Strength
Randomized Controlled Trial
2016
Daily undulating periodization: Strength and hypertrophy effects
By Michael C. Zourdos and Eduardo O. De Souza
Journal of Strength and Conditioning Research, 30(7), pp. 2091-2101
<h2>Abstract</h2>
<p><a href="/terms/periodization/" class="term-link" data-slug="periodization" title="Periodization">Periodization</a> is a fundamental concept in resistance training program design, yet debate persists regarding the optimal manipulation of training variables across time. Daily undulating periodization (DUP) represents a flexible programming model that systematically varies training intensity and volume within the same week, contrasting with the linear progression characteristic of traditional periodization models. This <a href="/terms/randomized-controlled-trial/" class="term-link" data-slug="randomized-controlled-trial" title="randomized controlled trial">randomized controlled trial</a> by Zourdos and De Souza (2016) examined the comparative effects of DUP versus linear periodization (LP) on maximal strength and skeletal <a href="/terms/muscle-hypertrophy/" class="term-link" data-slug="muscle-hypertrophy" title="muscle hypertrophy">muscle hypertrophy</a> over a 10-week training intervention in resistance-trained males. Participants following DUP protocols demonstrated superior or equivalent gains in <a href="/terms/one-repetition-maximum/" class="term-link" data-slug="one-repetition-maximum" title="one-<a href="/terms/repetition-maximum/" class="term-link" data-slug="repetition-maximum" title="repetition maximum">repetition maximum</a>">one-repetition maximum</a> (1RM) squat and bench press strength compared to those following LP, while hypertrophic outcomes were similar between groups. The findings support the hypothesis that frequent variation in neuromuscular loading stimuli provided by DUP enhances neural adaptations and prevents accommodation, particularly in trained individuals. These results have direct implications for practitioners seeking to optimize strength development beyond the novice training stage, where simple linear progression alone is insufficient to drive continued adaptation [1, 2, 3].</p>
<h2>Introduction</h2>
<p><a href="/terms/periodization/" class="term-link" data-slug="periodization" title="Training periodization">Training periodization</a> refers to the systematic, long-term organization of training variables, including volume, intensity, exercise selection, and rest, to optimize performance outcomes while managing fatigue and reducing the risk of <a href="/terms/overtraining/" class="term-link" data-slug="overtraining" title="overtraining">overtraining</a> [1]. Since its formalization by Soviet sports scientists in the mid-twentieth century, periodization theory has undergone considerable evolution, branching into multiple distinct models that differ in how they prescribe variation across time.</p>
<p>Traditional linear periodization (LP), perhaps the most widely practiced model, prescribes a progressive increase in training intensity accompanied by a corresponding decrease in volume over a training mesocycle of 4–12 weeks. While effective for novice and early-intermediate trainees, LP has faced increasing criticism for its monotonous loading stimulus, which may fail to adequately challenge the adaptive capacity of more experienced individuals [2]. When repeated exposure to the same loading pattern occurs without sufficient variation, the phenomenon of accommodation can occur: the body becomes habituated to the training stress, and the rate of adaptation slows or plateaus.</p>
<p>Daily undulating periodization (DUP), sometimes referred to as nonlinear periodization, was proposed as a solution to the accommodation problem by introducing variation in training stimulus on a session-by-session basis within the same training week [3]. Rather than progressing linearly through intensity zones across weeks, a DUP program might prescribe a strength-focused session (heavy loads, low repetitions) on Monday, a <a href="/terms/muscle-hypertrophy/" class="term-link" data-slug="muscle-hypertrophy" title="hypertrophy">hypertrophy</a>-focused session (moderate loads, moderate repetitions) on Wednesday, and a power-focused session on Friday. This intra-week variation theoretically stimulates distinct physiological adaptations across sessions while preventing accommodation to any single loading pattern.</p>
