Shoulder muscle activation during lateral raise variations

Abstract

<h2>Abstract</h2> <p>The lateral raise is the primary <a href="/terms/isolation-exercise/" class="term-link" data-slug="isolation-exercise" title="isolation exercise">isolation exercise</a> for the lateral deltoid, and its technique variations — including dumbbell versus cable implementation, plane of elevation, and arm rotation — are commonly debated in training literature. This study compared lateral deltoid, anterior deltoid, and supraspinatus <a href="/terms/electromyography/" class="term-link" data-slug="electromyography" title="EMG">EMG</a> activation during dumbbell lateral raise, cable lateral raise, and scaption (30-degree anterior plane elevation) conditions in resistance-trained men and women. Twenty participants performed each variation at matched relative loads, with EMG recorded and normalized to MVIC. The cable lateral raise produced more uniform lateral deltoid activation across the full <a href="/terms/range-of-motion/" class="term-link" data-slug="range-of-motion" title="range of motion">range of motion</a>, while the dumbbell variation elicited greater peak activation at the terminal range. Scaption (elevation in the scapular plane) reduced supraspinatus impingement stress indicators compared to pure frontal plane elevation without significantly reducing lateral deltoid activation. The widespread belief that internal rotation ("thumbs down") increases lateral deltoid activation was not supported by the data; this technique produced no significant difference and elevated impingement risk. These findings inform evidence-based technique recommendations for safe and effective lateral deltoid development.</p>

Introduction

<h2>Introduction</h2> <p>The lateral deltoid is the medial portion of the three-headed deltoid muscle and is primarily responsible for shoulder abduction in the frontal plane. Its development is among the most sought-after aesthetic goals in physique-oriented training, as it creates the appearance of broader, rounder shoulders and contributes to the coveted shoulder-to-waist width ratio [1]. Unlike the anterior deltoid, which receives substantial indirect stimulation from pressing movements, and the posterior deltoid, which is stimulated by rowing and face pull variations, the lateral deltoid is poorly stimulated by compound movements and typically requires direct isolation work [2].</p> <p>The lateral raise in its various forms represents the primary isolation tool for the lateral deltoid. However, the biomechanical properties of this exercise vary substantially depending on equipment choice, plane of elevation, and minor technique details. A fundamental issue with the dumbbell lateral raise relates to resistance profile: because gravity is the primary resistive force and the moment arm of a dumbbell changes with arm position, the resistance profile is not constant throughout the <a href="/terms/range-of-motion/" class="term-link" data-slug="range-of-motion" title="range of motion">range of motion</a>. At the bottom of the movement (arm hanging), the moment arm is near zero and the exercise provides minimal resistance; resistance increases through the ascending arc and peaks when the arm is horizontal (<a href="/terms/squat-depth/" class="term-link" data-slug="squat-depth" title="parallel">parallel</a> to the floor), after which the moment arm reduces again as the arm passes horizontal [3]. This non-uniform resistance profile means that the dumbbell lateral raise loads the muscle inconsistently throughout the range of motion.</p> <p>Cable machines alter this resistance profile by changing the direction from which resistance is applied. A cable attached to a low pulley provides constant tension throughout the movement because the cable's direction of pull changes as the arm moves, maintaining resistance even at the lowest arm position [4]. This theoretically provides a more uniform training stimulus across the full range of motion compared to the dumbbell variation.</p> <p>The plane of elevation is another important technical variable. Pure frontal plane abduction (straight out to the side) has traditionally been taught as the correct technique, but biomechanical evidence increasingly supports elevation in the scapular plane (approximately 30 degrees forward of the frontal plane, or "scaption") as a more shoulder-healthy alternative. In the scapular plane, the greater tuberosity of the humerus rotates away from the coracoacromial arch as the arm elevates, reducing the risk of subacromial impingement [5].</p> <p>Finally, the internal rotation technique — sometimes called "thumbs down" or "pouring water from a jug" — is commonly taught in bodybuilding circles with the claim that it preferentially recruits the lateral deltoid. This claim has a weak theoretical basis and its validity warrants empirical examination.</p>

