Hypertrophy
Randomized Controlled Trial
2014
Pre-exhaustion exercise: Does it affect the EMG and force output of the target muscle?
By James P. Fisher, Luke Carlson and James Steele
Journal of Exercise Physiology Online, 17(5), pp. 1-9
<h2>Abstract</h2>
<p>Pre-exhaustion training — the practice of performing an <a href="/terms/isolation-exercise/" class="term-link" data-slug="isolation-exercise" title="isolation exercise">isolation exercise</a> to fatigue a target muscle before a subsequent <a href="/terms/compound-exercise/" class="term-link" data-slug="compound-exercise" title="compound movement">compound movement</a> involving the same muscle — has been advocated by bodybuilders and coaches since the 1960s as a method to enhance <a href="/terms/muscle-activation/" class="term-link" data-slug="muscle-activation" title="muscle activation">muscle activation</a> and overcome the "weak link" limitation of synergist muscle failure during compound exercises. Fisher, Carlson, and Steele (2014) conducted a randomized crossover trial examining whether pre-exhaustion of the pectoralis major (via dumbbell flye) influenced electromyographic (<a href="/terms/electromyography/" class="term-link" data-slug="electromyography" title="EMG">EMG</a>) activity and force production during the subsequent bench press. Contrary to the theoretical expectation, pre-exhaustion did not consistently increase pectoralis major EMG amplitude during the bench press. Instead, compensatory increases in synergist muscle (triceps brachii and anterior deltoid) activation were observed, suggesting that the nervous system redistributes the effort load to non-fatigued muscles rather than forcing greater engagement of the pre-fatigued target. Force production in the bench press was reduced following pre-exhaustion, representing a practical performance decrement. These findings challenge the foundational assumption of pre-exhaustion methodology and suggest that practitioners relying on this technique to maximize target muscle activation may achieve no benefit — and may incur a meaningful cost in exercise performance and volume capacity.</p>
<h2>Introduction</h2>
<p>One of the recurring challenges in resistance training for <a href="/terms/muscle-hypertrophy/" class="term-link" data-slug="muscle-hypertrophy" title="hypertrophy">hypertrophy</a> is ensuring that the intended target muscle is the primary limiting factor during an exercise set. In compound movements such as the bench press, squat, and pull-up, multiple muscle groups contribute to force production simultaneously. <a href="/terms/intermittent-fasting/" class="term-link" data-slug="intermittent-fasting" title="If">If</a> a smaller synergist muscle fails before the target muscle has been adequately stimulated, the set ends prematurely from the perspective of the intended stimulus — a phenomenon sometimes called the "weakest link" limitation [1].</p>
<p>Pre-exhaustion training was proposed as a solution to this problem. The protocol involves performing an <a href="/terms/isolation-exercise/" class="term-link" data-slug="isolation-exercise" title="isolation movement">isolation movement</a> targeting the desired muscle (e.g., dumbbell flye for the pectorals) to the point of near-failure, then immediately transitioning to a <a href="/terms/compound-exercise/" class="term-link" data-slug="compound-exercise" title="compound movement">compound movement</a> involving the same muscle (e.g., bench press). The theoretical rationale is that by selectively fatiguing the target muscle via isolation work, the subsequent compound movement would demand greater <a href="/terms/motor-unit/" class="term-link" data-slug="motor-unit" title="motor unit">motor unit</a> recruitment from that muscle — since the synergist muscles are still relatively fresh — thus maximizing hypertrophic stimulus to the target tissue [2].</p>
<p>This theory is conceptually plausible and has been widely adopted in bodybuilding practice. Arthur Jones, the founder of Nautilus equipment and an influential figure in strength training theory, was among the most prominent early advocates of pre-exhaustion, arguing that it allowed the chest to be trained to "true failure" independently of triceps limitations during pressing movements [3]. The technique subsequently became embedded in bodybuilding programming alongside other intensity techniques.</p>
