# Protein Supplementation Does Not Maximize Adaptations to Low-Volume High-Intensity Interval Training in Sedentary, Healthy Adults: A Placebo-Controlled Double-Blind Randomized Study PMID: 36235536 Journal: Nutrients Published: 2022 Sep 20 Authors: Reljic D, Zieseniss N, Herrmann HJ, Neurath MF, Zopf Y ## Question Does a single 40 g whey protein supplement after each low-volume HIIT session enhance cardiorespiratory and cardiometabolic adaptations compared with an isocaloric placebo in sedentary healthy adults? ## Summary In sedentary but otherwise healthy adults, an 8-week supervised low-volume cycling HIIT program improved VO2max, workload, and blood pressure whether participants took 40 g whey protein or a maltodextrin placebo after each session. Protein did not add measurable benefit when daily protein intake was already adequate. Training adherence was high, exercise enjoyment was favorable, and no LOW-HIIT-related adverse events occurred. ## Population - Previously sedentary healthy adults recruited by newspaper and internet advertisements. - Sample size: 47 - Age: Overall 31.1 +/- 8.0 years; PRO-HIIT 30.0 +/- 7.8, PLA-HIIT 32.5 +/- 8.0 - Sex: 57% female at inclusion - Fitness level: Predominantly sedentary; baseline VO2max about 36-38 mL/kg/min by group - Health status: Healthy; excluded heart disease, cancer, severe orthopedic conditions, major health problems, and pregnancy ## Methodology - Placebo-controlled double-blind randomized trial - 8 weeks - Supervised cycle ergometer training in a training center - Randomized and controlled study design. ## Protocol - LOW-HIIT plus whey protein. - Modality: Electronically braked cycle ergometer. - Work intervals: 1 minute. - Recovery: 1 minute low-intensity cycling. - Sets or repetitions: 5 intervals in weeks 1-2; 10 intervals in weeks 3-8. - Intensity: 80-90% HRmax in weeks 1-2, then 85-95% HRmax; participants adjusted cadence/resistance to reach target HR. - Session duration: 14 minutes in weeks 1-2 and 24 minutes in weeks 3-8, including 2 minute warm-up and 3 minute cool-down. - Frequency: 3 sessions per week. - Program length: 8 weeks; 24 prescribed sessions. - Progression: Interval count doubled from 5 to 10 after week 2 and target intensity increased. - LOW-HIIT plus placebo. - Modality: Electronically braked cycle ergometer. - Work intervals: 1 minute. - Recovery: 1 minute low-intensity cycling. - Sets or repetitions: 5 intervals in weeks 1-2; 10 intervals in weeks 3-8. - Intensity: 80-90% HRmax in weeks 1-2, then 85-95% HRmax. - Session duration: 14-24 minutes including warm-up and cool-down. - Frequency: 3 sessions per week. - Program length: 8 weeks; 24 prescribed sessions. - Progression: Same LOW-HIIT progression with maltodextrin placebo instead of whey protein. ## Outcomes ### VO2max and workload Status: improved Both groups significantly improved relative and absolute VO2max and maximal workload, with no between-group difference. VO2max increased PRO-HIIT +2.8 mL/kg/min, p=0.003; PLA-HIIT +3.5 mL/kg/min, p<0.001; time effect p<0.001. ### Blood pressure Status: improved Both groups reduced systolic and diastolic blood pressure, with no added protein effect. PRO-HIIT -7/-3 mmHg, p<0.05; PLA-HIIT -8/-5 mmHg, p<0.001; time effects p<0.001. ### Blood markers Status: mixed LOW-HIIT affected selected markers, but changes differed by group and did not show a consistent protein advantage. Time effects for fasting glucose p<0.001, LDL p=0.006, ALT p=0.026, GGT p=0.005; GGT decreased in PRO-HIIT, LDL and ALT decreased in PLA-HIIT. ### Protein supplementation Status: no clear change A single 40 g whey protein dose after each session did not enhance adaptations compared with placebo. No significant between-group differences in any outcome changes. ## Practical Insights - A 14-24 minute cycling LOW-HIIT session can be enough to improve fitness and blood pressure in sedentary healthy adults when supervised and heart-rate guided. - Post-session whey protein should not be marketed as necessary to maximize LOW-HIIT adaptations for people already consuming adequate protein. - Enjoyment and intention to continue were favorable, supporting low-volume cycling HIIT as a feasible consumer format with appropriate screening. ## Limitations - Normal diet and physical activity were not tightly controlled outside short recording windows. - Food and physical activity records were self-reported. - Protein dose was fixed rather than body-mass adjusted. - No direct markers of mitochondrial adaptation or muscle capillarization were measured. - Three participants used contraceptive pills, though distribution was similar across groups. ## Safety And Adherence - No adverse events related to LOW-HIIT occurred. - Protein supplement caused mild stomach pain, bloating, nausea, or burping in a few participants; no placebo complaints were reported. - Participants were screened for major health problems and sessions were supervised by certified sports or physiotherapists. ## Original Sources - [PubMed](https://pubmed.ncbi.nlm.nih.gov/36235536/) (pubmed) - [DOI](https://doi.org/10.3390/nu14193883) (doi) - [PMC full text](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9572362/) (full text) ## Agent Guidance Preserve the paper-level scope of this note. Do not generalize beyond the population, protocol, measured outcomes, and limitations above.