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Tuesday, June 6, 2023

Forward Trunk Lean During Lunge Exercise Increases Posterior Chain Activity

Brent Brookbush

Brent Brookbush


Research Review: Forward trunk lean during lunge exercise increases posterior chain activity

By David Chessen DPT, PT, MBA, CSCS

Edited by Brent Brookbush DPT, PT, COMT, MS, PES, CES, CSCS, ACSM H/FS

Original Citation: Farrokhi, S., Pollard, C. D., Souza, R. B., Chen, Y. J., Reischl, S., & Powers, C. M. (2008). Trunk position influences the kinematics, kinetics, and muscle activity of the lead lower extremity during the forward lunge exercise. journal of orthopaedic & sports physical therapy, 38(7), 403-409. ABSTRACT

Why the Study Is Relevant: The forward lunge is an exercise commonly used in rehab, fitness, and performance settings to improve lower extremity strength; however, a relatively small amount of research exists on how trunk position influences muscle activity. In this 2008 study, researchers at the University of Southern California investigated whether a change in trunk position would alter muscle activity and kinematics of the lead lower extremity. The findings suggest that a forward trunk increases muscle activity of the hip extensors, specifically the gluteus maximus and biceps femoris .

Sagittal Plane Lunge
Caption: Sagittal Plane Lunge

Study Summary

DesignRepeated-measures design
Level of EvidenceIII Evidence from non-experimental descriptive studies, such as comparative studies, correlation studies and case-control studies

Subject Demographic:


  • Gender: 5 males and 5 females
  • Age (± Standard Deviation): 26.7 ± 3.2 years
  • Height: 1.73 ± 0.07 m
  • Mass: 62.5 ± 9.8 kg
  • Inclusion Criteria: No history of leg pain or pathology.
  • Exclusion Criteria: Knee surgery, history of traumatic patellar dislocation or neurological involvement that would influence performing the exercise.
MethodsMeasurement Protocol: Electromyography (EMG) Set-up
  • Electrodes were placed over the subjects' gluteus maximus, biceps femoris, vastus lateralis and the lateral gastrocnemius of the dominant lower leg (i.e., the leg used to kick a ball).
  • The electrodes were connected to an EMG receiver unit carried in a small pack on the subjects' backs.
  • EMG signals were normalized to the maximum EMG signal recorded during a maximum voluntary isometric contraction (MVIC).
  • MVIC testing was performed for the gluteus maximus, biceps femoris, vastus lateralis, and gastrocnemius.
  • All MVICs were held for 5 seconds, with the highest 1-second average used for normalization.

Reflective markers were placed over bony landmarks to quantify the motion of the hip, knee and ankle.

Ground reaction forces were recorded using a force plate.

  • The motion measured by the markers and, the ground reaction forces, were combined to calculate the internal net joint moments.

Lunge Protocol

  • Subjects were instructed to perform 5 repetitions of 3 lunge variations that differed in trunk and upper extremity position. The order of the lunges was randomized.
    • Subjects always started in a standing position, with the trunk upright and arms next to the body.
    • The length of the subjects' steps during the lunge was standardized according to the distance from the greater trochanter to the floor, as measured when standing.
    • Subjects lowered the trail and leading knees simultaneously to a point where the trail knee was about 2-3 cm from the ground.

  • For the normal lunge (NL) trunk erect exercise, subjects stepped forward with the dominant leg while maintaining a vertical trunk position.
  • The lunge with trunk forward (LTF) exercise was performed with the arms beyond the knee of the lead leg.
  • The lunge with trunk extension (LTE) exercise was performed with the arms raised overhead and backwards.
  • The speed and duration of each lunge was controlled by a metronome set at 60 beats per minute.
    • Each subject performed each lunge variation for 6 seconds: a 3-second descent and 3-second ascent.
    • A researcher provided simultaneous visual and auditory cues while the lunge was performed.

  • The lunge cycle was defined as the time from initial contact of the lead leg with the force platform to the time when contact was terminated.

Data Analysis

  • Joint impulse was calculated as the area under the moment-time curve during each lunge trial.
    • Impulse takes into account the magnitude and duration of the net joint moment, giving a better indicator of the total torque experienced by a joint during an activity.

