8.1 Muscular Strength vs Muscular Endurance
Whether associated with upper or lower body exercise, the concept of physical fitness is typically composed of the following five key elements (Healthline, 2022, para 3):
- Body Composition
- Cardiorespiratory Endurance
- Flexibility
- Muscular Strength
- Muscular Endurance
Comparing Muscular Strength and Endurance
When specifically examining upper body exercises, most of the benefits to one’s overall physical fitness are produced by improvements to both muscular strength and muscular endurance. While these two elements are quite similar and are often used synonymously, there are differences in how we can prioritize each of them through training.
| Item | Muscular Strength | Muscular Endurance |
|---|---|---|
| Definition (LifeFitness, 2024, para 3 & 4) | The ability to produce maximal force for short periods of time | The ability to produce lesser amounts of force for extended periods of |
| Weight/Resistance (Schoenfeld et al, 2021) | 80 to 100% 1RM | <60% 1RM |
| Repetitions (Schoenfeld et al, 2021) | 1 to 5 | 15+ |
| Muscle Fibres (Golden, 2025) | Large recruitment of fast-twitch (Type II) muscle fibres | Large recruitment of slow-twitch (Type I) muscle fibres |
| Energy Systems (Golden, 2025) | Primarily anaerobic | Increasingly aerobic as repetitions increase |
| Physiological Adaptations (Schoenfeld et al, 2021) | Training-related increases in neuromuscular efficiency (how well the nervous system recruits and contracts muscle fibres) and coordination contribute to increases in muscular strength | Training-related increases in metabolic activity (how efficiently oxygen can be delivered and used to create usable muscular energy) contribute to increases in muscular endurance |
This table does not include weight/resistance from 60 to 80% 1RM or repetitions between 6 and 14. Although both muscular strength and endurance can be improved using weights and repetitions that fall within these ranges, most repetition continuums define these ranges as prioritizing muscular hypertrophy (i.e., muscle growth). It is, however, important to note that although they provide approximate guidelines, repetition continuums may oversimplify the relationship between muscular strength, endurance, and hypertrophy. Each of these factors can be improved across a range of resistance and repetition schemes and is highly dependent on overall training volume and effort (Schoenfeld et al, 2021).
This information highlights the importance of incorporating a variety of resistance and repetition schemes into a training regimen if one is trying to maximize the benefits to their overall physical fitness.
Fitness Fact
Research by Helms et al (2018) and Krzysztofik et al. (2019) suggests that hypertrophy can occur (muscle can be built) with sets as high as 30+ repetitions as long as an individual is nearing muscular failure (the point at which another repetition is not possible) when completing their final repetitions of a given set. Nearing muscular failure is typically defined as having 1 to 4 repetitions in reserve, meaning an individual is 1 to 4 repetitions away from muscular failure.
