The Effects of a 9-day Intensified Training Period on Immune and Endocrine Biomarkers of Overtraining in Healthy Males and Females.
Athletes often increase the amount and intensity of their training for short periods to improve performance. When balanced with adequate recovery, this can lead to beneficial adaptations. However, excessive or poorly managed increases in training can result in non-functional overreaching or overtraining syndrome, where recovery may take weeks, months or even years. These conditions can be associated with reduced athletic performance, poor sleep, low mood and an increased susceptibility to infections. Identifying early indicators of maladaptation to intensive training is therefore important for protecting athletes' health and performance.
Stress hormones, particularly cortisol and testosterone, play important roles in regulating the body's response to exercise and supporting immune function. Previous research suggests that although resting levels of these hormones may remain relatively unchanged following intensified training, their responses to subsequent exercise can become reduced. This may indicate an altered stress response and could have implications for immune function. However, the effects of intensified training on specific immune cells, particularly dendritic cells (DCs), remain poorly understood.
DCs play an important role in recognising infections and activating the body's immune defences. They use specialised receptors, called Toll-like receptors (TLRs), to recognise viral genetic material and trigger the production of immune signalling proteins called cytokines. These responses help coordinate the body's defence against infection. Changes in stress hormones, particularly cortisol, may influence how DCs recognise and respond to potential infections. Consequently, changes in hormone responses following intensified training could affect the ability of these immune cells to function effectively.
The aim of this study is to investigate how a nine-day period of intensified training affects hormonal responses and immune function in recreationally active males and females. The study will measure cortisol and testosterone in saliva and blood, assess changes in circulating immune cell numbers, including T cells and DCs, and investigate the expression and function of DC Toll-like receptors and the production of cytokines following immune stimulation.
It is hypothesised that nine days of intensified training will blunt the normal cortisol and testosterone responses to an acute exercise and alter the changes in circulating T-cell and DC numbers following exercise. It is also hypothesised that intensified training will impair DC responses to immune stimulation, resulting in altered TLR activity and reduced or dysregulated production of cytokines.
Overall, this study aims to improve understanding of how short periods of intensified training affect hormonal regulation and immune function, potentially helping identify early biological indicators of inadequate recovery and increased susceptibility to illness in physically active individuals.
Studieöversikt
Status
Betingelser
Intervention / Behandling
Studietyp
Inskrivning (Faktisk)
Fas
- Inte tillämpbar
Kontakter och platser
Studieorter
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Nottingham, Storbritannien, NG11 8NS
- Nottingham Trent University
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Deltagandekriterier
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Tar emot friska volontärer
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Beskrivning
Inclusion Criteria:
- 18-50-years old
- males or females
- Females can either have regular menstrual cycles; Normal menstrual cycles means that you must have 9 or more periods within the past 12 months or be taking oral contraception.
- no underlying health conditions
- Physically active (exercise at least 3 times per week)
Exclusion Criteria:
- Upper respiratory illness within the past 2 weeks
- Known underlying health conditions
- Regular use of anti-inflammatory medications/supplements/herbal remedies
- Pregnant, attempting to become pregnant, or breastfeeding.
Studieplan
Hur är studien utformad?
Designdetaljer
- Primärt syfte: Grundläggande vetenskap
- Tilldelning: N/A
- Interventionsmodell: Enskild gruppuppgift
- Maskning: Ingen (Open Label)
Vapen och interventioner
Deltagargrupp / Arm |
Intervention / Behandling |
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Experimentell: Intervention Group
This group (all participants) underwent 9 days of intensified training (1.5 hour daily cycling at 75%VO2max in addition to their usual training load). |
9 days of daily cycling for 1.5 hours at 75% VO2max in addition to normal training load. |
Vad mäter studien?
Primära resultatmått
Resultatmått |
Åtgärdsbeskrivning |
Tidsram |
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Plasma/salivary cortisol
Tidsram: Measured at baseline (before the 9 day intensified training period) both at rest and in response to the 20/50 exercise stress test. Measured again at rest and in response to the 20/50 stress test after the 9 day intensified training period is completed.
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Measured using ELISA. We analysed raw and percentage change values. |
Measured at baseline (before the 9 day intensified training period) both at rest and in response to the 20/50 exercise stress test. Measured again at rest and in response to the 20/50 stress test after the 9 day intensified training period is completed.
