Recovery Of Muscle Strength And Total Work After High Intensity Long-term Anaerobic Exercise In Boys, Teens, And Men
Integra
Introduction
After high-intensity exercise, heart rate and oxygen consumption recover faster1, blood acidosis is lower2, muscle blood
flow is higher and acid-base regulation is better3 in children than in adults. The oxidative capacity may be higher in
children,4 as well. The above suggest that children may recover faster after high-intensity exercise than adults. Studies
that examined the recovery of total mechanical work and peak power in children and adults after 10 and 30 sec highintensity
exercise reported the ability of children to recover faster2. However, children may fatigue less than adults in
longer high-intensity exercise bouts5. The present study examined the recovery of peak muscle strength and total work
in children, teens, and adults after long-term (60 sec) high-intensity "anaerobic" exercise.
Methods
Ten boys (11.4±0.5 yrs), 9 teens (14.5±0.5 yrs) and 9 men (24.0±1.9 yrs) performed 2 sets of 34 consecutive maximal
knee extensions and flexions (~61 sec) with 2 min rest at 120º/sec using Cybex. Peak torque (PT, Nm), total mechanical
work (TMW, J), and fatigue index (FI, %) for concentric knee flexors (FL) and extensors (EX) actions were evaluated
and % recovery from the 1st to 2nd set for PTEX, PTFL and TMW was calculated. HR was recorded and blood lactate
(Lb, mmol/L) was measured. Two-way ANOVA, post-hoc, and t-tests were used for statistical analysis.
Results
Men had higher (p<0.001) absolute values than teens and boys for PTEX (191±21 vs. 138±30 and 79±12),
PTFL (124±24 vs. 100±24 and 57±10), and TMW (8878±1363 vs. 6826±1347 and 3747±679). Expressed per unit of
body weight, PTEX, PTFL, and TMW were higher (p<0.01) in men and teens than in boys (1st set values Table). In
boys, PTEX and PTFL did not change significantly from the 1st to the 2nd set, whereas in teens and adults PTEX and
PTFL values decreased in the 2nd set (p<0.01, Table). TW decreased in the 2nd set in boys (p<0.05), and teens and adults
(p<0.01). FI was similar in boys, teens and men in both sets. Furthermore, % recovery was higher (p<0.001) in boys
than in teens and men for PTEX PTFL, and TMW (Figure). After the 1st set the net HR recovered faster to its half value
(time to 50% recovery of net HR) in boys compared to teens and adults (65±26 sec vs. 111±35 sec and 104±15 sec;
p<0.05). At the completion of the 1st set, Lb was lower in boys than in adults (6.1±1.3 vs. 10.6±1.7; p<0.05).
Conclusion
In conclusion, muscle strength of knee extensors and flexors and total work recover faster in boys than in both teen and
men from high-intensity long-term "anaerobic" exercise, as indicated by the greater % recovery of PTEX, PTFL, and
TMW from the 1st set. This may be due to less reliance of boys on the "anaerobic" system for energy production and/or
better acid-base regulation.
References
[1]. Zanconato S., et al., J. Appl. Physiol. 71: 993-998, 1991
[2]. Hebestreit H., et al., J. Appl. Physiol. 74: 2875-2880, 1993
[3]. Ratel S., et al., J. Appl. Physiol. 92: 479-485, 2002
[4]. Taylor DJ., et al., Mol Cell Biochem 174: 321-324, 1997
[5]. Gaul CA., et al., Int. J. Sports Med. 16: 451-455, 1995
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