This study investigated whether adding strength training to regular endurance training improves performance and muscle function in competitive cyclists. Endurance training is essential for cycling performance, while strength training has been widely recognised as a complementary strategy that may enhance performance and reduce injury risk. However, in practice, strength training is often performed only during limited periods of the training season, and it remains unclear to what extent the adaptations achieved are maintained during subsequent phases of endurance-focused training. Male competitive cyclists were assigned to either a 10-week off-season combined strength and endurance training programme or an endurance-only training programme. The strength training group performed two weekly strength sessions in addition to their usual cycling training, while the control group continued with endurance training only. Participants were assessed at four time points: before the intervention, after the initial 10-week training period, after a high-volume endurance training camp, and during a competition preparation phase. Measurements included body composition, muscle strength, explosive force production, muscle and tendon structure, and cycling performance variables such as maximal power output and aerobic capacity. The primary aim of the study was to determine whether short-term strength training enhances neuromuscular performance and muscle-tendon characteristics in trained cyclists, and whether these adaptations are maintained or reduced when strength training is discontinued. A secondary aim was to examine how these changes interact with endurance adaptations across different phases of the training season. It was hypothesised that strength training would improve muscle strength, power, and muscle-tendon structure, but that these adaptations would be partially reduced during subsequent training phases without continued strength stimulus.
This study was designed to investigate the effects of adding a short-term strength training intervention to regular endurance training in competitive cyclists, with a particular focus on neuromuscular, muscle-tendon, and performance adaptations across different phases of the training season. The study also aimed to examine the persistence of these adaptations during subsequent periods characterised by endurance-only training. The intervention was implemented during the off-season period and consisted of a 10-week training phase in which participants completed either a combined strength and endurance programme (ST) or an endurance-only programme (END). The strength training programme was integrated into the athletes' regular training routine and included two weekly sessions targeting major lower-limb muscle groups, with the objective of improving maximal strength and explosive force production. Training load and content were aligned with the athletes' overall training plans to ensure ecological validity within a competitive cycling context. Following this initial training phase, all participants continued with their regular endurance training through two distinct phases of the competitive season. The first phase consisted of a high-volume endurance training camp, primarily aimed at increasing training load and aerobic conditioning. The second phase corresponded to a competition preparation period, characterised by adjustments in training intensity and volume to optimise performance for competition. This sequential design allowed the assessment of both the development and the retention of adaptations induced by strength training under realistic training conditions. A comprehensive non-invasive testing battery was implemented to capture adaptations across multiple physiological and performance domains. Neuromuscular assessments included measures of maximal strength, maximal voluntary contraction, rate of force development, and sprint-specific mechanical variables. Muscle-tendon characteristics were evaluated using imaging-based assessments of quadriceps muscle thickness and patellar tendon morphology. In addition, cycling-specific performance was assessed through measures of maximal power output, sprint performance, aerobic capacity, and gross efficiency. Anthropometric measurements were also collected to monitor potential changes in body composition. The study was conducted using a repeated-measures design with multiple time points spanning the transition from the off-season to the competition period. This approach enabled the evaluation of both short-term training effects and their evolution over time. Particular emphasis was placed on understanding the interaction between strength training-induced adaptations and subsequent endurance training stimuli, as well as the extent to which neuromuscular and structural adaptations are maintained in the absence of continued strength training. Overall, the study provides a comprehensive evaluation of the role of strength training in endurance-trained athletes, addressing both its effectiveness as a complementary training modality and the temporal stability of the adaptations it induces within a typical competitive season.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
BASIC_SCIENCE
Masking
SINGLE
Enrollment
24
Participants allocated to the combined strength and endurance training group completed two supervised strength training sessions per week for 10 weeks in addition to their habitual cycling training. The strength programme targeted major lower-limb muscle groups (e.g., quadriceps, hip extensors) and was designed to improve maximal strength and explosive force production using multi-joint resistance exercises. Training variables (e.g., load, volume, progression) were adjusted throughout the intervention according to training phase. The endurance-only group continued their usual cycling training without additional strength training. Following the intervention, all participants performed endurance-only training during a high-volume training camp and a subsequent competition preparation phase.
