Hypertophy

Hypertrophy: Hypertrophy is an increase in muscle mass/size due to an increase in the volume and cross-sectional area (CSA) of individual muscle cells. The increase in cross-sectional area can be attributed to an increase in contractile proteins and structural elements (myofibrillar hypertrophy), as well as an increase in glycogen storage and elements related to metabolism (sarcoplasmic hypertrophy). Hypertrophy is an adaptation of both cardiac and skeletal muscle fibers in response to progressive increases in workload.

Semantic Clarification

Hypertrophy vs. hyperplasia

• Muscle hypertrophy: Increase in size of existing muscle fibers, typically measured as fiber cross-sectional area or muscle thickness. Hypertrophy is the primary mechanism of muscle growth in response to resistance training and other forms of exercise.
• Muscle hyperplasia: Increase in the number of muscle fibers. Animal models suggest hyperplasia can occur under extreme conditions; evidence in humans is limited and controversial.

Myofibrillar vs. sarcoplasmic hypertrophy

• Myofibrillar hypertrophy: Growth driven mainly by increased contractile protein content (actin and myosin) and myofibril packing. This is considered the dominant contributor to strength-relevant muscle growth. PMC+1
• Sarcoplasmic hypertrophy: Disproportionate expansion of non-contractile components (sarcoplasm, enzymes, glycogen, fluid). Some high-volume protocols may transiently favor sarcoplasmic expansion, but current evidence suggests it is not a separate, superior “type” of growth; myofibrillar accretion remains central for long-term strength and function.

Normal vs. pathological hypertrophy

• Normal (physiological) hypertrophy: Physiological hypertrophy is the adaptive enlargement of skeletal muscle in response to growth, resistance training, and other repeated mechanical loading, supported by adequate nutrition and recovery. Strength, work capacity, and metabolic health generally improve in conjunction with gains in size, and the underlying muscle architecture remains organized. Normal hypertrophy also occurs in other tissues (for example, “athlete’s heart” in endurance and strength athletes). In the heart, physiological hypertrophy is characterized by preserved or enhanced cardiac function and a balanced increase in chamber size and wall thickness without fibrosis or clinical dysfunction.
• Pathological hypertrophy: Pathological hypertrophy refers to enlargement of muscle or organs that are driven by disease processes or chronic, non-resolving stress, and is often accompanied by impaired function. In the heart, pathological hypertrophy is associated with fibrosis, altered cell signaling, and an increased risk of heart failure, arrhythmias, and adverse cardiovascular events, even though the myocardium is larger.

Hypertrophy vs. strength

• Hypertrophy: Morphological change (bigger muscle fibers).
• Strength: Functional outcome (force production), influenced by hypertrophy, neural adaptations, tendon and connective tissue properties, and skill. Hypertrophy supports strength gains over time, but early strength changes are often dominated by neural adaptations.

Frequently Asked Questions (FAQs)

Is hypertrophy just “muscle growth”?

• Yes. In common fitness language, hypertrophy essentially means muscle growth. More formally, it refers to an increase in muscle fiber cross-sectional area and overall muscle mass, rather than an increase in fiber number (hyperplasia).

Do I have to train in the “8–12 rep range” to build hypertrophy?

• No. Hypertrophy can be achieved across a wide range of loads and repetitions, from ~5 reps per set up to 20+ reps, as long as sets are challenging and progressively overloaded. Classic 8–12 rep recommendations may be slightly more effective; however, higher and lower loads may result in similar benefits when sets are performed with similar effort and to volitional failure.

Is training to failure required for hypertrophy.

• Not in every set. Taking some sets to failure can be useful, but meta-analytic evidence suggests that training close to failure (often leaving 1–3 reps in reserve) can produce similar hypertrophy, with less fatigue and better recovery for many individuals.

Does more volume always mean more hypertrophy?

• Only up to a point. Studies show a dose-response relationship between weekly set volume and hypertrophy, but returns diminish and may reverse if volume exceeds the individual’s ability to recover. Effective volumes vary by training status, muscle group, and other stressors (e.g., sport practice, life stress, sleep). PubMed+2Ageing Muscle+2

What is the difference between “myofibrillar” and “sarcoplasmic” hypertrophy, and should I train for one specifically?

• Myofibrillar hypertrophy reflects increased contractile protein and is strongly linked to strength and performance. Sarcoplasmic hypertrophy describes the expansion of non-contractile components (e.g., glycogen, enzymes). Although some protocols may temporarily bias sarcoplasmic expansion, current evidence does not support distinct “types” of training that permanently separate one from the other or make sarcoplasmic hypertrophy a preferred target. Practical programming should focus on progressive overload, sufficient volume, and effort, rather than chasing a specific “type” of hypertrophy.

How long does it take to see hypertrophy?

• Measurable hypertrophy in trained individuals often appears over 6–12+ weeks of consistent training, with realistic gains on the order of 1-2 kg (3 - 4 pounds) of fat-free mass in that timeframe, depending on training status, genetics, nutrition, and adherence. Early strength gains may occur faster, but are not solely due to hypertrophy.

Can you gain strength without hypertrophy (or vice versa)?

