What muscles are developed during running in a healthy adult?

Primary Muscles Developed During Running

Running primarily develops the quadriceps, hamstrings, calf muscles (gastrocnemius and soleus), and hip extensors (gluteal group), with the specific activation pattern varying based on running intensity and terrain. 1, 2

Lower Extremity Muscle Activation Patterns

Horizontal Running

During horizontal running at high intensity, the muscles most activated include:

• Adductors: 90% activation, the highest of all muscle groups 1
• Hamstrings group: Semitendinosus (86%), biceps femoris (76%), and semimembranosus (75%) 1
• Hip adductors and gracilis: 76% activation 1
• Quadriceps group: Primary contributor to braking and support during early stance phase 2
• Calf muscles: Soleus and gastrocnemius are the greatest contributors to propulsion and support during the second half of stance 2

The overall lower extremity muscle activation during horizontal running reaches approximately 67% of total muscle volume 1.

Uphill Running

Uphill running shifts the activation pattern and increases total muscle recruitment to 73% of lower extremity muscle volume 1:

• Adductors: 83% activation (remain highly active) 1
• Gluteal group: 79% activation (substantially increased from horizontal running) 1
• Biceps femoris: 79% activation 1
• Vastus group (quadriceps): 75% activation, representing a 23% increase over horizontal running 1
• Gastrocnemius: 76% activation 1
• Soleus: 14% greater activation compared to horizontal running 1

Notably, uphill running requires considerably less activation of rectus femoris (29% decrease), gracilis (18% decrease), and semitendinosus (17% decrease) compared to horizontal running 1.

Functional Roles of Major Muscle Groups

Quadriceps Function

The quadriceps serve as the largest contributor to weight support and braking during early stance phase 2. These muscles work isometrically to promote work avoidance by facilitating a sliding motion of the hip over the ground contact, resulting in an approximately horizontal path of the center of mass 3.

Hamstrings Function

The hamstrings provide economical work supply by shortening over the entire stance duration without disrupting the linkages that result in work avoidance 3. This dual function—where hamstrings and quadriceps create opposing moments about both hip and knee joints while performing complementary roles—provides one answer to Lombard's paradox 3.

Calf Muscle Function

The gastrocnemius and soleus are the major contributors to propulsion and support during the second half of stance phase 2. Unlike walking, where calf activation occurs in late stance (26-55% of cycle), running shows calf activation in early stance (86-125%) together with quadriceps 4.

Hip Extensors and Stabilizers

The gluteal group and hip extensors increase activation substantially during uphill running (79% activation) and contribute to propulsion 1. Core and proximal hip strength are essential for optimizing lower extremity biomechanics and controlling excessive hip adduction during running gait 5, 6.

Speed-Dependent Variations

EMG profiles show that burst amplitude varies with running speed, with different speed dependencies between muscles of the same group 4. At low-speed running ("jogging"), stance phase extends to 46-57% of the cycle instead of 30-37% in normal running, creating additional differences in muscle activation patterns 4.

Strength Training Recommendations for Runners

Based on American College of Sports Medicine guidelines, runners should incorporate resistance training targeting 7:

• Calf strengthening: Essential for propulsion and tibial stress reduction 5
• Hip strengthening: Critical for controlling hip adduction and preventing injuries, particularly in female runners 5, 6
• Quadriceps and hamstring strengthening: Core contributors to support and propulsion 7
• Core strengthening: Optimizes lower extremity biomechanics 5
• Dorsiflexor and intrinsic foot muscle strengthening: Supports overall lower extremity function 7

The recommended prescription is 1 set of 8-12 repetitions for healthy adults, performed 2-3 days per week, involving major muscle groups including quadriceps extension or leg press, leg curls (hamstrings), and calf raises 7.

Common Pitfalls

Runners should avoid relying solely on running for lower extremity development without addressing muscle imbalances through targeted resistance training, as reduced muscle mass and strength are risk factors for running-related injuries 5. Resistance training provides protective mechanisms by attenuating shock and reducing loads on lower extremity structures 6.