Long-term Adaptations of Skeletal Muscle After Hybrid Training.

NCT07341711 | Not Yet Recruiting

• 1 other identifier: 2482/4.12.2024
• Study Type: interventional
• Target: 30
• Locations: 1 country
• Sites: 1

Brief Summary

Obesity is a major challenge for public health and renders it imperative to reduce its prevalence. High intensity interval training (HIIT) is a form of exercise training that can efficiently induce weight loss in adults with overweight or obesity, even in the absence of dietary intake manipulation. Hybrid type training represents a form of HIIT, that incorporates both cardiorespiratory and musculoskeletal stimuli, by combining multiple types of exercise into a circuit-type, interval style workout. Recent evidence suggests that long-term participation in hybrid HIIT results in significant health-related benefits. However, the molecular mechanisms driving the chronic effects of hybrid HIIT on cardiometabolic and musculoskeletal health remains to be elucidated.

Conditions

Obesity & Overweight

Keywords

obesity; overweight; high-intensity interval training; skeletal muscle

Outcome Measures

Primary Outcomes (24)

• Change in mitochondrial size

  Mitochondrial size will be measured using transmission electron microscope

  At baseline and at 6 months

• Change in mitochondrial density

  Mitochondrial density will be measured using transmission electron microscope

  At baseline and at 6 months

• Change in mitochondrial count

  Mitochondrial count will be determined using transmission electron microscope

  At baseline and at 6 months

• Change in mitochondrial distribution

  Mitochondrial distribution will be determined using transmission electron microscope

  At baseline and at 6 months

• Change in maximum oxygen consumption (VO2max)

  Maximum oxygen consumption (VO2max) will be assessed during a cardiopulmonary exercise testing by using a portable indirect calorimetry system

  At baseline and at 6 months

• Change in muscle fiber cross-sectional area

  Muscle fiber cross-sectional area (μm2) will be measured using immunohistochemical staining for myosin heavy chain

  At baseline and at 6 months

• Change in PAX7+ satellite cells count

  PAX7+ satellite cells will be determined using immunohistochemistry techniques.

  At baseline and at 6 months

• Change in total protein content

  Total protein content (total RNA) will be determined in skeletal muscle tissue using real time quantitative-Polymerase Chain Reaction (q-PCR) technique

  At baseline and at 6 months

• Change in myonuclei content

  Myonuclei content will be determined in skeletal muscle tissue using immunohistochemistry techniques

  At baseline and at 6 months

• Change in peroxisome proliferator-activated receptor-gamma coactivator -1a (PGC-1a) expression

  PGC-1a expression in skeletal muscle tissue will be assessed using immunoblotting techniques.

  At baseline and at 6 months

• Change in Krebs cycle (TCA cycle) enzymes activity

  Krebs cycle enzymes activity will be determined using the Seahorse XF Analyzer

  At baseline and at 6 months

• Change in protein expression of respiratory chain complexes

  Protein expression of respiratory chain complexes will be determined using immunoblotting techniques

  At baseline and at 6 months

• Change in cytochrome C oxidase amount and expression

  Cytochrome C oxidase amount and expression will be assessed using immunohistochemistry and immunoblotting techniques

  At baseline and at 6 months

• Change in ATP synthase amount and expression

  ATP synthase amount and expression will be assessed using immunohistochemistry and immunoblotting techniques

  At baseline and at 6 months

• Change in citrate synthase amount and expression

  Citrate synthase amount and expression will be assessed using immunohistochemistry and immunoblotting techniques

  At baseline and at 6 months

• Change in succinate dehydrogenase amount and expression

  Succinate dehydrogenase amount and expression will be assessed using immunohistochemistry and immunoblotting techniques

  At baseline and at 6 months

• Change in NADH dehydrogenase amount and expression

  NADH dehydrogenase amount and expression will be assessed using immunohistochemistry and immunoblotting techniques

  At baseline and at 6 months

• Change in mitochondrial oxygen consumption rate

  Mitochondrial oxygen consumption rate will be determined using the Seahorse XF Analyzer

  At baseline and at 6 months

• Change in spare respiratory capacity

  Spare respiratory capacity will be determined using the Seahorse XF Analyzer

  At baseline and at 6 months

• Change in mitochondrial maximal respiration

  Maximal mitochondrial respiration will be determined using the Seahorse XF Analyzer

  At baseline and at 6 months

• Change in mitochondrial basal respiration

  Mitochondrial basal respiration will be determined using the Seahorse XF Analyzer