The endurance-only group continued their usual cycling training without additional strength training. Following the intervention, all participants performed endurance-only training during a high-volume training camp and a subsequent competition preparation phase.
Lithuanian Sports University
Kaunas, Lithuania
Knee extensors strength - One repetition maximum (1RM) (kg)
Maximal strength (kg) for the leg extension was estimated from a five-repetition maximum (5RM) test conducted according to National Strength and Conditioning Association guidelines in two exercises (barbell squat and leg press). The corresponding 1RM values were estimated using the ExRx.net calculator.
Time frame: Baseline (Week 0), Week 10, Week 14, and Week 18
Quadriceps muscles thickness (mm)
Quadriceps muscle thickness (mm) (vastus lateralis, rectus femoris, vastus medialis) assessed using B-mode ultrasound imaging.
Time frame: Baseline (Week 0), Week 10, Week 14, and Week 18
Maximal voluntary isometric contraction (Nm)
Isometric maximal voluntary contraction (MVC) of the knee extensors assessed using an isokinetic dynamometer (System 3; Biodex Medical Systems, Shirley, NY, USA). Following a 5-min warm-up on a cycle ergometer at a self-selected workload and cadence, participants were seated upright in the dynamometer chair with double shoulder straps securing the upper body and were verbally encouraged to exert maximal effort. Three MVC trials were performed at a knee joint angle of 70 o (full extension = 0 deg) and the highest peak torque (Nm) was used for analysis. Each trial was separated by 1 minute of rest, and two submaximal warm-up contractions were completed before testing.
Time frame: Baseline (Week 0), Week 10, Week 14, and Week 18
Isokinetic peak torque (Nm)
Isokinetic concentric peak torque of the knee extensors assessed using an isokinetic dynamometer (System 3; Biodex Medical Systems, Shirley, NY, USA). Following a 5-min warm-up on a cycle ergometer at a self-selected workload and cadence, participants were seated upright in the dynamometer chair with double shoulder straps securing the upper body and were verbally encouraged to exert maximal effort. Three maximal concentric contractions performed at a knee joint angle of 70 deg (full extension = 0 deg) and at 60 deg/s, and the highest peak torque (Nm) was used for analysis. Each trial was separated by 1 minute of rest, and two submaximal warm-up contractions were completed before testing.
Time frame: Baseline (Week 0), Week 10, Week 14, and Week 18
Patellar tendon cross-sectional area (mm2)
Patellar tendon morphological changes assessed using B-mode ultrasound imaging - cross-sectional area (square millimetres).
Time frame: Baseline (Week 0), Week 10, Week 14, and Week 18
Body mass (kg)
Body mass (kg) assessed using standard anthropometric methods.
Time frame: Baseline (Week 0), Week 10, Week 14, and Week 18
Height (cm)
Height (cm) assessed using standard anthropometric methods.
Time frame: Baseline (Week 0), Week 10, Week 14, and Week 18
Body mass index (BMI) (kg/m2)
Body mass (kg) and height (m) will be used to calculate the body mass index (BMI) (kg/m2).
Time frame: Baseline (Week 0), Week 10, Week 14, and Week 18
Body fat %
To estimate body fat (%), skinfold thickness was assessed with a GIMA Skinfold Caliper, featuring a precision of 0.2 mm, at the following sites on the right side of the body: triceps, biceps, mid-axillary, chest, subscapular, abdominal, suprailiac, thigh, and calf. The percentage of fat mass (BF%) were derived using the Jackson and Pollock equation (7-sites) and by the Siri equation. BF% was calculated from body density (BD) using SIRI equation.
