Edited by: Lambros Lazuras, Sheffield Hallam University, United Kingdom
Reviewed by: Charalampos Yannis Tsormpatzoudis, Aristotle University of Thessaloniki, Greece; Luca Mallia, Foro Italico University of Rome, Italy
This article was submitted to Movement Science and Sport Psychology, a section of the journal Frontiers in Psychology
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The rapidly increasing interest in fitness related sports over the past few years has been accompanied by a booming industry of nutritional supplements. Many of these substances have unproven benefits and are even potentially harmful to the user. The aim of this study was to determine the prevalence and reasons for nutritional supplement (NS) use among fitness studio visitors in Mainz (Germany), emphasizing new multi-ingredient based supplements such as pre workout boosters (PWBs). Some of the PWBs contain stimulants such as DMAA, N,α-DEPEA, DMAE and DMBA with so far unknown risks, harms and benefits. Four-Hundred and Ninety Two participants in 13 fitness studios completed a questionnaire on the use of nutritional supplements. Descriptive statistics and chi-square tests were used to examine differences in supplement use regarding training- and intake-reasons. About 57.0% of the participants reported the use of NS during the last 4 weeks. The all-time prevalence of creatine use was 28.7%, whereas 12.2% of the participants stated creatine use during the past 4 weeks. The all-time prevalence of PWB intake was 25.8%, whereas the last month prevalence was 11.8%. Among the group of PWB users, 20.5% stated to search specifically for substances such as DMAA, N,α-DEPEA, DMAE or DMBA. Logistic regression analysis showed positive relations between creatine use and the predictor variables gender, strength training and bodybuilding, as well as the stated exercisers' training reasons to increase physical- and sports-performance, and quality of life. PWB consumption was related to the variables gender, training frequency, and the reason for sports performance enhancement. Specific ingredient focus was related to the predictor variables competition participation and increase of mental performance. The results of the study show a high prevalence of PWB consumption among fitness studios visitors, which is comparable with creatine use. The predicting variables for consumption seem to be slightly different between the supplements, especially if the users are searching for stimulating agents. The current findings help to create preliminary consumption patterns and can help to identify potential endangered fitness studio visitors for prevention and risk communication, especially for PWBs.
The nutritional supplement (NS) industry is a rapidly growing market. From 1994 to 2012, the number of nutritional supplements available in the USA increased from an estimated 4,000 to more than 55,000 (Cohen,
One of the current NS product types with a relevant market share are so called “pre workout boosters” (PWBs) which are sub classified by manufacturers e.g., in “hardcore boosters.” These supplements are being used to increase energy, extend endurance, and boost muscle gains (Eudy et al.,
According to a systematic review by Dunn (
It is mentionable that participants were not allowed to ingest additional caffeine containing beverages during the study period. The mixed consumption of different stimulant-like substances, including caffeine in high dosages can be highly problematic and can lead to severe adverse effects including cardiovascular risks (Cohen,
To our knowledge, the use of pre workout boosters containing stimulants in the group of commercial fitness studio visitors has not been investigated yet. In this study, we assessed the general use of NS among fitness studio visitors in Mainz (Germany) considering the supplements, sociodemographic and anthropometric characteristics, frequency and reasons for NS use and fitness training. Our main focus was to obtain a widespread first impression of the prevalence for PWBs that contain not only common stimulants like caffeine or taurine but also synthetic stimulants such as DMAA, N,α-DEPEA, DMAE, or DMBA. Furthermore, we investigated if the intake is predictable by the surveyed variables. We compared PWB supplements with creatine which is a well-studied supplement, used for performance enhancement. The creation of a consumption pattern can help to identify potential endangered fitness studio visitors, and might be used for prevention and risk communication, especially for PWB use.
A total of 492 fitness studio visitors took part in the study (Table
Basic characteristics of 492 fitness studio visitors.
