Limits...
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 distance covered (A) and stride kinetics (B, mean vertical force; C, mean horizontal force; D, mean resultant force). 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. 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 significant different from SL and MH, respectively (P < 0.05).
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4585155&req=5

Figure 2: Changes in distance covered (A) and stride kinetics (B, mean vertical force; C, mean horizontal force; D, mean resultant force). 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. 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 significant different from SL and MH, respectively (P < 0.05).

Mentions: Distance ran and associated running kinetics during the repeated-sprint exercise are displayed in Figure 2. No difference was found in distance ran during the first sprint between SL, MH and SH (24.2 ± 1.4, 24.1 ± 1.5, and 24.2 ± 2.0 m, respectively). However, sprint performance decreased to a larger extent in SH compared to SL, as evidenced by larger reductions in distance ran during sprint 4 (−9.9±5.2% vs. −5.3±2.8%; P < 0.05) and 8 (−11.7±5.2% vs. −8.9±4.1%; P < 0.05) in reference to sprint 1. Horizontal, but not vertical and total forces, significantly decreased from sprint 1 to 4 (P < 0.05). During sprint 8, values for vertical, horizontal and total forces were significantly lower (all conditions pooled; −2.3±1.9%, −8.6±6.5%, and −2.4±1.9%, respectively; P < 0.05) in reference to sprint 1.


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 distance covered (A) and stride kinetics (B, mean vertical force; C, mean horizontal force; D, mean resultant force). 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. 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 significant 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 2: Changes in distance covered (A) and stride kinetics (B, mean vertical force; C, mean horizontal force; D, mean resultant force). 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. 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 significant different from SL and MH, respectively (P < 0.05).
Mentions: Distance ran and associated running kinetics during the repeated-sprint exercise are displayed in Figure 2. No difference was found in distance ran during the first sprint between SL, MH and SH (24.2 ± 1.4, 24.1 ± 1.5, and 24.2 ± 2.0 m, respectively). However, sprint performance decreased to a larger extent in SH compared to SL, as evidenced by larger reductions in distance ran during sprint 4 (−9.9±5.2% vs. −5.3±2.8%; P < 0.05) and 8 (−11.7±5.2% vs. −8.9±4.1%; P < 0.05) in reference to sprint 1. Horizontal, but not vertical and total forces, significantly decreased from sprint 1 to 4 (P < 0.05). During sprint 8, values for vertical, horizontal and total forces were significantly lower (all conditions pooled; −2.3±1.9%, −8.6±6.5%, and −2.4±1.9%, respectively; P < 0.05) in reference to sprint 1.

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