  At baseline and at 6 months

• Change in non-mitochondrial respiration

  Non-mitochondrial respiration will be determined using the Seahorse XF Analyzer

  At baseline and at 6 months

• Change in body fat percentage

  Body fat percentage will be assessed using dual energy x-ray absorptiometry (DEXA)

  At baseline and at 6 months

• Change in diastolic arterial pressure

  Diastolic blood pressure will be measured using a sphygmomanometer

  At baseline and at 6 months

Secondary Outcomes (30)

• Change in density and distribution of capillaries

  At baseline and at 6 months

• Change in skeletal muscle fiber typing

  At baseline and at 6 months

• Change in GLUT-4 protein expression

  At baseline and at 6 months

• Change reduced glutathione content in skeletal muscle cells

  At baseline and at 6 months

• Change in glutathione peroxidase activity in skeletal muscle cells

  At baseline and at 6 months

Study Arms (2)

Intervention group

EXPERIMENTAL

Participants in this arm will participate in three hybrid-type HIIT sessions per week over a 6-month period while receiving a balanced diet

Other: Exercise training

Control group

ACTIVE COMPARATOR

Participants in this arm will receive a balanced diet over the 6-month period but will not participate in exercise training

Other: Control group

Interventions

Exercise training OTHER

Participants will perform a six-month hybrid training program while receiving a balanced diet. The periodization of hybrid training intervention will consist of three 2-month phases of gradually increased exercise intensity and volume. In every training will participate 5-8 individuals. The training will contain 6-12 different exercises (stations), depending on the phase of the intervention, which will be executed in a circuit for a total of 2-3 rounds, with 2-3 minutes of rest period between sets (depending on the phase). The exercise execution will last 20-45 seconds, and the rest between them will last 30-60 seconds (depending on the phase), while the exercise intensity will range from 75 to 85% of maximal heart rate. The stations of hybrid training will contain multi-joint exercises or neuromuscular activation exercises using either body weight resistance or portable equipment.

Intervention group

Control group OTHER

Participants will receive a balanced diet but will not participate in any type of exercise training over a six month period.

Control group

Eligibility Criteria

• Age: 30 Years - 50 Years
• Sex: all
• Healthy Volunteers: Yes
• Age Groups: Adult (18-64)

You may qualify if:

• BMI: \>25 kg/m2 and \<40 kg/m2
• Untrained individuals (abstain \>1 year from exercise training)
• No dietary intervention over the last 6 months preceding the study
• Low cardiorespiratory fitness level (VO2max: \<45 ml/kg/min)
• No use of any medication, dietary supplements
• Low risk for cardiovascular disease
• A weight loss \<10% over the last 6 months preceding the study
• Fee of non-communicable diseases (excluding metabolic syndrome)

You may not qualify if:

• Low participation rate (\<80% completion of the exercise training sessions)
• Unbalanced diet
• Participation in additional exercise training regimes
• Cosumption of anti-inflammatory of pain relief medication

Sponsors & Collaborators

• University of Thessaly: lead

Study Sites (1)

Department of Physical Education and Sport Science Trikala, University of Thessaly

Trikala, Thessaly, 42100, Greece

Location

MeSH Terms

Conditions

Obesity; Overweight

Interventions

Exercise; Control Groups

Condition Hierarchy (Ancestors)

Overnutrition; Nutrition Disorders; Nutritional and Metabolic Diseases; Body Weight; Signs and Symptoms; Pathological Conditions, Signs and Symptoms

Intervention Hierarchy (Ancestors)

Motor Activity; Movement; Musculoskeletal Physiological Phenomena; Musculoskeletal and Neural Physiological Phenomena; Epidemiologic Research Design; Epidemiologic Methods; Investigative Techniques; Research Design; Methods

Central Study Contacts

Ioannis G Fatouros, Professor

CONTACT

24310 47047; ifatouros@pe.uth.gr

Study Design

• Study Type: interventional
• Phase: not applicable
• Allocation: RANDOMIZED
• Masking: NONE
• Purpose: OTHER
• Intervention Model: PARALLEL
• Sponsor Type: OTHER
• Responsible Party: PRINCIPAL INVESTIGATOR
• PI Title: Professor

Study Record Dates

• First Submitted: January 5, 2026
• First Posted: January 14, 2026
• Study Start: January 8, 2026
• Primary Completion (Estimated): June 30, 2026
• Study Completion (Estimated): December 20, 2026
• Last Updated: January 14, 2026

Record last verified: 2025-10

Locations

GR (1)