The cumulative effects of strength and endurance training sessions on muscle force generation capacity over four days

[Extract] The incorporation of strength and endurance training sessions in the one training program is known as concurrent training (CT) (11). Numerous studies have shown that CT induces sub-optimal strength adaptations (7, 10, 15). This incompatibility existent between strength and endurance training sessions is known as the “interference phenomenon” (15) and has been under scrutiny amongst scientists for over 30 years. As a result, several hypotheses have been proposed in an attempt to explain the interference of strength development due to CT. The chronic hypothesis suggests that the muscle is unable to undergo optimal metabolic and morphological adaptations since the physiological responses induced by endurance training are vastly different and sometimes antagonistic to strength training (5). The acute hypothesis contends that the residual effects of fatigue generated by previous endurance training sessions impairs muscular contractility and thereby attenuates training stimuli for optimal strength development (5). Indeed, it has been reported that moderate to high intensity 60-minute cycling sessions can impair muscle force generation capacity for 6 hours post (2), suggesting that the quality of strength training sessions may be compromised if undertaken within the hours of an endurance training session.