1 RM Calculator vs. Fiber Types Summary
- Using a 1 RM calculator can be beneficial when planning a periodized training program.
- A recent study investigated the relationship between muscle fiber types and the number of repetitions to failure during resistance training.
- The study found that slow-twitch (ST) individuals performed substantially higher total repetitions than fast-twitch (FT) individuals at 60% and 80% 1RM.
- Training at lower loads of 40% of a 1-RM induced more metabolic fatigue; however, no significant relationship was found between muscle fiber types and the total number of repetitions at 40% 1RM.
- The study suggests that muscle fiber types may play a role in determining individuals’ optimal training load and repetition range rather than a % 1RM. For example, ST individuals may benefit from higher repetition ranges. FT individuals may benefit from lower repetition ranges with heavier loads.
Introduction: 1RM Calculator and Muscle Growth
Muscle growth is a complex process many lifters and bodybuilders will use be guided by using a 1 Repetition Maximum (1RM) calculator. Volume is often expressed as the total number of repetitions performed per exercise, and load is typically expressed as a percentage of maximal strength (e.g., percentage of one-repetition maximum (%1RM). (Schoenfeld et al., 2021)
% 1RM or rep max is the “percentage of one-repetition maximum or single repetition.” It is a way to measure how much weight you should lift during resistance training strength exercises.
Let’s say you can lift a maximum of 100 pounds on the barbell bench press. If you were told to lift at 80% 1RM, you would lift 80 pounds. This is because 80% of your maximum weight is 80 pounds. So, % 1RM helps determine how much weight you should use to challenge your muscles during exercise. The percentage of one-repetition maximum (1RM) and one-rep max recommended for muscle hypertrophy (muscle growth) varies depending on the source. Still, a common recommendation is lifting weights about 60-80% of your 1RM.(Refalo et al., 2021)
This range is often recommended because it allows for a sufficient volume of work (number of sets and repetitions) while still providing a challenging load. Typically, this translates to the amount of weight you can lift for about 8-12 repetitions per set before reaching muscular failure.
However, you should note that you can achieve muscle hypertrophy outside of this range. Some studies indicate that if you lift lighter weights (30-60% of 1RM) for a higher number of reps (15-20 or more per set) and work your muscles to the point of fatigue or failure, you can also stimulate muscle growth. However, a recent study suggests an alternative approach based on individual muscle fiber types, which could yield better results than the traditional 1 RM chart or 1 RM Calculator. Use the 1 RM calculator at the top of the page.
Understanding Muscle Fiber Types: Beyond the 1RM Rep Calculator
Muscle fiber types, including Type I (slow-twitch) and Type II (fast-twitch) fibers, play a crucial role in muscle growth. Fast-twitch fibers are responsible for generating quick and powerful movements. A powerlifting champion will likely have a high portion of fast twitch fibers. In contrast, slow-twitch fibers are better suited for endurance activities such as distance running. The distribution of these fibers varies from person to person, with some individuals having more fast-twitch fibers and others having more slow-twitch fibers.
Fast-twitch fibers can generate more power during strength training but fatigue faster. In comparison, slow-twitch fibers are more fatigue-resistant but generate less power. Understanding the differences between these fiber types can help athletes and trainers tailor their workouts to optimize performance and achieve their goals.
Some studies found that those with FT fibers completed fewer reps at a weight lower than <70% of a 1 RM when training to failure (Douris et al., 2006; Hall et al., 2021; HICKSON et al., 1994); however, there were no differences at weights about >70% of a 1 RM max lifts.(HICKSON et al., 1994; Terzis et al., 2008)
The Limitations of 1 RM Calculators and 1 RM Charts
A 1 RM calculator is a common tool used in training to determine the maximum amount of weight a person can lift for one repetition. However, this method, along with the traditional 1 RM chart, has its limitations. They may not be the most effective for everyone, especially regarding muscle growth, as they don’t consider individual muscle fiber types.
