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Updated: May 25, 2026

A Real-World High-Intensity Interval Training Protocol for Cardiorespiratory Fitness Improvement
Published on: February 22, 2022
Cardiovascular and neuromuscular performance responses induced by 8 weeks of basic training followed by 8 weeks of
Matti Santtila1, Keijo Häkkinen, Bradley C Nindl
1Defence Forces, Personnel Division of Defence Command, Helsinki, Finland. matti.santtila@mil.fi
Abstract:
The purpose of this study was to examine the changes in cardiovascular and neuromuscular performances induced by 8 weeks of basic training (BT) period followed by 8 weeks of special training period (STP). Fifty-seven male soldiers (age: 19.2 ± 0.9 years, height: 1.79 ± 0.06 m, body mass: 73.8 ± 12.4 kg) volunteered for tests of peak oxygen uptake (VO2peak) and maximal bilateral isometric force of the leg and arm extensor muscles. During the first 8 weeks, VO2peak increased by 5.6% (45.0 ± 8 vs. 48.8 ± 7 ml·kg(-1)·min(-1)), but no further changes were observed during the next 8 weeks (49.1 ± 8 ml·kg(-1)·min(-1)). Maximal isometric force of the arm and leg extensors increased during the first 8 weeks (arm: 680 ± 182 vs. 774 ± 182 N; leg: 2,584 ± 724 vs. 2,730 ± 823 N) by 3.8% (p < 0.001) and 8.1% (p < 0.001), respectively, with no further increases by week 16 (arm: 718 ± 170 N; leg: 2,679 ± 967 N). Body fat percentage (pre: 10.4 ± 4, post-BT: 9.0 ± 4, post-STP: 9.3 ± 3%), and waist circumference decreased (83.4 ± 10, 80.9 ± 8, 80.8 ± 7 cm) during BT, whereas no changes were noticed thereafter. In conclusion, it was found that physical fitness of conscripts improved significantly during the Finnish military 8-week BT at the beginning of their military service. A plateau in the improvement of physical performance during STP is largely attributed to a lack of continued progression or periodization in their training program. For optimal improvements in physical performance during STP, it might be reasonable to include a structured physical training with greater intensity and training volume with optimal periodization than during BT.
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