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Responders to Wide-Pulse, High-Frequency Neuromuscular Electrical Stimulation Show Reduced Metabolic Demand: A 31P-MRS Study in Humans.

Wegrzyk J, Fouré A, Le Fur Y, Maffiuletti NA, Vilmen C, Guye M, Mattei JP, Place N, Bendahan D, Gondin J - PLoS ONE (2015)

Bottom Line: Furthermore, a fatigue index based on FTI loss at the end of each protocol compared with the beginning of the protocol was calculated.Only for the responder group, the ∆PCr/FTI ratio of WPHF (0.74 ± 0.19 M/N.s) was significantly lower compared to CONV (1.48 ± 0.46 M/N.s) but similar to VOL (0.65 ± 0.21 M/N.s).Moreover, the fatigue index was not different between WPHF (-16%) and CONV (-25%) for the responders.

View Article: PubMed Central - PubMed

Affiliation: Aix-Marseille Université, CNRS, CRMBM UMR 7339, Marseille, France.

ABSTRACT
Conventional (CONV) neuromuscular electrical stimulation (NMES) (i.e., short pulse duration, low frequencies) induces a higher energetic response as compared to voluntary contractions (VOL). In contrast, wide-pulse, high-frequency (WPHF) NMES might elicit--at least in some subjects (i.e., responders)--a different motor unit recruitment compared to CONV that resembles the physiological muscle activation pattern of VOL. We therefore hypothesized that for these responder subjects, the metabolic demand of WPHF would be lower than CONV and comparable to VOL. 18 healthy subjects performed isometric plantar flexions at 10% of their maximal voluntary contraction force for CONV (25 Hz, 0.05 ms), WPHF (100 Hz, 1 ms) and VOL protocols. For each protocol, force time integral (FTI) was quantified and subjects were classified as responders and non-responders to WPHF based on k-means clustering analysis. Furthermore, a fatigue index based on FTI loss at the end of each protocol compared with the beginning of the protocol was calculated. Phosphocreatine depletion (ΔPCr) was assessed using 31P magnetic resonance spectroscopy. Responders developed four times higher FTI's during WPHF (99 ± 37 × 10(3) N.s) than non-responders (26 ± 12 × 10(3) N.s). For both responders and non-responders, CONV was metabolically more demanding than VOL when ΔPCr was expressed relative to the FTI. Only for the responder group, the ∆PCr/FTI ratio of WPHF (0.74 ± 0.19 M/N.s) was significantly lower compared to CONV (1.48 ± 0.46 M/N.s) but similar to VOL (0.65 ± 0.21 M/N.s). Moreover, the fatigue index was not different between WPHF (-16%) and CONV (-25%) for the responders. WPHF could therefore be considered as the less demanding NMES modality--at least in this subgroup of subjects--by possibly exhibiting a muscle activation pattern similar to VOL contractions.

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Related in: MedlinePlus

Individual force profiles for all 18 subjects and for each protocol calculated as the sum of the force time integral (FTI) for all 20 contractions.K-means analysis of Extra Forces resulted in the classification of 11 non-responders and 7 responders for the latter of which the FTI was significantly higher for WPHF NMES as compared to the other two exercise modalities. Note the high inter-individual variability of FTI for WPHF NMES.
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pone.0143972.g002: Individual force profiles for all 18 subjects and for each protocol calculated as the sum of the force time integral (FTI) for all 20 contractions.K-means analysis of Extra Forces resulted in the classification of 11 non-responders and 7 responders for the latter of which the FTI was significantly higher for WPHF NMES as compared to the other two exercise modalities. Note the high inter-individual variability of FTI for WPHF NMES.

Mentions: As illustrated in Fig 2, the total FTI for WPHF showed a high variability between individuals. According to the k-means clustering analysis 7 subjects (6 men /1 woman) were identified as responders to WPHF whereas 11 subjects (7 men / 4 women) were classified as non-responders. MVC values were significantly higher (P < 0.05) for responders (1232 ± 206 N) than for non-responders (949 ± 217 N); this could be explained by the fact that the proportion of men was higher within the responders.