Male | 295 | 59.96 |
Female | 194 | 39.43 |
15–20 | 95 | 19.31 |
21–25 | 182 | 36.99 |
26–30 | 86 | 17.48 |
31–35 | 37 | 7.52 |
36–40 | 17 | 3.46 |
41–45 | 16 | 3.25 |
46–50 | 18 | 3.66 |
≥ 51 | 37 | 7.52 |
A-levels | 304 | 61.79 |
Student/pupil/apprentice | 232 | 47.20 |
Unmarried | 396 | 80.49 |
< 18.5 underweight | 19 | 3.86 |
18.5–24.9 normal weight | 305 | 61.99 |
25.0–29.9 overweight | 131 | 26.63 |
>30.0 obese | 29 | 5.89 |
Fitness training | 197 | 40.04 |
Weight training | 164 | 33.33 |
Bodybuilding | 45 | 9.15 |
Other sports | 83 | 16.87 |
≤ 1 | 106 | 21,54 |
1–2 | 119 | 24,19 |
3–4 | 157 | 31,91 |
≥4 | 108 | 21,95 |
sporadic | 34 | 6.91 |
1–2 times | 120 | 24.39 |
3–4 times | 236 | 47.97 |
5–6 times | 78 | 15.85 |
Daily | 23 | 4.67 |
≤ 60 min | 145 | 29.47 |
60–90 min | 238 | 48.37 |
≥ 90 min | 108 | 21.95 |
Male | 191 | 68.21 |
Female | 87 | 17.68 |
No | 154 | 55.80 |
Very low | 71 | 25.72 |
Minor | 25 | 9.06 |
Partial | 16 | 5.80 |
Major | 7 | 2.54 |
Very high | 3 | 1.09 |
Of all fitness studio visitors, 53.9% have ≥2 years training experience. About 29.5% of the fitness studio visitors have an average training session ≤ 60 min. The largest group (48.4%) trains between 60 and 90 min, whereas 22.0% trains ≥90 min. The largest group of the participants (
The questionnaire consisted of six major parts. The first two parts asked about general fitness studio and training related characteristics like training frequency, training session duration, training years, as well as competition participation in likert skales. Additionally, the participants were asked to choose between the health orientated training types prevention and rehabilitation training or the performance reason enhancement and preservation as their main sport specific training reason. In the third part, participants were asked about their last month NS-consumption in general. The consumption of specific performance enhancing substances (e.g., creatine, PWB, DMAA) was focused in part four. Consumption prevalence was divided into the last month and all time intake. An adjusted survey of the Federal Institute for Risk Assessment (Germany) (Röder et al.,
The pre-determined questions are based on qualitative interviews which were held in four unspecific focus groups. The reasons were asked using a Likert scale from 1 (do not agree) to 7 (fully agree) and included 12 pre-determined questions about performance related reasons like, improving physical, mental, and sports performance as well as health related reasons such as compensation for deficiency symptoms of aging, compensation of lifestyle related deficiency symptoms, compensation of natural deficiency symptoms (e.g., iodine deficiency), malnutrition, compensation of weak food quality and improving the quality of life. Additionally, the questionnaire assesses the reasons for NS intake to silence the conscience (e.g., caused by unhealthy eating behavior) and that NS are modern or on-trend (e.g., newly released supplements). Furthermore, we asked for the acceptance of potential health risks caused by NS intake using a Likert scale from 1 (no acceptance) to 6 (very high acceptance). The last part of the questionnaire deals with socio-demographic characteristics including age (5 year steps), gender, educational level and self-reported weight and height. Weight and height was included because PWBs contain both muscle and therefore weight gaining and weight losing ingredients, e.g., creatine, DMAA and Caffeine.
The aim of the study was to determine which of the training specific factors, NS intake reasons, training reasons, as well as social factors and BMI are related to creatine and PWB supplement intake.
