Interference between Concurrent Resistance and Endurance Exercise: Molecular Bases and the Role of Individual Training Variables

Abstract

Concurrent training is defined as simultaneously incorporating both resistance and endurance exercise within a periodized training regime. Despite the potential additive benefits of combining these divergent exercise modes with regards to disease prevention and athletic performance, current evidence suggests that this approach may attenuate gains in muscle mass, strength, and power compared with undertaking resistance training alone. This has been variously described as the interference effect or concurrent training effect. In recent years, understanding of the molecular mechanisms mediating training adaptation in skeletal muscle has emerged and provided potential mechanistic insight into the concurrent training effect. Although it appears that various molecular signaling responses induced in skeletal muscle by endurance exercise can inhibit pathways regulating protein synthesis and stimulate protein breakdown, human studies to date have not observed such molecular 'interference' following acute concurrent exercise that might explain compromised muscle hypertrophy following concurrent training. However, given the multitude of potential concurrent training variables and the limitations of existing evidence, the potential roles of individual training variables in acute and chronic interference are not fully elucidated. The present review explores current evidence for the molecular basis of the specificity of training adaptation and the concurrent interference phenomenon. Additionally, insights provided by molecular and performance-based concurrent training studies regarding the role of individual training variables (i.e., within-session exercise order, between-mode recovery, endurance training volume, intensity, and modality) in the concurrent interference effect are discussed, along with the limitations of our current understanding of this complex paradigm.

Concurrent exercise incorporating high-intensity interval or continuous training modulates mTORC1 signaling and microRNA expression in human skeletal muscle

“…Further work is required to define the molecular events that mediate chronic phenotypic adaptations to training and potentially their progression during a training program. Such information is likely to also provide further mechanistic insight into the concurrent interference effect (38). We also conducted all muscle analyses using mixed whole muscle homogenate, which may have masked any fiber-type specific differences in measured postexercise responses, including glycogen content, signaling responses and gene expression (65).…”

“…From a practical standpoint, elucidation of the roles of specific training variables (e.g., training intensity, volume, and modality) is required to inform exercise prescription guidelines for minimizing potential interference during concurrent training (38). One important practical consideration is the intensity of endurance training employed in a concurrent training program.…”

The efficacy of protein supplementation during recovery from muscle-damaging concurrent exercise

“…Concurrent exercise involves the simultaneous incorporation of both endurance and resistance exercise, (Fyfe et al, 2014) and is a prevalent training method for elite and recreational athletes that are aiming to elicit divergent physiological adaptations in parallel. Previous work examining recovery from EIMD has used resistance (Harrison andGaffney, 2004, Miyama andNosaka, 2004) or endurance (Bell et al, 2014, Betts et al, 2009) stimuli in isolation.…”

Progressive resistance‐loaded voluntary wheel running increases hypertrophy and differentially affects muscle protein synthesis, ribosome biogenesis, and proteolytic markers in rat muscle

“…Specifically, the muscle-specific overexpression of 4EBP1 in mice has been shown to promote increases in mitochondrial markers (Tsai et al, 2015). Therefore, it remains possible that gastrocnemius MPS was lower in EX rats because of the endurance-type phenotype that this model imposes, as certain literature suggests that endurance training can reduce MPS levels and anabolic skeletal muscle signalling (Fyfe, Bishop, & Stepto, 2014;Hawley, 2009). It should be noted, however, that Mosoni and coworkers (Mosoni et al, 1995) reported that 30 weeks (5 days/week) of treadmill training in rats does not alter basal tibialis anterior MPS rates and increases basal soleus MPS rates by 71%.…”