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Neuro-mechanical determinants of repeated treadmill sprints - Usefulness of an "hypoxic to normoxic recovery" approach.

Girard O, Brocherie F, Morin JB, Millet GP - Front Physiol (2015)

Bottom Line: During first sprint of the subsequent normoxic set, the distance covered (99.6, 96.4, and 98.3% of sprint 1 in SL, MH, and SH, respectively), the main kinetic (mean vertical, horizontal, and resultant forces) and kinematic (contact time and step frequency) variables as well as surface electromyogram of quadriceps and plantar flexor muscles were fully recovered, with no significant difference between conditions.Despite differing hypoxic severity levels during sprints 1-8, performance and neuro-mechanical patterns did not differ during the four sprints of the second set performed in normoxia.Hence, the recovery of performance and associated neuro-mechanical alterations was complete after resting for 6 min near sea level, with a similar fatigue pattern across conditions during subsequent repeated sprints in normoxia.

View Article: PubMed Central - PubMed

Affiliation: Department of Physiology, Faculty of Biology and Medicine, Institute of Sport Sciences, University of Lausanne Lausanne, Switzerland ; Athlete Health and Performance Research Center, Aspetar, Qatar Orthopaedic and Sports Medicine Hospital Doha, Qatar.

ABSTRACT
To improve our understanding of the limiting factors during repeated sprinting, we manipulated hypoxia severity during an initial set and examined the effects on performance and associated neuro-mechanical alterations during a subsequent set performed in normoxia. On separate days, 13 active males performed eight 5-s sprints (recovery = 25 s) on an instrumented treadmill in either normoxia near sea-level (SL; FiO2 = 20.9%), moderate (MH; FiO2 = 16.8%) or severe normobaric hypoxia (SH; FiO2 = 13.3%) followed, 6 min later, by four 5-s sprints (recovery = 25 s) in normoxia. Throughout the first set, along with distance covered [larger sprint decrement score in SH (-8.2%) compared to SL (-5.3%) and MH (-7.2%); P < 0.05], changes in contact time, step frequency and root mean square activity (surface electromyography) of the quadriceps (Rectus femoris muscle) in SH exceeded those in SL and MH (P < 0.05). During first sprint of the subsequent normoxic set, the distance covered (99.6, 96.4, and 98.3% of sprint 1 in SL, MH, and SH, respectively), the main kinetic (mean vertical, horizontal, and resultant forces) and kinematic (contact time and step frequency) variables as well as surface electromyogram of quadriceps and plantar flexor muscles were fully recovered, with no significant difference between conditions. Despite differing hypoxic severity levels during sprints 1-8, performance and neuro-mechanical patterns did not differ during the four sprints of the second set performed in normoxia. In summary, under the circumstances of this study (participant background, exercise-to-rest ratio, hypoxia exposure), sprint mechanical performance and neural alterations were largely influenced by the hypoxia severity in an initial set of repeated sprints. However, hypoxia had no residual effect during a subsequent set performed in normoxia. Hence, the recovery of performance and associated neuro-mechanical alterations was complete after resting for 6 min near sea level, with a similar fatigue pattern across conditions during subsequent repeated sprints in normoxia.

No MeSH data available.


Related in: MedlinePlus

Changes in exercise responses (A, SpO2; B, heart rate; C, RPE). Mean ± SD (n = 13). The repeated-sprint exercise protocol included a first set of eight sprints performed at sea level (SL), moderate (MH), or severe hypoxia (SH), while the second set of four sprints was always performed at SL. SpO2, arterial oxygen saturation (estimated by pulse oxymetry); RPE, rating of perceived exertion. C, T, and I, respectively refer to ANOVA main effects of condition, time, and interaction between these two factors with P-value and partial eta-squared into brackets. a, b, c, and d significantly different from sprint 1, 4, 8, and 9, respectively (P < 0.05). 1 and 2 significantly different from SL and MH, respectively (P < 0.05).
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Figure 1: Changes in exercise responses (A, SpO2; B, heart rate; C, RPE). Mean ± SD (n = 13). The repeated-sprint exercise protocol included a first set of eight sprints performed at sea level (SL), moderate (MH), or severe hypoxia (SH), while the second set of four sprints was always performed at SL. SpO2, arterial oxygen saturation (estimated by pulse oxymetry); RPE, rating of perceived exertion. C, T, and I, respectively refer to ANOVA main effects of condition, time, and interaction between these two factors with P-value and partial eta-squared into brackets. a, b, c, and d significantly different from sprint 1, 4, 8, and 9, respectively (P < 0.05). 1 and 2 significantly different from SL and MH, respectively (P < 0.05).

