Effect of Early vs Delayed Rehabilitation Following Acute Muscle Strain Injury: A Randomized Controlled Trial
Study Overview and Design
This randomized controlled trial investigated whether starting rehabilitation soon after a muscle strain (acute thigh or calf injury) leads to better outcomes than delaying rehab. The study involved 50 amateur athletes (mean age ~34) with confirmed acute muscle strains in the thigh (~60% of cases) or calf (~40%). All participants were recruited within 48 hours of injury and then randomized into two groups: an Early Rehabilitation group (rehab initiated 2 days post-injury) and a Delayed Rehabilitation group (rehab initiated 9 days post-injury). The patients were followed for 12 months to assess recovery and any re-injury. The primary outcome was time to return to sports, defined as the first pain-free full participation in sport after completing a functional test (Numeric Pain Rating ≤1).
Rehabilitation Protocols for Each Group
Both groups followed the same structured 12-week rehabilitation program, consisting of four progressive stages. The only difference was when this program began: the Early group started at 2 days post-injury, whereas the Delayed group rested for about a week and began rehab at 9 days post-injury.
The rehab protocol was as follows:
Week 1 (Stage 1): Daily static stretching of the injured muscle.
Weeks 2–4 (Stage 2): Daily isometric muscle contractions with gradually increasing load.
Weeks 5–8 (Stage 3): Dynamic loading exercises with progressive resistance, performed three times per week
Weeks 9–12 (Stage 4): Functional exercises specific to the sport, combined with heavy strength training, three times per week.
Both groups completed these same stages in sequence. The Early group began Stage 1 within 2 days of injury, whereas the Delayed group essentially waited an extra week (likely performing only rest/acute injury management) before commencing Stage 1 at day 9. Aside from this 1-week lag, the content and progression of rehab were identical. This design allowed the study to isolate the effect of timing of rehab initiation on recovery.
Recovery Timeline: Early vs Delayed Start
Time to return to sport was significantly shorter in the Early Rehab group. The median time from injury to achieving pain-free full return was 62.5 days (~9 weeks) with early rehabilitation, compared to 83 days (~12 weeks) with delayed rehabilitation. In other words, starting rehab at 2 days post-injury led to recovery about 3 weeks faster than waiting until day 9. Figure 1 in the study illustrates that the early group’s recovery curve was shifted to the left, with a higher percentage of athletes returning by each time point (see Panel A/B). The difference in return-to-sport timelines was statistically significant (P = 0.01).
Notably, pain resolution was faster in the early-start group as well. Participants who began therapeutic exercise at 2 days experienced quicker reductions in pain levels, whereas those who rested longer tended to have pain persist for more days. The trial authors observed that delaying rehabilitation led to prolonged pain and a delayed return to sports, underscoring how extended rest/immobilization can slow down recovery. By contrast, controlled early loading of the injured muscle appeared to accelerate the healing process, allowing athletes to become pain-free and functional sooner. In practical terms, many early-group athletes were back to full sport by around the 9–10 week mark, whereas the delayed group’s return often stretched closer to 12 weeks or longer (some outliers in the delayed group took well beyond 3 months to recover).
Reinjury Rates and Safety
Importantly, initiating rehab early did not lead to a higher reinjury rate. Over the 12-month follow-up, re-injuries were low in both groups: 1 athlete (4%) in the Early group suffered a reinjury, compared to 0 athletes (0%) in the Delayed group. This difference was not statistically significant given the small numbers, and the authors specifically noted that earlier loading “did not significantly increase the risk of reinjury”. In other words, the faster return to play achieved by the early rehab group did not come at the cost of more frequent setbacks. Both approaches were generally safe, but the early rehabilitation strategy managed to expedite recovery without compromising tissue healing or stability. (It’s worth noting that a few participants in each group dropped out of the intervention – 5 in the early group vs 3 in the delayed group – but among those who completed rehab, reinjury incidence remained very low).
Functional Outcomes and Performance
By the time of return-to-play clearance, all athletes had to meet the same functional criteria: they needed to be essentially pain-free (≤1 on 0–10 pain scale) and pass functional sport-specific tests before resuming full activity. Both groups ultimately achieved comparable functional recovery in terms of being able to perform sport movements and heavy strengthening exercises by the end of the rehab program. The key difference was when they reached this milestone. The Early group attained pain-free functional status significantly sooner, whereas the Delayed group reached that point later due to the extra week of rest at the outset.
