The effects of a nutritional intervention on the sports nutrition knowledge and nutritional status of track and field athletes: protocol for a randomized controlled trial | Trials

Plans for assessment and time collection of outcomes {18a}

The research team will provide sufficient training to the data collectors to minimize intra- and inter-observer variations. This includes being familiarized with the research questionnaire and data collection instruments, as well as receiving training on the usage of equipment and measurement techniques. A pre-test will be undertaken using a small group and data will be collected by a research team.

1. 1.

   Demographic details, events/sports-related variables, and health history.

An interviewer-administered semi-structured questionnaire will be used to collect detailed demographic information, events/sports-related variables, and health history. The demographic details will include age, sex, educational level, occupation, and residential area. Events/sports-related variables such as sports category, main event, number of years of sports experience, competitiveness, personal best, seasonal best, records, and performance targets will also be collected. The health history section will assess any previous injuries, chronic illnesses, dietary habits, and supplement use to provide a comprehensive profile of the participants.

1. 2.

   Assessment of sports nutrition knowledge.

SNK will be assessed pre- and post-intervention using the newly developed and validated Sri Lankan Sports Nutrition Knowledge Questionnaire (SLn-SNKQ) [22, 23]. The SLn-SNKQ comprises 32 questions across 12 sub-sections, with a total of 123 individual items. These questions cover two primary sections: the General Nutrition Knowledge (GNK) section, which includes 15 questions with sub-sections on macronutrients (n = 4), micronutrients (n = 3), energy balance (n = 4), hydration (n = 3), and weight management (n = 1); and the SNK section, which contains 17 questions under 7 sub-sections, including carbohydrate loading (n = 1), pre-training meals (n = 1), training meals (n = 1), post-training meals (n = 2), sports supplements (n = 6), supplement label reading, alcohol, isotonic drinks, and doping (n = 4), and energy intake and food habits (n = 2).

The included questions have three options—‘agree’, ‘disagree’, and ‘unsure’—while some questions offer five response options, with the most accurate answer being considered for scoring. A correct answer will be awarded a plus 1 mark, while an incorrect answer will receive a minus 1 mark. An unsure response will receive a score of 0. Each item will be scored individually without additional weightage, as per author consensus [24]. To assess the nutrition knowledge of each athlete, the mean total score will be calculated across all questions.

In the case of participants facing difficulties in understanding the questionnaire due to low literacy levels or other reasons, an investigator will clarify the questions. The questionnaire will be administered online and in the participants’ native language to ensure ease of understanding.

1. 3.

   Assessment of dietary status.

This will be assessed at the pre-intervention (-2^nd week to 0 week) and the post-intervention (end of the 16th week) via 7-day food diaries. A particular training season (off-season or in-session games) has not been specifically focused on dietary assessment. It is ensured that both groups are assessed under similar conditions, with food records being collected consistently at the same points in time across all participants. By avoiding the inclusion of a particular training season, any potential variations in dietary intake due to seasonality or specific training phases are controlled. Consequently, the intervention’s effect on dietary status can be assessed without confounding seasonal influences.

Total intake for 7 days will be then averaged and given as pre- and post-intervention. The subjects will be given written and verbal instructions in a booklet for completing a 7-day food record. The portion sizes for each food item will be estimated using a local food atlas [25], which will help ensure accuracy in portion estimation and reflect the local dietary patterns. The total intake for the 7 days will be averaged to provide both pre- and post-intervention dietary assessments.

Standard energy values based on the local food atlas and typical portion sizes will be used to calculate the energy content of the foods. The daily energy intake will be determined using Nutri-Survey 2000 software (EBISpro). Additionally, the intake of macronutrients and micronutrients will be analyzed with the Nutri-Survey Software, modified to include Sri Lankan food composition data, to ensure the analysis reflects the local food types and nutritional context.

1. 4.

   Anthropometry.

Anthropometric measurements will be performed using calibrated equipment by trained research assistants adhering to international recommendations.

Body weight will be measured to the nearest 0.1 kg using a calibrated digital weighing scale (seca 874, Hamburg, Germany) with the participants wearing indoor light clothing and emptying the bladder. Two measurements will be taken for each person and the average weight will be considered as the actual weight for each person.

