TY - JOUR
T1 - Prior heavy knee extension exercise does not affect VO 2 kinetics during subsequent heavy cycling exercise
AU - Thistlethwaite, John R.
AU - Thompson, Benjamin C.
AU - Gonzales, Joaquin U.
AU - Scheuermann, Barry W.
N1 - Funding Information:
Acknowledgments The investigators would like to thank the subjects who took part in this study. This study was funded in part by a University of Toledo DeArce Memorial Fellowship to B.W.S.
PY - 2008/3
Y1 - 2008/3
N2 - This study examined the magnitude of the oxygen uptake slow component (VO 2 SC) during heavy exercise when preceded by heavy knee extension (KE) exercise. Nine males (26.6 ±1.7 years, ±SE) performed repeated bouts of heavy exercise, each lasting 6 min with 6 min of recovery. Cycling-cycling trials (CYC1, CYC2) involved step transitions to a workrate corresponding to 50% of the difference between peak VO 2 and the lactate threshold (Δ 50%). During bilateral KE-cycling trails (KE, CYC3), KE was performed at an intensity requiring twofold greater muscle activation relative to CYC1 followed by a cycling transition to Δ 50%. VO 2 was measured breath-by-breath and was modeled using three exponentials to determinate the amplitudes (A 2', A 3') and time constants (τ 2, τ 3) of the primary phase and VO 2 SC. Electromyography (EMG) recorded from the vastus lateralis and medialis was averaged and reported relative to maximal voluntary contraction (%MVC). EMG was higher (p < 0.05) during KE (37.6 ±8.1 %MVC) than CYC1 (20.8 ± 1.9 %MVC), CYC2 (21.6 ± 5.7 %MVC) and CYC3 (19.8 ± 6.3 %MVC). The amplitude of the VO 2 SC was lower (p < 0.05) in CYC2 (197 ± 120 ml min -1) and CYC3 (163 ± 51 ml min -1) compared to CYC1 (325 ± 126 ml min -1). No difference in VO 2 SC was observed between CYC2 and CYC3. Although the activation of additional motor units during KE exercise reduced the amplitude of the VO 2 SC, the decrease was similar to that observed following heavy cycling exercise. Thus, the activation of motor units in excess of those required for the activity does not alter the VO 2 response during a subsequent bout of exercise.
AB - This study examined the magnitude of the oxygen uptake slow component (VO 2 SC) during heavy exercise when preceded by heavy knee extension (KE) exercise. Nine males (26.6 ±1.7 years, ±SE) performed repeated bouts of heavy exercise, each lasting 6 min with 6 min of recovery. Cycling-cycling trials (CYC1, CYC2) involved step transitions to a workrate corresponding to 50% of the difference between peak VO 2 and the lactate threshold (Δ 50%). During bilateral KE-cycling trails (KE, CYC3), KE was performed at an intensity requiring twofold greater muscle activation relative to CYC1 followed by a cycling transition to Δ 50%. VO 2 was measured breath-by-breath and was modeled using three exponentials to determinate the amplitudes (A 2', A 3') and time constants (τ 2, τ 3) of the primary phase and VO 2 SC. Electromyography (EMG) recorded from the vastus lateralis and medialis was averaged and reported relative to maximal voluntary contraction (%MVC). EMG was higher (p < 0.05) during KE (37.6 ±8.1 %MVC) than CYC1 (20.8 ± 1.9 %MVC), CYC2 (21.6 ± 5.7 %MVC) and CYC3 (19.8 ± 6.3 %MVC). The amplitude of the VO 2 SC was lower (p < 0.05) in CYC2 (197 ± 120 ml min -1) and CYC3 (163 ± 51 ml min -1) compared to CYC1 (325 ± 126 ml min -1). No difference in VO 2 SC was observed between CYC2 and CYC3. Although the activation of additional motor units during KE exercise reduced the amplitude of the VO 2 SC, the decrease was similar to that observed following heavy cycling exercise. Thus, the activation of motor units in excess of those required for the activity does not alter the VO 2 response during a subsequent bout of exercise.
KW - Knee-extension
KW - Muscle activation
KW - O cost
KW - Prior heavy exercise
KW - Time constant
UR - http://www.scopus.com/inward/record.url?scp=45549085912&partnerID=8YFLogxK
U2 - 10.1007/s00421-007-0614-5
DO - 10.1007/s00421-007-0614-5
M3 - Article
C2 - 18026978
AN - SCOPUS:45549085912
SN - 1439-6319
VL - 102
SP - 481
EP - 491
JO - European journal of applied physiology
JF - European journal of applied physiology
IS - 4
ER -