Large inter-individual variations exist in the number of repetitions performed to failure at a given percentage of 1RM for a given exercise.(Shimano et al., 2006) I remember when I was in college watching the track and field distance runners workout. They had an unbelievable repetition capacity for high reps. Still, the sprinters could do more weight but fewer reps. It is thus clear that the need to individualize the number of repetitions per athlete arises instead of sticking to the “one-fits-all” training principle.
The idea of tailoring training according to muscle fiber types instead of using a % RM is an innovative approach suggested by some new research. This method is more effective for muscle growth than a 1RM calculator or a 1 RM chart, as it considers the unique characteristics of an individual’s muscle fibers. This approach demonstrated that FT; individuals fatigue more and need longer recovery than ST individuals after high-intensity exercise. (Lievens et al., 2020)
If you have FT twitch fibers, it’s reasonable to conclude that if put on the same training program as someone with ST fibers, that person is at greater risk for overreaching and impaired recovery between workouts.
Training According to Fiber Types: An Alternative to the 1RM Calculator
A new study aimed to investigate the relationship between muscle typology (muscle fiber type composition) and maximal strength, as well as the variability in the number of repetitions to failure during resistance training.
The study included 95 resistance training novices and assessed their maximal isometric knee extension strength and muscle fiber types. Muscle fiber types were estimated by measuring carnosine levels in the muscles.
The study in focus estimated muscle fiber types by measuring carnosine in the soleus, gastrocnemius, and vastus lateralis using proton magnetic resonance spectroscopy. Fast-twitch fibers have a 1.7–2.2 times higher carnosine concentration compared to slow-twitch fibers and a positive correlation between the percentage area occupied by fast-twitch fibers and the muscle carnosine concentrations. So, if you have high carnosine levels, you have a propensity for more fast-twitch muscle fibers.
The results found no difference in dynamic strength between slow and fast fiber individuals. The study also found that the total number of repetitions during resistance training was related to muscle fiber types at higher loads (80% and 60% of 1RM), with slow fiber type individuals performing more repetitions to failure. The total number of repetitions ranged from 63 to 122 at 60% 1RM and 30 to 60 at 80% 1RM.
The study found a lower number of repetitions in FT individuals in most of the sets, indicating a higher within-set fatigue. Additionally, the finding was only corroborated in men and was not observed in women. These findings suggest that muscle fiber types partly determine the number of repetitions to failure during resistance training.
Although training at lower loads of 40% induces more metabolic fatigue, no significant relationship was found between muscle fiber types and the total number of repetitions at 40% 1RM. This study recommends prescribing fewer repetitions to FT individuals at the same %1RM as for ST individuals. On the other hand, muscle typology variation equally affects the estimation of 1RM from the number of repetitions at submaximal loads.
The study suggests that muscle fiber types play a role in determining individuals’ optimal training load and repetition range. Therefore, athletes and fitness enthusiasts may benefit from understanding their muscle typology to tailor their resistance training program to their specific needs. For example, ST individuals may benefit from higher repetition ranges. FT individuals may benefit from lower repetition ranges with heavier loads. This knowledge may help individuals optimize their training and achieve their fitness goals more efficiently.
Comparing the Two Methods: 1RM Calculator vs. Fiber Type Training
When comparing training based on muscle fiber types and using a 1RM calculator or a 1 RM chart, each method has its benefits and drawbacks. However, the study’s findings suggest that training according to muscle fiber types could yield better results, especially regarding muscle growth. This insight, which goes beyond the traditional 1 RM chart, has significant implications for resistance training prescriptions and could lead to more effective training routines.
How to determine your Fiber Types Invasively
Unless you have access to an exercise physiology lab or want to get a muscle biopsy, there are a few tests to determine what type of fiber types you have. These tests have not been tested scientifically, but here is a quick test:
After a warm-up, have the athlete rest and then load the bar such as a squat with 80% of their 1RM weight, and perform as many repetitions as possible in one set. Count the repetitions performed correctly making sure the athletes uses correct exercise technique and form.
If the athlete lifts:
Less than seven reps – more fast twitch muscles present
Between seven and 12 reps – a balanced slow and fast twitch muscle composition
More than 12 reps – more fast twitch fibers.
