# Recommendations for Advancing the Resistance Exercise Overtraining Research
## 3 Developing Resistance Exercise Overtraining Protocols Is a Challenging Task
It is well established that when a group of individuals undertake the same resistance exercise program, their response to that program will vary, even in groups comprising small sample sizes [39]. Some individuals will present meaningful improvements in performance, whereas others will present an adverse response [40; 41]. Such variation is largely controlled by genetic and epigenetic factors [42; 43; 44; 45] and modulated by genotype [46; 47], muscle fibre typology [48; 49], age, and biological maturation [50]. Additional factors such as the level of competition/training status [51] and the individual's \"stress capacity\" [52; 53] will also affect performance outcomes. For example, men and women undertaking 12 weeks of resistance exercise reported one-repetition maximum strength changes ranging from 0 to 250% and skeletal muscle hypertrophy of \(-\)2 to 59%, suggesting some participants experienced performance changes indicative of FOR, whilst others did not [47]. Whilst it is likely that the physiological response to the same program of training will differ between a group of athletes, current understanding of inter- and intra-individual variation in response to resistance exercise remains limited [54], especially in studies designed to induce FOR. Much of the previous research in this area has focused on group-based analysis, where the mean pre-to-post change in an intervention group (typically referred to as an \"overtraining\" group) is compared to the mean pre-to-post change in a control group (a \"normal\" training group) [40; 55]. Therefore, there is a strong rationale for exploring the individual response to periods of resistance exercise OT. Similar recommendations have been made by [PERSON] [7], who suggested that future research exploring FOR should focus on the inter-individual response to exercise training and the variable development of performance outcomes following periods of high training demand. Previous research has reported that trained individuals undertaking periods of either single or multiple sets of high-intensity resistance exercise (including a challenging protocol of 8 sets of back squats at 80% of repetition maximum to volitional exhaustion twice per week) can be classified as \"high responders\" (>20%) or \"low responders\" (<10%) based on changes in strength [56]. Interestingly, whilst some participants reported improved performance (which could be considered FOR) and others reported a decline in performance, there was no change in energy intake between responder groups either prior to or during the study, suggesting variation in response could not have been attributed to energy intake. A second point to note was that the \"peaking phase\" of the training protocol (a 4-week high-intensity, low-volume phase designed to reduce the risk of NFOR) was only effective for high responders. Whilst the authors were unsure as to why this was the case, they proposed that the training that preceded the peaking phase was sufficient to evoke the \"realization\" of strength development. This poses an additional but interesting question relating to the importance of individualizing the tapering phase as well as the organization of increased resistance exercise training demand. This is an area of research that has received minimal attention [14; 57] but should be considered in future experimental studies. It is anticipated that by adopting an individualized approach to resistance exercise, sports scientists and practitioners might optimize resistance exercise OT to achieve FOR and mitigate the negative effects of NFOR or OTS.