Achilles tendonitis, now often termed tendinopathy, is a condition involving pain and stiffness in the Achilles tendon, which connects the calf muscles to the heel bone. This injury is a common overuse issue, particularly for those who engage in activities that demand repeated, powerful push-off movements. The dilemma for a fitness-focused individual is how to maintain strength and conditioning without worsening the injury. This guidance will focus on practical, evidence-based strategies to safely continue strength training during Achilles tendon recovery.
Immediate Weight Lifting Guidelines
The primary rule when dealing with an irritated Achilles tendon is to manage the load based on pain response. Heavy weight lifting that directly engages the calf muscles is generally ill-advised during the acute, most painful phase of the injury. The goal at this stage is to prevent further tissue aggravation and allow the tendon to settle down.
A reliable method for determining appropriate activity is the “pain as the limiting factor” rule. Any activity that causes pain greater than a three on a ten-point pain scale should be significantly reduced or stopped immediately. If the pain spikes or increases in severity within 24 hours of a workout, the previous session’s load was too high, and the exercise must be modified for the next attempt.
It is helpful to differentiate between an acute, inflammatory injury and a chronic tendinopathy, which is characterized by tendon degeneration. While acute injuries demand relative rest from aggravating activities, chronic cases benefit from controlled loading. In either scenario, any exercise causing sharp, immediate pain should be temporarily removed from the training regimen.
High-Risk Exercises to Avoid
Certain strength training movements place excessive stress on the Achilles tendon and must be avoided during recovery. Exercises that involve the stretch-shortening cycle, where the muscle-tendon unit rapidly lengthens and then shortens, are particularly risky. This includes any plyometric movements like box jumps, jump rope, or burpees, which require an explosive push-off and quick energy storage in the tendon.
High-volume or heavy calf raises, especially the standing variation with a straight knee, also pose a significant threat. These exercises maximize the load on the gastrocnemius muscle and its attachment to the Achilles tendon, risking microtrauma and pain flare-ups. Even movements like deep squats or lunges can be problematic because they force the ankle into deep dorsiflexion under load, which can compress the Achilles tendon against the heel bone and aggravate symptoms, particularly in cases of insertional tendinopathy.
Similarly, Olympic lifts like the clean and jerk or snatch, which demand explosive ankle movement and a rapid transition from eccentric to concentric contraction, should be avoided entirely.
Safe Strength Training Modifications
Maintaining overall fitness is possible by substituting high-risk exercises with movements that lock out the ankle joint or shift the focus to the upper body and core. Upper body training, including exercises like overhead presses, rows, and bench presses, can typically be performed without any adverse effect on the Achilles tendon. Core work, such as planks, pallof presses, and stability ball exercises, also provides an effective way to maintain strength without stressing the lower leg.
For lower body training, the focus must be on exercises that minimize ankle movement and impact. Seated leg press and knee extensions are generally safe alternatives, provided the range of motion is carefully limited to prevent deep ankle flexion. Hamstring curls and glute bridges are also excellent options for isolating the posterior chain without requiring any significant contribution from the calf or Achilles tendon.
Low-impact cardio is a suitable way to maintain cardiovascular health. Swimming is an ideal choice, though one should avoid aggressive push-offs from the wall. Cycling is also a viable option, but it is best performed on a stationary bike with a high seat and low resistance to limit the amount of stretch and force applied to the tendon during the pedal stroke.
Incorporating Therapeutic Loading
As pain subsides, weight lifting transitions from a risk factor to a necessary component of long-term recovery. The tendon requires controlled, progressive mechanical loading to restore its structure and capacity. Two evidence-based protocols are the gold standard for this phase: eccentric training and Heavy Slow Resistance (HSR) training.
Eccentric Training
Eccentric training, often performed as heel drops off a step, focuses on the controlled lengthening phase of the muscle contraction, which is known to stimulate collagen production and fiber realignment within the tendon. The exercise involves using both legs to raise up, then slowly lowering the body down on only the injured leg over a count of three to five seconds.
Heavy Slow Resistance (HSR) Training
HSR training, in contrast, uses heavy weights with a slow tempo for both the lifting (concentric) and lowering (eccentric) phases, typically using machines like a leg press or seated calf raise.
Research suggests that both eccentric and HSR protocols yield equally good long-lasting clinical results in improving symptoms and function, though HSR may be associated with better patient compliance. The loads used in this phase are intended to rebuild tendon strength and tolerance, not for general muscle hypertrophy, and must be introduced gradually based on the pain-monitoring rule. It is strongly recommended that this phase of rehabilitation be initiated and progressed under the guidance of a physical therapist to ensure proper technique and loading progression.