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The Effects of a 9-day Intensified Training Period on Immune and Endocrine Biomarkers of Overtraining in Healthy Males and Females.

6 de noviembre de 2026 actualizado por: John Hough, Nottingham Trent University

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.

Descripción general del estudio

Estado

Terminado

Condiciones

Intervención / Tratamiento

Tipo de estudio

Intervencionista

Inscripción (Actual)

14

Fase

  • No aplica

Contactos y Ubicaciones

Esta sección proporciona los datos de contacto de quienes realizan el estudio e información sobre dónde se lleva a cabo este estudio.

Ubicaciones de estudio

      • Nottingham, Reino Unido, NG11 8NS
        • Nottingham Trent University

Criterios de participación

Los investigadores buscan personas que se ajusten a una determinada descripción, denominada criterio de elegibilidad. Algunos ejemplos de estos criterios son el estado de salud general de una persona o tratamientos previos.

Criterio de elegibilidad

Edades elegibles para estudiar

18 años a 50 años (Adulto)

Acepta Voluntarios Saludables

Sí

Géneros elegibles para el estudio

Todos

Descripción

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.

Plan de estudios

Esta sección proporciona detalles del plan de estudio, incluido cómo está diseñado el estudio y qué mide el estudio.

¿Cómo está diseñado el estudio?

Detalles de diseño

  • Propósito principal: Ciencia básica
  • Asignación: N / A
  • Modelo Intervencionista: Asignación de un solo grupo
  • Enmascaramiento: Ninguno (etiqueta abierta)

Armas e Intervenciones

Grupo de participantes/brazo
Intervención / Tratamiento
Experimental: 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.

¿Qué mide el estudio?

Medidas de resultado primarias

Medida de resultado
Medida Descripción
Periodo de tiempo
Plasma/salivary cortisol
Periodo de tiempo: 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 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.
Plasma/salivary testosterone
Periodo de tiempo: 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 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.
T cell and Dendritic cell counts
Periodo de tiempo: 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 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.
Dendritic cell toll like receptor 7, 8 and 9 expression
Periodo de tiempo: 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.
T cell (interleukin-10) and Dendritic cell (Tumor necrosis factor-a and interferon-a) cytokine expression
Periodo de tiempo: 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.

Medidas de resultado secundarias

Medida de resultado
Medida Descripción
Periodo de tiempo
Recovery stress questionnaire (REST-Q)
Periodo de tiempo: Completed twice during the study. Once at baseline (before the 9 day intensified training period), and once after the 9 day training period.

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.
10km cycling time trial
Periodo de tiempo: Completed twice during the study. Once at baseline (before the 9 day intensified training period), and once after the 9 day training period.

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.
Training diary for training impulse (TRIMP) calculation
Periodo de tiempo: 7 days prior to the study starting and throughout the full 9 day intervention.

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.

Colaboradores e Investigadores

Aquí es donde encontrará personas y organizaciones involucradas en este estudio.

Patrocinador

Fechas de registro del estudio

Estas fechas rastrean el progreso del registro del estudio y los envíos de resultados resumidos a ClinicalTrials.gov. Los registros del estudio y los resultados informados son revisados ​​por la Biblioteca Nacional de Medicina (NLM) para asegurarse de que cumplan con los estándares de control de calidad específicos antes de publicarlos en el sitio web público.

Fechas importantes del estudio

Inicio del estudio (Actual)

1 de noviembre de 2023

Finalización primaria (Actual)

2 de septiembre de 2024

Finalización del estudio (Actual)

2 de septiembre de 2024

Fechas de registro del estudio

Enviado por primera vez

2 de noviembre de 2026

Primero enviado que cumplió con los criterios de control de calidad

6 de noviembre de 2026

Publicado por primera vez (Actual)

13 de noviembre de 2026

Actualizaciones de registros de estudio

Última actualización publicada (Actual)

13 de noviembre de 2026

Última actualización enviada que cumplió con los criterios de control de calidad

6 de noviembre de 2026

Última verificación

1 de noviembre de 2026

Más información

Términos relacionados con este estudio

Otros números de identificación del estudio

  • 1748383

Plan de datos de participantes individuales (IPD)

¿Planea compartir datos de participantes individuales (IPD)?

NO

Información sobre medicamentos y dispositivos, documentos del estudio

Estudia un producto farmacéutico regulado por la FDA de EE. UU.

No

Estudia un producto de dispositivo regulado por la FDA de EE. UU.

No

Esta información se obtuvo directamente del sitio web clinicaltrials.gov sin cambios. Si tiene alguna solicitud para cambiar, eliminar o actualizar los detalles de su estudio, comuníquese con register@clinicaltrials.gov. Tan pronto como se implemente un cambio en clinicaltrials.gov, también se actualizará automáticamente en nuestro sitio web. .