- Remember, in the study, they found that slow-twitch (ST) individuals performed substantially higher total repetitions than fast-twitch (FT) individuals at 60% and 80% 1RM.
Conclusion: Rethinking the 1RM Calculator
In conclusion, training according to muscle fiber types could be more beneficial for muscle growth than a 1RM calculator or a 1 RM chart. The study’s findings suggest that this approach could improve training outcomes. Therefore, it’s worth considering this approach in your training routines, moving beyond the traditional 1RM calculator and 1 RM chart. These findings will help coaches to understand the importance of individualized training prescriptions. This can be performed by multiple RM tests per athlete (1RM, 8RM, 10RM, etc.) or by non-invasively estimating the muscle typology.
Douris, P. C., White, B. P., Cullen, R. R., Keltz, W. E., Meli, J., Mondiello, D. M., & Wenger, D. (2006). The relationship between maximal repetition performance and muscle fiber type as estimated by noninvasive technique in the quadriceps of untrained women. J Strength Cond Res, 20(3), 699-703. https://doi.org/10.1519/17204.1
Hall, E. C. R., Lysenko, E. A., Semenova, E. A., Borisov, O. V., Andryushchenko, O. N., Andryushchenko, L. B., Vepkhvadze, T. F., Lednev, E. M., Zmijewski, P., Popov, D. V., Generozov, E. V., & Ahmetov, I. I. (2021). Prediction of muscle fiber composition using multiple repetition testing [journal article]. Biology of Sport, 38(2), 277-283. https://doi.org/10.5114/biolsport.2021.99705
HICKSON, R. C., HIDAKA, K., & FOSTER, C. (1994). Skeletal muscle fiber type, resistance training, and strength-related performance. Medicine & Science in Sports & Exercise, 26(5), 593-598. https://journals.lww.com/acsm-msse/Fulltext/1994/05000/Skeletal_muscle_fiber_type,_resistance_training,.11.aspx
Lievens, E., Klass, M., Bex, T., & Derave, W. (2020). Muscle fiber typology substantially influences time to recover from high-intensity exercise. Journal of Applied Physiology, 128(3), 648-659. https://doi.org/10.1152/japplphysiol.00636.2019
Refalo, M. C., Hamilton, D. L., Paval, D. R., Gallagher, I. J., Feros, S. A., & Fyfe, J. J. (2021). Influence of resistance training load on measures of skeletal muscle hypertrophy and improvements in maximal strength and neuromuscular task performance: A systematic review and meta-analysis. Journal of Sports Sciences, 39(15), 1723-1745. https://doi.org/10.1080/02640414.2021.1898094
Schoenfeld, B., Fisher, J., Grgic, J., Haun, C., Helms, E., Phillips, S., Steele, J., & Vigotsky, A. (2021). Resistance Training Recommendations to Maximize Muscle Hypertrophy in an Athletic Population: Position Stand of the IUSCA. International Journal of Strength and Conditioning, 1. https://doi.org/10.47206/ijsc.v1i1.81
Shimano, T., Kraemer, W. J., Spiering, B. A., Volek, J. S., Hatfield, D. L., Silvestre, R., Vingren, J. L., Fragala, M. S., Maresh, C. M., Fleck, S. J., Newton, R. U., Spreuwenberg, L. P., & Häkkinen, K. (2006). Relationship between the number of repetitions and selected percentages of one repetition maximum in free weight exercises in trained and untrained men. J Strength Cond Res, 20(4), 819-823. https://doi.org/10.1519/r-18195.1
Terzis, G., Spengos, K., Manta, P., Sarris, N., & Georgiadis, G. (2008). Fiber Type Composition and Capillary Density in Relation to Submaximal Number of Repetitions in Resistance Exercise. The Journal of Strength & Conditioning Research, 22(3), 845-850. https://doi.org/10.1519/JSC.0b013e31816a5ee4
What is a 1rm calculator?
A 1RM calculator is a tool used to estimate an individual’s one-repetition maximum (1RM) in weightlifting. It considers factors such as the weight lifted and the number of repetitions performed to estimate the maximum weight a person can lift for a single repetition.