  • The EMG variable of interest was the highest 1-second average of a normalized EMG signal.
    • This was performed to avoid averaging low levels of EMG during the lunge cycle with high levels of EMG.

  • Differences among the lunge variations were assessed using a one-way analysis of variance (ANOVA), with repeated measures.
  • Post hoc testing included paired t tests with a Bonferroni correction.
    • Performed when a significant ANOVA test was defined (P < .015).

  • The critical threshold for significance was reduced to P < 0.15.
Outcome Measures
ResultsAnkle Joint
  • Peak ankle dorsiflexion (DF) was significantly greater during the LTE condition (mean ± SD, 31.4° ± 3.5°) compared to the NL (mean ± SD, 25.3° ± 5.7°; P = 0.008) and LTF conditions (mean ± SD, 24.3° ± 4.9°; P = 0.004).
  • Ankle plantar flexor impulse was significantly greater during the LTF condition (mean ± SD, 2.5 ± 0.4 N·m·s/kg) compared to the NL condition (mean ±  SD, 1.7 ± 0.4 N·m·s/kg; P .001) and LTE condition (mean ± SD, 2.0 ± 0.5 N·m·s/kg; P = .005).

Knee Joint

  • Peak knee flexion angle during LTE condition was significantly greater than the LTF condition (mean ± SD, 113.4° ± 7.4° versus 104.3° ± 11.1°; P = .003).
  • Knee extensor impulse was significantly greater for the LTE condition compared to the LTF condition (mean ± SD, 2.6 ± 0.6 versus 2.1 ± 0.5 N·m·s/kg; P = .008).

Hip Joint

  • Peak hip flexion angle was significantly greater during the LTF condition (mean ± SD, 107.9° ± 9.7°)

    compared to the NL condition (mean ± SD, 87.4° ± 11.8°; P .001) and LTE condition (mean ± SD, 79.7° ± 11.5°; P .001).

  • Hip extensor impulse for the LTF condition (mean ± SD, 5.2 ± 1.0 N·m·s/kg) was significantly greater compared to the NL (mean ± SD, 3.9 ± 0.7 N·m·s/kg; P = .001) and LTE conditions (mean ± SD, 3.5 ± 0.9 N·m·s/kg; P .001).
  • The EMG of the gluteus maximus for the LTF condition (mean ± SD, 22.3% ± 12.0% MVIC) was significantly greater than the NL condition (mean ± SD, 18.5% ± 11.0% MVIC; P = .009).
  • The EMG of the biceps femoris for the LTF condition (mean ± SD, 17.9% ± 9.6% MVIC) was significantly greater when compared to the NL condition (mean ± SD, 11.9% ± 6.4% MVIC; P = .005).
Our ConclusionsHuman movement professionals may recommend a lunge with a forward trunk lean to aid in increasing activity of the gluteus maximus and biceps femoris.
Researchers' ConclusionsTrunk position in lunge exercises significantly influences the muscle use patterns and kinematics in the lead leg during a lunge exercise.

Static Lunge to Row (Posterior Oblique Subsystem) Integration Progressions
Caption: Static Lunge to Row (Posterior Oblique Subsystem) Integration Progressions

Review & Commentary

This study contributes to a growing body of research comparing the muscle activity and kinematics of various exercises, or variations of exercises. This study compared activity of lower extremity muscles during a lunge performed with different trunk positions. The findings indicate that lunges performed in a trunk-forward position increase posterior chain activity.

The trunk-forward variation significantly increased the hip extensor impulse and hip extensor electromyography (EMG), specifically the gluteus maximus and biceps femoris . As would be expected in this variation, there is a concurrent increase in the vertical ground reaction force in the lead limb. The plantar flexor impulse was also increased. These results were attributed to the anterior translation of the center of mass relative to the hip joint and base of support.

The study had many methodological strengths, including:

  • This study used both EMG and kinematic analysis to compare motion at several joints during variations of a commonly recommended exercise. This provides the reader with information regarding how joint and bone position may be related to muscle activity, and how changes in form during this common exercise may effect outcomes.
  • The lunge is a commonly recommended exercise, performed in rehab, fitness, and performance settings. The use of a common exercise in this study increases it's clinical relevance/practical application.
  • The study described a well thought-out protocol for positioning the subjects for the variations of the forward lunge, and used validated methods for recording EMG and kinematic data.

