written by Meg Garvey, PhD.
Human Powered Health: Executive Summary
Cyclists are exposed to a variety of environmental challenges which puts them at risk of additional physiological strain and cognitive function due to dehydration. The purpose of this study was to determine the feasibility of deploying Nix Biosensors’ as a non-invasive hydration monitoring tool during training sessions for an elite cycling team during training camp.
Sweat rate and electrolyte concentration were measured using Nix Biosensors on cyclist athletes on Team Human Powered Health (HPH) (n=13, 100% male) participating in a training camp (collecting data during a round of threshold testing and one long ride on different days). All cyclists indicated the sensors were barely noticeable and they all articulated interest in further use of the product.
The average fluid and electrolyte losses were 65.3 (± 20.1) oz and 3,563 (1,378.2) mg respectively. The average sweat rate was 10.5(± 3.4) oz/hr. It was found that fluid loss, sweat rate, total electrolytes lost, and electrolyte concentration varied among cyclists, particularly between the different formats of training. Although more research is needed, measuring individual sweat rate and concentration with Nix Biosensors can provide valuable information to create individual hydration recommendations.
While cycling is commonly viewed as an individual sport, a team is only as strong as its peloton. For elite athletes the difference between a leaderboard standing and the middle of the pack are measured by very small margins. One performance parameter that has received recent attention is hydration.
It was communicated to the Nix Physiology Team that the coaches and other providers had noticed some Team HPH athletes were much heavier and saltier sweaters than others. As it is always a goal to be able to sustain high working levels over longer periods of time it began a conversation around how they could utilize electrolyte and fluid loss information to help fuel and refuel their athletes. A particular area of concentration centered around travel and drastic climate changes (i.e. desert to snow, humid to dry, etc.).
The purpose of this study was to determine the feasibility of deploying Nix Biosensors as a real-time hydration monitoring tool during practice rides during training camp to provide insight for hydration strategies during both training and competition.
The primary objectives for this study were as follows:
- What is the feasibility of utilizing Nix Biosensors for sweat testing and hydration strategy building for the athletes within the team?
- Is the sensor a practical solution to supporting this population’s hydration strategy during training and travel?
- How quickly does dehydration occur in representative environmental conditions?
- How much variation in sweat rate exists between teammates within the Partner’s organization?
- How much variation in sweat rate exists between race locations and conditions?
- How much variation in electrolyte concentration requirements exists between teammates within the Partner’s organization?
Study Design & Methods
The sensors were delivered directly to the HPH team. Representatives from Nix Biosensors provided remote support leading up to data collection and during the process.
Data & Results
- Day One was a lactate threshold test: 40km warm-up ride, followed by 4 repeat efforts of 10 min, steady, 5-7% steep climb at 92% max functional threshold power. Rest between the efforts at least equal to the interval time. For some it could have been 20-25 minutes of rest.
- Ambient temp was 56°F with 83% humidity.
- The short interval nature of the lactate testing on Day One was not conducive to consistent sweat production by the athletes. The length of time elapsed between intervals permitted drying of the sweat in the channel. This use case is known to yield potentially compromised data due to evaporation.
- Day Two consisted of a 370 minute ride: 210 minutes with a sustained workload of 30 Kj/kg, 2-5 minute max pushes, and a warm up/cool-down.
- Ambient temp and humidity were reportedly similar to Day One.
- The riding protocol on Day Two yielded good results and can be utilized as a sweat data point for 76% of the riders involved with that data collection.
Nix Hydration Assessment
From this training ride, Team HPH can start to get a sense of the variation of sweat rates and electrolyte losses within the team during the same conditions and at similar workloads. This articulates the need for individual rehydration strategies. Based on Team HPH relationships with Thorne and FastFood this helps direct product evaluation for your athletes, particularly for electrolyte needs. For a full report of individual athlete data, please see the Appendix below.
