Effectiveness of strength “snacks” for improving strength, muscle mass, and muscular performance in healthy males.

1. Efficacy of strength “snacks” for improving strength, muscle mass, and neuromuscular performance in healthy males. 2. Resistance training (RT) is the only known non-pharmacological intervention for improving strength and muscle mass, both of which play significant roles in maintaining and improving human health. Despite this, engagement in RT remains poor, with common barriers to participation including a lack of time and a high perception of difficulty associated with commonly-recommended RT programs. There is a need, therefore, for identification of RT interventions that are time efficient, low in complexity, and enjoyable to perform. Recent evidence suggests that high-load, low-volume RT can achieve outcomes that are similar-to-superior to traditional lower-load and higher-volume RT, with the added benefit of eliciting more positive affective responses (Buckner et al, 2018). Hence these RT protocols have the potential to promote more engagement in RT and be more sustainable long-term, both of which are likely to lead to improved population health outcomes. This project will provide new evidence for the effectiveness of low complexity, high-load and low-volume RT for improving strength, muscle mass, and neuromuscular performance, as well as the influence of these interventions for eliciting positive affective responses that may improve long-term RT adherence. 3. All of the necessary resources described below are currently available for use within the School of Exercise and Nutrition Sciences laboratories, Building J, Deakin University Burwood campus: Resistance training intervention: Machine-based plate-loaded resistance training equipment, specifically leg press, chest press, seated row, leg extension, and leg curl machines. Strength assessments: Dynamic (1-RM) strength assessment requires a leg press and chest press machine. Isometric (MVIC) strength assessment requires an isokinetic dynamometer. Thigh muscle mass assessment: Requires a pQCT (peripheral quantitative computed tomography) scanner. Body composition assessment: Requires a DXA (dual x-ray absorptiometry) scanner. Neuromuscular performance assessment: Requires a portable force platform, isometric mid-thigh pull (IMTP) rig, and associated software (e.g., Ballistic Measurement System). Subjective responses assessment: Requires access to the relevant questionnaires (session rating of perceived exertion, session rating of perceived discomfort, the feeling scale, perceived recovery scale, and the self-efficacy for exercise questionnaire), which are all freely available online. 4. Procedures Study overview: The study will follow a randomised, parallel-group design. Participants will undertake one of two resistance training interventions for 8 weeks (2 sessions per week): 1) low-volume, high-load strength “snacking” (SNACK group) or 2) traditional higher-volume, lower-load resistance training (TRAD group). The primary outcome measure will be maximal dynamic (1-RM) upper- and lower-body strength. Secondary outcome measures will be maximal isometric strength (MVIC), thigh muscle mass (pQCT), total body and regional lean mass and fat mass (DXA), neuromuscular performance (CMJ and IMTP), and affective responses to individual resistance training sessions and the entire resistance training intervention. Familiarisation: During the first visit to the laboratory (PRE visit 1), participants will be familiarised with the maximal strength and neuromuscular performance assessments. This will involve completing these assessments in full (as described below), which will then be repeated when participants return to the laboratory the following week for PRE visits 2 and 3 (baseline testing). Participants will also practice performing each exercise to be performed in the resistance training program, with the aim of identifying appropriate starting training loads for each exercise. Randomisation: After baseline testing (PRE visits 2 and 3), participants will be pair-matched based on 1-RM leg press strength and randomly allocated to either the SNACK or TRAD group. Group randomisation will be performed by the principal investigator (JF) Resistance training intervention: Resistance training will consist of five exercises (leg press, chest press, seated row, leg extension, and leg curl) performed twice weekly for 8 weeks. One warm-up set (six repetitions at ~75% of load in each work set) will be performed for each exercise. The SNACK group will then perform a single set of six repetitions at the six-repetition maximum load (i.e., 6-RM; the load predicting momentary muscle failure on the 7th repetition), while the TRAD group will perform three work sets for each exercise at the 12-RM load (i.e., the load predicting momentary muscle failure on the 13th repetition). Two minutes of passive recovery will be allowed between sets for the TRAD group. Appropriate loads will be determined during familiarisation where participants will perform sets (of either six or twelve repetitions depending on the group) at increasing loads until the 6-RM (SNACK) or 12-RM (TRAD) is determined. Participants in both groups will be instructed to perform both the concentric and eccentric phase of each repetition in a controlled manner (~2 s). All resistance training sessions will be monitored by a qualified exercise professional and strong verbal encouragement will be provided during each work set. Once the researchers are confident participants could exceed the prescribed number of repetitions with the current load while maintaining correct form and movement control, load progression (~2.5-5 kg depending on the exercise) will be applied for the next training session. Exercise/nutrition control: For 24 h before the first pre-testing visit, participants will be asked to avoid any structured exercise and record a detailed food (and fluid intake) diary. Participants will then be asked to replicate this dietary and fluid intake as closely as possible for the 24 h prior to all subsequent testing visits. On the morning of the pQCT and DXA scans (PRE visit 1 and POST visit 1), participants will be required to report to the laboratory after an 8-10 h fast. 5. All strength/neuromuscular performance testing and resistance training sessions will be implemented and supervised by qualified and experienced exercise professionals educated in exercise science/physiology. All DXA and pQCT scans will be performed by individuals who have undertaken clinical densitometry training and hold a current radiation use license with the Department of Health. 6. All testing sessions and the resistance training intervention will be delivered face-to-face. 7. All testing and resistance training sessions will be undertaken within the exercise physiology laboratories in Building J (levels 1 and 5), Deakin University, Melbourne Burwood campus. 8. Participants will undertake one of two resistance training interventions for 8 weeks (2 sessions per week): 1) low-volume, high-load strength “snacking” (SNACK group) or 2) traditional higher-volume, lower-load resistance training (TRAD group). Resistance training will consist of five exercises (leg press, chest press, seated row, leg extension, and leg curl). One warm-up set (six repetitions at ~75% of load in each work set) will be performed for each exercise. The SNACK group will then perform a single set of six repetitions at the six-repetition maximum load (i.e., 6-RM; the load predicting momentary muscle failure on the 7th repetition), while the TRAD group will perform three work sets for each exercise at the 12-RM load (i.e., the load predicting momentary muscle failure on the 13th repetition). Two minutes of passive recovery will be allowed between sets for the TRAD group. Appropriate loads will be determined during familiarisation where participants will perform sets (of either six or twelve repetitions depending on the group) at increasing loads until the 6-RM (SNACK) or 12-RM (TRAD) is determined. Participants in both groups will be instructed to perform both the concentric and eccentric phase of each repetition in a controlled manner (~2 s). All resistance training sessions will be monitored by a qualified exercise professional and strong verbal encouragement will be provided during each work set. 9. Resistance training loads will be individualised so that participants in the SNACK group will perform a single set of six repetitions at the six-repetition maximum load (i.e., 6-RM; the load predicting momentary muscle failure on the 7th repetition), while the TRAD group will perform three work sets for each exercise at the 12-RM load (i.e., the load predicting momentary muscle failure on the 13th repetition). Once the researchers are confident participants could exceed the prescribed number of repetitions with the current load while maintaining correct form and movement control, load progression (~2.5-5 kg depending on the exercise) will be applied for the next training session. 11. Adherence to the intervention will be determined as the number of resistance training sessions completed by participants compared to the total number planned (16 over 8 weeks).