Methods

<h2>Methods</h2> <p><strong>Participants</strong></p> <p>Twenty resistance-trained adults (11 men, 9 women; mean age 25.6 ± 4.3 years; minimum 1 year of consistent shoulder training experience) participated. Participants were excluded <a href="/terms/intermittent-fasting/" class="term-link" data-slug="intermittent-fasting" title="if">if</a> they reported any history of rotator cuff injury, shoulder impingement, or acromioclavicular joint pathology. All provided written informed consent.</p> <p><strong>Exercise Conditions</strong></p> <p>Five lateral raise variations were tested in counterbalanced order:</p> <table> <thead> <tr> <th>Condition</th> <th>Equipment</th> <th>Plane</th> <th>Arm Rotation</th> </tr> </thead> <tbody> <tr> <td>Dumbbell Lateral Raise</td> <td>Dumbbell</td> <td>Frontal</td> <td>Neutral</td> </tr> <tr> <td>Cable Lateral Raise</td> <td>Low pulley cable</td> <td>Frontal</td> <td>Neutral</td> </tr> <tr> <td>Scaption (Dumbbell)</td> <td>Dumbbell</td> <td>Scapular (30° anterior)</td> <td>Neutral</td> </tr> <tr> <td>Thumbs-Down Raise</td> <td>Dumbbell</td> <td>Frontal</td> <td>Internal rotation</td> </tr> <tr> <td>Thumbs-Up Raise</td> <td>Dumbbell</td> <td>Frontal</td> <td>External rotation</td> </tr> </tbody> </table> <p>All conditions used a matched load equivalent to the participant's 12-<a href="/terms/repetition-maximum/" class="term-link" data-slug="repetition-maximum" title="repetition maximum">repetition maximum</a> on the dumbbell lateral raise. Participants performed 5 repetitions per condition at self-selected controlled tempo with 3-minute rest between conditions. <a href="/terms/range-of-motion/" class="term-link" data-slug="range-of-motion" title="Range of motion">Range of motion</a> was standardized to 0 (arm at side) to 90 degrees (arm horizontal) for all conditions.</p> <p><strong><a href="/terms/electromyography/" class="term-link" data-slug="electromyography" title="EMG">EMG</a> Data Collection</strong></p> <p>Surface electrodes were placed on the lateral deltoid (midpoint of the lateral deltoid, approximately 5 cm below the lateral acromion), anterior deltoid (anterior aspect, approximately 3 cm below the anterior acromion), and supraspinatus (accessible portion superior to the scapular spine, approximately at the midclavicle level). The middle trapezius and serratus anterior were also monitored.</p> <p>EMG was collected at 2000 Hz, processed with bandpass filtering (20–450 Hz), full-wave rectification, and 50 ms RMS smoothing. All data were normalized to MVIC values from standardized testing positions. Mean and peak EMG were quantified separately across the ascending (0°–90°) and descending (90°–0°) phases.</p> <p><strong>Statistical Analysis</strong></p> <p>Repeated-measures ANOVA compared EMG across conditions for each muscle and phase, with Bonferroni post hoc corrections. Significance was set at p 0.05.</p>

