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Trial registered on ANZCTR

Registration number
Ethics application status
Submitted, not yet approved
Date submitted
Date registered
Date last updated
Date data sharing statement initially provided
Type of registration
Prospectively registered

Titles & IDs
Public title
Performance and metabolic effects following a single course of antibiotic treatments in healthy individuals
Scientific title
Performance and metabolic effects following a single course of cephalexin in healthy individuals
Secondary ID [1] 304549 0
Universal Trial Number (UTN)
Trial acronym
Linked study record

Health condition
Health condition(s) or problem(s) studied:
Athletic Performance 322424 0
Condition category
Condition code
Metabolic and Endocrine 320077 320077 0 0
Normal metabolism and endocrine development and function

Study type
Description of intervention(s) / exposure
1.1 Overview
The study will adopt a single-arm trial design, using pre- and post-outcomes to test the hypotheses. Eligibility and health screening questionnaire will be conducted by phone. Participants will attend three laboratory sessions at Murdoch University physiology laboratory; a familiarisation session with VO2peak assessment, and two experimental sessions with no less than 5 days separating sessions. Familiarisation session will used to familiarise participants with the equipment and the time-trial adopted within the study and attain lactate values of corresponding power outputs for experimental sessions.

1.2 Procedures

1.2.1 Familiarisation session and VO2peak
Participants will attend following an overnight fast >10hrs to best replicate testing conditions. Following collection of height and body mass, participants will complete a maximal aerobic performance test (VO2max), using an electromagnetically braked Velotron cycle ergometer (Racermate, USA). Expired ventilation will be collected continuously using a metabolic cart (TrueOne 2400, ParvoMedics, USA). All participants will start at a workload of 50W which will be increased by 35 W every two minutes. Finger-stick lactate will be collected in the final 30 seconds of each stage. Once RER has reached 1.0, workload (35W) will be increased every minute until volitional exhaustion. From this a work output corresponding to a blood lactate of 3mM will be calculated for use in the constant-work component in the experimental sessions. Participants will then be familiarised with the time-trial, which will begin ~20 minutes after completion of the VO2max test. The time-trial will be based on completion of a caloric goal, which will be standardised at 400 Calories for all participants. Participants are able to self-select their cadence as well as gearing and will be able to adjust these throughout the time-trial. Participants will be able to consume water ad libitum before and during the time trial.

1.2.2 Experimental Trials
Both experimental trials will be conducted in the morning following an overnight fast >10hrs. Participants will be asked to maintain a 72-hour food and exercise diary prior to the first experimental trial. Normal exercise may be continued leading up to the first experimental trial and participants should best replicate the diary conditions leading up to the second experimental trial. Heavy training in the 24 hour period immediately prior to trials will be discouraged.
Each trial consists of a 60 minute steady state (fixed power) cycling at power output corresponding to 3mM of lactate on a Velotron cycle ergometer (Racermate, USA), followed immediately by a time trial for 400 calories. Gas exchange data will be collected using a metabolic cart during the fixed power cycling (TrueOne 2400, ParvoMedics, USA), with heart rate date collected using a heart rate monitor (Garmin, USA). Ratings of perceived exertion (RPE) will be collected using the 6-20 Borg scale (10) and measured every 15 min during fixed power exercise, and every 5 min during the time trial and 5 minutes post completion. During the time-trial, only heart rate and RPE will be collected at each 100 Calorie point.

Following experimental trial one, participants will be asked to commence a five-day course of oral Cephalexin 500mg, with dosing as 06:00, 12:00, 18:00, and 20:00. First dose should commence at 12:00 on day one, with the final dose taken at 06:00 on the day of experimental trial two (Day 6). Participants will be monitored in the laboratory for one hour post administration of the first dose to assess for serious side effects (11). Adherence to the Cephalexin dosing will be monitored through a diary and participants will receive two text messages during the 5-day course as a reminder. At the completion of experimental trial two, participants will be asked regarding compliance and report whether any doses were missed.

1.2.3 Blood sampling and analysis
Blood sampling in each trial will occur from a cubital fossa vein. A 20 gauge peripheral venous cannula will be placed using sterile technique. 4ml of blood will be collected via using lithium heparin vacutainer tubes. The cannula will be flushed with 10ml 0.9% saline after each sample is taken. 4mL of blood will be taken and discarded prior to collection of sample two and three to ensure no saline remains in the cannula. Samples will be taken prior to commencement of activity, after the fixed output session, and immediately after the completion of the time trial.

