Description
ABSTRACT
Background: The ever-increasing sport level makes every single detail of the
athlete’s cardiorespiratory profile count and therefore, it’s deemed crucial to
clarify how the anterior cruciate ligament reconstruction (ACLR) affects the
energy economy of an athlete compared to the ACL-deficient and healthy
subjects. The purpose of this review was to systematically analyze the studies
that have investigated the correlation between the energy-oxygen cost in patients
following ACLR, in unreconstructed, and in intact ACLs.
Methods: This systematic review was conducted according to the Preferred
Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA). PubMed,
Cochrane and Google Scholar databases were searched and eight articles
describing miscellaneous methods for the assessment of oxygen consumption in
patients with ACL deficiency or ACL reconstructed knees were included.
Results: In total, 285 subjects were recorded with mean age of 29.61. The type
of exercise that the patients were subjected to, varied among the studies,
including one-leg cycling, exercise in closed kinetic chain and walking, jogging or
running in various speeds and treadmill inclinations. The energy expenditure of
an ACL-deficient patient is considerably higher than a healthy subject.
Additionally, chronicity of the ACL tear is not correlated with the energy
expenditure. ACL deficiency leads to higher energy consumption, not only during
walking but during jogging as well. ACLR could improve the efficiency of walking
by lowering the demands for energy. After ACLR the aerobic capacity (VO2max)
of professional soccer players is improved significantly.
Conclusions: ACL insufficiency affects substantially the metabolic energy costs,
resulting in increased energy expenditure. ACLR can help to partially reverse this
condition, as significant improvements and a more efficient, energy-wise,
locomotion is expected according to current literature. However, further research
is necessary, to clarify if ACLR can completely normalize again the energy
expenditure.
Alterations of energy expenditure after anterior cruciate
ligament tear and reconstruction. A Systematic Review.
Introduction
Sports participation is increasing steadily, subsequently leading to more
sports-related injuries1. In the United States, the incidence of anterior cruciate
ligament (ACL) injuries exceeds 250,000 cases per year2. It is the commonest
ligamentous injury, with football players being the most vulnerable group (53% of
total tears), followed by the skiers and gymnasts who are at high risk too3.
However, 20-25% of professional players are unfit to return to sport (RTS) after
ACLR at the same level as before the injury, and young athletes who RTS have a
30% chance to sustain a secondary injury within 2 years4. ACL deficiencies can
cause gait pattern alterations, and consequently the energy cost of walking
changes as well. This is estimated by measuring the oxygen expenditure, which
is higher in the injured limb compared to the healthy one5.
The ever-increasing sport level makes every single detail of the athlete’s
cardiorespiratory profile count and therefore, it’s deemed crucial to clarify how
the ACLR affects the energy economy of an athlete compared to the ACLdeficient
and healthy subjects.
The purpose of this review was to systematically analyze the studies
that have investigated the correlation between the energy-oxygen cost in
patients following ACLR, in unreconstructed, and in intact ACLs.
Materials and Methods
This systematic review was conducted according to the Preferred
Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA). It
contains articles describing miscellaneous methods for the assessment of
oxygen consumption in patients with ACL deficiency or ACL reconstructed
knees.
Two authors did a thorough systematic search of the literature on the 24th
of October 2022, including articles from three databases (PubMed, Cochrane
and Google Scholar). The following search strategy was utilized to find any
relevant articles: (ACL reconstruction OR ACL deficiency) AND (oxygen
consumption OR energy expenditure OR energy cost OR walking economy OR
VO2max). Any discrepancy between the authors with regards to selection of
retrieved studies was resolved by a third author.
Results
In this systematic review 8 studies were included. Out of them, 2 were
Randomized clinical trials (RCTs) [12,16], 5 were prospective comparative
studies [1-3,11,14] and 1 prospective cohort study [5]. In total, 285 subjects
were participated, 235 males and 50 females, with mean age of 29.61, mean
heigh of 1.76 m, mean body mass of 75.62 kg and mean BMI of 24.8. The mean
time of injury since the ACLR was 5,33 months. The type of exercise that the
patients were subjected to, varied among the studies, including one-leg cycling,
exercise in closed kinetic chain and walking, jogging or running in various
speeds and treadmill inclinations. The graft type in the group of ACLR was bone
patellar tendon bone (BPTB) autograft in 53 patients, Hamstrings tendons in 43.
The energy expenditure of an ACL-deficient patient is considerably higher
than a healthy subject, not only during walking but during jogging as well. This
finding can be attributed to altered gait kinematics that are usually developed in
ACL-deficient patients, and primarily to “quadriceps avoidance” pattern, meaning
a sustained knee flexor moment during mid- stance. ACLR could improve the
efficiency of walking by lowering the demands for energy. Moreover, the type of
ACL graft (Hamstrings vs BPTB) and its role on metabolic energy cost is still
uncertain, but to date both graft types are proven equal, without significant
differences in respect of walking economy.
Discussion
The premise of this systematic review was that the metabolic cost and
the energy consumption, in various sports activities, is higher in subjects
with ACL deficiency, but is this also observed in athletes after ACLR?
Undoubtedly, a native ACL constitutes a valuable knee stabilizer and energy
sparer and as a result, the point of interest is focused, nowadays, on the energy
consumption of an athlete with ACL deficiency or after ACLR. The ever-increasing
sport level, especially in sports requiring frequent cutting maneuvers like football,
makes every single detail of the athlete’s cardiorespiratory profile count and
therefore, it’s deemed crucial to clarify how the ACLR affects the energy economy
of an athlete compared to the ACL-deficient and healthy subjects.
Conclusion
ACL insufficiency affects substantially the metabolic energy costs,
resulting in increased energy expenditure during walking and exercise, but
could also lead to poor cardiorespiratory fitness. ACLR can help reverse this
condition, as significant improvements and a more efficient, energy-wise,
locomotion is expected according to current literature. This is definitely an
additional benefit to improved functional outcomes after ACLR and therefore, it
should also be considered and brought up during consultation with patients
that sustained an ACL tear. However, further high-quality research is
warranted, in order to delineate, if ACLR is capable of bringing metabolic
energy costs back to normal and also if graft types could have any impact
on the outcome.