• Yes. Early strength gains are primarily neural and can occur with minimal visible hypertrophy. Conversely, muscle size can increase with relatively small changes in maximal strength if training emphasizes volume and local fatigue over increasing maximal strength. Over months and years, however, greater hypertrophy generally supports higher strength potential.

Brookbush Institute's Hypertrophy Training Model: Comprehensively Evidence-based and Outcome-driven

1. Tempo: 2 or more seconds eccentric: 0-2 seconds isometric: maximum velocity or longer concentric (2+: 0-2: MaxV+)
2. Reps-to-Failure/set: Ideal for hypertrophy, unless the individual is also an athlete performing high-volume training.
3. Reps and Load:
   1. Most: Moderate: 8 - 12 RM/set (70 - 80% of 1-RM)
   2. Some: Heavy: 3 - 8 RM/set (80 - 95% of 1-RM)
   3. A little: Light 12 - 25 RM/set (50 - 70% of 1-RM).
   4. Avoid: Very Heavy: 1-2 RM/set (95 - 100% of 1-RM)
   5. Avoid: Very Light: 25 or more RM/set (≤50% of 1-RM).
4. Range of Motion (ROM): Exercise should be performed with the largest ROM that can be performed without pain and with good form (That is, form that is free from signs correlated with dysfunction, injury, or pain). However, increasing load to improve strength and hypertrophy is likely to be beneficial, even if it results in a temporary reduction in exercise ROM.
5. Rest Between Sets and Circuits: Moderate (2 min) to long (3 min) rest between sets for similar muscle groups, or circuit training with short (30-60 sec) rest between exercises
6. Set strategies: Drop sets are recommended as a progression for advanced exercisers who can benefit from higher exercise volumes (currently performing 3 or more conventional sets/muscle group).
   • Agonist/antagonist supersets or circuit training are recommended to increase workout efficiency.
7. Sets/Muscle Group/Session: A progressive increase from 1-5 sets/muscle group/session
   1. Novice Exercisers (6-12 weeks): 1 - 2 sets/upper body muscle group, 2-3 sets/lower body muscle group
   2. Experienced Exercisers: 2-5 sets
   3. Supersets and Drop-sets: 1-4 sets
8. Training Frequency:
   • General recommendation: 1.5 - 3 sessions/muscle group/week and 2-5 days rest between sessions
     • Starting a new routine: 3 sessions/muscle group/2 weeks and 3 - 7 days rest between sessions. Alternatively, consider scheduling "de-loading weeks" after the first session of a new routine (not the last session of a routine).
     • Initial Training Period (8-12 weeks): 1 - 3 sessions/muscle group/week
     • Maintenance: 1-2 sessions/muscle group/week
     • High-volume (Advanced) Training: 4 or more resistance-training sessions/week require split routines.
9. Recommended Training Splits:
   • 1 - 2 days/week = total body
   • 3 days/week = total body or upper/lower split
   • 4 days/week = upper/lower split
   • 5 - 6 days a week (not recommended for resistance training) = Upper/lower/recovery split or Push/Pull/Legs
10. Periodization for Hypertrophy
    • Maximize exposure to goal-specific acute variables: Most time spent with moderate loads, followed by heavy loads, with some lighter load training when necessary to reduce intensity or introduce a new stimulus. Note that drop sets may reduce the need for light-load/high-rep training.
    • Load adjustments: Auto-regulated, frequent, adaptive intra-session or session-to-session load adjustments. Increase load when more reps than the upper limit of the rep range can be performed, and decrease load if the lower limit of the rep range can not be performed.
    • Novice Exercisers: Periodization will not result in better outcomes for at least the initial 12 weeks. Perform moderate loads and reps/set with auto-regulated load adjustments.
    • Experienced Exercisers: True linear periodization with daily undulation is likely the most effective strategy. Although block periodization is unlikely to result in additional benefits, it can be helpful to organize a training program into phases and then blend those phases with a linear progression of loads.
      • Recommended progressions
        • True linear periodization (frequent, auto-regulated load adjustments), with moderate loads
        • True linear periodization (frequent, auto-regulated load adjustments), with moderate loads and the addition of drop sets.
        • True linear periodization with daily undulation (moderate and heavy days), with intermittent periods of light load training or incorporating light load days.
        • True linear periodization with daily undulation, including a high volume day of moderate loads with drop sets, and a low volume day of more total sets with heavy loads, with intermittent periods of light load training or incorporating light load days.
11. Exercise Selection: Moderately stable exercise and progressions that can be performed with sufficient loads, and periodic change (e.g., 1 time/4-12 weeks) in exercise selection as set performance goals are reached.
12. Exercise Order:
    • Start with your most important exercises
    • Start with large muscle groups and multi-joint movements
    • When priorities are equal, perform upper-body exercises before lower-body exercises
    • Program back exercises before chest when both are trained in the same routine
    • Perform strength training before aerobic training
    • To optimize performance on a key lift, avoid training similar muscles in the same session

Additional Content

Additional Courses

• Hypertrophy Training: Evidence-based Model

Additional Articles:

• Drop Sets: Comprehensive Systematic Review and Training Recommendations
• Circuit Training for Hypertrophy, Strength, and Power?
• Is 3 Sets per Muscle Group the Upper Limit?

Additional Glossary Terms

• Drop sets
• Lengthened partials