Differences in muscle strength after ACL reconstruction do not influence cardiorespiratory responses to isometabolic exercise.
OBJECTIVE
To investigate whether the muscle strength decrease that follows anterior cruciate ligament (ACL) reconstruction would lead to different cardiorespiratory adjustments during dynamic exercise.


METHODS
Eighteen active male subjects were submitted to isokinetic evaluation of knee flexor and extensor muscles four months after ACL surgery. Thigh circumference was also measured and an incremental unilateral cardiopulmonary exercise test was performed separately for both involved and uninvolved lower limbs in order to compare heart rate, oxygen consumption, minute ventilation, and ventilatory pattern (breath rate, tidal volume, inspiratory time, expiratory time, tidal volume/inspiratory time) at three different workloads (moderate, anaerobic threshold, and maximal).


RESULTS
There was a significant difference between isokinetic extensor peak torque measured in the involved (116.5 ± 29.1 Nm) and uninvolved (220.8 ± 40.4 Nm) limbs, p=0.000. Isokinetic flexor peak torque was also lower in the involved limb than in the uninvolved limb (107.8 ± 15.4 and 132.5 ± 26.3 Nm, p=0.004, respectively). Lower values were also found in involved thigh circumference as compared with uninvolved limb (46.9 ± 4.3 and 48.5 ± 3.9 cm, p=0.005, respectively). No differences were found between the lower limbs in any of the variables of the incremental cardiopulmonary tests at all exercise intensities.


CONCLUSIONS
Our findings indicate that, four months after ACL surgery, there is a significant deficit in isokinetic strength in the involved limb, but these differences in muscle strength requirement do not produce differences in the cardiorespiratory adjustments to exercise. Based on the hypotheses from the literature which explain the differences in the physiological responses to exercise for different muscle masses, we can deduce that, after 4 months of a rehabilitation program after an ACL reconstruction, individuals probably do not present differences in muscle oxidative and peripheral perfusion capacities that could elicit higher levels of peripheral cardiorepiratory stimulus during exercise.
Department of Physiology, Universidade Federal de São Paulo, São Paulo, SP, Brazil.
Marília S
MS
Andrade
Department of Human and Exercise Physiology, Faculty of Physical Education, Universidade Federal de Goiás, Goiânia, GO, Brazil.
Claudio A B
CA
Lira
Center for Physical Education and Sport, Universidade Federal do Espírito Santo, Vitória, ES, Brazil.
Rodrigo L
RL
Vancini
Department of Physiology, Universidade Federal de São Paulo, São Paulo, SP, Brazil.
Fernanda P
FP
Nakamoto
Department of Orthopedics and Traumatology, UNIFESP, São Paulo, SP, Brazil.
Moisés
M
Cohen
Department of Physiology, Universidade Federal de São Paulo, São Paulo, SP, Brazil.
Antonio C
AC
Silva
D000328:Adult; D059549:Anterior Cruciate Ligament Reconstruction; D005080:Exercise Test; D006321:Heart / Q000502:physiology; D006801:Humans; D007866:Leg / Q000502:physiology; D008297:Male; D008660:Metabolism; D053580:Muscle Strength; D012119:Respiration