The Correct Interpretation of the Size Principle and Its Practical Application to Resistance Training

High- and Low-Load Resistance Training: Interpretation and Practical Application of Current Research Findings

Our current state of knowledge regarding the load (lighter or heavier) lifted in resistance training programmes that will result in 'optimal' strength and hypertrophic adaptations is unclear. Despite this, position stands and recommendations are made based on, we propose, limited evidence to lift heavier weights. Here we discuss the state of evidence on the impact of load and how it, as a single variable, stimulates adaptations to take place and whether evidence for recommending heavier loads is available, well-defined, currently correctly interpreted or has been overlooked. Areas of discussion include electromyography amplitude, in vivo and in vitro methods of measuring hypertrophy, and motor schema and skill acquisition. The present piece clarifies to trainers and trainees the impact of these variables by discussing interpretation of synchronous and sequential motor unit recruitment and revisiting the size principle, poor agreement between whole-muscle cross-sectional area (CSA) and biopsy-determined changes in myofibril CSA, and neural adaptations around task specificity. Our opinion is that the practical implications of being able to self-select external load include reducing the need for specific facility memberships, motivating older persons or those who might be less confident using heavy loads, and allowing people to undertake home- or field-based resistance training intervention strategies that might ultimately improve exercise adherence.

The Chronic Effects of Low- and High-Intensity Resistance Training on Muscular Fitness in Adolescents

To compare the effects of high-load, low-repetition maximum (LRM) and low-load, high-repetition maximum (HRM) resistance training regimens on muscular fitness in untrained adolescents. Forty-five untrained adolescents of both sexes (13.7±0.8 years; 161.3±7.5 cm, 56.8±13.4 kg) were randomly assigned into one of three groups: 1) LRM (n = 17): volunteers performed three sets of 4-6-repetition maximum (RM); 2) HRM (n = 16): volunteers performed three sets of 12–15 RM; and 3) control (CON, n = 12). Training was performed two times a week for 9 weeks. After training, there were significant increases in 1 RM chest press (LRM = 14.8% and HRM = 14.2%, p<0.05) and squat (LRM = 26.4% and HRM = 25.7%, p<0.05), with no differences between the LRM and HRM groups (p>0.05). Additionally, muscular endurance increased significantly for the chest press (LRM = 14.5% and HRM = 21.8%, p<0.05) and squat test (LRM = 31.4% and HRM = 32.4%, p<0.05) following resistance training, with no difference between the LRM and HRM groups (p>0.05). These results suggest that both high-load, low-repetition and moderate-load, high-repetition resistance training can be prescribed to improve muscular fitness in untrained adolescents.

Developing a new treatment paradigm for disease prevention and healthy aging

An increasingly prevalent pattern of risk factors has emerged in middle-aged and older adults that includes the presence of type 2 diabetes or prediabetes, overweight or obese weight status with central obesity and very high body fat, low cardiorespiratory fitness (CRF), low strength, and a low lean-body-mass-to-body-fat ratio. Traditionally, these problems have been approached with a low-fat and low-calorie diet and with lower to moderate intensity activity such as walking. While the treatment has some clear benefits, this approach may no longer be optimal because it does not reflect more recent findings from nutrition and exercise sciences. Specifically, these fields have gained a greater understanding of the metabolic and functional importance of focusing on reducing body fat and central obesity while maintaining or even increasing lean body mass, a quality weight loss, and how to efficiently and effectively increase CRF and strength. Evidence is presented for shifting the treatment paradigm for disease prevention and healthy aging to include the DASH nutrition pattern but with additional protein, higher intensity, brief aerobic training, effort-based, brief resistance training, and structured physical activity. Recent interventions based on social cognitive theory for initiating and then maintaining health behavior changes show the feasibility and efficacy of the approach we are advocating especially within a multiple health behavior change format and the potential for translating the new treatment paradigm into practice.