There was a high level of success from the second day of data collection as it yielded sweat data for 76.5% of the athletes present. For the individuals whose data was omitted from analyses, two had the model run with weights that may have been accidentally inputted in kg vs. pounds and two had data that were outside of the typical human dynamic range, both indicating potential protocol error. Due to these errors, the data is inappropriate to report on. In Nix data collections, these errors occur very rarely, our recommendation is for future data collections that the Nix Physiology Team be on site to support and troubleshoot collection efforts.
In summary, when comparing the athletes across the board for the second day a sweat rate range was determined to be 5.8-16.0 oz/hr, for a total loss range for 35.7-99.4 oz. This indicates that while some of the HPH athletes would need four 24 oz bottles of fluid for a 370 minute ride, others would suffice with two bottles.
Graph 1 & Graph 2
The range of sweat loss was 35.7 - 99.4 oz and the sweat rate was 5.8 - 16.0 oz/hr. This represents a 2.8x range in sweat loss, illustrating the need for individual hydration strategies.
In regards to electrolyte losses, the HPH team experienced roughly a 3-fold variation between athletes. This would represent 2.5 scoops of Thorne Catalyte (781 mg) on the lower end compared to just under 7.5 scoops on the higher end. This 3-fold loss was also observed over a consistent rate throughout the 370-minute ride. Whereas FastFood lemon lime Hydrator has a higher electrolyte content per scoop (1082 mg) and would decrease the amount of scoops needed on the upper end by 2 scoops. The sweat composition (mg/oz) is further broken down in Graph 5.
Graph 3 & Graph 4
The range of electrolyte loss was 2023.4 - 5,861.7 mg and the electrolyte loss rate was 343.6 - 945.4 mg/hr. This represents a 2.9x range in electrolyte loss, illustrating the need for individual hydration strategies.
Synthesizing all of the data, it becomes apparent that the variations between athletes are nuanced. The athlete with the highest total electrolyte loss and electrolyte loss rate is not also the athlete with the highest sweat loss and sweat rate. The heaviest sweater, based on this observation, would need to change out their 24 oz. bottle every hour and a half and have those bottles contain 1.4 scoops of Thorne Catalyte or 1 scoop of FastFood Lemon Lime Hydrator. For Team HPH’s “saltiest” sweater, they would need to change out their 24 oz. bottle every two hours and have either 2.5 scoops of Thorne Catalyte or 1.8 scoops of FastFood Lemon Lime Hydrator.
Sweat Composition is Nix’s measure of the concentration of all electrolytes in aggregate (sodium, chloride, and potassium magnesium, and calcium) in sweat. The HPH team had a sweat composition range between 38.2 - 76.4 mg/oz. This represents a 2.0x range, illustrating the need for individual hydration strategies. This difference is similar to a scoop of Thorne Catalyte (661 mg of the electrolytes above) diluting in 17 oz of water vs only 8.5 oz. or a scoop of a Lemon Lime Hydrator from Fast Food (1082 mg) diluting in 28 oz of water vs 14 oz of water.
Summary & Next Steps
Sweat rates and electrolyte losses will vary within athlete as well as athlete to athlete, due to this it is important to have enough data to get a better understanding of where an athlete’s range is and how to best strategize their refueling to optimize their performance. During this initial data collection, Team HPH athletes showed roughly a 2.8X range between athlete sweat rate and 2.9X range in electrolyte losses on this particular data collection ride. This articulates the value for individualized sweat analysis and hydration strategy.
For your particular team, the Nix Physiology Team would recommend continued testing with your athletes in a variety of conditions that will mimic the rides that they will encounter in their competition season:
- Hill repeats and long climbs
- Shorter distances at faster speeds
- Flat rides at higher distances
In addition to these protocol variations, it is also important to test under a variety of environmental conditions as well. For example, test on particularly hot and colder days, when solar load is maximal vs. cloudier days, and dry vs. rainy days. These environmental variance testing will equip Team HPH with optimal data to conduct hydration strategies for upcoming competitions.
In order to reduce the error occurrences within the data collection process it would be advantageous for at least one member of the Nix Physiology Team to be on-site to help facilitate the protocol. Once a few more conditions are completed, the Nix Team would be able to report on a larger scale to assist Team HPH nutritionists in their refueling recommendations for your athletes.