The lifespan of a training load in resistance exercise

Abstract

This doctoral thesis has focused on two primary areas of investigation: firstly, it delves into the lifespan of a training load (TL) for the first time; and secondly, it examines the impact of training intensity and subjects' sex on a wide range of performance variables.

The lifespan of a TL can be defined as the number of sessions within a training cycle during which the TL induces positive adaptations. Understanding the lifespan of a TL directly influences the programming process, preventing progression from being excessively slow or rapid. This knowledge contributes to maximising the benefits of each TL, ensuring the achievement of as many positive adaptations as possible and prolonging the athletic life. Thus, given the potential relevance of this topic and the lack of attention received in the scientific literature, the purpose of this study was to investigate the lifespan of two absolute training loads (ATLs) based on daily performance monitoring in recreationally trained individuals. Thirty-eight subjects (22 men and 16 women) were randomly assigned to two groups with different volumes and intensities but initially equal relative volume loads (rVL = Sets × Repetitions × % One-Repetition Maximum [1RM]): 3×12×40% 1RM (G40), and 3×6x80% 1RM (G80). Over 6 weeks, both groups performed twice a week the full back squat (SQ) exercise on a force platform synchronised with a linear velocity transducer (LVT) for daily monitoring purposes but without any adjustments to their initial ATL (repetitions or kg lifted). In each session, countermovement jump (CMJ) height, force (AF60), and velocity (AV60) against 60% 1RM in SQ were recorded, as well as the average force (AF) and average velocity (AV) with their respective ATL. A linear mixed model was used to analyse daily performance changes. Significant time effects were found for all variables and groups (p < .001; and p = .008 for V60 in G80), except for CMJ height in G40 (p = .077). Overall improvements relative to the first session in G40 were found around the 5th session [range 3rd-7th], attaining its peak performance in the 10th or 11th sessions but already achieving a similar performance from the 6th and 7th sessions. G80 took approximately 9 sessions [6-11] to reach significant results, and its last session (11th) was always the best one, obtaining a similar performance between the 3rd and 9th sessions. In conclusion, daily performance monitoring against a constant ATL enabled us to assess the adaptations achieved with that load and examine its lifespan. This may provide insights into its suitability and continuity within a training cycle, lasting for at least several sessions in recreationally trained individuals.

On the other hand, the use of heavy over light loads is usually recommended when the goal is to develop muscular strength. This debate about whether heavy or light loads promote better results may have been biased towards heavier loads, underestimating the potential benefits generated by lighter loads due to the fewer similarities between the TL and the testing load (usually the 1RM). Furthermore, while this topic has been widely studied in both men and women separately, often yielding conflicting outcomes, the inclusion of both variables (intensity and sex) could offer a deeper insight into its potential interaction. Therefore, the purpose of this study was to investigate the effects of light and heavy loads in the SQ exercise on kinematics and mechanical variables in recreationally trained men and women. Twenty-two men and sixteen women were assigned to 4 groups: 40% and 80% of 1RM male (M40 and M80) and female (F40 and F80). Over 6 weeks, participants performed the SQ exercise twice a week with initially equated rVLs. All groups performed different amounts of work (p < .05), while the relative work (work · 1RM-1) only differed between load groups (p < .001). There was no significant time × sex × load interaction. Based on the magnitude of effect sizes (ESs): M80 achieved small improvements in SQ maximum isometric force (MIF; ES [95% confidence interval (CI)] = 0.43 [0.16, 0.81]); small gains in SQ 1RM were observed in the 80% 1RM groups (M80: 0.42 [0.18, 0.77]; F80: 0.44 [0.26, 0.76]) and the F40 group (0.42 [0.17, 0.81]); all groups made moderate to large gains in the average velocity attained against heavy loads (> 60% 1RM; F40: 1.20 [0.52, 2.27]; F80: 2.20 [1.23, 3.93]; M40: 0.85 [0.29, 1.59]; M80: 1.03 [0.55, 1.77]), as well as small to moderate improvements in the average velocity against light loads (< 60% 1RM; F40: 0.49 [0.24, 1.68]; F80: 1.10 [0.06, 3.16]; M40: 0.80 [0.41, 1.35]; M80: 0.93 [0.25, 1.84]). Lastly, only the F40 group showed small improvements in CMJ height (ES = 0.65 [0.14, 1.37]). In conclusion, light and heavy loads produced similar strength gains in men and women when initially equated by rVL. However, based on standardised mean differences, heavier loads appear to elicit greater maximum and near-maximum force adaptations (MIF and 1RM) in men. In contrast, women may benefit equally from both low and high load magnitudes to enhance near-maximum dynamic force production (1RM). Although light loads (40% 1RM) may be more specific to optimise force application in tasks using only body weight as workload (e.g., jump tasks in the F40 group), this `potential benefit' may be compromised in stronger subjects (i.e., the M40 group), who tend to decelerate more aggressively at the end of the lift.