The study was approved by the ethics committee of the University of Mainz (Germany). An additional data security approval was obtained by the data protection department of Rhineland-Palatinate (Germany). A self-reported paper and pencil questionnaire was distributed to fitness studio visitors in Mainz (Germany) between May and June 2016. Thirty-six fitness studios were located in Mainz and the surrounding suburbs. All lady fitness studios, electro muscle stimulating training studios, crossfit boxes, and fight club fitness studios were excluded from the study. A total of 26 fitness studios were included and asked personally to participate in the survey. Per request, additional information was sent via email to the fitness studios. Thirteen of the remaining 26 fitness studios with approximately 12,456 members agreed to participate in the study. Four studios are located in the inner city, three in the city center, and six studios in the outer area of Mainz. The data was collected at least for 10 h in every studio. To reach the different types of studio visitors, the survey was implemented for a minimum of 3 h in the morning, afternoon and evening. Overall, 785 fitness studio visitors were asked to fill out the questionnaire. The final sample included surveys from 521 (66.3%) fitness studio members. 29 collected surveys were not included in the data set due to incomplete (or uninterpretable) responses. At the beginning of the questionnaire, athletes were informed about their anonymity and voluntary participation. The participants gave their written consent to participate in the survey. To increase the level of anonymity of the survey, the collection of personal data was reduced to a minimum. Only a German version of the questionnaire was distributed. No sample size calculation was performed because the proportion of individuals consuming PWB was unknown.
An ANOVA was used to analyze the training reasons between NS users and NS non-users. The results were considered statistically significant at
In the second part individual χ2-tests were computed to determine group differences between creatine use, PWB use, and PWB use including DMAA, N,α-DEPEA, DMAE, and DMBA with different predictor variables as a pre-analysis to reduce number of variables for the logistic regression analysis.
The variables of training parameters, training reasons, consumption reasons, and acceptance of health related risks were split at their means and recoded in dichotomous ones (e.g., training session duration < 60 min and training session duration > 60 min).
In part three, all remaining significant variables of the previous χ2-tests (listed in Table
The major training reasons of the 492 participants are listed in Table
Main aspect for fitness training of 492 fitness studios visitors.
Prevention | 14 (5.0) | 35 (16.5) | 0.000 |
Rehabilitation | 9 (3.2) | 8 (3.8) | 0.715 |
Preservation | 81 (28.9) | 83 (39.2) | 0.012 |
Performance enhancement | 172 (61.4) | 80 (37.7) | 0.000 |
Missings | 4 (1.4) | 6 (2.8) |
Table
Reasons for NS use (Likert scale 1–7; 1 = do not agree, 7 = fully agree).
Improve physical performance | 5.43 | 1.89 |
Improve mental performance | 3.75 | 2.12 |
Improve sports performance | 5.29 | 1.89 |
Health benefits | 4.69 | 1.84 |
Compensation for deficiency symptoms of aging | 2.47 | 1.88 |
Compensation of lifestyle related deficiency symptoms (lifestyle) | 2.80 | 1.92 |
Compensation of natural deficiency symptoms (e.g., iodine deficiency) | 3.14 | 2.13 |
Malnutrition | 4.99 | 2.16 |
Groceries do not contain everything you need (food quality) | 3.26 | 2.06 |
Improve quality of life | 4.41 | 2.02 |
Silence the conscience | 2.76 | 2.07 |
NS are modern and on-trend | 1.59 | 1.28 |
Among the 492 fitness studio members, 280 (56.9%) of the surveyed participants used NS during the last month. The supplements with the highest use were proteins such as shakes or bars (48.0%), minerals (35.6%), vitamins (34.1%), caffeine (25.6%), Omega-3 fatty acids (24.0%), sports beverages (23.6%), BCAA (21.1%), and amino acids (20.1%). Less than 20% of the fitness studio members use carbohydrate supplements (15.9%), taurine (13.4%), guarana (11.0%), l-carnitine (10.8%), weight gainer (6.7%), glucosamine and collagen (5.5%), citrulline malate (5.3%), l-carnosine (5.1%), CLA (3.7%), HMB (2.8%), androstenedione (2.6%), and HCA (2.4%) (see Figure
Prevalence and frequency of NS consumption of 492 fitness center visitors.
