Beat the heat: Summer training support

As temperatures climb in the UK and across many US states, familiar runs can suddenly feel much harder. In the heat, your body is trying to do two big jobs at once: send blood to the skin to cool you down, and deliver oxygen and nutrients to working muscles. When that balance tips, pace feels heavy, your heart rate drifts up, and even steady efforts can start to feel like a slog. 

CurraNZ New Zealand blackcurrant extract has been shown in multiple human studies to support vascular function, blood flow and cardio‑metabolic responses during exercise, including in hot conditions. Taken daily, the anthocyanins can enhance vasodilation and increase limb blood flow, while lowering vascular resistance and blood pressure in various groups. Those changes mean muscles can receive more oxygen‑rich blood for the same cardiovascular effort, helping legs feel lighter and supporting performance when the mercury rises.

“Summer legs”: Blood flow in the heat

In warmer weather, more blood is shunted to the skin for cooling. That can leave less available for your working muscles and gut, contributing to that “heavy, cooked” feeling late in a run.

Research on our supplement has shown meaningful increases in artery diameter and limb blood flow during exercise, alongside reductions in cardiovascular strain. 

Athletes in climbing and intermittent‑sprint protocols have also demonstrated faster muscle re‑oxygenation and better maintenance of high‑intensity efforts, suggesting improved delivery and use of oxygen at the muscle.

Cardio‑metabolic and gut support in hot conditions

Hot‑weather exercise usually pushes metabolism towards greater carbohydrate use and higher physiological strain. In a 60‑minute treadmill run at 65% VO₂max in 34°C heat, seven days of New Zealand blackcurrant extract (600 mg CurraNZ) increased fat oxidation and reduced carbohydrate use, without negatively affecting heart rate or core temperature. 

Other work has shown improved insulin sensitivity, lower blood pressure and reduced arterial stiffness in different populations, pointing to wider cardio‑metabolic support that matters for everyday athletes training hard through summer.

The gut also takes a hit in the heat, as blood is diverted away from the intestines. CurraNZ has been shown to reduce markers of intestinal cell damage and improve indices of gut barrier permeability during exertional heat stress, while follow‑up analyses reported fewer and less severe gastrointestinal symptoms during 60 minutes of running in hot conditions. 

For runners and triathletes, that combination of better circulation, fuel use and GI comfort is highly relevant for long races and key sessions.

Putting it into practice

For best effect, position CurraNZ as part of a broader hot‑weather strategy, not a replacement for good practice. Aim for 600 mg daily for at least seven days before important sessions or races, then continue through the summer block. Pair it with solid hydration and sodium intake based on sweat losses, and adjust pace to heart rate and RPE on the first truly hot days.

Planning big goals between June and September? 

A CurraNZ subscription that keeps your daily supply covered through your build‑up and race‑day period. Lock in your summer supply before the heat really kicks in, and give your circulation, gut and cardio‑metabolic system extra support for the sessions that matter most.

Grab your summer training bundle HERE

*Only valid on CurraNZ Original. Offer expires May 31, 2026

Start a subscription HERE

*US customers: We dispatch from a 3PL in Texas for fast shipping within the US!