Height will be taken to the nearest 0.1 cm, as the maximum distance to the uppermost position on the head from heels, with the individual standing barefoot and in full inspiration using a calibrated stadiometer (seca 213 portable stadiometer) adhering to a consistent technique.

Mid upper arm circumference (MUAC): the measuring point of MUAC will be marked at the midpoint between the acromion and the olecranon process in the right upper arm when the right elbow is 90° flexed placing the forearm palm down across the trunk. The measurement at the marked site will be taken using a plastic flexible tape (seca 201, Germany) to the nearest 0.1 cm when the right arm is extended alongside the body with the palm facing upwards.

Waist circumference will be measured using a non-elastic measuring tape (seca 201, Germany) to the nearest 0.1 cm midpoint between the lower rib margin and the top of the iliac crest, and the measurement will be taken at the end of normal expiration. A mean value will be recorded after three consecutive measurements.

Skinfold thickness: triceps skinfold thickness will be assessed using a Harpenden skinfold calliper (Model HSC-4, British Indicators, West Sussex, UK). Each skin fold measurement will be taken in duplicate on the non-dominant side, and the average of two readings will be recorded following the standard ISAK protocols using a consistent technique [26].

1. 5.

   Body composition

Bio-electrical impedance analysis (BIA): total body water will be assessed, and total body fat predicted using resistance, reactance, phase angle, and impedance values (Bodystat 1500, Bodystat Ltd., Isle of Man, British Isles). Participants will be instructed to lie supine while electrodes from the BIA device are attached to the right hand and foot [27]. All metal objects will be removed from the body, and measurements will be conducted at room temperature. Fat-free mass (FFM) and body fat percentage (BF%) will be calculated using resistance and reactance values applied to an ethnicity-specific prediction equation designed for Asians [28].

Dual-energy X-ray absorptiometry (DEXA): DEXA will be used to derive bone mineral density, BF%, and FFM. DEXA scans (QDR 4500A, Waltham, USA) will be conducted at the accredited radiography unit, Nawaloka Hospital, Colombo, Sri Lanka, at both the 0^th week (baseline) and the 16^th week of the study.

1. 6.

   Hydration

Urine samples will be collected from each participant before the intervention (from 2 weeks to immediately before starting) and at the end of the intervention (16 weeks) for assessing urine-specific gravity using a clinical refractometer (model 300 CL; Atago Company Ltd., Tokyo, Japan). To conduct this procedure, an early morning mid-stream urine sample will be collected and transported within 2 h to the data collection centre.Additionally, participants will assess their urine samples in relation to urine colour against a standardized urine colour chart [29] prior to and after training on three typical training days, for a total of four instances, as instructed by the data collectors. Participants’ thirst levels before and after training during three typical sessions will also be evaluated using a seven-point Likert scale (ranging from 1, ‘Not Thirsty at All,’ to 7, ‘Very, Very Thirsty’) [30]

Hand grip strength

Hand-grip strength will be measured in kilogrammes using a pre-calibrated hydraulic hand dynamometer (Model SH5001^®; SAEHAN Corporation, YangdeokDong, Masan, South Korea), with a resolution of 2 kg. This measurement will follow the guidelines established by the American Society of Hand Therapists [31].

Measurements will be obtained in standardized conditions with the participants in the seated position, elbow at 90°, handle adjusted to the second position, after receiving an explanation of the procedures, and after familiarizing themselves with the instrument, they should apply the maximum grip strength for 3 to 5 s. The procedure will be performed three times with each hand alternately, with an interval of 1 min between each measurement.

1. 7.

   Physical activity and training

Total energy expenditure estimate: activity diary records will be kept for seven consecutive days. A modification of the method originally described by Bouchard et al. will be used in this study [32].