Mentions: Responses to exercise across the three conditions are depicted in Figure 1. During the initial set of sprints, SpO2 was significantly reduced for each simulated altitude ascent (P < 0.05). Lower SpO2 values were recorded for both sprints 4 and 8 (no difference) vs. sprint 1 in MH and SH, while no change occurred at SL. In response to sprint 1, HR was significantly higher in MH and SH compared to SL (P < 0.05), while RPE values were similar. Both HR and RPE increased significantly from sprint 1–4 (P < 0.05), while only RPE further increased at sprint 8 in reference to sprint 4 (P < 0.05), yet with similar values across conditions. Compared to prior to the warm-up (96.9 ± 0.4%), SpO2 were not different among conditions 4 min into recovery between the two repeated-sprint sets (96.2 ± 0.5%; all conditions compounded, P>0.05). During sprint 9, after 6 min of rest, SpO2, HR, and RPE values recovered significantly in relation to those achieved in sprint 4 and 8 (P < 0.05), with no difference between conditions. Whereas RPE values remained elevated compared to those measured in response to sprint 1, HR values recorded after sprint 1 and 9 were not different. At sprint 12, HR, and RPE values did not differ between conditions, while RPE was larger than in sprint 4 (P < 0.05).


Neuro-mechanical determinants of repeated treadmill sprints - Usefulness of an "hypoxic to normoxic recovery" approach.

Girard O, Brocherie F, Morin JB, Millet GP - Front Physiol (2015)

Changes in exercise responses (A, SpO2; B, heart rate; C, RPE). Mean ± SD (n = 13). The repeated-sprint exercise protocol included a first set of eight sprints performed at sea level (SL), moderate (MH), or severe hypoxia (SH), while the second set of four sprints was always performed at SL. SpO2, arterial oxygen saturation (estimated by pulse oxymetry); RPE, rating of perceived exertion. C, T, and I, respectively refer to ANOVA main effects of condition, time, and interaction between these two factors with P-value and partial eta-squared into brackets. a, b, c, and d significantly different from sprint 1, 4, 8, and 9, respectively (P < 0.05). 1 and 2 significantly different from SL and MH, respectively (P < 0.05).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4585155&req=5

Figure 1: Changes in exercise responses (A, SpO2; B, heart rate; C, RPE). Mean ± SD (n = 13). The repeated-sprint exercise protocol included a first set of eight sprints performed at sea level (SL), moderate (MH), or severe hypoxia (SH), while the second set of four sprints was always performed at SL. SpO2, arterial oxygen saturation (estimated by pulse oxymetry); RPE, rating of perceived exertion. C, T, and I, respectively refer to ANOVA main effects of condition, time, and interaction between these two factors with P-value and partial eta-squared into brackets. a, b, c, and d significantly different from sprint 1, 4, 8, and 9, respectively (P < 0.05). 1 and 2 significantly different from SL and MH, respectively (P < 0.05).
Mentions: Responses to exercise across the three conditions are depicted in Figure 1. During the initial set of sprints, SpO2 was significantly reduced for each simulated altitude ascent (P < 0.05). Lower SpO2 values were recorded for both sprints 4 and 8 (no difference) vs. sprint 1 in MH and SH, while no change occurred at SL. In response to sprint 1, HR was significantly higher in MH and SH compared to SL (P < 0.05), while RPE values were similar. Both HR and RPE increased significantly from sprint 1–4 (P < 0.05), while only RPE further increased at sprint 8 in reference to sprint 4 (P < 0.05), yet with similar values across conditions. Compared to prior to the warm-up (96.9 ± 0.4%), SpO2 were not different among conditions 4 min into recovery between the two repeated-sprint sets (96.2 ± 0.5%; all conditions compounded, P>0.05). During sprint 9, after 6 min of rest, SpO2, HR, and RPE values recovered significantly in relation to those achieved in sprint 4 and 8 (P < 0.05), with no difference between conditions. Whereas RPE values remained elevated compared to those measured in response to sprint 1, HR values recorded after sprint 1 and 9 were not different. At sprint 12, HR, and RPE values did not differ between conditions, while RPE was larger than in sprint 4 (P < 0.05).

