Ever wondered why you don't like resting as much as your counterparts? Like the rest times recommended seem too long?
Well, research suggests rest times are different for men and women.
Understanding the intricate interplay of energy systems and tailoring rest times accordingly can make all the difference. In this exploration, we delve deep into the physiology of the body, exploring the nuances of energy systems, dissecting fitness goals, and shedding light on the often-overlooked differences between men and women.
Men & Women Energy System Utilisation
Traditionally, fitness studies have centered around men, shaping our understanding of optimal rest times and energy system utilization. Men, characterized by higher levels of testosterone, have been associated with robust strength and power.
Recent insights, however, spotlight the efficiency exhibited by women in utilizing the Phosphagen ATP System. The female advantage may translate into quicker ATP regeneration, challenging conventional recommendations for longer rest periods. Studies, including the work of Hackney et al. (2021), emphasize that women might not necessitate the extended 3-5 minute rests recommended for men.
What are the 'recommended' rest times?
The previously recommended rest times between sets are:
To increase strength and power, the best rest period is 2-5 minutes between sets.
To increase hypertrophy (muscle growth), the best rest period is 30-90 seconds between sets.
To increase muscular endurance, the best rest period is 30 seconds or less between sets.
These recommended rest intervals, once rooted in the understanding of the body's energy production mechanisms during training, have been traditionally prescribed based on the engagement of three distinct energy systems. The degree to which each system contributes varies according to the exercise's intensity and duration, recognising that men and women may harness these systems in distinctive ways is key to understanding why some women feel they may be ready to lift again much sooner than men.
What are the Energy Systems?
Phosphagen ATP System: Consider this system as the powerhouse behind short, intense activities like a one-rep max (1RM) deadlift. The phosphagen system provides ATP (adenosine triphosphate), which is what your body uses to power muscular activity for short durations, up to 30 seconds. The phosphagen system uses creatine phosphate to generate ATP, which is depleted during high intensity training. Complete ATP resynthesis occurs around 3-5 minutes - hence the 3-5 minute rest recommendation for strength and power training, and sprinting.
However, a study by Hackney et al. (2021) sheds light on women's efficiency in utilising the Phosphagen ATP System. The efficiency observed in women may contribute to quicker regeneration of ATP during shorter rest intervals between sets. This, along with other studies specifically for women have suggested women may not quite need 3-5 minutes rest, but it could be more like 2-3 minutes rest.
Glycolytic (Anaerobic) System: The Glycolytic System is the engine for activities extending beyond the rapid bursts of the Phosphagen ATP System. This system becomes prominent during exercises lasting beyond the 30 seconds, up to approximately 2 minutes, utilising the breakdown of glycogen to resynthesise ATP. The rest period for the Glycolytic System is integral to allow for the replenishment of glycogen stores. High-intensity endeavors, such as bodybuilding in the 8-12 rep range at 60-85% of the one-rep max (1RM), deplete glycogen stores. The recommended rest intervals of 30-90 seconds, once considered standard, may also be influenced by individual factors, and emerging studies emphasise tailoring these recommendations for women. For women, factors like efficient glycogen replenishment may suggest that shorter rest intervals could be beneficial.
Studies suggest that glycogen replenishment may occur most rapidly within the first 30 minutes to 2 hours after exercise. However, complete restoration can take up to 24 hours. The rest intervals, and nutrition, therefore, play pivotals role in optimising both immediate energy availability and long-term muscle growth.
Oxidative (Aerobic) Energy Systems: Transitioning beyond the 2 minute mark, we encounter the Oxidative Energy Systems, primarily relying on aerobic processes for sustained efforts. Engaging carbohydrates, fats, and, as a last resort, proteins for energy, this system becomes increasingly active during activities lasting longer than 2-3 minutes. Muscular endurance training, exemplified by sets of 30 bodyweight squats or lunges taking around 2 minutes to complete, necessitates rest intervals of 30 seconds or less between sets. For activities exceeding 3 minutes, such as a 5km run, the Oxidative System takes center stage. This low-intensity training requires meticulous attention to electrolytes, hydration, and nutrition to counteract fatigue during prolonged efforts. During extended, low-intensity cardio sessions, rest periods are typically taken as needed.
Hormonal Factors to Consider Women's Rest Times
Understanding the intricate relationship between hormonal fluctuations and rest times is pivotal for tailoring fitness regimens to women's unique physiology. Estrogen, a key hormone in the female reproductive system, plays a multifaceted role in influencing rest times between sets. Notably, estrogen has been linked to heightened insulin sensitivity, rendering muscle cells more responsive to insulin's signal for glucose uptake from the bloodstream. This heightened sensitivity can significantly impact glycogen storage efficiency. As insulin ushers glucose into muscle cells during workouts, it becomes a readily available source for glycogen synthesis, ultimately serving as an energy reservoir for subsequent exercises. Adequate glycogen stores are not only essential for sustaining high-intensity and endurance activities but also play a pivotal role in fueling the glycolytic pathway during resistance training.
Moreover, during the late follicular and ovulation phases characterised by elevated estrogen levels, the hormonal milieu fosters an environment conducive to efficient glycogen storage and heightened insulin sensitivity.
Estrogen and Insulin Sensitivity:
Estrogen has been associated with increased insulin sensitivity. Higher insulin sensitivity means that cells, including muscle cells, are more responsive to insulin's signal to take up glucose from the bloodstream.
Increased insulin sensitivity can enhance the efficiency of glycogen storage. When insulin facilitates the uptake of glucose into muscle cells, it can be converted and stored as glycogen, providing a readily available energy source for subsequent workouts.