No major deficits in strength or function were reported at the final follow-up for either group, suggesting that the end-result (full muscle recovery) was similar – the Early group simply got there faster. By weeks 9–12, both groups were engaged in high-level strengthening and functional drills, indicating that muscle performance was largely restored in both cohorts by the end of rehab. Thus, the functional outcome (successful return to sport) was positive for nearly all participants; the early-start protocol just shortened the path to that outcome. Additionally, quicker pain resolution in the early group contributed to better functional status in the early weeks of rehab, whereas the delayed group spent that first week with limited activity due to pain and fear of movement.
Implications for Optimal Rehabilitation Strategies
Starting rehab early after a muscle strain clearly confers significant benefits in recovery speed without added risk. This study’s findings suggest that the traditional “rest longer until pain subsides” approach may unnecessarily prolong the rehabilitation. Key implications for clinicians and athletes include:
Avoiding Prolonged Immobilization: Extended rest after acute muscle injury can be detrimental. Even a one-week delay in introducing rehab exercises led to markedly slower recovery and longer-lasting pain. Muscle and tendon tissues begin to atrophy and stiffen with disuse; in fact, research shows that immobilization quickly degrades muscle-tendon structure and function. Therefore, completely “babying” a muscle for too long might hinder healing.
Benefits of Early Controlled Loading: Initiating gentle, controlled loading of the injured muscle within a couple of days helps stimulate the repair process. In this trial, rehabilitating starting at 2 days post-injury shortened the time to pain-free recovery by about 3 weeks, without increasing reinjury risk. Early rehab likely promotes better organized healing of muscle fibers and connective tissue, whereas delayed rehab may allow excessive scar tissue or stiffness to set in. The authors noted that regular mechanical loading early on can positively influence muscle-tendon regeneration and prevent excessive fibrosis.
Structured Progressive Rehab Programs: An important caveat is that early rehab should be done safely and progressively. In the study, the early group wasn’t doing intense exercise right away – they started with gentle stretching and gradually increased the load week by week. This underscores that an optimal strategy is a phased rehabilitation protocol: begin with low-intensity activity (even during the acute phase), then steadily ramp up through isometrics, then dynamic strengthening, and finally sports-specific training. Such a program allows the tissue to adapt to increasing stress. The success of the early group suggests that as long as the progression is tolerable (e.g. staying within pain limits), starting sooner is beneficial.
“Pain-Threshold” vs “Pain-Free” Approach: The early rehabilitation strategy essentially follows a pain-threshold approach – meaning athletes were allowed to do exercises before complete pain resolution, as long as pain was minimal and tolerable. The delayed strategy corresponded to a pain-free approach – waiting until nearly no pain before doing rehab. The results indicate that the pain-threshold (early start) approach can speed up recovery without causing harm, challenging the notion that one must be totally pain-free to exercise. In practice, this means clinicians should feel confident prescribing light activity early (within the patient’s tolerance) rather than enforcing strict rest until zero pain. This aligns with contemporary sports medicine trends favoring early mobilization for soft-tissue injuries.
Patient Education: Athletes and patients should be educated that an active rehab started early will likely reduce their downtime and pain. As the blog conclusion summed up, a “wait and see” approach is not ideal – getting an injury assessed and beginning a guided rehab program within the first 48 hours is recommended for optimal recovery. Early rehab got patients “back to sport quicker,” which is typically everyone’s goal purephysio.com.au. There is also a psychological benefit: being proactive in rehab can give athletes a sense of progress and may prevent fear of movement that sometimes accompanies injuries.
In summary, the optimal rehabilitation strategy for muscle strains is to start therapeutic exercises as soon as safely possible after injury, rather than delaying for a week or more. This trial demonstrated that early initiation of a structured rehab program led to faster return to full function (~3 weeks sooner) and did not increase re-injury rates. Delaying rehab, on the other hand, was associated with longer pain and a slower recovery. Clinically, this means that while the acute inflammatory phase (the first couple of days) should be managed prudently, one should introduce gentle movement and loading early on. Overall, early rehabilitation accelerates recovery from muscle strain injuries and should be incorporated into best practices for sports injury management, provided it is done with appropriate guidance and progression.
Sources: The information above is based on the findings of the referenced RCT (PMID: 28953439) as summarized in the New England Journal of Medicine correspondence researchgate.net and related analyses purephysio.com.au. These results highlight the clear advantage of early vs delayed rehab in the context of acute muscle strains, helping inform evidence-based rehabilitation protocols.