Data were collected as part of a laboratory study. 

Twelve healthy male participants (mean ± SD: age 23.8 ± 5.3 years; height 1.77 ± 0.05 m; body mass 76.8 ± 6.2 kg) provided written informed consent to participant in the study, which had been approved by the ethics committee of the University of Essex (ref. ETH2021-1981), and which adhered to the Declaration of Helsinki. Participants were recruited to the study only after ethics approval had been granted. 

Participants visited the laboratory on five occasions, with a minimum of 48 hours between each visit. During their first visit, participants were familiarised with all testing equipment/procedures, and the settings for the dynamometer were recorded. During the next four visits, participants performed a series of targeted intermittent isometric knee extension contractions prior to, immediately after, and ten minutes after, one of four knee extensor SS conditions (presented in a randomised order): 1) no stretch (i.e., control); 2) 30 second stretch; 3) 60 second stretch; and 4) 120 second stretch. 

During all visits, participants sat in the chair of a Biodex System 4 isokinetic dynamometer (Biodex Medical Systems Inc., New York, USA), initialised and calibrated according to the manufacturer’s instructions. The participant’s right leg was attached to the lever arm of the dynamometer, with the seating position adjusted to ensure that the lateral epicondyle of the femur was in line with the axis of rotation of the lever arm. Participants sat with relative hip and knee angles of 85° and 90°, respectively, with full extension being 0°. The lower leg was securely attached to the lever arm above the malleoli with a padded Velcro strap, while straps secured firmly across the thigh, waist and shoulders prevented any extraneous movement and the use of the hip extensors during the isometric contractions. The seating position was recorded during the familiarisation and replicated during subsequent visits.

All visits began with the instrumentation of the participants and the (re-)establishment of the correct dynamometer seating position. Participants performed two tasks: 1) MVCs, to assess muscle force generating capacity; and 2) constant force task (i.e., targeted isometric contractions), to assess muscle force control. These measures were taken prior to, one minute after completion of the SS conditions (to allow re-seating of participant in the dynamometer) and ten minutes after completion of the SS protocol.

Maximal Voluntary Contraction task: Prior to SS, participants performed a series of brief (3-second) isometric knee extension MVCs. These MVCs were separated by sixty seconds of rest and continued until the peak force in three consecutive contractions were within 5% of each other. In the measures taken immediately and ten minutes after the SS protocol, only one MVC was performed at each time point. 

Constant force task: After the establishment of maximal force, participants rested for five minutes before performing a series of intermittent isometric knee extensor contractions at 25, 50 and 75% MVC, in order to establish force control across the spectrum of voluntary forces. The target forces were determined from the highest instantaneous force obtained during the preceding MVCs. Participants performed three contractions at each intensity, with contractions held for six seconds and separated by four seconds of rest [28]. The intensities were performed in a randomised order, with sixty seconds rest separating them. 

Static stretching intervention: After performing the pre-stretching MVC and constant force tasks, participants rested for two minutes before performing one of four SS conditions: 1) no stretch (control); 2) 30-second stretch; 3) 60-second stretch; and 4) 120-second stretch. The stretch performed was a standing quadriceps stretch, held at the position of onset of discomfort [5]. Participants stood upright with their right knee flexed and heel pulled towards their buttocks, while extending the hip [11]. In the no stretch condition, participants walked around the laboratory for 120 seconds with this activity equivalent to the longest stretch duration.

Immediately after the cessation of stretching, participants were re-seated in the dynamometer. The post-stretch MVC task, consisting of only a single MVC, commenced one minute after the cessation of stretching. The post-stretch force control task commenced a further thirty seconds later and consisted of the same procedure, and target forces, used prior to the SS intervention. This procedure was repeated ten minutes after the cessation of stretching.