm, 79.1 ± 8.2 kg) inhaled either hyperoxic (HOX) or normoxic (NOX) air during 6-min recovery periods between five repetitions of high-intensity bench swimming, each involving 40 maximal armstrokes. Oxygen partial pressure (pO(2)) and saturation (SO(2)), [H(+)], pH, base excess and blood lactate concentration were measured before and after all intervals. The production of the reactive oxygen species (ROS) hydrogen peroxide was measured before, directly after and 15 min after the test. P(peak) and P(mean) with HOX recovery were significantly higher than with NOX throughout the third, fourth and fifth intervals (P<0.001-0.04). With HOX, electromyography activity was lower during the third, fourth and fifth intervals than during the first (P=0.05-0.001), with no such changes in NOX (P=0.99). There were no differences in blood lactate, pH, [H(+)] or base excess and ROS production at any time point with either HOX or NOX recovery. These findings demonstrate that the P(peak) and P(mean) of elite swimmers performing high-intensity intervals can be improved by exposure to oxygen-enriched air during recovery.