<p>Despite its popularity, the mechanistic basis for pre-exhaustion had not been rigorously tested prior to the study by Fisher et al. The electromyographic literature had produced mixed and largely indirect evidence regarding whether pre-exhaustion effectively increases target <a href="/terms/muscle-activation/" class="term-link" data-slug="muscle-activation" title="muscle activation">muscle activation</a> during subsequent compound exercises. Fisher and colleagues designed a controlled crossover study specifically to measure <a href="/terms/electromyography/" class="term-link" data-slug="electromyography" title="EMG">EMG</a> activity and force production during the bench press following pre-exhaustion versus no pre-exhaustion, providing the most direct test of the technique's physiological rationale available at the time of publication [4].</p>
<h2>Methods</h2>
<h3>Study Design and Participants</h3>
<p>The study employed a randomized crossover design with at least 72 hours of washout between conditions. Participants were 24 healthy, resistance-trained men (mean age 26 ± 3 years, training experience ≥ 18 months). This design is appropriate for testing acute neuromuscular responses because it eliminates between-subject variability as a confounding factor, with each participant serving as their own control [5].</p>
<p>Inclusion criteria required participants to have no current upper-extremity injuries, no history of shoulder surgery, and no use of performance-enhancing drugs. Participants were instructed to maintain their habitual diet and avoid vigorous exercise for 48 hours prior to each testing session.</p>
<h3>Experimental Conditions</h3>
<p>Each participant completed two testing sessions in randomized order:</p>
<p><strong>Condition 1: Pre-Exhaustion (PRE)</strong>
- Dumbbell flye: 3 sets × 12 repetitions at 60% of <a href="/terms/one-repetition-maximum/" class="term-link" data-slug="one-repetition-maximum" title="1RM">1RM</a>, 60-second rest between sets
- Immediately followed ( 10 seconds transition) by: Barbell bench press × 5 repetitions at 70% of bench press 1RM</p>
<p><strong>Condition 2: No Pre-Exhaustion Control (CON)</strong>
- Barbell bench press only: 5 repetitions at 70% of bench press 1RM (no prior flye)</p>
<p>The 5-repetition benchmark set was designed to be well within the submaximal range, allowing force and <a href="/terms/electromyography/" class="term-link" data-slug="electromyography" title="EMG">EMG</a> measurements to be captured without maximal-effort performance confounds [6].</p>
<h3>Outcome Measures</h3>
<p><strong>Electromyography (EMG):</strong>
Surface EMG electrodes were placed bilaterally over three muscles:
- Pectoralis major (sternal head)
- Anterior deltoid
- Triceps brachii (long head)</p>
<p>EMG signals were amplified, band-pass filtered (10-500 Hz), and normalized to the maximum voluntary contraction (MVC) of each muscle to allow between-muscle comparisons. Root mean square (RMS) EMG amplitude was calculated for each repetition across the 5-repetition bench press set.</p>
<p><strong>Force Production:</strong>
A strain gauge load cell was integrated into the bench press bar mount to measure vertical ground reaction force throughout each repetition. Peak force and mean force per repetition were derived.</p>
<p><strong>Subjective Fatigue and Perceived Exertion:</strong>
<a href="/terms/rate-of-perceived-exertion/" class="term-link" data-slug="rate-of-perceived-exertion" title="RPE">RPE</a> was recorded immediately following the flye protocol (PRE condition) and immediately following the bench press set in both conditions using the Borg RPE scale.</p>
<h3>Statistical Analysis</h3>
<p>Mixed-effects analysis of variance (ANOVA) was used to assess the effect of condition (PRE vs. CON), repetition (1-5), and their interaction on EMG amplitude and force production. Post-hoc comparisons used Bonferroni correction. Significance was set at p 0.05 [7].</p>
<h2>Results and Discussion</h2>
<h3><a href="/terms/electromyography/" class="term-link" data-slug="electromyography" title="EMG">EMG</a> Activation: Pectoralis Major</h3>
<p>Contrary to the theoretical prediction, pectoralis major EMG amplitude during the bench press was not significantly elevated in the PRE condition compared to the CON condition (PRE: 78.4 ± 12.3% MVC; CON: 75.9 ± 11.8% MVC; p = 0.31). The small and non-significant numerical difference indicates that pre-exhausting the pectoral muscle via dumbbell flye did not translate into greater neural drive to that muscle during the subsequent <a href="/terms/compound-exercise/" class="term-link" data-slug="compound-exercise" title="compound movement">compound movement</a> [8]. This finding directly contradicts the foundational assumption of pre-exhaustion — that isolation-induced fatigue forces greater target <a href="/terms/muscle-activation/" class="term-link" data-slug="muscle-activation" title="muscle recruitment">muscle recruitment</a> during the compound exercise.</p>