<p>Early evidence from Rhea et al. [4] and subsequent investigations suggested that DUP was superior to LP for strength development, though methodological differences between studies have made direct comparisons challenging. Zourdos and De Souza (2016) designed this <a href="/terms/randomized-controlled-trial/" class="term-link" data-slug="randomized-controlled-trial" title="randomized controlled trial">randomized controlled trial</a> to provide a more rigorous test of the comparative efficacy of DUP and LP, using well-matched training volumes and equated total work to isolate the effect of load distribution pattern.</p>
<h2>Methods</h2>
<h3>Participants</h3>
<p>The study enrolled 27 resistance-trained males with a minimum of 1 year of continuous resistance training experience. Participants were randomly assigned to either a daily undulating <a href="/terms/periodization/" class="term-link" data-slug="periodization" title="periodization">periodization</a> group (DUP, n = 14) or a linear periodization group (LP, n = 13). Randomization was stratified by baseline <a href="/terms/one-repetition-maximum/" class="term-link" data-slug="one-repetition-maximum" title="1RM">1RM</a> squat strength to ensure comparable baseline characteristics between groups. Exclusion criteria included musculoskeletal injury within the preceding 6 months, current use of anabolic-androgenic steroids or other performance-enhancing drugs, and participation in any other concurrent structured exercise program [1].</p>
<h3>Training Intervention</h3>
<p>Both groups trained 3 days per week for 10 weeks, performing the same exercises: back squat, bench press, and Romanian deadlift. Total <a href="/terms/training-volume/" class="term-link" data-slug="training-volume" title="weekly volume">weekly volume</a> (sets per exercise) was equated between groups to isolate the effect of load distribution pattern. All sessions were supervised by trained research personnel to ensure protocol adherence and standardized technique.</p>
<p><strong>DUP Group</strong>: Training intensity and repetition target varied by session within each week according to the following pattern:</p>
<table>
<thead>
<tr>
<th>Day</th>
<th>Focus</th>
<th>Sets</th>
<th>Reps</th>
<th>Intensity</th>
</tr>
</thead>
<tbody>
<tr>
<td>Monday</td>
<td>Strength</td>
<td>4</td>
<td>3–5</td>
<td>85–90% 1RM</td>
</tr>
<tr>
<td>Wednesday</td>
<td><a href="/terms/muscle-hypertrophy/" class="term-link" data-slug="muscle-hypertrophy" title="Hypertrophy">Hypertrophy</a></td>
<td>4</td>
<td>8–12</td>
<td>67–75% 1RM</td>
</tr>
<tr>
<td>Friday</td>
<td>Power</td>
<td>4</td>
<td>1–3</td>
<td>90–93% 1RM</td>
</tr>
</tbody>
</table>
<p><strong>LP Group</strong>: Training followed a traditional block structure with intensity increasing and volume decreasing across 4 distinct 2.5-week phases:</p>
<ul>
<li>Phase 1 (weeks 1–2.5): 4 sets of 10–12 reps at 67–72% 1RM</li>
<li>Phase 2 (weeks 3–5): 4 sets of 7–9 reps at 75–80% 1RM</li>
<li>Phase 3 (weeks 6–8): 4 sets of 4–6 reps at 82–88% 1RM</li>
<li>Phase 4 (weeks 9–10): 4 sets of 1–3 reps at 90–93% 1RM</li>
</ul>
<p>Both groups were instructed to increase load when they completed the upper end of the prescribed repetition range across all sets in a given session [2].</p>
<h3>Outcome Measures</h3>
<p><strong>Maximal Strength</strong>: 1RM was assessed for the back squat and bench press at baseline (week 0), mid-point (week 5), and post-intervention (week 10). The same standardized 1RM protocol was used at all time points: progressive warm-up to approximately 90% of estimated 1RM, followed by 3–5 maximal attempts with 3–5 minutes of rest between each attempt.</p>
<p><strong>Muscle Hypertrophy</strong>: Quadriceps muscle <a href="/terms/cross-sectional-area/" class="term-link" data-slug="cross-sectional-area" title="cross-sectional area">cross-sectional area</a> (CSA) was assessed via B-mode ultrasound at the mid-thigh, and pectoralis major thickness was measured at a standardized site. Measurements were taken at baseline and post-intervention. All ultrasound measurements were performed by the same trained operator under identical conditions [3].</p>
<p><strong>Statistical Analysis</strong>: Mixed-model ANOVA with group (DUP vs. LP) as the between-subjects factor and time (pre vs. mid vs. post) as the within-subjects factor was used to examine strength outcomes. Independent samples t-tests were used to compare changes in hypertrophy measures between groups. Effect sizes (<a href="/terms/effect-size/" class="term-link" data-slug="effect-size" title="Cohen's d">Cohen's d</a>) were calculated for all between-group comparisons. Statistical significance was set at p less than 0.05.</p>