Descriptive statistics were used to show prevalence of creatine and PWB intake. χ2-tests and logistic regression analyses were used to asses relations between the sociodemographic and anthropometric characteristics, the training specific parameters and intake reasons with the consumption of creatine, PWB, or PWB containing DMAA or similar agents.
The all-time prevalence for the use of PWB (45.4% among NS users) was similar to the prevalence of creatine use (50.4%), whereas these NS were consumed during the last month by a total of 21.4% users for creatine and 20.7% users for PWB (see Table
Prevalence of creatine and pre workout booster (PWB) use.
All time prevalence of consume | 141 | 28.7 | 50.4 | ||
Consume during the last month | 60 | 12.2 | 21.4 | ||
All time prevalence of consume | 127 | 25.8 | 45.4 | ||
Consume during the last month | 58 | 11.8 | 20.7 | ||
Explicit focus on specific substances | 49 | 10.0 | 17.5 | 38.6 | |
DMAA, N,α-DEPEA, DMAE, DMBA | 26 | 5.3 | 9.3 | 20.5 | |
Synephrine | 11 | 2.2 | 3.9 | 8.7 | |
Niacine | 6 | 1.2 | 2.1 | 4.7 | |
Caffeine | 43 | 8.7 | 15.4 | 33.9 | |
Beta alanine | 32 | 6.5 | 11.4 | 25.2 | |
Other | 11 | 2.2 | 3.9 | 8.7 |
Mixed last month consume of 60 creatine and 58 PWB users.
χ2-test to determine group differences of dichotomized basic characteristics and creatine and pre workout booster (PWB) use during the last 4 weeks.
Gender: male | 23.494 | 5.665–97.428 | 37.7 | < 0.001 | 6.549 | 2.752–15.586 | 22.9 | < 0.001 | 17.870 | 2.401–133.012 | 14.7 | < 0.001 |
Age > 25 | 1.658 | 0.760–3.620 | 0.227 | 0.894 | 0.453–1.766 | 0.724 | 0.754 | 0.292–1.942 | 0.603 | |||
School education: A-level | 1.031 | 0.591–1.797 | 1.000 | 1.571 | 0.901–2.738 | 0.112 | 1.445 | 0.653–3.196 | 0.408 | |||
Job: full time | 0.764 | 0.437–1.334 | 0.383 | 1.787 | 1.023–3.123 | 0.054 | 1.377 | 0.618–3.071 | 0.527 | |||
Student/pupil/apprentice | 1.151 | 0.666–1.990 | 0.677 | 1.747 | 0.987–3.094 | 0.066 | 1.121 | 0.507–2.477 | 0.842 | |||
Family status: single | 3.811 | 1.161–12.509 | 5.5 | 0.020 | 1.570 | 0.647–3.805 | 0.429 | 1.403 | 0.410–4.797 | 0.782 | ||
Having a child | 4.065 | 1.239–13.331 | 6.2 | 0.013 | 2.823 | 0.991–8.039 | 0.054 | 1.525 | 0.447–5.208 | 0.784 | ||
BMI ≥ 25 | 2.655 | 1.534–4.593 | 12.8 | 0.001 | 1.982 | 1.123–3.496 | 5.7 | 0.022 | 2.502 | 1.129–5.546 | 5.4 | 0.030 |
Training ≥2 years | 2.105 | 1.172–3.780 | 6.4 | 0.012 | 2.239 | 1.234–4.065 | 7.3 | 0.008 | 2.405 | 0.992–5.831 | 0.067 | |
Training frequency ≥2 times a week | 32.471 | 4.455–236.673 | 28.0 | < 0.001 | 15.146 | 3.646–62.923 | 23.8 | < 0.001 | 12.260 | 1.646–91.325 | 9.6 | 0.001 |
Training session duration ≥ 60 min | 1.435 | 0.762–2.701 | 0.293 | 1.230 | 0.660–2.292 | 0.646 | 2.394 | 0.810–7.073 | 0.124 | |||