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Plasma/salivary testosterone
Tidsram: Measured at baseline (before the 9 day intensified training period) both at rest and in response to the 20/50 exercise stress test. Measured again at rest and in response to the 20/50 stress test after the 9 day intensified training period is completed.
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Measured using ELISA. We analysed raw and percentage change values. |
Measured at baseline (before the 9 day intensified training period) both at rest and in response to the 20/50 exercise stress test. Measured again at rest and in response to the 20/50 stress test after the 9 day intensified training period is completed.
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T cell and Dendritic cell counts
Tidsram: Measured at baseline (before the 9 day intensified training period) both at rest and in response to the 20/50 exercise stress test. Measured again at rest and in response to the 20/50 stress test after the 9 day intensified training period is completed.
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Measured using Flowcytometry. We analysed absolute cell count changes. |
Measured at baseline (before the 9 day intensified training period) both at rest and in response to the 20/50 exercise stress test. Measured again at rest and in response to the 20/50 stress test after the 9 day intensified training period is completed.
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Dendritic cell toll like receptor 7, 8 and 9 expression
Tidsram: Measured at baseline (before the 9 day intensified training period) both at rest and in response to the 20/50 exercise stress test. Measured again at rest and in response to the 20/50 stress test after the 9 day intensified training period is completed.
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Measured using Flowcytometry. We analysed mean fold change from unstimulated to stimulated median fluorescent intensities. |
Measured at baseline (before the 9 day intensified training period) both at rest and in response to the 20/50 exercise stress test. Measured again at rest and in response to the 20/50 stress test after the 9 day intensified training period is completed.
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T cell (interleukin-10) and Dendritic cell (Tumor necrosis factor-a and interferon-a) cytokine expression
Tidsram: Measured at baseline (before the 9 day intensified training period) both at rest and in response to the 20/50 exercise stress test. Measured again at rest and in response to the 20/50 stress test after the 9 day intensified training period is completed.
|
Measured using Flowcytometry. We analysed mean fold change from unstimulated to stimulated median fluorescent intensities. |
Measured at baseline (before the 9 day intensified training period) both at rest and in response to the 20/50 exercise stress test. Measured again at rest and in response to the 20/50 stress test after the 9 day intensified training period is completed.
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Sekundära resultatmått
Resultatmått |
Åtgärdsbeskrivning |
Tidsram |
|---|---|---|
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Recovery stress questionnaire (REST-Q)
Tidsram: Completed twice during the study. Once at baseline (before the 9 day intensified training period), and once after the 9 day training period.
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The 76-item REST-Q uses 76 Likert scale questions to assess perceived stress and recovery over the last 3 days. The questionnaire comprises of 19 scales in total; 7 pertaining to general stress, 3 to sport-specific stress, 5 to general recovery and 4 to sport-specific recovery. REST-Q scores were summed to give a general stress and recovery score, a sport stress and recovery score and an overall stress and recovery score. |
Completed twice during the study. Once at baseline (before the 9 day intensified training period), and once after the 9 day training period.
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10km cycling time trial
Tidsram: Completed twice during the study. Once at baseline (before the 9 day intensified training period), and once after the 9 day training period.
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Participants instructed to cycle 10km as quickly as possible as a measure of performance. |
Completed twice during the study. Once at baseline (before the 9 day intensified training period), and once after the 9 day training period.
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Training diary for training impulse (TRIMP) calculation
Tidsram: 7 days prior to the study starting and throughout the full 9 day intervention.
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For seven days before and throughout the study, participants completed a training diary to calculate TRIMP scores, quantifying normal training load. Participants recorded each sessions mode, duration and RPE alongside their average, minimum and maximum HR. TRIMP scores across the training period, including the supervised cycles were compared to participants' 7-day pre-training scores to confirm training load had increased. TRIMP scores were calculated using equation: t x HR ratio x y Where t = the session duration in minutes, HR ratio = (Average HR during exercise - Resting HR)/(maximum HR during exercise - Resting HR), y = a weighting factor 0.64e1.92x for males and 0.86e1.67x for females, with e = 2.712 and x = HR ratio. |
7 days prior to the study starting and throughout the full 9 day intervention.
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