Real VO2 test results

Your muscles brought receipts.

At an easy pace, your body gets a greater share of its energy from fat. As you push harder, your body will switch to carbohydrates to keep up.

A VO₂ assessment is an exercise test that analyzes your breathing to measure oxygen use and help estimate how your body uses fat and carbs for fuel. These real test results show how that balance changes as the workout gets harder.

83–94% of the energy these athletes burned in the workout zone came from carbs

Rah popup flyer: a flexing arm holding a VO2 test chart

Tester 1

Male · 39 · 5'9" · 200 lb

1-hour HIIT workout · 151 BPM average

Carb calories per hour
804
Fat calories per hour
71
Energy from carbs 92%

Averaged across the highlighted workout-zone stages.

Calories burned per hour, by heart rate Carbs Fat
See the numbers
Tester 1: calories burned per hour at each heart rate
Heart rate Carb cal/hr Fat cal/hr From carbs
83 BPM 33 187 15%
97 BPM 38 361 10%
122 BPM 281 306 48%
135 BPM 454 269 63%
145 BPM Workout zone 679 135 83%
152 BPM Workout zone 793 77 91%
158 BPM Workout zone 940 1 100%
164 BPM 990 0 100%
167 BPM 1,001 0 100%

Tester 2

Female · 44 · 5'5" · 140 lb

1-hour workout · 144 BPM average

Carb calories per hour
567
Fat calories per hour
113
Energy from carbs 83%

Averaged across the highlighted workout-zone stages.

Calories burned per hour, by heart rate Carbs Fat
See the numbers
Tester 2: calories burned per hour at each heart rate
Heart rate Carb cal/hr Fat cal/hr From carbs
91 BPM 32 249 11%
105 BPM 29 333 8%
121 BPM 182 341 35%
134 BPM Workout zone 425 196 68%
146 BPM Workout zone 627 61 91%
152 BPM Workout zone 649 84 89%
157 BPM 718 42 94%
165 BPM 858 0 100%

Tester 3

Male · 47 · 5'10" · 150 lb

1-hour workout · 138 BPM average

Carb calories per hour
733
Fat calories per hour
43
Energy from carbs 94%

Averaged across the highlighted workout-zone stages.

Calories burned per hour, by heart rate Carbs Fat
See the numbers
Tester 3: calories burned per hour at each heart rate
Heart rate Carb cal/hr Fat cal/hr From carbs
89 BPM 79 223 26%
98 BPM 146 299 33%
124 BPM Workout zone 551 130 81%
141 BPM Workout zone 796 0 100%
149 BPM Workout zone 854 0 100%
156 BPM 916 0 100%
164 BPM 1,024 0 100%

How to read these results. Each result is from a graded treadmill VO2 test that raises speed or incline about once a minute. Values are the test's estimated calories burned per hour at each stage's heart rate. Workout-zone figures average the highlighted stages. Your numbers will depend on fitness, body size and what you've eaten. This is for education, not medical advice.

Easy pace burns fat. Workout pace burns sugar. Fuel the work. Rip. Fuel. Go.

Why it matters

Low and slow runs on fat. High heart rate runs on sugar. Fuel the workout you're actually doing.

Carbohydrate is your body's fastest fuel, and it's what your muscles reach for as intensity climbs. Your body only stores a limited amount, so topping up before a hard session helps keep the tank from running low. Rah keeps it simple: fast-digesting carbs from raw Colorado honey and sodium from Redmond Real Salt®, nothing else.

Carbs power intensity

In the workout zone, carbohydrate supplied 83–94% of these athletes' energy.

Fat fuels the easy stuff

At easy-pace heart rates, fat did most of the work. Both matter; they just show up at different speeds.

Top up before you go

Rip a packet about 10 minutes before a hard session: 23g of carbs from raw Colorado honey plus 330mg of sodium.

The sugar matters

Two sugars. Two ways in.

Honey is naturally a mix of glucose and fructose, the same pairing sports scientists now build into endurance fuel on purpose.

Inside one packet 23g of carbs, two kinds of sugar
  • Fructose ~11.5g
  • Glucose ~9.9g
  • Other sugars ~1.6g

Estimated from USDA averages for honey. Raw alfalfa honey varies a little by season and bloom.

Why two beats one Carbs your gut can absorb per hour

Glucose alone ~60 g/hr

Glucose + fructose ~90 g/hr

  • Glucose enters through its own transporter (SGLT1), which tops out near 60 g/hr.
  • Fructose uses a separate one (GLUT5), adding roughly 30 g/hr more.

Two sugars, two pathways

Glucose and fructose are absorbed through separate transporters, so your gut can take in more fuel per hour than from glucose alone.

Already broken down

Honey's sugars are single sugars. There's no extra digestion step before your body can absorb them.

Close to the ratio research favors

Endurance research has moved toward near-equal glucose and fructose. Honey lands close to 1:1 on its own.

How much per hour

Each packet is 23g of carbs. Take it with a few sips of water, and try new amounts in training before race day.

  1. Under an hour 1 packetAbout 10 minutes before you start.
  2. 1 to 2½ hours 1–3 packets an hourAbout 30–60g of carbs an hour. Start early, then every 20–40 minutes.
  3. 2½ hours + Up to 4 packets an hourUp to about 90g an hour, if you've built up to it in training.

How the sugars compare

Rah honey Glucose-only fuel Table sugar
Sugars Glucose + fructose Glucose only Sucrose (bonded pair)
Ways in 2 pathways 1 pathway 2, after splitting
Processing Raw, unfiltered Refined Refined

Sources: USDA FoodData Central, Honey (SR Legacy). Jeukendrup, Sports Med 2014. Rowlands et al., Sports Med 2015. Earnest et al., J Strength Cond Res 2004. Thomas, Erdman & Burke, Med Sci Sports Exerc 2016.

Fuel the high-heart-rate work

Bring your own receipts.

Rah Fuel 20 Pack

$50.0020 packets · $2.50 each
  • 20 single-serve 28g packets
  • 80 calories, 23g carbs and 330mg sodium each
  • No caffeine, artificial flavors, colors or preservatives
Purchase option

Free shipping across ColoradoMade in DenverSecure checkout

Rah Fuel 20 Pack $50.00