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Brain serotonin and dopamine modulators, perceptual responses and endurance performance during exercise in the heat following creatine supplementation.

Hadjicharalambous M, Kilduff LP, Pitsiladis YP - J Int Soc Sports Nutr (2008)

Bottom Line: Twenty one endurance-trained males performed, in a double-blind fashion, two constant-load exercise tests to exhaustion at 63 +/- 5% V(O2) max in the heat (ambient temperature: 30.3 +/- 0.5 degrees C, relative humidity: 70 +/- 2%) before and after 7 days of Cr (20 g.d-1 Cr + 140 g.d-1 glucose polymer) or placebo (Plc) (160 g.d-1 glucose polymer) supplementation. 3-way interaction has shown that Cr supplementation reduced rectal temperature, heart rate, ratings of perceived leg fatigue (P < 0.05), plasma free-tryptophan (Trp) (P < 0.01) and free-Trp:tyrosine ratio (P < 0.01) but did not influence the ratio of free-Trp:large neutral amino acids or contribute in improving endurance performance (Plc group, n = 10: 50.4 +/- 8.4 min vs. 51.2 +/- 8.0 min, P > 0.05; Cr group, n = 11: 47.0 +/- 4.7 min vs. 49.7 +/- 7.5 min, P > 0.05).The present results may also suggest the demanding of the pre-experimental identification of the participants into "responders" and "non-responders" to Cr supplementation before performing the main experimentation.Otherwise, the possibility of the type II error may be enhanced.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Life & Health Sciences, University of Nicosia, Nicosia, Cyprus. hadjicharalambous.m@unic.ac.cy

ABSTRACT

Background: The present experiment examined the responses of peripheral modulators and indices of brain serotonin (5-HT) and dopamine (DA) function and their association with perception of effort during prolonged exercise in the heat after creatine (Cr) supplementation.

Methods: Twenty one endurance-trained males performed, in a double-blind fashion, two constant-load exercise tests to exhaustion at 63 +/- 5% V(O2) max in the heat (ambient temperature: 30.3 +/- 0.5 degrees C, relative humidity: 70 +/- 2%) before and after 7 days of Cr (20 g.d-1 Cr + 140 g.d-1 glucose polymer) or placebo (Plc) (160 g.d-1 glucose polymer) supplementation.

Results: 3-way interaction has shown that Cr supplementation reduced rectal temperature, heart rate, ratings of perceived leg fatigue (P < 0.05), plasma free-tryptophan (Trp) (P < 0.01) and free-Trp:tyrosine ratio (P < 0.01) but did not influence the ratio of free-Trp:large neutral amino acids or contribute in improving endurance performance (Plc group, n = 10: 50.4 +/- 8.4 min vs. 51.2 +/- 8.0 min, P > 0.05; Cr group, n = 11: 47.0 +/- 4.7 min vs. 49.7 +/- 7.5 min, P > 0.05). However, after dividing the participants into "responders" and "non-responders" to Cr, based on their intramuscular Cr uptake, performance was higher in the "responders" relative to "non-responders" group (51.7 +/- 7.4 min vs.47.3 +/- 4.9 min, p < 0.05).

Conclusion: Although Cr influenced key modulators of brain 5-HT and DA function and reduced various thermophysiological parameters which all may have contributed to the reduced effort perception during exercise in the heat, performance was improved only in the "responders" to Cr supplementation. The present results may also suggest the demanding of the pre-experimental identification of the participants into "responders" and "non-responders" to Cr supplementation before performing the main experimentation. Otherwise, the possibility of the type II error may be enhanced.

No MeSH data available.


Related in: MedlinePlus

RPE (breathing) (top panel) and RPE (legs) (bottom panel) in the Cr (left side) and placebo (right side) supplemented groups during exercise. *: indicates a significant difference between pre (●) to post (○) supplementation. Values are given as mean (SD).
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Figure 2: RPE (breathing) (top panel) and RPE (legs) (bottom panel) in the Cr (left side) and placebo (right side) supplemented groups during exercise. *: indicates a significant difference between pre (●) to post (○) supplementation. Values are given as mean (SD).

Mentions: Relative to the Plc group, Cr supplementation increased intracellular water (ICW), TBW and body mass (Table 1) and reduced rectal temperature (Trec), mean body temperature (Tb) (Figure 1), heart rate (HR), sweat rate and ratings of perceived leg fatigue (Figure 2) (3-way interaction; p < 0.05). However, Cr did not influence skin temperature (Tskin) (Figure 1), total sweat loss, changes in plasma volume, blood [glucose] and [lactate], O2, carbon dioxide production (CO2), respiratory exchange ratio (RER), minute ventilation (E) and perception of breathlessness (Figure 2). Endurance performance was not different between and within Plc group and Cr groups, as a whole (Plc: 50.4 ± 8.4 min vs. 51.2 ± 8.0 min, p < 0.05; Cr group: 47.0 ± 4.7 min vs. 49.7 ± 7.5 min, p > 0.05). However, after dividing the participants into "responders" and "non-responders" to Cr supplementation based on their intramuscular Cr uptake [29,30], performance increased in the "responders" relative to "non-responders" to Cr group (51.7 ± 7.4 min vs.47.3 ± 4.9 min, p < 0.05). Five out of the eleven participants in the Cr group reported that they found the post-supplementation trial easier, while two out of the ten participants in the Plc group rated the post-supplementation trial to be easier. No side effects were reported following Cr and/or Plc supplementations.