Testing and sampling will be completed by Dr Ewan Smith, medical doctor 8 years. Laboratory supervision by Associate Professor in Exercise Physiology Timothy Fairchild. Ethics approval is has been applied for with the Murdoch University Human Research Ethics Committee.
Intervention code [1] 320898 0
Treatment: Drugs
Comparator / control treatment
No Control group
Control group

Primary outcome [1] 327952 0
A change in time trial performance from the first time trial as assessed by time to completion of a 400 calorie time trial on an electronically braked cycle ergometer.
Timepoint [1] 327952 0
At time of second trial (Day 6)
Secondary outcome [1] 397079 0
Changes to perceived exertion using Borg scale at submaximal power outputs.
Timepoint [1] 397079 0
At time of second trial (Day 6)
Secondary outcome [2] 397080 0
Changes in serum long chain serum acylcarnitines as measured by analysis of plasma using a mass spectrometer.
Timepoint [2] 397080 0
At time of second trial (Day 6)
Secondary outcome [3] 397122 0
Changes respiratory exchange ratio during submaximal cycling effort as assessed by continuous gas collection with a metabolic cart.
Timepoint [3] 397122 0
At time of second trial (Day 6)
Secondary outcome [4] 397123 0
Heart rate during submaximal power output assessed using a heart rate monitor
Timepoint [4] 397123 0
At time of second trial (Day 6)
Secondary outcome [5] 398113 0
Changes to perceived exertion using Borg scale at maximal power outputs.
Timepoint [5] 398113 0
Time of second time trial (day 6)
Secondary outcome [6] 398114 0
Heart rate maximal power output assessed using a heart rate monitor
Timepoint [6] 398114 0
At time of second trial (day 6)
Secondary outcome [7] 398115 0
Changes in serum 5-methoxy-3-indoleacetic acid as measured by analysis of plasma using a mass spectrometer.
Timepoint [7] 398115 0
At time of second trial (Day 6)

Key inclusion criteria
Sixteen recreationally trained cyclists (cycling a minimum 200 km/week) ages 18-40 will be recruited to participate in the study.
Minimum age
18 Years
Maximum age
40 Years
Both males and females
Can healthy volunteers participate?
Key exclusion criteria
The participants will be screened via email and telephone using the Exercise and Sports Science Australia (ESSA) risk stratification questionnaire. Further exclusion criteria include cephalosporin or penicillin allergy, hypo/hyperthyroidism, type 1 or 2 diabetes, and chronic renal failure.

Study design
Purpose of the study
Allocation to intervention
Non-randomised trial
Procedure for enrolling a subject and allocating the treatment (allocation concealment procedures)
Methods used to generate the sequence in which subjects will be randomised (sequence generation)
Masking / blinding
Open (masking not used)
Who is / are masked / blinded?

Intervention assignment
Single group
Other design features
Not Applicable
Type of endpoint(s)
Statistical methods / analysis
Using data from a previously published 16.1 km time-trial (1626±72 sec) in club level cyclists (1), 14 participants were required to detect a 2.5% improvement in the primary outcome of the study, namely time-trial performance (two-tailed; a=0.05; power=0.8). To allow for drop-out and missing data, a total of sixteen participants will be recruited.

A paired sample t-test will be used to assess differences (p<0.05; IBM SPSS Statistics 22) in the time-trial performance (primary outcome). Absolute differences (p<0.05) between the trials will be presented with 95% confidence intervals (CI) and effect size estimates will be calculated using Hedge’s g (unbiased).

For measures of RER, HR, and RPE (which are collected multiple times throughout each experimental phase), random intercept, linear mixed models will be used to examine the effects of condition (Pre vs Post) and time (repeated measure within trial) on each outcome measure. Condition and time will be modelled as fixed effects. Both the condition by time interaction as well as main effects of condition and time will be explored using least significance difference (LSD).

Metabolite data will be combined into a single data matrix. Data will be scaled and visualised using principal component analysis (PCA) and hierarchical cluster analysis (HCA). For each identified metabolite, the null hypothesis that there is no difference in population means across time points will be tested using repeated measures analysis of variance. Correction for multiple comparisons will be performed and both p values and corrected q values reported.. All identified metabolites will then be combined into a multivariate model using PCA and bootstrap resampling used to determine metabolite significance (Matlab scripting language v.R2017a).

