A paper by Grondin et al. (2022) sought to identify objective strength measures that could help clinicians decide whether a patient is ready to begin running approximately 4 months after ACL reconstruction (ACLR) using a hamstring tendon graft. The authors retrospectively analyzed 413 patients and found that quadriceps strength symmetry was the strongest predictor of successful return to running.
The authors conclude that these isokinetic measures provide objective criteria to guide return-to-running decisions after ACL reconstruction.
The research team is primarily composed of sports medicine physicians, physical medicine and rehabilitation specialists, orthopedic surgeons, and rehabilitation clinicians, whose goal is to determine when a patient can safely begin jogging without excessive risk rather than when they are prepared for high-performance athletic demands.
A strength and conditioning coach or exercise prescription specialist would likely approach the problem differently.
From a strength and conditioning perspective, jogging is a low-force locomotor task that bears little resemblance to:
A strength coach would argue that athletic readiness depends on integrated qualities such as:
Many strength and conditioning professionals would challenge this assumption.
Peak hamstring and ACL loading occurs during:
Instead, tissue preparation may be better achieved through progressive exposure to:
However, limb symmetry can be misleading.
For example:
The athlete satisfies the criterion despite possessing relatively poor absolute strength.
Conversely:
This athlete is vastly stronger despite a similar asymmetry.
Strength and conditioning practitioners generally prioritize absolute force-producing capacity, not simply symmetry.
Sport performance requires athletes to tolerate:
From a coaching perspective, additional considerations would include:
However, from the perspective of a strength and conditioning coach or kinesiologist specializing in exercise prescription and athletic performance, it should be viewed as an early rehabilitation checkpoint.
The paper answers the question:
This study provides useful objective criteria for determining when an athlete may be ready to begin running after ACL reconstruction. However, as coaches and clinicians, we must remember that jogging is only one step in the return-to-performance process. Restoring the strength, power, stiffness, reactive ability, movement competency, and confidence required for sport demands a much broader approach than simply achieving a limb symmetry threshold.
And don't forget one of the most important parts of the return-to-play process: what happens before you ever get under the knife.
The quality of your pre-operative preparation can have a significant impact on post-operative outcomes, strength recovery, movement quality, and your overall return-to-sport timeline.
Download my free ACL Pre-Op eBook here to learn how to maximize your preparation before surgery and set yourself up for a more successful recovery.
— Carmen Bott, MSc, BHK
Summary
The authors argue that return to running should not rely solely on time after surgery but should incorporate objective strength testing. Their major findings include:- 63.2% of patients successfully returned to running by 6 months after surgery.
- Patients who returned to running demonstrated significantly greater:
- Quadriceps strength
- Hamstring strength
- Limb symmetry indexes (LSI)
- Functional Lysholm scores
- Patients who did not return to running had substantially higher rates of complications such as arthrofibrosis and anterior knee pain.
- Quadriceps LSI at 60°/s ≥65%
- Hamstring LSI at 180°/s ≥80%
The authors conclude that these isokinetic measures provide objective criteria to guide return-to-running decisions after ACL reconstruction.
Critique from a Strength & Conditioning / Kinesiologist Perspective
This paper is valuable, but it should be interpreted within the context of its authorship and clinical purpose.The research team is primarily composed of sports medicine physicians, physical medicine and rehabilitation specialists, orthopedic surgeons, and rehabilitation clinicians, whose goal is to determine when a patient can safely begin jogging without excessive risk rather than when they are prepared for high-performance athletic demands.
A strength and conditioning coach or exercise prescription specialist would likely approach the problem differently.
1. The outcome is "return to running," not "return to performance"
From a physiotherapy perspective, successfully jogging 15–30 minutes is considered an important rehabilitation milestone.From a strength and conditioning perspective, jogging is a low-force locomotor task that bears little resemblance to:
- maximal sprinting
- repeated acceleration
- deceleration
- cutting
- jumping
- reactive agility
- collision sport demands
2. Isokinetic strength is only one piece of tissue preparedness
The paper relies heavily on isolated knee extension and flexion torque measured on an isokinetic dynamometer.A strength coach would argue that athletic readiness depends on integrated qualities such as:
- maximal force production
- rate of force development
- eccentric braking capacity
- reactive strength index
- tendon stiffness
- stretch-shortening cycle efficiency
- intermuscular coordination
- trunk and hip control
3. Running itself may not be the best way to prepare tissues for sprinting
The underlying assumption is that progressing from walking → jogging → faster running gradually prepares tissues.Many strength and conditioning professionals would challenge this assumption.
Peak hamstring and ACL loading occurs during:
- maximal velocity sprinting
- rapid deceleration
- explosive change of direction
Instead, tissue preparation may be better achieved through progressive exposure to:
- plyometrics
- skipping and bounding drills
- track drills
- resisted acceleration work
- maximal strength training
- progressive surface manipulation (grass → turf → track)
4. The paper measures symmetry rather than athletic capacity
The principal recommendation is a 65% quadriceps limb symmetry index (LSI).However, limb symmetry can be misleading.
For example:
- Operated leg = 100 units
- Non-operated leg = 150 units
The athlete satisfies the criterion despite possessing relatively poor absolute strength.
Conversely:
- Operated leg = 250 units
- Non-operated leg = 300 units
This athlete is vastly stronger despite a similar asymmetry.
Strength and conditioning practitioners generally prioritize absolute force-producing capacity, not simply symmetry.
5. Athletic movement is multi-planar
The return-to-running decision in this study is based almost entirely on sagittal-plane knee torque.Sport performance requires athletes to tolerate:
- frontal plane loading
- transverse plane loading
- rotational moments
- unpredictable perturbations
- multiplanar deceleration
6. The psychological and physical demands of sport exceed jogging
The authors acknowledge that motivation, fear of reinjury, and psychosocial factors influence return to running but are not captured by strength testing.From a coaching perspective, additional considerations would include:
- confidence under speed
- exposure to chaotic environments
- fatigue resistance
- decision-making under pressure
- repeated high-intensity efforts
- sport-specific skill execution
Overall appraisal
This is a well-designed rehabilitation paper that provides objective criteria for initiating recreational running after ACL reconstruction. Its findings help reduce reliance on arbitrary time-based milestones and support evidence-informed clinical decision-making.However, from the perspective of a strength and conditioning coach or kinesiologist specializing in exercise prescription and athletic performance, it should be viewed as an early rehabilitation checkpoint.
The paper answers the question:
"Is this patient likely ready to begin jogging safely?"It does not answer the more performance-oriented question:
"Has this athlete restored the strength, power, stiffness, reactive ability, eccentric braking capacity, and movement competencies necessary to tolerate the chaotic demands of sport?"That distinction reflects the differing priorities of rehabilitation clinicians—whose focus is minimizing harm and restoring basic function—and strength and conditioning professionals, whose objective is to optimize tissue capacity and prepare athletes for the highest mechanical demands they will encounter in competition
Final Thoughts
This study provides useful objective criteria for determining when an athlete may be ready to begin running after ACL reconstruction. However, as coaches and clinicians, we must remember that jogging is only one step in the return-to-performance process. Restoring the strength, power, stiffness, reactive ability, movement competency, and confidence required for sport demands a much broader approach than simply achieving a limb symmetry threshold.
And don't forget one of the most important parts of the return-to-play process: what happens before you ever get under the knife.
The quality of your pre-operative preparation can have a significant impact on post-operative outcomes, strength recovery, movement quality, and your overall return-to-sport timeline.
Download my free ACL Pre-Op eBook here to learn how to maximize your preparation before surgery and set yourself up for a more successful recovery.
— Carmen Bott, MSc, BHK