Brain serotonin and dopamine modulators, perceptual responses and endurance performance during exercise in the heat following creatine supplementation.

Hadjicharalambous M, Kilduff LP, Pitsiladis YP - J Int Soc Sports Nutr (2008)

RPE (breathing) (top panel) and RPE (legs) (bottom panel) in the Cr (left side) and placebo (right side) supplemented groups during exercise. *: indicates a significant difference between pre (●) to post (○) supplementation. Values are given as mean (SD).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2570654&req=5

Figure 2: RPE (breathing) (top panel) and RPE (legs) (bottom panel) in the Cr (left side) and placebo (right side) supplemented groups during exercise. *: indicates a significant difference between pre (●) to post (○) supplementation. Values are given as mean (SD).
Mentions: Relative to the Plc group, Cr supplementation increased intracellular water (ICW), TBW and body mass (Table 1) and reduced rectal temperature (Trec), mean body temperature (Tb) (Figure 1), heart rate (HR), sweat rate and ratings of perceived leg fatigue (Figure 2) (3-way interaction; p < 0.05). However, Cr did not influence skin temperature (Tskin) (Figure 1), total sweat loss, changes in plasma volume, blood [glucose] and [lactate], O2, carbon dioxide production (CO2), respiratory exchange ratio (RER), minute ventilation (E) and perception of breathlessness (Figure 2). Endurance performance was not different between and within Plc group and Cr groups, as a whole (Plc: 50.4 ± 8.4 min vs. 51.2 ± 8.0 min, p < 0.05; Cr group: 47.0 ± 4.7 min vs. 49.7 ± 7.5 min, p > 0.05). However, after dividing the participants into "responders" and "non-responders" to Cr supplementation based on their intramuscular Cr uptake [29,30], performance increased in the "responders" relative to "non-responders" to Cr group (51.7 ± 7.4 min vs.47.3 ± 4.9 min, p < 0.05). Five out of the eleven participants in the Cr group reported that they found the post-supplementation trial easier, while two out of the ten participants in the Plc group rated the post-supplementation trial to be easier. No side effects were reported following Cr and/or Plc supplementations.

Bottom Line: Twenty one endurance-trained males performed, in a double-blind fashion, two constant-load exercise tests to exhaustion at 63 +/- 5% V(O2) max in the heat (ambient temperature: 30.3 +/- 0.5 degrees C, relative humidity: 70 +/- 2%) before and after 7 days of Cr (20 g.d-1 Cr + 140 g.d-1 glucose polymer) or placebo (Plc) (160 g.d-1 glucose polymer) supplementation. 3-way interaction has shown that Cr supplementation reduced rectal temperature, heart rate, ratings of perceived leg fatigue (P < 0.05), plasma free-tryptophan (Trp) (P < 0.01) and free-Trp:tyrosine ratio (P < 0.01) but did not influence the ratio of free-Trp:large neutral amino acids or contribute in improving endurance performance (Plc group, n = 10: 50.4 +/- 8.4 min vs. 51.2 +/- 8.0 min, P > 0.05; Cr group, n = 11: 47.0 +/- 4.7 min vs. 49.7 +/- 7.5 min, P > 0.05).The present results may also suggest the demanding of the pre-experimental identification of the participants into "responders" and "non-responders" to Cr supplementation before performing the main experimentation.Otherwise, the possibility of the type II error may be enhanced.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Life & Health Sciences, University of Nicosia, Nicosia, Cyprus. hadjicharalambous.m@unic.ac.cy

ABSTRACT

Background: The present experiment examined the responses of peripheral modulators and indices of brain serotonin (5-HT) and dopamine (DA) function and their association with perception of effort during prolonged exercise in the heat after creatine (Cr) supplementation.

Methods: Twenty one endurance-trained males performed, in a double-blind fashion, two constant-load exercise tests to exhaustion at 63 +/- 5% V(O2) max in the heat (ambient temperature: 30.3 +/- 0.5 degrees C, relative humidity: 70 +/- 2%) before and after 7 days of Cr (20 g.d-1 Cr + 140 g.d-1 glucose polymer) or placebo (Plc) (160 g.d-1 glucose polymer) supplementation.

Results: 3-way interaction has shown that Cr supplementation reduced rectal temperature, heart rate, ratings of perceived leg fatigue (P < 0.05), plasma free-tryptophan (Trp) (P < 0.01) and free-Trp:tyrosine ratio (P < 0.01) but did not influence the ratio of free-Trp:large neutral amino acids or contribute in improving endurance performance (Plc group, n = 10: 50.4 +/- 8.4 min vs. 51.2 +/- 8.0 min, P > 0.05; Cr group, n = 11: 47.0 +/- 4.7 min vs. 49.7 +/- 7.5 min, P > 0.05). However, after dividing the participants into "responders" and "non-responders" to Cr, based on their intramuscular Cr uptake, performance was higher in the "responders" relative to "non-responders" group (51.7 +/- 7.4 min vs.47.3 +/- 4.9 min, p < 0.05).

Conclusion: Although Cr influenced key modulators of brain 5-HT and DA function and reduced various thermophysiological parameters which all may have contributed to the reduced effort perception during exercise in the heat, performance was improved only in the "responders" to Cr supplementation. The present results may also suggest the demanding of the pre-experimental identification of the participants into "responders" and "non-responders" to Cr supplementation before performing the main experimentation. Otherwise, the possibility of the type II error may be enhanced.

No MeSH data available.


Related in: MedlinePlus