Your hydration strategy should match the session you are doing. A 2.5 hour long run creates different hydration needs to a 60-90 minute hybrid session made up of running, sleds, carries and high-intensity work. Both can involve significant sweat losses, but the duration, intensity, conditions and opportunities to drink are different.

Long runs: endurance.

The longer you run, the more opportunity there is for fluid and sodium losses to accumulate and impact your performance. Someone running for 45 minutes may finish perfectly comfortable without drinking anything during the session. Stretch that run out to two or three hours, particularly in hotter temperatures, and hydration becomes much more crucial.

There is no universal litres-per-hour target because sweat rates vary considerably between athletes.[1] A useful approach is to estimate your own sweat rate during long runs and use that as a guide. As discussed in our article on how much sodium you're actually losing, sweat rate can be estimated using pre- and post-session body weight alongside any fluid consumed during the run.

You don't necessarily have to replace every millilitre of sweat as you lose it. Instead, you should tailor your hydration plan to your individual body, session, and sweat rate, so that you're getting enough fluid to limit excessive dehydration without drinking more than you are losing.[1,2]

Hybrid or HYROX sessions: higher intensity, shorter window.

Hybrid sessions are often shorter than your standard long run, but that also does not mean hydration is unnecessary. Combining running intervals with movements like sled pushes, lunges, farmers carries or burpees is still a demanding session, and athletes may still sweat heavily, particularly in a warm gym or outdoor environment. The notable difference is that there are usually fewer convenient opportunities to drink.

During a steady long run you can usually sip regularly from a bottle or hydration vest. During a hybrid session, you might complete several work blocks before pausing for a drink. For most athletes, this means hydrating around the session: start your session already well-hydrated, take advantage of natural breaks, and replace meaningful fluid losses after the session.

Start hydrated.

This applies to both session types. You want to begin your session in a normal hydrated state rather than trying to fix a fluid deficit once the session has already started. Sports hydration guidelines recommend normal food and fluid intake in the hours beforehand, with additional fluid where required.[2]

You don't need to force huge amounts of water immediately before training. Excessive fluid consumption can actually create its own problems. Ideally, you'll have had some fluid prior to the session and be feeling ready, not thirsty.

When is water enough?

For shorter sessions where sweat losses are relatively low, water may be all you need. As sessions get longer, hotter or sweatier, an electrolyte drink can be helpful because sweat contains both fluid and electrolytes [predominantly sodium and chloride].

Session	Hydration standard
Short hybrid session in cool conditions	Water may be sufficient
Hard hybrid session in heat	Fluid + electrolytes may be useful
90+ min long run	Start considering fluid and sodium losses
2–3 hr long run in heat	A planned fluid and electrolyte strategy becomes increasingly relevant

These are general examples rather than fixed rules. An athlete who sweats heavily may need to think about hydration earlier than someone with a relatively low sweat rate.

Sodium intake.

Sodium requirements vary considerably between athletes because both sweat rate and sweat sodium concentration differ from person to person. A long run gives those sodium losses more time to accumulate, which is why sodium intake is important to consider during prolonged endurance sessions.

Hybrid athletes should also be aware of sodium losses. A very high sweat rate during a hard session in hot conditions can still create notable sodium losses over a shorter period. The key is to think about sodium in the context of how much you sweat and how much fluid you are actually drinking, rather than assuming the highest-sodium product must be the best option.

Factor in heat and humidity.

As conditions become hotter or more humid, heat stress increases and sweat losses can rise as the body works harder to regulate temperature. Fluid requirements can therefore change significantly between a winter training session and the same session during an Aussie summer.[1]

Research in elite endurance athletes competing in hot, humid conditions also shows that planned hydration strategies are common, but individual responses and body mass losses still vary considerably.[3] For long runs, that might mean carrying more fluid or planning refill points. For hybrid sessions, it may involve just making sure fluid is accessible between rounds and paying more attention to what you replace afterwards.

Use training to work it out.

Your hydration strategy should be tested in the same way as your fuelling strategy. Pay attention to:

• how much fluid you start with
• how much you drink
• changes in body weight
• how salty your sweat appears to be
• weather and temperature
• whether you finish excessively thirsty
• how you feel later in the session

For long runs, sweat-rate testing can help you build a more deliberate race-day plan. For hybrid sessions, it may be enough to identify whether you consistently finish significantly dehydrated or not, and adjust your pre-, intra- and post-session fluid intake accordingly.

There is no one-size-fits-all hydration plan.

A runner might need a structured fluid and sodium strategy for a three-hour marathon-specific session, then require considerably less during a 60-minute hybrid workout later in the week. This is normal. Hydration should reflect the duration and intensity of the session, your individual sweat losses and the conditions you're training in.

There is no reason to force the same electrolyte intake into every session. Work out what the session is actually asking of you, then build the hydration plan around that.

 

References.

1. Baker LB. Sweating Rate and Sweat Sodium Concentration in Athletes: A Review of Methodology and Intra/Interindividual Variability. Sports Medicine. 2017;47(Suppl 1):111–128.
2. McDermott BP, Anderson SA, Armstrong LE, et al. National Athletic Trainers' Association Position Statement: Fluid Replacement for the Physically Active. Journal of Athletic Training. 2017;52(9):877–895.
3. Racinais S, Alhammoud M, Nasir N, et al. Hydration and cooling in elite athletes: relationship with performance, body mass loss and body temperatures during the Doha 2019 IAAF World Athletics Championships. British Journal of Sports Medicine. 2021;55(23):1335–1341.
4. Sawka MN, Burke LM, Eichner ER, et al. American College of Sports Medicine position stand. Exercise and fluid replacement. Medicine & Science in Sports & Exercise. 2007;39(2):377–390.