Activities will be categorized into nine levels according to their average energy costs, representing multiples of basal metabolic rate (BMR) (physical activity ratio = PAR), from the lowest activity level, 1, representing sleep or rest in bed, to the highest level, 9, during very intense manual work or maximal sports activity. Each day will be divided into 96 periods of 15 min each. All 96 periods will be represented by squares in the pre-printed diary form, with four squares in each row representing 1 h. For each 15 min, the participant entered into the appropriate square the categorical value corresponding to the dominant activity of that period. A list of common activities together with their categorical value will be printed on the record form. When an activity is not listed, the participant will be instructed to apply a categorical value closest to an activity of comparable intensity or to write an alphabetic code in the square and to write this code together with a description of the activity in 1 ± 2 words in a section for notes in the record form. Each participant will be given a detailed explanation and demonstration of the activity diary form and method. He or she completes a retrospective recording of the last 2 days’ activities. The record will be then discussed with the investigators. Special emphasis will be placed on the choice of appropriate categorical values for different activities. Participants will be encouraged to contact the investigators by telephone at any time during the following 7 days if in any doubt about the recording. After 7 days, the activity records will be scrutinized and discussed.

Currently, there is no specific Sri Lankan formula for calculating basal metabolic rate (BMR). The BMR prediction formulae used in this study are based on international compendiums and have been widely validated across various populations. Therefore, the international formulas used in this study [33], BMR = 0.074 × kg BW + 2.754 MJ/days for men, and BMR = 0.056 × kg BW + 2.898 MJ/days for women, are appropriate for estimating BMR in the study participants [34].

1. 8.

   Laboratory procedures/evaluations

Serum vitamin D₃

Serum will be separated from the 5.0 mL venous blood sample collected and tested within 3 h using MAGLUMI 2000 analyser by competitive chemiluminescence immunoassay (CLIA) (Snibe; Shenzhen, People’s Republic of China). This test quantitatively measures the sum of both 25-(OH) vitamin D₃ (cholecalciferol) and 25-(OH) vitamin D₂ (ergocalciferol) in the specimen.

Serum ferritin

This will be measured in Cobas e601 device with ECLIA technology (Roche Diagnostics International AG Rotkreuz, Switzerland).

Full blood count (FBC)

The FBC will be analyzed using the SYSMEX XE-2100 Haematology Automated Analyser (Block Scientific Inc., US). Several blood parameters relevant to potential nutrition-related deficiencies will be examined, particularly focusing on haemoglobin levels, which are indicative of anaemia. Additional parameters, such as mean corpuscular volume (MCV), mean corpuscular haemoglobin (MCH), and mean corpuscular haemoglobin concentration (MCHC), will be assessed. These parameters are crucial for differentiating between types of anaemia, such as microcytic hypochromic anaemia, commonly associated with iron deficiency, and macrocytic anaemia, often linked to deficiencies in vitamin B₁₂ or folate.

All biochemical parameters will be carried out at an accredited laboratory (Nawaloka Metropolis laboratory, Nawaloka Hospital PLC) following the standard procedures.

Plans to promote participant retention and complete follow-up {18b}

All participants will be engaged through direct communication via personal WhatsApp to address their queries and provide the necessary support throughout the study period. Compliance will be evaluated weekly by telephone communication and follow-up consultations. It is believed that frequent communication will increase the compliance and retention rate. In general, this population is highly motivated and determined to follow sports nutrition advice.

Data management {19}

Data will be collected and recorded by a well-trained team of data collectors. Any data collected as part of this research project will be stored in a locked filing cabinet at the Department of Physiology, Faculty of Medicine, University of Colombo for 5 years, under the supervision of the principal investigator (RJ). The data will be stored in a de-identifiable format. Simultaneously, softcopies will be kept password-protected for the above-prescribed period. Following the completion of the due period, the documents will be shredded and the softcopies will be permanently deleted.

Confidentiality {27}

The data sheets and electronic data files will not contain any personal information. Each participant will be given a unique study code. The document containing the information on the study code and the identity of the patient will be kept separate from the study data files and data sheets.

Plans for collection, laboratory evaluation, and storage of biological specimens for genetic or molecular analysis in this trial/future use {33}

None of the blood samples will be utilized for any other purpose outside the intended tests, and no genetic or molecular analysis will be done. Blood samples will not be given to external bodies and sent abroad. All blood samples will be stored for a month to allow for the completion of the tests and safely destroyed.