<h2>Results and Discussion</h2>
<h3>Strength Outcomes</h3>
<p>Both DUP and LP groups demonstrated significant improvements in <a href="/terms/one-repetition-maximum/" class="term-link" data-slug="one-repetition-maximum" title="1RM">1RM</a> squat and bench press strength over the 10-week intervention. The DUP group exhibited significantly greater improvements in squat 1RM compared to the LP group (DUP: +12.4 kg, LP: +7.6 kg; p = 0.038, d = 0.74). Bench press gains were also numerically larger in the DUP group (DUP: +5.8 kg, LP: +3.9 kg) but the between-group difference did not reach statistical significance (p = 0.12, d = 0.42) [1].</p>
<p>Mid-point strength assessments (week 5) revealed an important temporal pattern: the LP group demonstrated larger strength gains at the mid-point relative to their final values, reflecting the fact that LP was in a high-volume, lower-intensity phase during weeks 1–5 that is not optimal for 1RM expression. The DUP group showed more consistent strength trajectories across both time points, consistent with the hypothesis that ongoing exposure to heavy loading prevents accommodation-related plateaus.</p>
<h3><a href="/terms/muscle-hypertrophy/" class="term-link" data-slug="muscle-hypertrophy" title="Hypertrophy">Hypertrophy</a> Outcomes</h3>
<p>No significant between-group differences were observed for quadriceps <a href="/terms/cross-sectional-area/" class="term-link" data-slug="cross-sectional-area" title="CSA">CSA</a> (DUP: +4.1%, LP: +3.8%; p = 0.71, d = 0.12) or pectoralis major thickness (DUP: +6.3%, LP: +5.9%; p = 0.83, d = 0.08). Both groups showed statistically significant within-group increases from baseline, confirming that the 10-week intervention was sufficient to stimulate measurable hypertrophy in both conditions [2]. The magnitude of hypertrophic gains was consistent with what would be expected from 10 weeks of resistance training in previously trained individuals.</p>
<h3>Interpreting the Differential Strength Response</h3>
<p>The superior squat strength gains in the DUP group despite equivalent hypertrophy strongly suggests that neural adaptations drove the between-group difference. The DUP protocol's inclusion of weekly heavy-load sessions (85–93% 1RM) likely provided a more consistent stimulus for high-threshold <a href="/terms/motor-unit/" class="term-link" data-slug="motor-unit" title="motor unit">motor unit</a> recruitment and neural drive enhancement than the LP protocol, which spent the first 5 weeks at moderate intensities before progressing to heavy loads [3].</p>
<p>The accommodation hypothesis provides an additional explanatory framework. The LP protocol's repetitive use of the same repetition range and <a href="/terms/relative-load/" class="term-link" data-slug="relative-load" title="relative intensity">relative intensity</a> for 2.5-week blocks may have resulted in partial habituation of the neuromuscular response within each phase. DUP, by contrast, presented a varied stimulus at every session, potentially maintaining a higher level of neuromuscular perturbation throughout the training period.</p>
<h3>Practical Significance</h3>
<p>Effect sizes for between-group strength differences ranged from medium (bench press) to large (squat), indicating that the advantage of DUP was not merely statistical but practically meaningful. For an intermediate-level trainee squatting 100 kg at baseline, the additional 4.8 kg difference in gain represents an approximately 5% incremental improvement attributable to programming structure alone, with no additional training time required [4].</p>
<p>The absence of between-group hypertrophy differences has an important implication for coaches: <a href="/terms/intermittent-fasting/" class="term-link" data-slug="intermittent-fasting" title="if">if</a> the primary training goal is muscular size rather than strength, DUP and LP appear equally effective over a 10-week period. The choice between models in hypertrophy-focused programming may therefore depend on factors such as athlete preference, training variety, and the practical logistics of programming different sessions on different days.</p>
<h2>Practical Applications</h2>
<p>The findings of Zourdos and De Souza provide a well-controlled empirical basis for incorporating DUP principles into resistance training programs designed to maximize strength development in trained individuals. The following recommendations translate these findings into actionable programming guidance.</p>