Responders to Wide-Pulse, High-Frequency Neuromuscular Electrical Stimulation Show Reduced Metabolic Demand: A 31P-MRS Study in Humans.

Wegrzyk J, Fouré A, Le Fur Y, Maffiuletti NA, Vilmen C, Guye M, Mattei JP, Place N, Bendahan D, Gondin J - PLoS ONE (2015)

Individual force profiles for all 18 subjects and for each protocol calculated as the sum of the force time integral (FTI) for all 20 contractions.K-means analysis of Extra Forces resulted in the classification of 11 non-responders and 7 responders for the latter of which the FTI was significantly higher for WPHF NMES as compared to the other two exercise modalities. Note the high inter-individual variability of FTI for WPHF NMES.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4664273&req=5

pone.0143972.g002: Individual force profiles for all 18 subjects and for each protocol calculated as the sum of the force time integral (FTI) for all 20 contractions.K-means analysis of Extra Forces resulted in the classification of 11 non-responders and 7 responders for the latter of which the FTI was significantly higher for WPHF NMES as compared to the other two exercise modalities. Note the high inter-individual variability of FTI for WPHF NMES.
Mentions: As illustrated in Fig 2, the total FTI for WPHF showed a high variability between individuals. According to the k-means clustering analysis 7 subjects (6 men /1 woman) were identified as responders to WPHF whereas 11 subjects (7 men / 4 women) were classified as non-responders. MVC values were significantly higher (P < 0.05) for responders (1232 ± 206 N) than for non-responders (949 ± 217 N); this could be explained by the fact that the proportion of men was higher within the responders.

Bottom Line: Furthermore, a fatigue index based on FTI loss at the end of each protocol compared with the beginning of the protocol was calculated.Only for the responder group, the ∆PCr/FTI ratio of WPHF (0.74 ± 0.19 M/N.s) was significantly lower compared to CONV (1.48 ± 0.46 M/N.s) but similar to VOL (0.65 ± 0.21 M/N.s).Moreover, the fatigue index was not different between WPHF (-16%) and CONV (-25%) for the responders.

View Article: PubMed Central - PubMed

Affiliation: Aix-Marseille Université, CNRS, CRMBM UMR 7339, Marseille, France.

ABSTRACT
Conventional (CONV) neuromuscular electrical stimulation (NMES) (i.e., short pulse duration, low frequencies) induces a higher energetic response as compared to voluntary contractions (VOL). In contrast, wide-pulse, high-frequency (WPHF) NMES might elicit--at least in some subjects (i.e., responders)--a different motor unit recruitment compared to CONV that resembles the physiological muscle activation pattern of VOL. We therefore hypothesized that for these responder subjects, the metabolic demand of WPHF would be lower than CONV and comparable to VOL. 18 healthy subjects performed isometric plantar flexions at 10% of their maximal voluntary contraction force for CONV (25 Hz, 0.05 ms), WPHF (100 Hz, 1 ms) and VOL protocols. For each protocol, force time integral (FTI) was quantified and subjects were classified as responders and non-responders to WPHF based on k-means clustering analysis. Furthermore, a fatigue index based on FTI loss at the end of each protocol compared with the beginning of the protocol was calculated. Phosphocreatine depletion (ΔPCr) was assessed using 31P magnetic resonance spectroscopy. Responders developed four times higher FTI's during WPHF (99 ± 37 × 10(3) N.s) than non-responders (26 ± 12 × 10(3) N.s). For both responders and non-responders, CONV was metabolically more demanding than VOL when ΔPCr was expressed relative to the FTI. Only for the responder group, the ∆PCr/FTI ratio of WPHF (0.74 ± 0.19 M/N.s) was significantly lower compared to CONV (1.48 ± 0.46 M/N.s) but similar to VOL (0.65 ± 0.21 M/N.s). Moreover, the fatigue index was not different between WPHF (-16%) and CONV (-25%) for the responders. WPHF could therefore be considered as the less demanding NMES modality--at least in this subgroup of subjects--by possibly exhibiting a muscle activation pattern similar to VOL contractions.

Show MeSH
Related in: MedlinePlus