Weakness that should be noted prior to clinical integration of the findings include:

  • The subject sample consisted of a group of young healthy individuals. Consideration should be given before attempting to apply these findings in an injured, or at risk population.
  • There was no mention of a standardized method to ensure proper form. Based on the description it appears as if some common compensation patterns may have been allowed which could have effected outcomes.
  • Participants were permitted to vary their joint kinematics in each lunge variation. This may have compromised the findings on whether trunk position is responsible for the results of the study.

Why This Study Is Important

This study adds to a growing body of research comparing exercises and variations of exercises. Comparative, practical research is essential for optimizing exercise selection. The lunge is a commonly recommended exercise in rehab, fitness, and performance settings, and may have high transference to activities of daily living (ADL's) and sport.

The combination of kinematic and EMG analysis, allows the human movement professional to make decisions about trunk position based on the client's goals or impairments, with the intent of affecting range of motion, muscle activity or both. Further, while joint motion can be seen and assessed, it is not possible to see the relative amounts of muscle activity. Studies like this one aid in moving beyond conjecture and hypothesis relative to the affect altered motion has on muscle recruitment. This study confirms the hypothesis that increased forward lean increases gluteus maximus and biceps femoris activity.

How the Findings Apply to Practice

This study implies that cuing a forward lean during a lunge will increase gluteus maximus and biceps femoris activity, as well as require greater range of motion (ROM) for hip flexion and dorsiflexion. If these increases coincide with a patient/clients goals, a forward lean may be recommended.

Related Brookbush Institute Content

As supported by this study, the Brookbush Institute recommends performing a front, reverse and/or static lunge with a forward lean to increase hip extensor activity. However, it is also noted in the Brookbush Institute Leg Strength Progression that these exercises require optimal dorsiflexion. For individuals exhibiting lumbopelvic hip complex dysfunction (LPHCD) , sacroiliac joint dysfunction (SIJD) , and/or lower leg dysfunction (LLD) it may be recommended that mobility and activation techniques precede resistance training. Further, it may be necessary to regress the exercise until optimal mobility and better muscular recruitment has been achieved. Has described in the article Leg Strength Progression the lunge is one of the last exercises to be integrated in a progression that includes leg press, ball wall squats, squats, step-ups, lunges and single leg squat touch downs.

Although not mentioned in this study, the Brookbush Institute also recommends using a forward lean during all progression of a lunge including static, dynamic, reverse, forward, frontal, transverse and integrated progressions.

Below are a few sample progressions of the lunge exercise:

Sagittal Plane Lunge

Static Lunge Row POS Integration Progression

Dynamic Lunge with Chest Press AOS Progression


  1. Farrokhi, S., Pollard, C. D., Souza, R. B., Chen, Y.-J., Reischl, S., & Powers, C. M. (2008). Trunk position influences the kinematics, kinetics, and muscle activity of the lead lower extremity during the forward lunge exercise. The Journal of Orthopaedic and Sports Physical Therapy, 38(7), 403–409.
  2. Ford, K. R., Nguyen, A.-D., Dischiavi, S. L., Hegedus, E. J., Zuk, E. F., & Taylor, J. B. (2015). An evidence-based review of hip-focused neuromuscular exercise interventions to address dynamic lower extremity valgus. Open Access Journal of Sports Medicine, 6, 291–303.
  3. Bouillon, L. E., Wilhelm, J., Eisel, P., Wiesner, J., Rachow, M., & Hatteberg, L. (2012). Electromyographic assessment of muscle activity between genders during unilateral weight-bearing tasks using adjusted distances. International Journal of Sports Physical Therapy, 7(6), 595–605.
  4. Hofmann, C. L., Holyoak, D. T., & Juris, P. M. (2017). Trunk and Shank Position Influences Patellofemoral Joint Stress in the Lead and Trail Limbs During the Forward Lunge Exercise. The Journal of Orthopaedic and Sports Physical Therapy, 47(1), 31–40.
  5. Riemann, B. L., Lapinski, S., Smith, L., & Davies, G. (n.d.). Biomechanical analysis of the anterior lunge during 4 external-load conditions. Journal of Athletic Training, 47(4), 372–8.

© 2016 Brent Brookbush

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