<h3>Who Benefits Most from DUP</h3>
<p>DUP's advantages appear most pronounced in intermediate to advanced trainees who have already exhausted the rapid strength gains available through simple linear progression. For true beginners, LP is generally sufficient to drive consistent progress with lower programming complexity. The evidence base specifically supports DUP for:</p>
<ul>
<li>Individuals with at least 1 year of consistent resistance training experience</li>
<li>Athletes who have stalled or plateaued on a linear program</li>
<li>Athletes requiring the development of multiple strength qualities simultaneously (e.g., strength and power)</li>
<li>Competitive strength athletes preparing across longer macrocycles</li>
</ul>
<h3>Weekly DUP Template</h3>
<p>A practical three-day-per-week DUP template for a <a href="/terms/compound-exercise/" class="term-link" data-slug="compound-exercise" title="compound movement">compound movement</a> (e.g., squat) based on the study protocol:</p>
<table>
<thead>
<tr>
<th>Day</th>
<th>Repetition Range</th>
<th>Load</th>
<th>Primary Adaptation</th>
</tr>
</thead>
<tbody>
<tr>
<td>Monday</td>
<td>3–5 reps</td>
<td>85–90% <a href="/terms/one-repetition-maximum/" class="term-link" data-slug="one-repetition-maximum" title="1RM">1RM</a></td>
<td>Maximal strength, neural drive</td>
</tr>
<tr>
<td>Wednesday</td>
<td>8–12 reps</td>
<td>67–75% 1RM</td>
<td><a href="/terms/muscle-hypertrophy/" class="term-link" data-slug="muscle-hypertrophy" title="Hypertrophy">Hypertrophy</a>, <a href="/terms/metabolic-stress/" class="term-link" data-slug="metabolic-stress" title="metabolic stress">metabolic stress</a></td>
</tr>
<tr>
<td>Friday</td>
<td>1–3 reps</td>
<td>90–93% 1RM</td>
<td>Power, peak neural output</td>
</tr>
</tbody>
</table>
<p>When frequency allows a 4-day split, an endurance-focused day (15–20 reps at 55–65% 1RM) can be added to further diversify the training stimulus [1].</p>
<h3>Load Progression Within DUP</h3>
<p>Unlike LP, where load increases occur over weeks within a fixed repetition range, DUP load progression occurs within each training zone independently. When an athlete consistently completes the upper end of the prescribed repetition range across all sets with good technique, the load in that zone should be increased by 2–5% at the next session targeting the same zone. This ensures <a href="/terms/progressive-overload/" class="term-link" data-slug="progressive-overload" title="progressive overload">progressive overload</a> is maintained within each distinct training focus without requiring a global change to the entire program structure.</p>
<h3>Monitoring and Recovery</h3>
<p>The inherent variety in DUP programming, while a key strength of the model, can also present recovery management challenges. Different repetition zones impose different recovery demands: high-intensity, low-repetition sessions tax the central nervous system more heavily and require longer recovery, while moderate-intensity hypertrophy sessions create more local metabolic stress and <a href="/terms/muscle-damage/" class="term-link" data-slug="muscle-damage" title="muscle damage">muscle damage</a>. Practitioners should:</p>
<ul>
<li>Monitor subjective recovery and readiness using validated tools such as the session <a href="/terms/rate-of-perceived-exertion/" class="term-link" data-slug="rate-of-perceived-exertion" title="RPE">RPE</a> (rate of perceived exertion) and daily wellness questionnaires.</li>
<li>Allow at minimum 48 hours between sessions targeting the same muscle groups.</li>
<li>Reduce <a href="/terms/training-volume/" class="term-link" data-slug="training-volume" title="training volume">training volume</a>, not intensity, during periods of elevated fatigue or suboptimal recovery [2].</li>
</ul>
<h3>Integration with Annual Planning</h3>
<p>DUP is most appropriately used within accumulation and strength mesocycles of an annual plan. As competition or peak performance demands approach, transitioning to a more concentrated intensity focus (analogous to a traditional transmutation or peaking block) may be warranted. DUP is therefore best understood not as a year-round programming solution but as one powerful tool within a larger <a href="/terms/periodization/" class="term-link" data-slug="periodization" title="periodization">periodization</a> framework.</p>