Bottom Line: During first sprint of the subsequent normoxic set, the distance covered (99.6, 96.4, and 98.3% of sprint 1 in SL, MH, and SH, respectively), the main kinetic (mean vertical, horizontal, and resultant forces) and kinematic (contact time and step frequency) variables as well as surface electromyogram of quadriceps and plantar flexor muscles were fully recovered, with no significant difference between conditions.Despite differing hypoxic severity levels during sprints 1-8, performance and neuro-mechanical patterns did not differ during the four sprints of the second set performed in normoxia.Hence, the recovery of performance and associated neuro-mechanical alterations was complete after resting for 6 min near sea level, with a similar fatigue pattern across conditions during subsequent repeated sprints in normoxia.

View Article: PubMed Central - PubMed

Affiliation: Department of Physiology, Faculty of Biology and Medicine, Institute of Sport Sciences, University of Lausanne Lausanne, Switzerland ; Athlete Health and Performance Research Center, Aspetar, Qatar Orthopaedic and Sports Medicine Hospital Doha, Qatar.

ABSTRACT
To improve our understanding of the limiting factors during repeated sprinting, we manipulated hypoxia severity during an initial set and examined the effects on performance and associated neuro-mechanical alterations during a subsequent set performed in normoxia. On separate days, 13 active males performed eight 5-s sprints (recovery = 25 s) on an instrumented treadmill in either normoxia near sea-level (SL; FiO2 = 20.9%), moderate (MH; FiO2 = 16.8%) or severe normobaric hypoxia (SH; FiO2 = 13.3%) followed, 6 min later, by four 5-s sprints (recovery = 25 s) in normoxia. Throughout the first set, along with distance covered [larger sprint decrement score in SH (-8.2%) compared to SL (-5.3%) and MH (-7.2%); P < 0.05], changes in contact time, step frequency and root mean square activity (surface electromyography) of the quadriceps (Rectus femoris muscle) in SH exceeded those in SL and MH (P < 0.05). During first sprint of the subsequent normoxic set, the distance covered (99.6, 96.4, and 98.3% of sprint 1 in SL, MH, and SH, respectively), the main kinetic (mean vertical, horizontal, and resultant forces) and kinematic (contact time and step frequency) variables as well as surface electromyogram of quadriceps and plantar flexor muscles were fully recovered, with no significant difference between conditions. Despite differing hypoxic severity levels during sprints 1-8, performance and neuro-mechanical patterns did not differ during the four sprints of the second set performed in normoxia. In summary, under the circumstances of this study (participant background, exercise-to-rest ratio, hypoxia exposure), sprint mechanical performance and neural alterations were largely influenced by the hypoxia severity in an initial set of repeated sprints. However, hypoxia had no residual effect during a subsequent set performed in normoxia. Hence, the recovery of performance and associated neuro-mechanical alterations was complete after resting for 6 min near sea level, with a similar fatigue pattern across conditions during subsequent repeated sprints in normoxia.

No MeSH data available.


Related in: MedlinePlus