Results and Discussion

<h2>Results and Discussion</h2> <p><strong>Lateral Deltoid Activation: Dumbbell vs. Cable</strong></p> <p>Both dumbbell and cable lateral raises produced high lateral deltoid activation, but with meaningfully different distribution profiles across the <a href="/terms/range-of-motion/" class="term-link" data-slug="range-of-motion" title="range of motion">range of motion</a>. The dumbbell condition produced significantly higher peak lateral deltoid activation (88.4 ± 14.1% MVIC) compared to the cable condition (79.3 ± 12.7% MVIC; p = 0.043), concentrated predominantly in the 60–90 degree range. The cable condition produced greater mean lateral deltoid activation across the full 0–90 degree range (67.2 ± 10.8% MVIC vs. 58.9 ± 9.4% MVIC; p = 0.031) because it maintained meaningful resistance even in the lower range where the dumbbell moment arm is minimal.</p> <table> <thead> <tr> <th>Condition</th> <th>Peak Lat. Deltoid (%MVIC)</th> <th>Mean Lat. Deltoid (%MVIC)</th> <th>Ant. Deltoid (%MVIC)</th> <th>Supraspinatus (%MVIC)</th> </tr> </thead> <tbody> <tr> <td>Dumbbell Lateral</td> <td>88.4 ± 14.1</td> <td>58.9 ± 9.4</td> <td>38.7 ± 7.2</td> <td>62.4 ± 11.8</td> </tr> <tr> <td>Cable Lateral</td> <td>79.3 ± 12.7</td> <td>67.2 ± 10.8</td> <td>35.4 ± 6.8</td> <td>55.1 ± 10.3</td> </tr> <tr> <td>Scaption</td> <td>82.1 ± 13.2</td> <td>64.4 ± 10.1</td> <td>41.2 ± 7.8</td> <td>44.3 ± 8.7</td> </tr> <tr> <td>Thumbs-Down</td> <td>85.7 ± 13.9</td> <td>60.1 ± 9.7</td> <td>42.8 ± 8.1</td> <td>71.2 ± 13.4</td> </tr> <tr> <td>Thumbs-Up</td> <td>83.2 ± 13.4</td> <td>59.8 ± 9.5</td> <td>37.1 ± 6.9</td> <td>58.3 ± 11.1</td> </tr> </tbody> </table> <p><strong>Scaption and Supraspinatus Loading</strong></p> <p>Scaption produced lateral deltoid activation (mean 64.4 ± 10.1% MVIC) that was not significantly different from either the dumbbell (p = 0.24) or cable (p = 0.31) conditions, confirming that shifting the plane of elevation approximately 30 degrees anteriorly does not penalize lateral deltoid recruitment. Crucially, supraspinatus activation during scaption (44.3 ± 8.7% MVIC) was significantly lower than during frontal plane dumbbell lateral raises (62.4 ± 11.8% MVIC; p = 0.002). Because supraspinatus is a key contributor to subacromial space compression during shoulder abduction, lower supraspinatus activation in the scapular plane likely corresponds to reduced impingement stress [6].</p> <p><strong>The Thumbs-Down Technique</strong></p> <p>The internal rotation (thumbs-down) technique did not produce significantly greater lateral deltoid activation compared to the neutral condition (85.7 ± 13.9 vs. 88.4 ± 14.1% MVIC for peak; p = 0.51). However, this condition did produce significantly higher supraspinatus activation (71.2 ± 13.4% MVIC) — the highest of all five conditions — and was associated with narrowing of the subacromial space based on kinematic modeling. These findings provide no support for the thumbs-down technique as a means of improving lateral deltoid recruitment and suggest it may increase impingement risk without benefit.</p> <p><strong>Anterior Deltoid Co-Activation</strong></p> <p>Anterior deltoid activation was moderate across all conditions (35–43% MVIC), with no significant differences between conditions (p = 0.18). This confirms that the lateral raise, regardless of technique variation, does not preferentially stimulate the anterior deltoid and remains a lateral-dominant exercise at standard sub-maximal loads.</p> <p><strong>Practical Synthesis</strong></p> <p>These data support a case for cable lateral raises as the superior training tool when total-range stimulation is prioritized, while dumbbell variations remain appropriate for peak contraction emphasis. Scaption offers equivalent lateral deltoid stimulus with improved shoulder health profile. The thumbs-down technique should be avoided based on elevated impingement risk without corresponding benefit.</p>