1. Black MI, Durant J, Jones AM, Vanhatalo A. Critical power derived from a 3-min all-out test predicts 16.1-km road time-trial performance. European Journal of Sport Science. 2014;14(3):217-23.

Recruitment status
Not yet recruiting
Date of first participant enrolment
Date of last participant enrolment
Date of last data collection
Sample size
Accrual to date
Recruitment in Australia
Recruitment state(s)

Funding & Sponsors
Funding source category [1] 308918 0
Name [1] 308918 0
Murdoch University
Address [1] 308918 0
90 South St, Murdoch WA 6150
Country [1] 308918 0
Primary sponsor type
Murdoch University
90 South St, Murdoch WA 6150
Secondary sponsor category [1] 309840 0
Name [1] 309840 0
Address [1] 309840 0
Country [1] 309840 0

Ethics approval
Ethics application status
Submitted, not yet approved
Ethics committee name [1] 308810 0
Human Research Ethics Committee Murdoch University
Ethics committee address [1] 308810 0
90 South St, Murdoch WA 6150
Ethics committee country [1] 308810 0
Date submitted for ethics approval [1] 308810 0
Approval date [1] 308810 0
Ethics approval number [1] 308810 0

Brief summary
The purpose of this study is to (1) identify changes in performance and metabolism due to cephalexin in endurance exercise, and (2) improve prescribing practice by increasing the body of knowledge associated with cephalexin.

The hypothesis being tested is that cephalexin, when given at therapeutic levels, will decrease endurance performance. The mechanism by which this occurs is being assessed through testing of specific metabolites suggested to be impacted by the administration of cephalexin.

Trial website
Trial related presentations / publications
Public notes
Antibiotics and athletic performance
Antibiotic prescription in athletes occurs around twice the rate of the general population (1), despite increasing bacterial resistance, and without substantive reasoning (2, 3). There are limited studies showing the effect of antibiotics on sports performance, and not all classes of antibiotics are represented in this data. Studies to date have not isolated any impact on sports performance by beta-lactam antibiotics. Cephalexin has not been examined in the literature, and represents almost 21% of oral antibiotics prescriptions in Australia, being the most commonly prescribed oral antibiotic in Australia (4).

1. Alaranta A, Alaranta H, Heliövaara M, Airaksinen M, Helenius I. Ample Use of Physician-Prescribed Medications in Finnish Elite Athletes. International Journal of Sports Medicine. 2006;27(11):919-25.
2. Alaranta A, Alaranta H, Helenius I. Use of Prescription Drugs in Athletes. Sports Medicine. 2008;38(6):449-63.
3. Fayock K, Voltz M, Sandella B, Close J, Lunser M, Okon J. Antibiotic precautions in athletes. Sports Health. 2014;6(4):321-5.
4. AURA. Third Australian Report on Antimicorbial Use and Resistance In Human Health. Sydney: Australian Commission on Safety and Quality in Health Care 2019.

Principal investigator
Name 111970 0
Dr Ewan Smith
Address 111970 0
Murdoch University
90 South St,
Murdoch WA 6150
Country 111970 0
Phone 111970 0
+61 08 9360 2959
Fax 111970 0
Email 111970 0
Contact person for public queries
Name 111971 0
Dr Ewan Smith
Address 111971 0
Murdoch University
90 South St,
Murdoch WA 6150
Country 111971 0
Phone 111971 0
+61 08 9360 2959
Fax 111971 0
Email 111971 0
Contact person for scientific queries
Name 111972 0
Dr Ewan Smith
Address 111972 0
Murdoch University
90 South St,
Murdoch WA 6150
Country 111972 0
Phone 111972 0
+61 08 9360 2959
Fax 111972 0
Email 111972 0

Data sharing statement
Will individual participant data (IPD) for this trial be available (including data dictionaries)?
What data in particular will be shared?
Individual participant data that underlie the results reported in this article, after deidentification (text, tables, figures, supplementary data)
When will data be available (start and end dates)?
Beginning 3 months and ending 5 years following article publication.
Available to whom?
Researchers who provide a sound methodological proposal.
Available for what types of analyses?
How or where can data be obtained?
Proposals should be directed to
What supporting documents are/will be available?
Ethical approval
How or where can supporting documents be obtained?
Type [1] 12177 0
Ethical approval
Citation [1] 12177 0
Link [1] 12177 0
Email [1] 12177 0
Other [1] 12177 0
Attachment [1] 12177 0
Summary results
No Results