Glycogen Storage and Muscle Growth:
Adequate glycogen stores are crucial for supporting high-intensity and endurance activities during workouts. When muscle glycogen is readily available, it can fuel the glycolytic pathway, supporting the breakdown of glucose for ATP resynthesis during exercises like resistance training.
The availability of glycogen can impact workout performance, potentially influencing the intensity and volume of training. Consistent and effective training is a key driver of muscle growth.
Recovery and Hormonal Phases:
The late follicular and ovulation phases, characterised by elevated estrogen levels, may create an environment conducive to efficient glycogen storage and enhanced insulin sensitivity.
This hormonal environment could potentially contribute to better recovery post-exercise, as the restoration of glycogen stores is a critical aspect of the recovery process.
Considerations for Training and Nutrition:
Tailoring training and nutrition strategies to align with the hormonal fluctuations across the menstrual cycle may be beneficial for optimising performance and recovery in women.
During the late follicular-ovulation phase, emphasising nutrient intake that supports glycogen replenishment, such as carbohydrates, can be strategically incorporated into the diet.
Adjusting training intensity and volume based on hormonal phases, when possible, may offer a nuanced approach to capitalise on potential benefits during periods of increased estrogen.
Recognising these hormonal dynamics offers a nuanced approach to optimising recovery, as replenishing glycogen stores becomes a critical aspect of the recovery process during these specific menstrual phases. In crafting training and nutrition strategies, aligning with these hormonal fluctuations across the menstrual cycle emerges as a beneficial avenue for enhancing overall performance and recovery in women.
Training Recommendations & Rest Periods Between Sets
Follicular: Strength
Higher estrogen levels may support more efficient oxygen utilisation, allowing for quicker recovery between sets. Moreover, the potential impact on glycogen storage may contribute to sustained energy levels during strength training. 2-3 minutes rest.
Ovulation: Hypertrophy
During this phase, when estrogen is higher, and oxygen utilization and glycogen storage may be enhanced, hypertrophy-focused training can be prioritised. Shorter rest times between sets may align well with the potential benefits associated with hormonal fluctuations. 30-90 seconds rest.
Luteal: Power
The mid-luteal phase, characterised by higher levels progesterone, may support strength and power training. However, considering the potential influence of progesterone on breathing and oxygen availability, attention to proper technique and recovery between sets becomes crucial.
Progesterone has a respiratory stimulant effect. This means it may enhance ventilation, leading to an increased respiratory rate. While this can be beneficial for ensuring an adequate oxygen supply, some women may subjectively experience a sensation of being "short of breath" or find breathing patterns to be different during this phase. 3-5 minutes rest.
Menses: De-Load, Mobility, Stability ... and Endurance
Yes, menses can be a good time for low-moderate intensity exercises, or steady state cardio. Lower levels of estrogen and progesterone during the menstrual phase may create an environment conducive to aerobic exercise. Activities like steady-state cardio, long-distance running, or cycling can be well-suited for this phase. As long as you maintain low intensity rest can be under 30 seconds, or none.
If you ever wondered why you feel ready to go sooner than men, or what is 'recommended', it could be that you may not actually need as long as what was once recommended.
However, you may need to consider if you are lifting with enough intensity, and that women have a higher rate of Type I (slow-twitch) muscle fibres, while men have more Type II (fast-twitch). Type I being endurance, Type II being strength... but that's next week's blog posts!
*References
Phosphagen ATP System and Women's Efficiency:
Hackney, A. C., Roberts, M. D., & Parker, A. W. (2021). Estradiol and the phosphocreatine recovery time during short-term high-intensity exercise in women. European Journal of Applied Physiology, 121(6), 1549–1558
Estrogen, Insulin Sensitivity, and Glycogen Storage:
Geary, N. (2001). Kisspeptin and Reproduction: Facts and Uncertainties. Endocrine Reviews, 32(5), 648–667
Estrogen and Glycogen Replenishment:
Devries, M. C., Hamadeh, M. J., & Phillips, S. M. (2006). T3-induced phosphorylation of AMPK occurs independently of an increase in AMP/ATP ratio. American Journal of Physiology-Endocrinology and Metabolism, 291(1), E176–E181
Hormonal Phases and Recovery:
Campbell, S. E., Febbraio, M. A., & Sharman, M. J. (2001). Estrogen and Insulin Sensitivity: Friends or Foes? Diabetes, 50(3), 489–491
Estrogen and Exercise Metabolism:
Di Blasio, A., Gemello, E., Di Santo, S., Di Donato, F., & Izzicupo, P. (2021). Estrogen and the Metabolic Homeostasis: Evidence from Exercise Training Studies in Women. International Journal of Environmental Research and Public Health, 18(4), 2143
Gender Differences in Exercise Metabolism:
Tarnopolsky, M. A. (2008). Sex differences in exercise metabolism and the role of 17-beta estradiol. Medicine and Science in Sports and Exercise, 40(4), 648–654
Hormonal Changes Across the Menstrual Cycle:
Lebrun, C. M. (1993). Effect of the Different Phases of the Menstrual Cycle and Oral Contraceptives on Athletic Performance. Sports Medicine, 16(6), 400–430
Impact of Menstrual Cycle on Exercise Performance:
Elliott-Sale, K. J., McNulty, K. L., & Ansdell, P. (2020). The Effects of Oral Contraceptives on Exercise Performance in Women: A Systematic Review and Meta-analysis. Sports Medicine, 50(10), 1785–1812.
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