Competition participation | 0.839 | 0.419–1.681 | 0.735 | 1.392 | 0.738–2.625 | 0.303 | 2.480 | 1.090–5.643 | 4.9 | 0.044 | ||
Strength training and bodybuilding | 7.264 | 3.666–14.391 | 40.6 | < 0.001 | 2.350 | 1.333–4.142 | 9.0 | 0.004 | 3.192 | 1.360–7.493 | 7.8 | 0.007 |
Performance enhancement | 4.057 | 2.090–7.874 | 19.3 | < 0.001 | 2.949 | 1.590–5.470 | 12.6 | < 0.001 | 4.091 | 1.516–11.036 | 8.9 | 0.004 |
Health benefit | 1.106 | 0.619–1.978 | 0.769 | 1.112 | 0.617–2.003 | 0.766 | 0.601 | 0.260–1.388 | 0.295 | |||
Lifestyle | 1.160 | 0.650–2.069 | 0.659 | 1.513 | 0.840–2.723 | 0.180 | 1.664 | 0.734–3.771 | 0.301 | |||
Quality of life | 3.744 | 1.939–7.232 | 16.7 | < 0.001 | 1.885 | 1.027–3.459 | 0.052 | 1.486 | 0.648–3.404 | 0.411 | ||
Natural deficiency symptoms | 1.204 | 0.669–2.168 | 0.553 | 0.963 | 0.529–1.751 | 1.000 | 1.953 | 0.837–4.557 | 0.148 | |||
Malnutrition | 1.617 | 0.903–2.893 | 0.110 | 1.052 | 0.589–1.878 | 0.883 | 0.968 | 0.432–2.172 | 1.000 | |||
Food quality | 1.432 | 0.800–2.561 | 0.244 | 1.592 | 0.879–2.881 | 0.140 | 2.127 | 0.892–5.072 | 0.100 | |||
Aging deficiency symptoms | 1.091 | 0.615–1.936 | 0.773 | 1.149 | 0.640–2.063 | 0.658 | 1.562 | 0.682–3.576 | 0.310 | |||
Sports performance | 9.084 | 3.375–22.006 | 31.2 | < 0.001 | 10.400 | 4.001–27.035 | 31.6 | < 0.001 | 1.844 | 1.645–2.067 | 20.3 | < 0.001 |
Physical performance | 6.877 | 3.579–13.212 | 38.8 | < 0.001 | 5.713 | 3.002–10.872 | 31.8 | < 0.001 | 2.196 | 0.968–4.982 | 0.061 | |
Mental performance | 3.357 | 1.853–6.083 | 16.8 | < 0.001 | 3.576 | 1.945–6.574 | 17.9 | < 0.001 | 3.353 | 1.435–7.835 | 8.5 | 0.005 |
Silence the conscience | 2.188 | 1.176–4.070 | 6.2 | 0.016 | 2.338 | 1.245–4.393 | 7.1 | 0.010 | 2.539 | 1.029–6.263 | 4.3 | 0.040 |
Modern and on-trend | 1.278 | 0.670–2.437 | 0.498 | 1.358 | 0.710–2.599 | 0.391 | 1.370 | 0.567–3.311 | 0.481 | |||
Risk-taking | 2.612 | 1.442–4.730 | 10.4 | 0.002 | 2.318 | 1.272–4.225 | 7.7 | 0.007 | 3.874 | 1.571–9.551 | 9.7 | 0.003 |
χ2-tests were performed to study group differences between the dependent variable creatine use (
The consumption of PWB was significantly related to gender (male) and a higher BMI, more than 2 training years and more than 2 training sessions per week. Similar to creatine intake, strength training and bodybuilding, as well as performance enhancement as reasons for training are accompanied with PWBs use. All performance increasing aspects as reasons for NS use (physical performance, sports performance, and mental performance) seem to predict a higher possibility for PWB intake. Additionally, the NS consumption reason to silence the conscience, and an acceptance of health-related risks are predictors for PWB intake.