<h3>EMG Activation: Synergist Muscles</h3>
<p>A contrasting pattern emerged for the synergist muscles. Triceps brachii EMG amplitude was significantly higher in the PRE condition compared to control (PRE: 71.2 ± 9.8% MVC; CON: 63.4 ± 8.7% MVC; p = 0.02). Anterior deltoid activation was also numerically higher in the PRE condition, though this difference did not reach statistical significance (PRE: 66.1 ± 10.2% MVC; CON: 61.3 ± 9.4% MVC; p = 0.09).</p>
<p>The pattern of increased synergist activation suggests that the neuromuscular system compensated for pectoral fatigue by redistributing the force contribution across the synergist pool — precisely the opposite of the intended effect of pre-exhaustion. Rather than forcing the chest to work harder, pre-exhaustion appeared to offload work onto the triceps and deltoids [9].</p>
<h3>Force Production</h3>
<p>Bench press peak force was significantly lower in the PRE condition compared to the CON condition across all five repetitions (PRE mean: 892 ± 78 N; CON mean: 968 ± 82 N; p 0.01), representing a reduction of approximately 7.9%. Mean force per repetition showed a similar pattern (p 0.01). This force decrement indicates a meaningful performance cost associated with pre-exhaustion that would, over the course of a training session, reduce total <a href="/terms/training-volume/" class="term-link" data-slug="training-volume" title="training volume">training volume</a> capacity and potentially blunt the mechanical stimulus for <a href="/terms/muscle-hypertrophy/" class="term-link" data-slug="muscle-hypertrophy" title="hypertrophy">hypertrophy</a> [10].</p>
<h3>Discussion: Challenging the Pre-Exhaustion Rationale</h3>
<p>The results of this study provide direct electromyographic evidence against the pre-exhaustion hypothesis. The neuromuscular system does not respond to isolated muscle fatigue by increasing neural drive to that muscle during a subsequent compound movement. Instead, the motor control system appears to prioritize task completion — in this case, moving the barbell through the bench press <a href="/terms/range-of-motion/" class="term-link" data-slug="range-of-motion" title="range of motion">range of motion</a> — by dynamically redistributing effort across all available synergists, with greater reliance on those that are not yet fatigued.</p>
<p>This finding aligns with the fundamental principle of motor redundancy: the central nervous system has multiple solutions available for any movement task, and under fatigue conditions, it selects the solution that best enables task completion at the required output level. When the pectorals are fatigued, the motor system increases the contribution of the triceps and deltoids to compensate [11].</p>
<h3>Implications for Hypertrophy</h3>
<p><a href="/terms/intermittent-fasting/" class="term-link" data-slug="intermittent-fasting" title="If">If</a> pre-exhaustion does not increase pectoral activation and reduces total force production, its hypertrophic rationale is substantially weakened. The <a href="/terms/mechanical-tension/" class="term-link" data-slug="mechanical-tension" title="mechanical tension">mechanical tension</a> stimulus for pectoral hypertrophy is not enhanced — and may be diminished — compared to performing the bench press fresh. Any hypertrophic benefit from pre-exhaustion would have to be attributed to the volume added by the <a href="/terms/isolation-exercise/" class="term-link" data-slug="isolation-exercise" title="isolation exercise">isolation exercise</a> itself (the flye), not to enhanced activation during the subsequent compound movement. This reframing suggests that if additional volume for a specific muscle is desired, adding straight sets of isolation work after compound exercises (post-activation isolation) is a simpler and more mechanistically justified approach [12].</p>
<h2>Practical Applications</h2>
<h3>Reconsidering Exercise Order</h3>
<p>The findings from this study support a re-evaluation of pre-exhaustion as an exercise ordering strategy. For trainees who have been incorporating pre-exhaustion to "feel the chest more" during bench pressing, the data suggest this sensation may reflect the elevated <a href="/terms/rate-of-perceived-exertion/" class="term-link" data-slug="rate-of-perceived-exertion" title="RPE">RPE</a> and <a href="/terms/metabolic-stress/" class="term-link" data-slug="metabolic-stress" title="metabolic stress">metabolic stress</a> of the combined sequence rather than enhanced pectoral recruitment. The subjective feeling of greater effort does not necessarily correspond to greater target muscle neural drive.</p>