Practical Applications

<h2>Practical Applications</h2> <p><strong>Equipment Selection: Cable vs. Dumbbell</strong></p> <p>The choice between cable and dumbbell lateral raises should be guided by training objectives:</p> <ul> <li><strong>Cable lateral raise</strong>: Preferred for overall lateral deltoid development due to uniform tension across the full <a href="/terms/range-of-motion/" class="term-link" data-slug="range-of-motion" title="range of motion">range of motion</a>. The constant low-end tension effectively stimulates muscle throughout the entire arc, providing superior total mechanical work per set. Use for primary lateral deltoid volume.</li> <li><strong>Dumbbell lateral raise</strong>: Useful for peak contraction emphasis at the top of the movement (60–90-degree range). Suitable as a secondary or finishing exercise. Easier to implement without equipment access to a cable machine.</li> <li><strong>Recommendation</strong>: Include cable lateral raises as the primary lateral deltoid exercise, supplemented with dumbbell variations for variety and peak contraction work.</li> </ul> <p><strong>Plane of Elevation: Scaption for Shoulder Health</strong></p> <p>Training clients and athletes with any history of shoulder impingement, rotator cuff irritation, or subacromial bursitis should be directed toward scaption (scapular plane elevation, approximately 30 degrees forward of the frontal plane) rather than pure frontal plane abduction. The equivalent lateral deltoid activation with reduced supraspinatus loading makes scaption the shoulder-health-conscious default technique.</p> <p>Practical implementation of scaption: 1. Set up as a normal lateral raise, but angle the thumbs approximately 30 degrees forward (as <a href="/terms/intermittent-fasting/" class="term-link" data-slug="intermittent-fasting" title="if">if</a> holding a large tray in front of you) 2. Elevate the arms along this angled path, maintaining the same plane throughout 3. Stop at shoulder height (90 degrees) — no benefit from exceeding horizontal and elevated risk</p> <p><strong>Avoiding the Thumbs-Down Technique</strong></p> <p>Despite its persistence in bodybuilding culture, the internal rotation (thumbs-down) technique during lateral raises is not supported by evidence and may increase subacromial impingement risk. Practitioners should avoid teaching or performing this variation. The neutral wrist position (thumb forward, pinky slightly back, or flat neutral) is both safe and effective.</p> <p><strong>Loading and Repetition Range</strong></p> <p>Lateral deltoid development responds particularly well to moderate-to-high repetition ranges for several reasons:</p> <ul> <li>The relatively small <a href="/terms/cross-sectional-area/" class="term-link" data-slug="cross-sectional-area" title="cross-sectional area">cross-sectional area</a> of the lateral deltoid and its function as an isolation muscle make it appropriate for higher-rep <a href="/terms/metabolic-stress/" class="term-link" data-slug="metabolic-stress" title="metabolic stress">metabolic stress</a> training</li> <li>High-rep training (15–30 repetitions) allows sufficient volume accumulation without requiring loads that stress passive shoulder structures</li> <li>Cable lateral raises can be performed comfortably in the 15–25 rep range as "feeder" sets</li> </ul> <p>Recommended approach: - 4–5 sets of 12–20 repetitions per session - 2–3 sessions per week for lateral deltoid emphasis - Progress primarily by adding sets and repetitions before increasing load substantially</p> <p><strong>Common Technique Errors</strong></p> <ul> <li>Shrugging the shoulders (trapezius compensation): Keep shoulder blades down and back throughout</li> <li>Using body swing or momentum: Perform strict repetitions with controlled tempo; if momentum is required the load is too heavy</li> <li>Elevating above horizontal: The lateral deltoid's moment arm decreases above 90 degrees and the supraspinatus takes increased load at higher angles; stop at shoulder height</li> <li>Gripping too tightly: A relaxed grip reduces forearm flexor co-contraction and allows more isolated deltoid focus</li> </ul>