Energy requirements and physical demands of professional football players during rehabilitation from an anterior cruciate ligament reconstruction

Anterior Cruciate Ligament (ACL) rupture has a great impact on athletes,
emphasizing the challenges it poses to an athlete's career due to surgery and a
prolonged rehabilitation period. The return-to-sport rates vary, with
professional male football players showing a nearly 100% return, but only 65%
at the same level three years post-reconstruction. The risk of re-rupture is
significant, especially in females, but may be reduced with an optimal
rehabilitation.

The rehabilitation process at the KNVB Football Medical Center spans four
phases over approximately nine months, focusing on recovery, muscle strength,
neuromuscular control, running, agility, jumping, and prevention of recurrence.
During rehabilitation, athletes experience a drastic change in activity
patterns, impacting energy expenditure.

Besides changes in activity pattern, several physiological consequences occur
after an ACL rupture. The energy requirement might decrease due to
immobilization. However, energy and macronutrient intakes should still be
adequate to reduce muscle loss, and mitigate the negative effects of surgery
and immobilization. Physical demands will gradually increase and differ per
phase during the rehabilitation period, so do the nutritional requirements.
However, to date it is unclear what exact energy requirements are and how they
develop throughout the rehabilitation period.

Therefore this study aims to explore the energy requirements of professional
football players during different phases during the rehabilitation from an ACL
reconstruction. Total daily energy expenditure, resting metabolic rate,
physical activity, and body composition will be assessed. The goal is to
provide insights into the evolving nutritional needs during rehabilitation and
form best-practice nutrition strategies for the rehabilitation from an ACL
reconstruction.

In the current study, we aim to assess the energy requirements of professional
football players during different phases in the rehabilitation from an ACL
reconstruction. As such, this study will identify the energy and nutritional
requirements, adjusted to the evolving physical demands of the
ACL-rehabilitation period. Hence, this study forms the basis for a
best-practice nutrition protocol for optimal recovery from an
ACL-reconstruction.

The current study is a longitudinal cohort study, with repeated assessments of
energy expenditure, physical activity patterns, body composition and dietary
intake during a rehabilitation period of ~9 months. For all participants, data
will be collected from ~1 week post-surgery until the end of the rehabilitation
period (~36 weeks post-surgery). In the regular protocol, DLW measurements will
take place in the first and second phase of rehabilitation. For the extended
protocol, additional measurements with DLW will be conducted in two
participants.

For all participants, between 5 to 10 days post-surgery (~week 1) and in week
7, energy expenditure will be determined by the doubly labelled water method
for a period of 2 weeks. These measurements require the ingestion of a single
bolus of doubly labelled water, combined with repeated urine collections over a
2-week period. Along with the DLW method, the resting metabolic rate will be
measured by ventilated hood indirect calorimetry, and physical activity
patterns will be assessed by physical activity monitors (wrist-worn
accelerometers and local position monitoring). All physical activity will also
be logged in an activity diary. The energy expenditure by DLW, RMR and physical
activity will again be monitored around weeks 16, 22 and 30 (1 week after the
start of a new phase in the field rehabilitation) in the *DLW extended
protocol*. For the regular protocol, only physical activity and RMR will be
measured again, without DLW.

Anthropometric measurements will be conducted as soon as possible after
surgery. These anthropometric measurements include body weight, height,
skinfold thickness and several girths. Anthropometric measurements will
continue throughout the rehabilitation period in intervals of ~5 weeks.
Additionally, dietary habits and food intake will be assessed by the dietary
history method, and will repeatedly be monitored. Both monitoring of the food
intake and anthropometry by ISAK are already part of the standard KNVB
ACL-rehabilitation protocol.

Potential value of the research
The study provides novel insight into the energy expenditure, resting metabolic
rate, physical activity patterns, body composition changes and dietary intake
in professional football players during different phases in the rehabilitation
of an ACL-reconstruction. As such, this study eventually provides an important
framework for dietary counselling in long-term rehabilitating professional
football players.

Benefits participants
For the participating football players, their rehabilitation period will be
optimised directly. After each dietary history, ISAK measurement and RMR
assessment, participants will receive direct feedback and their nutritional
advice will be adjusted accordingly.

Risk for participants
Energy expenditure will be assessed by the DLW method, on two or five different
time points. Because the stable isotopes used in the DLW are non-radioactive,
and non-toxic in the doses used, the DLW method has been used extensively in
human volunteers, and even in infants and pregnant women. Per DLW assessment
period, collection of 7 urine samples over a period of 14 days is required,
which poses minimal burden to the participants.

Furthermore, the burden associated with the assessment of the resting metabolic
rate is limited to an investment of maximally 5x50 min in the morning.
Participants do have to arrive and stay in a fasted state, which can actually
be seen as a short delay in breakfast consumption. An overnight stay in a hotel
at, or near the KNVB Campus will be offered to minimize the discomfort. The
wrist-worn physical activity monitor does not hinder daily activities, but may
provide minimal discomfort for the participants. The dietary history and ISAK
measurements are already part of the standard rehabilitation protocol at the
KNVB Medical Center.

Altogether, it can be concluded that the burden and risks associated with this
study are low.