Limits...
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.

Show MeSH

Related in: MedlinePlus

ΔPCr/FTI (in M/N.s) ratio for the non-responders and responders for each protocol.* Significantly different within groups for P < 0.05, † non-significant tendency (P = 0.07), # WPHF significantly different between groups for P < 0.05. Results are presented as means ± SE.
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4664273&req=5

pone.0143972.g005: ΔPCr/FTI (in M/N.s) ratio for the non-responders and responders for each protocol.* Significantly different within groups for P < 0.05, † non-significant tendency (P = 0.07), # WPHF significantly different between groups for P < 0.05. Results are presented as means ± SE.

Mentions: A significant effect of protocol was noted for the ΔPCr/FTI ratio so that lower values were obtained for VOL (P< 0.05) compared to the two NMES protocols. Interestingly, a significant group × protocol (P < 0.05) interaction was observed for the ΔPCr/FTI ratio (Fig 5). For the responders, this ratio was significantly lower for WPHF than for CONV (P < 0.05) with a statistical power of 0.88. On the contrary, in the non-responder group, ΔPCr/FTI ratio was not significantly different (P >0.05) between CONV and WPHF. When comparing the ΔPCr/FTI ratio of WPHF between groups, responders showed a significant lower metabolic demand (P < 0.05) compared to non-responders with a statistical power of 0.87.


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)

ΔPCr/FTI (in M/N.s) ratio for the non-responders and responders for each protocol.* Significantly different within groups for P < 0.05, † non-significant tendency (P = 0.07), # WPHF significantly different between groups for P < 0.05. Results are presented as means ± SE.
© Copyright Policy
Related In: Results  -  Collection

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

pone.0143972.g005: ΔPCr/FTI (in M/N.s) ratio for the non-responders and responders for each protocol.* Significantly different within groups for P < 0.05, † non-significant tendency (P = 0.07), # WPHF significantly different between groups for P < 0.05. Results are presented as means ± SE.
Mentions: A significant effect of protocol was noted for the ΔPCr/FTI ratio so that lower values were obtained for VOL (P< 0.05) compared to the two NMES protocols. Interestingly, a significant group × protocol (P < 0.05) interaction was observed for the ΔPCr/FTI ratio (Fig 5). For the responders, this ratio was significantly lower for WPHF than for CONV (P < 0.05) with a statistical power of 0.88. On the contrary, in the non-responder group, ΔPCr/FTI ratio was not significantly different (P >0.05) between CONV and WPHF. When comparing the ΔPCr/FTI ratio of WPHF between groups, responders showed a significant lower metabolic demand (P < 0.05) compared to non-responders with a statistical power of 0.87.

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