The subgroup of PWBs containing DMAA and similar ingredients are more often used by men and overweight athletes. The type of supplement is more frequently used by subjects who train more than twice a week and take part in competitions. Similar to both other supplements the use of PWBs containing DMAA or similar agents was higher in the group of participants who refer strength training and bodybuilding, as well as performance enhancement training reasons as the reasons for training. Furthermore, fitness studio visitors who want to increase their sports or mental performance by NS use more often use PWB products containing these pharmacologically active substances. Finally, the group of fitness studio visitors who stated a higher focus to silence the conscience as a reason for NS use, as well as the group of participants who stated a higher health risk acceptance were more likely to use PWBs including DMAA or similar agents.
A stepwise logistic regression was performed for each of the dependent variables creatine use, PWB use, and PWB use including DMAA or similar agents, to determine potential significant interaction effects of previously found significant variables. Variables with a
ORs with 95% confidence intervals for each significant predictor variable.
Gender: male | 13.516 | 2.589–70.572 | 0.002 | 2.837 | 0.998–8.062 | 0.050 | 9.002 | 1.006–80.583 | 0.049 |
Training frequency ≥2 times a week | 9.253 | 1.126–76.023 | 0.038 | ||||||
Competition participation | 4.369 | 1.352–14.119 | 0.014 | ||||||
Strength training and bodybuilding | 4.478 | 1.710–11.727 | 0.002 | ||||||
Quality of life | 2.822 | 1.050–7.587 | 0.040 | ||||||
Sports performance | 3.872 | 1.009–14.851 | 0.048 | 6.290 | 1.659–23.846 | 0.007 | |||
Physical performance | 2.969 | 1.047–8.414 | 0.041 | ||||||
Mental performance | 3.466 | 1.157–10.387 | 0.026 |
Regarding creatine, for male participants the odds is 13.5-fold larger than for female exercisers (CI: 2.589–70.572). A positive relation for creatine intake was confirmed for the training types, strength training and bodybuilding (OR: 4.5; CI: 1.710–11.727). Exercisers who want to increase their life quality (OR: 2.8; CI: 1.050–7.587), sports performance (OR: 3.9; CI: 1.009–14.851) and physical performance (OR: 3.0; CI: 1.047–8.414) have a slightly increased OR to take creatine. The current model coefficient testing vs. the baseline model shows significance χ2 = 100.6, d.f. = 14,
In the second regression, fitness studio visitors who stated a training frequency of more than twice a week showed a 9.3-fold greater chance to use PWBs (CI: 1.126–76.023). The relation was estimated with an OR of 6.3 between the intake of PWBs and the aim to increase sports performance (CI: 1.659–23.846). Just a very weak relation was found for gender (males) (OR: 2.8; CI 0.998–8.062). Omnibus test of the current model was significant (χ2 = 68.4, d.f. = 11,
Within the third regression analysis, a significant relationship between PWBs containing DMAA or similar agents was found. For male gender, competition participation and increase of mental performance capacity showed OR: 9.0 (CI: 1.006–80.583), OR: 4.4 (CI: 1.352–14.119) and OR: 3.5 (CI: 1.157–10.387), respectively. The test of the current model against the baseline model shows significance as well χ2 = 54.4, d.f. = 10,
The aim of the study was to determine the prevalence of NS use, training characteristics and the intake reasons among fitness studio visitors in Mainz with a special emphasis on new multi-ingredient based PWBs, of which some contain stimulants such as DMAA, N,α-DEPEA, DMAE, and DMBA.
