In the first part of this STEAKS Lab Report, we provided information on thermoregulation of the human body and the factors influencing it. In the second part, we want to share the results of a field study we undertook, in which we tested the effects that our women’s Contact Wear Tops have on the skin temperature of athletes wearing them. Once again our trusted engineer and roller derby skater Block Sabbath helped with this field study and wrote up the results. A huge thank you also goes out to the skaters participating in this study, the Rhein-Neckar Delta Quads from Mannheim, Germany, who made sure the heat sensors stayed in place during an entire tournament day. We also want to acknowledge and thank all roller derby photographers and referees, who’s timestamps and stats documentation helped to match the data to the tournament time table. Last but not least we want to thank our STEAKS Crew who participated in the pre-study to this field test and who let us equip them with sensors during RollerCon 2018.
Our Field Study – Material & Methods
During a roller derby game day, we conducted a field test using temperature sensors (Orthotimer, Rollerwerk Medical Engineering, Germany) placed between the skaters’ boobs, logging temperature every 15 minutes with an accuracy of < 0.5 ° C. The test started at 10 am and went on until 8 pm, logging temperature throughout the entire game day. With the very low measuring frequency of 15 minutes, this method only allows a rough idea of the temperature development during the day. Other values such as core temperature, humidity and air flow were not considered.
9 individual roller derby skaters with different schedules during the day participated in the field test:
Table 1: Overview of the game day activity and the garments worn by skaters as well as the reference measurements; colour coding: white (not played/ no data), orange (wearing a STEAKS® Contact Wear padded contact top in the game), grey (wearing regular sports bras and shirts and no STEAKS® Contact Wear tops).
Participants wore a sports bra as a base layer and a team jersey as a top layer. When wearing the STEAKS® Contact Wear top (either Smackanwa Vest, Pro Top or Puzzle Full Armour Shirt), this was either the middle layer (Smackanawa Vest, Puzzle Full Armour Shirt) or the base layer (Pro Top, which includes a built-in sports bra). As a reference, the room temperature was monitored next to the track with a sensor placed at the bench case (Bench) and one in the locker room area (Locker room) where changing and warm up took place. One person who did not participate in any physical activity wore a sensor as well (Lucy) and functioned as a human reference.
With 8 skaters participating in the tournament individual datasets for a total of 16 games played were collected. The datasets consisted of 7 games in which a person was wearing a STEAKS® Contact Wear top and 9 without.
The Results of our Field Study
Figure 1: Data points captured via temperature sensors during a whole tournament day.
Some additional information to help you understand figure 1:
- Temperature data was captured during the whole game day.
- Figure 1 shows the sensor values captured from 09:15 am until 10:00 pm.
- The skaters and the reference (Bench, Locker, Lucy) were equipped around 10:00 am except for Ryan who arrived late.
- The coloured graphs represent the data coming from the individual skaters.
- The time frames for the three games are shadowed in grey.
- The physical activity for all games started with an off-skate session
- Game 1 had a longer half time interruption around 12:00 pm.
- Not all skaters participated in all three games (see table 1).
- Devlin had to leave the tournament after Game 1.
- Lenina removed the sensor after Game 2.
- Most of the remaining skaters removed their sensors after Game 3, only exceptions are Roz and Lucy who probably forgot about them and removed them at the end of a long roller derby day.
Discussion: Does STEAKS Contact Wear influence our skin temperature?
The overall picture illustrates a clear difference between the reference measures in the room (Bench, Locker room) and measurements on humans. We can determine from the data, that temperature development is quite individual.
Compared to Lucy as the human reference, who was not engaged in physical activity, five skaters showed higher temperatures in one or more of the games during the whole day (Ryan, Devlin, Roz, Birdee, and Sidda). While other skaters (Leigh, Lenina, Harper) stayed below Lucy’s temperature. In summary 5 skaters showed higher values than the human reference during the day while 3 stayed lower the whole time.
Who do you think had a higher skin temperature? The blocker line-up from VRDL or the jammer from Angel City Roller Derby? Turns out, the answer is not that simple! Captured by Marko Niemelä during WFTDA Champs 2018.
When looking into the game schedule (table 1) we can see that only Devlin (wearing our Smackanawa Vest) was skating during their peak values, while Roz was bench coaching during this time (wearing our Pro Top) and Birdee and Sidda were hanging around at the location (wearing regular sports bras and no STEAKS® Contact Wear tops).
Roz who played in Game 2 and 3 showed the most constant temperature throughout the whole day. We can see a small increase in the time bevor Game 2 during which off- and on-skate warm-up took place. For the 2nd and 3rd game some skaters’ local skin temperature was lower than Lucy’s (human reference: passive bench staff) values. These values could indicate that the cooling mechanisms of these skaters work. Also airflow, insulation through the different amount of soft tissue (boob size) was not taken into account.
Individual responses support that the perceived temperature is subjective and plays a great role in feeling comfortable. Ryan tested our contact wear top for the first time in GAME 2 and decided to play GAME 3 without because they felt hot and sweaty. The data, however, shows that their skin temperature was lower during GAME 2 in which they played with the contact wear top. Lenina, who played GAME 1 and 2 tested the top for GAME 2 and liked it a lot. The data also shows no increase in their local skin temperature.
In order to exactly measure how surface temperature changes with physical activity the logging intervals of the sensor with 15 minutes in between measurements is too wide. The presented field test, however, gives a rough estimation of skin temperature in individual athletes during the day. Scientific studies investigating this topic normally also take other factors into account, such as humidity and several other measurements as heart rate, individual sweat production, baseline, body core temperature as well as calorie and water intake, which we did not include in this field study. The presented data only gives a rough visualization of how body temperature changes during a day like described.
The collected data from this field test suggests that the measured local skin temperature during athletic performance is quite individual and can differ from perceived temperature (eg. Ryan). We could not clearly identify that STEAKS® Contact Wear influences the skin temperature.
In part 1 of this STEAKS Lab Report, we summarized influencing factors on thermoregulation such as sweat production, garment as well as calorie and water intake. When choosing sportswear make sure it is either airy or tight to promote heat loss and try not to pile up too many layers.
And don’t feel bad about sweating, be proud of the mechanisms working in your body, it is cool or at least cooling! (How does it work? See in part 1 of this STEAKS Lab Report on thermoregulation.)
About the author:
Block Sabbath is an engineer working in prosthetic/orthotic research using movement analysis and a skater with the Rhein-Neckar Delta Quads, Mannheim (Germany). She enjoys transferring the biomechanics and material properties from work to roller derby gear and exercise. Some say that makes her a nerd.
In her first year of roller derby/doing sport it was a relief to learn that getting hot and sweaty in situations where that didn’t occur before (like rushing to the train) was a sign of effective training.