Time frame: Baseline (Week 0), Week 10, Week 14, and Week 18
Maximal oxygen consumption (VO2max) (L/min, ml/min/kg)
For the determination of VO2max, participants initiated with a standardized warm-up at 120 W for 5-min, followed by an incremental ramp test protocol (20 W/min) on an electromagnetically braked ergometer (Lode Excalibur Sport, Lode BV). The cyclists were free to choose their pedaling cadence, and the ergometer's configuration was tailored to individual preferences and requisites. Real-time analysis of gas exchange was conducted using a spiroergometric device operating in breath-by-breath mode (MetaLyzer 3B, Cortex Biophysik), with the gas analyzer calibrated prior to each session. Heart rate was continuously monitored via a chest strap heart rate monitor (Polar H10, Polar Electro). The VO2max was determined as the highest consecutive 30-second rolling average value attained during the test.
Time frame: Baseline (Week 0), Week 10, Week 14, and Week 18
Maximal aerobic power (MAP) (W, W/kg)
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For the determination of maximal aerobic power (MAP), participants initiated with a standardized warm-up at 120 W for 5-min, followed by an incremental ramp test protocol (20 W/min) on an electromagnetically braked ergometer (Lode Excalibur Sport, Lode BV). The cyclists were free to choose their pedaling cadence, and the ergometer's configuration was tailored to individual preferences and requisites. The maximal aerobic power (MAP) was identified as the maximum sustained power value achieved for a minimum duration of 1 second during the test. Both variables were quantified i
Time frame: Baseline (Week 0), Week 10, Week 14, and Week 18
Cycling gross efficiency (%)
Cycling gross efficiency (GE) was measured employing the MetaLyzer (MetaLyzer 3B, Cortex Biophysik) for gas exchange analysis and the Excalibur Sport bike ergometer (Lode Excalibur Sport, Lode BV). After a 5-min warm up, participants sustained a consistent cadence of 75±2 rpm while pedaling for 8-min, exerting efforts at intensities corresponding to 45% of the MAP achieved during the maximal incremental exercise test. Gross efficiency (%) was calculated for each stage using the formula: (Total work)/(Energy expended )×100. Data validity was ascertained when the respiratory exchange ratio remained stable below 1, and calculations excluded the initial minute to ensure the attainment of gas exchange plateau.
Time frame: Baseline (Week 0), Week 10, Week 14, and Week 18
Sprint peak power (W, W/kg)
To ensure procedural familiarity, each athlete participated in two simulation trials (i.e., spinning till sprint start and holding the sprint session for 1-2 seconds approximately) before the official 6-sec sprint commenced. Subsequently, participants exerted their utmost sprinting effort throughout the entire 6 s duration while receiving robust verbal encouragement. The Excalibur Sport bike ergometer (Lode Excalibur Sport, Lode BV) was employed for this sprint test, with the resistance (torque factor) set at 0.75 N×kg-1 of body mass and equipped with cyclist preferred pedals. The resistance was applied with a cadence threshold of 100 rpm, following a 30 s warm-up at 150 W. The sprint 1-s peak power was quantified both in absolute terms and relative to the participant's body mass (W, W/kg).
Time frame: Baseline (Week 0), Week 10, Week 14, and Week 18
Sprint peak crank torque (Nm, Nm/kg)
To ensure procedural familiarity, each athlete participated in two simulation trials (i.e., spinning till sprint start and holding the sprint session for 1-2 seconds approximately) before the official 6-sec sprint commenced. Subsequently, participants exerted their utmost sprinting effort throughout the entire 6 s duration while receiving robust verbal encouragement. The Excalibur Sport bike ergometer (Lode Excalibur Sport, Lode BV) was employed for this sprint test, with the resistance (torque factor) set at 0.75 N×kg-1 of body mass and equipped with cyclist preferred pedals. The resistance was applied with a cadence threshold of 100 rpm, following a 30 s warm-up at 150 W. The sprint 1-s peak crank torque was quantified both in absolute terms and relative to the participant's body mass (Nm, Nm/kg).
Time frame: Baseline (Week 0), Week 10, Week 14, and Week 18