Introduction
     Extensive research has underscored resistance training (RT) as a potent driver of physiological muscular aptations (Schoenfeld et al., 2021). In combination with progressive overload, increases in muscle size, maximal strength and local muscular endurance are evident after several weeks (Schoenfeld et al., 2021). Though, a long-held belief is that a specific adaptive response can be achieved through the careful manipulation of sets, reps, and intensity (Schoenfeld et al., 2021). Subsequent research led to the development of the repetition continuum, whereby the number of reps is proposed to elicit a biased adaptive response to size, strength, or endurance (Schoenfeld et al., 2021). For several years, the premise of repetition continuum became a foundational component in exercise prescription, that is until more recent evidence has challenged this long-standing paradigm. Emerginge evidence suggests that the so called hypertrophy zone is more broad than once believed and lies between 6-35 reps (Baz-Valle et al,. 2021; Schoenfeld et al.,2015).              

Figure 1. Showing the Repetition Continuum.
Picture adapted from Schoenfeld et al. (2021)

     A pivotal meta-analysis by Schoenfeld el at. (2017), partly exposed the differential effects of varying training intensities, revealing a greater effect size (ES = 1.69 ± 0.23 vs. 1.32 ± 0.23) for heavier loads (>60% 1RM) in augmenting maximal strength, compared to lighter loads (<60% 1RM). Notably, there was a tendency for trained subjects to have a higher response when training with heavier loads. In contrast to the prevailing dogma, heavy loads (ES= 0.53 ± 0.10) and light loads (ES = 0.42 ± 0.08) seem to have little to no effect on the degree of muscle hypertrophy. Subsequent research by Lopez et al. (2021) echoed similar findings, reinforcing the concept that while heavier loads (≤8 RM) facilitate greater strength gains, muscle hypertrophy remains relatively load-independent. Based on these broad analyses, some may fail to appreciate the nuances of prescribing varying rep ranges and ubiquitously advocate for heavier loads (≤8 RM) in all instances.

     Similarly, Schoenfeld et al. (2014) compared hypertrophic outcomes between heavy (7x3) and moderate (3x10) loading protocols, performing thee exercises, three-times a week, over 8 weeks with equated volume. Likewise, the study demonstrated similar hypertrophic gains between the two loading modalities, along with superior gains in strength using heavy loads. A notable aspect of this study was the participants' feedback, with those in the heavy load protocol reporting greater feelings of fatigue, both physical and mental, compared to their moderate load counterparts. Participants subjected to moderate loads reported a higher resilience to volume, despite the session duration (70 vs. 17 minutes) being double that of the heavy protocol. This suggests that equating volume across different intensities may not yield comparable training experiences, as high-volume training may incur less mental and physical fatigue compared to heavy-load protocols.
       
     Furthermore, an examination of the protocols within the meta-analyses reveals an average study duration ranging between 8 to 12 weeks, with only one study out of a combined total of 37 extending to a full year. This underscores the conceptual challenges in translating research findings to real-world scenarios, as the short durations of these studies may not fully recognise the long-term effects of training at different intensities. Namely, the stimulus: fatigue ratio is a crucial consideration in resistance training programming, reflecting the balance between training intensity and volume, along with the resultant fatigue. Short-term studies, while informative, often do not capture the nuanced, accumulative effects of varying rep ranges and intensities over extended periods, nor do they adequately represent the adaptive responses that occur with long-term consistent training.

     Additionally, from a practical standpoint, certain exercises seem to be more suitable within confined rep ranges, rather than applying a broad spectrum of 6-35 reps across all exercises. For instance, while theoretically similar hypertrophic gains in the back squat may be seen when a 25-35RM protocol is compared to a more traditional 8-10RM protocol, in some populations, the cardiovascular system of the lifter might become the limiting factor before the targeted muscles ever reach sufficient fatigue. In contrast, prescribing 5RM for a lateral deltoid raise might not be as effective due to the limitations imposed by accessory muscles involved in gripping the dumbbell. Again, this stands as further testament to the notion that most studies fail to acknowledge the practicalities of exercise prescription.             

    

  From more of a physiological perspective, some contend that there are distinct forms of muscle hypertrophy in response to RT, namely myofibrillar and sarcoplasmic hypertrophy (Haun et al., 2019). The general contention is that heavier (>80%) loads preferentially results in myofibrillar hypertrophy (Erskine et al., 2010) and more moderate (70-75%) loads with high volumes targets sarcoplasmic hypertrophy (Haun et al., 2019). However, th eevidence supporting this premise occurring in humans is indirect and largely based on the concept of changes in specific tension (Haun et al., 2019). In brief, it is estimated that 80% of space in a muscle fiber is occupied by myofilaments, with the remaining 15-20% consisting of the sarcoplasm and other non-contractile components (Jorgenson et al., 2020).      

     Presumably, changes to the respective percentages in response to different forms of RT would indicate a specific adaptive response. However, a critical analysis by Dankel et al.(2019) challenges this implied dichotomy between the two modes of training. Their meta-analysis concluded that RT does not significantly alter specific tension relative to CSA across a spectrum of training intensities (30-80% 1RM) and protocols (6-15 reps, 1-4 sets). This analysis implies that RT may lead to a proportionate increase in both contractile and non-contractile components of muscle fibers, rather than favouring a distinctive form of hypertrophy over the other. Equally, the large spectrum of training variables analysed could have had a wash-out effect, diluting the ability to identify distinct hypertrophic responses between protocols. Indeed, the occurrence of a distinctive responses to RT seems less likely but worth acknowledging and requires further research. Nevertheless, prescribing heavier (>80%) loads to populations requiring maximal force output while being limited by certain weight classes may be advantageous, where as a spectrum of loads may benefit populations interested in reducine mental and physical fatigue.  

Conclusion             
     Historically, the repetition continuum was positioned as foundational component in understanding the adaptive response to RT and served as a mechanism guiding the prescription of exercise. However, recent evidence challenges the rigid adherence to the repetition continuum, revealing a broad spectrum ranging between 6-35 reps capable of eliciting comparable hypertrophic responses. Indeed, the pendulum swings in the direction of muscle hypertrophy being a relatively load-independent adaptative response as well, with both heavy and light loads leading to similar changes if sufficient fatigue is reached. This body of research emphasizes the pursuit of muscle hypertrophy can be effectively approached through a varietyof loading strategies. 

     Incontrast, based on these recent analyses, it seems some have implicated that prescribing 6-35 repetitions can be ubiquitously applied across different exercises and varying populations without consideration. While higher intensities (7x3) yield greater gains in strength along with a similar hypertrophic response to moderate intensities (3x10), it seems to come at a mental and physical cost that may be unsustainable for some populations. Equal consideration should be given to the practicalities of the prescription, with respect to the exercise being performed, and physical limitations of the individual achieve a desired rep range. Additionally, though unconfirmed, the different potential mechanisms of hypertrophy and the variables proposed to achieve that response may require more careful consideration, especially when dealing with athletic and aesthetic goal-oriented populations.  

     Given these considerations, there is clear justification that rep ranges do matter, contrary to the prevailing idiom. As such,the determination of optimal rep ranges and loading schemes should behighly individualized, considering not only the physiological adaptations but also the psychological readiness and resilience of the person in question. This nuanced approach allows for the developmentof training programs that are not only effective in achieving desired outcome sbut also sustainable and enjoyable for the individual. Undoubtedly, large strides have been made in reaching a deeper understanding of exercise prescription but there is still much to be learned. Continued research into the nuanced effects of different training variables will further our ability tooptimize resistance training for diverse objectives, from athletic performance to health and longevity.