180 Chapter 8: Exercise Programming greater delivery of oxygen, macronutrients, and anabolic factors, which may in turn help facilitate the muscle’s ability to remodel. In terms of application, individuals interested in maximizing or preserving hypertrophy should consider the volume, intensity, mode, and scheduling of endurance training. Research suggests that volume has the biggest impact (negative) on hypertrophy (Schoenfeld, 2021). Performing endurance training can overwhelm the body’s capacity to recover. Additionally, long, frequent bouts of endurance training can create a catabolic hormonal environment and lead to chronic muscle glycogen depletion (Mikkola et al., 2012). As a result, the frequency of endurance training should remain low if the primary goal is hypertrophy. A good recommendation is to limit the frequency of endurance training to no more than 3-4 times per week when the intensity is moderate to high. That said, sedentary individuals may benefit from slightly higher training frequencies (Schoenfeld, 2022). In terms of intensity, research suggests that high-intensity training is more detrimental to intercellular anabolic signaling than moderate-intensity endurance training (Coffey et al., 2009a, Coffey et al., 2009b). As a result, low-intensity endurance training may be preferable over high-intensity endurance training if the primary goal is hypertrophy. A good recommendation is to limit HIIT sessions to approximately 20 minutes, even less if the session involves very high-intensity sprints (Schoenfeld, 2022). In terms of mode, research shows that running has a much more profound (negative) effect on hypertrophic adaptions as compared to non-weight bearing alternatives (e.g., cycling, elliptical trainer, rowing, swimming) (Lemon & Mullin, 1980; Schoenfeld, 2021). This may be due to excessive muscle damage caused by the high eccentric forces associated with running which, in turn, interferes with post-exercise recovery (Schoenfeld, 2022). Additionally, Beardsley (2019) proposes that exercises that produce higher levels of systemic fatigue (like running) create a greater competing signal (interference effect) than exercises that produce more local fatigue (like cycling). Collectively, these findings would suggest that running should be avoided, or at least significantly restricted, if the primary goal is hypertrophy. Most individuals can tolerate long, leisurely walks on a daily basis without substantially impeding their ability to recover. However, excessive walking may also interfere with recovery and anabolic processes (Schoenfeld, 2022). This is likely due to the fact that long duration, low-intensity aerobic exercise has been shown to cause central fatigue (Beardsley, 2019). In terms of scheduling, research shows that performing endurance training immediately before resistance training produces residual fatigue which can compromise force production during subsequent resistance training (Jagatheesan, 2011). That said, other research suggests the impact may be intensity dependent. For example, Fyfe et al., 2014 reported that high-intensity endurance training performed immediately before resistance training did in fact impede subsequent force production, whereas low-intensity endurance training had a lesser effect on residual fatigue. A good recommendation for combining endurance and resistance training is to perform them on separate days or insert a lengthy intervening recovery period (e.g., 4-8 hours) between sessions if performed on the same day (Israetel, 2021; Lemon & Mullin, 1980; Schoenfeld, 2021).
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