Statistical methods

Statistical methods for primary and secondary outcomes {20a}

For each group in this study, summary statistics will be calculated and reported. Continuous variables will be described using means and standard deviations, while categorical variables will be summarized as proportions. To compare baseline and end-of-study characteristics between the groups, independent sample
t-tests will be used, and to assess changes within each group, paired t-tests will be utilized for normally distributed continuous variables. The normality of these variables will be evaluated using the Kolmogorov–Smirnov test.

For continuous variables that do not follow a normal distribution, differences between and within groups will be assessed using the Mann–Whitney U test for independent samples and the Wilcoxon signed-rank test for paired comparisons. These non-parametric tests will be employed to handle asymmetrical data distributions.

Interim analysis {21b}

There is no interim analysis in this study.

Methods for additional analysis (e.g. subgroup analysis) {20b}

There is no additional analysis in this study.

Methods in analysis to handle protocol non-adherence and any statistical methods to handle missing data {20c}

Each participant’s adherence to the research procedure will be periodically monitored via direct phone calls and WhatsApp. Through this method, any queries regarding the research procedure will be addressed, and participants will be encouraged to adhere to the intervention. Additionally, monthly follow-up sessions will be conducted during the fourth and eight weeks to monitor their progress both quantitatively and qualitatively.

If a participant is unable to adhere to the intervention procedure continuously for more than 7 days due to any reason, they will be considered “non-adherent” to the intervention and categorized as a ‘drop-out.’ However, for the analysis, an intention-to-treat (ITT) approach will be employed to include all randomized participants, regardless of their adherence status. A per-protocol analysis will also be conducted to evaluate the effects of the intervention among participants who fully adhered to the protocol. Both sets of results will be presented to provide a comprehensive assessment of the treatment effects.

If any data points are missing, we will first attempt to contact participants to retrieve the missing information. If this is not possible, we will use multiple imputations as the primary method to handle missing data. The nature and extent of missing data will be assessed to ensure that multiple imputations are appropriate, and sensitivity analyses will be conducted to evaluate the impact of missing data handling on the study outcomes.

Plans to give access to the full protocol, participant-level data, and statistical code {31c}

Full protocol, participant data, and statistical code will be available from the principal investigator upon reasonable request after the publication of the study results.

Oversight and monitoring

Composition of the coordinating centre and trial steering committee {5d}

The coordinating centre is located at the Department of Physiology, Faculty of Medicine, University of Colombo. The principal investigator and the data collection team are responsible for ensuring the protocol is implemented as planned, reviewing the study progress regularly, and upholding good clinical practice at all times. The principal investigator, coinvestigators, and research assistants will be responsible for all aspects of the logistics and organization of the trial.

Composition of the data monitoring committee, its role, and reporting structure {21a}

An independent board of senior researchers who have no competing interests will be appointed as the data safety monitoring committee. The accumulated study data for participants’ safety and study progress will be reviewed and evaluated on a monthly basis by the data safety monitoring committee. Serving in an individual capacity, their expertise and recommendations will be provided throughout the study. Recommendations concerning the continuation, modification, or termination of the trial will be made to the research team by the committee.

Adverse event reporting and harms {22}

It is very unlikely to get an adverse event in this kind of behavioural intervention in very healthy young adults.

Frequency and plans for auditing trial conduct {23}

The independent data safety monitoring board and investigators will communicate throughout the trial period to notify the Ethics Review Committee of the Faculty of Medicine, University of Colombo, if there are any issues. Any protocol amendments will be properly notified to the Ethics Review Committee, and approval will be obtained prior to the implementation.

Plans for communicating important protocol amendments to relevant parties (e.g. trial participants, ethical committees) {25}

Any amendment to the protocol will be submitted by the principal investigator to be approved by the Institutional Ethical Review Committee, Faculty of Medicine, University of Peradeniya, Sri Lanka.

Dissemination plans {31a}

The findings of the trial will be published in peer-reviewed scientific journals and presented at international scientific conferences.