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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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Representative force generation profiles during the first four (C4) and the last four (C20) contractions of the WPHF, CONV and VOL protocols for one non-responder (A) and one responder subject with similar MVC values Note that force production was higher and fatigue was lower for the responder as compared to non-responder during the WPHF protocol.
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pone.0143972.g003: Representative force generation profiles during the first four (C4) and the last four (C20) contractions of the WPHF, CONV and VOL protocols for one non-responder (A) and one responder subject with similar MVC values Note that force production was higher and fatigue was lower for the responder as compared to non-responder during the WPHF protocol.

Mentions: Fig 3 depicts for one non-responder and one responder subjects, the force profiles for the first four and the last four contractions of WPHF, CONV and VOL protocols. With regard to FTI time course, a significant group × protocol interaction was found. For all the contractions (C4—C20), the average FTI of WPHF in the responder group was significantly higher (P < 0.05) as compared to the other exercise modalities within the same group and significantly higher than all exercise modalities within the non-responder group. Moreover, a significant protocol × contractions interaction was observed (Fig 4A and 4B). For both the responder and non-responders, WPHF-induced FTI was significantly higher for the initial contractions (C4) than for the subsequent ones (C8, C12, C16, C20). With regard to the CONV protocol, both groups showed higher FTI values for C4 as compared to C12 (P = 0.06), C16 and C20 (P < 0.05). The VOL protocol showed no significant time-related changes in FTI.


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)

Representative force generation profiles during the first four (C4) and the last four (C20) contractions of the WPHF, CONV and VOL protocols for one non-responder (A) and one responder subject with similar MVC values Note that force production was higher and fatigue was lower for the responder as compared to non-responder during the WPHF protocol.
© Copyright Policy
Related In: Results  -  Collection

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

pone.0143972.g003: Representative force generation profiles during the first four (C4) and the last four (C20) contractions of the WPHF, CONV and VOL protocols for one non-responder (A) and one responder subject with similar MVC values Note that force production was higher and fatigue was lower for the responder as compared to non-responder during the WPHF protocol.
Mentions: Fig 3 depicts for one non-responder and one responder subjects, the force profiles for the first four and the last four contractions of WPHF, CONV and VOL protocols. With regard to FTI time course, a significant group × protocol interaction was found. For all the contractions (C4—C20), the average FTI of WPHF in the responder group was significantly higher (P < 0.05) as compared to the other exercise modalities within the same group and significantly higher than all exercise modalities within the non-responder group. Moreover, a significant protocol × contractions interaction was observed (Fig 4A and 4B). For both the responder and non-responders, WPHF-induced FTI was significantly higher for the initial contractions (C4) than for the subsequent ones (C8, C12, C16, C20). With regard to the CONV protocol, both groups showed higher FTI values for C4 as compared to C12 (P = 0.06), C16 and C20 (P < 0.05). The VOL protocol showed no significant time-related changes in FTI.

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