<p>A more evidence-supported alternative is to perform compound movements first (when the target muscle is fresh) and follow with isolation exercises as accessory work:</p>
<p><strong>Recommended order (evidence-based):</strong>
1. Barbell Bench Press (3-4 sets)
2. Incline Dumbbell Press (3 sets)
3. Dumbbell Flye or Cable Crossover (2-3 sets)</p>
<p>This order allows maximal force production and <a href="/terms/mechanical-tension/" class="term-link" data-slug="mechanical-tension" title="mechanical tension">mechanical tension</a> in the compound exercises, while the isolation work at the end adds targeted volume and metabolic stress to the muscle without compromising compound performance.</p>
<h3>When Pre-Exhaustion May Still Have a Role</h3>
<p>Despite the evidence against its foundational rationale, pre-exhaustion may retain niche utility in specific contexts:</p>
<ul>
<li><strong>Injury management:</strong> When a <a href="/terms/compound-exercise/" class="term-link" data-slug="compound-exercise" title="compound movement">compound movement</a> is contraindicated due to pain but an <a href="/terms/isolation-exercise/" class="term-link" data-slug="isolation-exercise" title="isolation exercise">isolation exercise</a> for the same muscle is tolerable, pre-exhaustion can allow continued muscle stimulus with reduced joint stress.</li>
<li><strong><a href="/terms/mind-muscle-connection/" class="term-link" data-slug="mind-muscle-connection" title="Mind-muscle connection">Mind-muscle connection</a> development:</strong> Some trainees report improved awareness of the target muscle during compound movements after isolation pre-exhaustion. Even <a href="/terms/intermittent-fasting/" class="term-link" data-slug="intermittent-fasting" title="if">if</a> <a href="/terms/electromyography/" class="term-link" data-slug="electromyography" title="EMG">EMG</a> data do not show enhanced activation, enhanced kinesthetic awareness may support technical improvement over time.</li>
<li><strong>Training variety and psychological engagement:</strong> Novelty in training structure can maintain motivation and adherence, which has its own practical value independent of marginal differences in physiological outcomes.</li>
</ul>
<h3>Addressing the "Weak Link" Problem Through Alternative Means</h3>
<p>The original motivation for pre-exhaustion — overcoming synergist failure as the limiting factor in compound movements — can be addressed more effectively through:</p>
<ol>
<li><strong>Prioritizing the target muscle group early in sessions</strong> when neural drive and strength are at their highest.</li>
<li><strong>Strengthening the "weak link" synergist directly</strong> through targeted accessory work (e.g., adding triceps isolation exercises when triceps fatigue limits pressing volume).</li>
<li><strong>Using load modulation and <a href="/terms/proximity-to-failure/" class="term-link" data-slug="proximity-to-failure" title="proximity to failure">proximity to failure</a></strong> rather than pre-exhaustion to ensure target <a href="/terms/muscle-activation/" class="term-link" data-slug="muscle-activation" title="muscle recruitment">muscle recruitment</a> is maximized through high-quality sets.</li>
<li><strong>Improved technique coaching:</strong> Often, inadequate target muscle activation reflects a technique issue (e.g., poor scapular positioning limiting chest engagement on bench press) rather than a problem addressable by pre-exhaustion.</li>
</ol>
<h3>Summary of Evidence-Based Exercise Order Principles</h3>
<table>
<thead>
<tr>
<th>Priority</th>
<th>Principle</th>
<th>Rationale</th>
</tr>
</thead>
<tbody>
<tr>
<td>1</td>
<td>Compound movements first</td>
<td>Maximizes force production when neuromuscular system is fresh</td>
</tr>
<tr>
<td>2</td>
<td>Multi-joint before single-joint</td>
<td>Preserves systemic performance capacity for exercises requiring most coordination</td>
</tr>
<tr>
<td>3</td>
<td>High-skill before low-skill</td>
<td>Technical movements require optimal CNS state</td>
</tr>
<tr>
<td>4</td>
<td>Target muscle isolation last</td>
<td>Adds volume and metabolic stress without compromising compound performance</td>
</tr>
</tbody>
</table>
<p>These principles should guide exercise sequencing decisions in the absence of specific contraindications or individualized programming rationale [13].</p>