The most consumed NS in fitness studios were protein supplements such as shakes or bars (see Figure
The use of the performance enhancing supplement creatine, which is often an ingredient in PWBs as well, shows intake prevalence in fitness studio visitors between 8.0 (Goston and Correia,
We found five predictors for creatine use which are gender, sports type strength training and bodybuilding, the NS intake reasons increasing physical and sports performance, as well as increasing quality of life. The positive relation of creatine use with gender is in accordance with Froiland et al. (
For PWB intake we found three predictors, which are gender (male), training frequency ≥2 times a week and sports performance. For PWBs including DMAA or similar agents the variables gender (male) competition participation and the increase of mental performance showed significance. The prevalence for creatine and PWB use were comparable for both, the all-time and the last month consumption. Similarly to creatine consumption, the gender (male) was related to the use of PWBs and PWBs containing DMAA or similar substances. Again, this is probably, because among fitness studio visitors, the training reason performance enhancement is mainly described for males (Froiland et al.,
As shown in this study, fitness center visitors often use different kinds of NS simultaneously, even though the long term effect of mixed consume of different NS is not yet investigated. Additionally, larger studies including women are required and further toxicological markers and cardiac function must be critically evaluated to gain a more comprehensive insight into the physiological effects of PWBs. The risk profile of many substances included in PWBs and especially their combinations have not yet been evaluated in detail and were not tested sufficiently in long term (Kim et al.,
However, it cannot be expected that the results of DMAA are identical to comparable substances such as BMPEA or DMBA, of which the safety profile has never been studied in humans, especially in combination with other substances (Cohen et al.,
Tian et al. (
The study results are limited to the specific population group of fitness study visitors. In different population groups like competitive athletes, recreational athletes from different sports, or non-athletes the prevalence might be different. Another potential restriction is caused by the use of a self-administered questionnaire for sensitive questions for physiologically active substances. Therefore, true prevalence might be higher. It should be considered that logistic regression analysis cannot prove final causal relations between the dependent and the independent variable in the used model. Additionally, because of the restricted number of surveyed questions, the analysis does not cover all possible reasons and aspects. In future studies open response questions should be added to enable further relevant aspects for training and intake reasons. Because the knowledge about prevalence and intake reasons of PWBs are limited for sociodemographic and anthropometric characteristics, training characteristics, and reasons for NS use and fitness training we obtained a widespread but more unspecific first impression. For example asking for motivational reasons like “physical appearance” would have helped to cover other aspects reliably. Further studies should focus on training and intake motives for a better understanding of motivational aspects with standardized instruments.
Despite NS may serve as a practical assistance to meet sports specific goals, evidence shows that NS are typically not required if athletes have a balanced diet. Exercisers in fitness studios consume a large number of different supplements like creatine and PWB, some of which contain stimulants such as DMAA, N,α-DEPEA, DMAE, and DMBA to increase sports performance capacity. The current findings show surprisingly high intake prevalence for PWB supplements. Reasons for consumption seem to be slightly different from creatine use, especially if the users are searching for stimulating ingredients. The results might help to create a consumption pattern and support to identify potential endangered fitness studio visitors for prevention and risk communication of NS and especially PWBs. Especially the mixed consumption of NS might have adverse effects and hides potential risks and harms. Therefore, the study of long-term effects and the enlightenment of fitness studio visitors about the cost-benefit ratio is of unique importance.
MD, PS, TE, and EN designed the experiment. MD and EN analyzed the study results. PS and TE helped in data analysis. MD and EN wrote the article and all authors interpreted and discussed the results.
The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
We thank the team of students for their help with survey data collection and the participating fitness studio visitors. Furthermore, we thank the reviewers for their insightful reading of the manuscript and the very constructive and helpful comments.
The Supplementary Material for this article can be found online at: