High-Intensity Interval Training — alternating short bursts of maximum effort with recovery periods — is one of the most extensively researched exercise approaches in sports science. Its central appeal is efficiency: significant cardiovascular, metabolic, and even strength adaptations from sessions of 20–30 minutes. But understanding what HIIT actually does, and who should be using it, is more useful than simply adding it to your routine because everyone is talking about it.
The Physiology
During a high-intensity interval — working at 85–100% of maximum heart rate — the body is pushed beyond its aerobic capacity. Oxygen delivery can't keep pace with energy demand, so the body supplements aerobic metabolism with anaerobic glycolysis, producing ATP rapidly from glucose and generating lactate as a byproduct. This recruits fast-twitch muscle fibres that steady-state cardio doesn't access, producing adaptations that complement — rather than duplicate — lower-intensity training.
Recovery intervals allow partial phosphocreatine replenishment and lactate clearance, preparing for the next effort. The work:rest ratio determines the training stimulus: shorter rest periods produce a more demanding cardiovascular challenge; longer rest allows more complete recovery and higher quality work intervals.
What the Evidence Actually Shows
VO2 max improvement — arguably the single best predictor of long-term health and longevity — occurs rapidly with HIIT. A 2017 meta-analysis found HIIT produced similar or superior VO2 max improvements to moderate-intensity continuous training in roughly one-third to one-half the time. Insulin sensitivity improvements are rapid and substantial — a single HIIT session can improve glucose uptake by skeletal muscle for 24–72 hours, with regular HIIT producing sustained improvements comparable to some pharmaceutical interventions for people at risk of type 2 diabetes. The post-exercise calorie burn (EPOC) is greater than after steady-state exercise — typically 50–200 extra calories — real but often significantly overstated in popular fitness culture.
Who It's Appropriate For
HIIT is not for everyone. Deconditioned individuals, people with cardiovascular disease, or those new to regular exercise should build an aerobic base through moderate-intensity training before introducing genuine HIIT. "HIIT" in most gym classes is often moderate-to-high intensity rather than true maximum effort — and that's appropriate for beginners. True HIIT at genuinely maximum effort requires a fitness foundation to be safe and productive.
For trained individuals, two to three HIIT sessions per week with adequate recovery between them is appropriate. The adaptations occur during recovery, not during the session — insufficient recovery produces overtraining: declining performance, persistent fatigue, and immune suppression.
Nutrition Around HIIT
HIIT depletes muscle glycogen significantly. A post-session combination of carbohydrates for glycogen replenishment and 20–30g of protein for muscle synthesis — a grain bowl, a protein box, Greek yoghurt with fruit — within 30–60 minutes optimises recovery. Pre-session, a small carbohydrate snack 60–90 minutes before training supports performance without causing digestive discomfort during intense effort.
Fuel Your HIIT Training With Vanda's Kitchen
The nutritional principles that support hiit training are most effectively implemented through consistent daily food choices rather than occasional efforts. Vanda's Kitchen's office lunch delivery — certified halal, 100% nut-free, freshly prepared Filipino-inspired food — provides a daily nutritional foundation that supports your training and performance. Lean proteins for muscle maintenance, complex carbohydrates for sustained energy, fresh vegetables for micronutrients: the building blocks of a genuinely sports-supportive diet delivered to your desk every working day.
Our EC4 kitchen near St Paul's Cathedral serves City professionals who balance demanding careers with active lifestyles. Fresh, nutritious food that fuels the working day and the training session — without the processed alternatives that undermine both. Order for your office or read our healthy office lunch delivery guide.
For related reading, see recovery foods after sport and gym nutrition guide. WhatsApp us or get in touch.
Fresh, Nutritious Food at Vanda's Kitchen
Vanda's Kitchen near St Paul's Cathedral EC4 provides one of the most nutritionally complete and allergen-safe food options in the City of London. Our Filipino-inspired menu is built around lean proteins, fresh vegetables, and complex carbohydrates — the nutritional combination that supports sustained energy, cognitive performance, and the various health outcomes covered in this article. Our food is certified halal, prepared in a 100% nut-free kitchen, and fully allergen-labelled, making it appropriate for the broadest range of dietary requirements in London's diverse workforce.
For City professionals who want genuinely nutritious daily lunches without leaving the office, our Freedom Tray delivery service provides fresh, labelled food to your desk from our EC4 kitchen. Our Selfridges Food Hall presence confirms the quality standard we maintain. To order for your team or to discuss corporate delivery, view our team lunch options, WhatsApp us, or send an enquiry. Read our healthy office lunch delivery guide for more on what we offer.
Why London Professionals Choose Vanda's Kitchen
Whether you are managing dietary requirements for a team, looking for a nutritious daily lunch, or sourcing catering for a corporate event, Vanda's Kitchen near St Paul's Cathedral EC4 provides a consistent answer. Our kitchen is 100% nut-free as a permanent standard — no exceptions, no special requests needed. We are independently certified halal through the Halal Friendly List. We hold a 5-star food hygiene rating and our products are stocked in Selfridges Food Hall.
Our food is freshly prepared daily from our EC4 kitchen, rooted in Filipino culinary tradition and designed to deliver both nutritional quality and genuine flavour. For corporate lunch delivery, team catering, and event food across London, we offer a complete solution with the allergen credentials, dietary certifications, and food quality that London's most demanding clients require. View our team lunch options, WhatsApp us, or send an enquiry — we respond the same day.