title: Effects of resistance training with hydrolysed collagen supplementation on changes in muscle-tendon properties in young male and female athletes
Creators: name: Lee, J
Publisher: name: Liverpool John Moores University
Year: 2024

description: Human tendon adapts to mechanical loading (i.e. resistance exercise (RE)) by chang-ing its morphological, mechanical, and material properties. Type Ⅰ collagen is the most abundant protein in tendon, and an exercise-induced increase in the rate of type Ⅰ collagen synthesis has been proposed as one of the key factors that drives human tendon adaptation. In addition to the role of exercise on tendon adaptation, a recent study has found that jump-rope exercise with gelatine ingestion increases whole body type Ⅰ collagen synthesis in a dose-response manner, with 15 g being superior to 5 g and 0 g gelatine in the same group of young men. In a separate study, however, moderate intensity re-sistance exercise with 30 g hydrolysed collagen (HC) ingestion did not appear to increase muscle connective tissue protein synthesis in separate groups of mixed-sex cohorts. However, there are numerous limitations with these studies that preclude a definitive conclusion on the effects of RE with collagen supplementation on collagen synthesis. Accordingly, the first aim of this thesis was to investigate the effects of high-intensity RE combined with different doses of HC on a systemic marker of collagen synthesis, and to investigate a dose-response relationship between HC ingestion with an acute bout of RE and markers of collagen turnover in resistance-trained men (Chapter Three). For this study, 10 healthy, resistance-trained, young men were recruited, the findings demonstrated the dose ⨯ time area under the curve (AUC) of a biomarker of type Ⅰ collagen synthesis (serum procollagen type Ⅰ amino-terminal propeptide, PⅠNP) was higher in the 30 g HC intervention compared to the 15 g (P = 0.039) and 0 g (P = 0.005) HC interventions but there was no difference between 15 g and 0 g (P = 0.675) HC. Similarly, the dose ⨯ time AUCs for glycine and proline (the most abundant amino acids in collagen) were greater for 30 g than for 15 g and 0 g HC (P &lt; 0.05). However, a biomarker of type Ⅰ collagen breakdown (plasma beta-isomerized C-terminal telopeptide, β-CTX) decreased after 6 h post-exercise (P &lt; 0.05) regardless of HC dose, suggesting RE suppressed collagen breakdown regardless of collagen ingestion. The first aim of the second experimental study (Chapter Four) was to investigate whether the collagen synthetic response to high-intensity RE could be increased following 30 g HC ingestion in a eumenorrheic, resistance-trained, young woman. The second aim of this study was to determine if this effect was associated with circulating endogenous oestrogen concentration. In this case study (n = 1), RE with and without 30 g HC was performed when circulating oestrogen concentration was low (onset of menses, OM); and when it was high (late follicular phase, LF) during two consecutive menstrual cycles. Serum 17β-oestradiol concentration was 5-fold greater at LF (891 ± 116 pmol∙L-1) than at OM (180 ± 13 pmol∙L-1). The PINP AUC was higher in the 30 g OM intervention (201 μg∙L-1∙h) than the 30 g LF (144 μg∙L-1∙h), 0 g OM (151 μg∙L-1∙h), and 0 g LF (122 μg∙L-1∙h) interventions. Plasma β-CTX concentration decreased 1.4-fold after 6 h post-RE, regardless of HC dose or menstrual cycle phase. Thus, high endogenous oestrogen concentration was associated with lower collagen synthesis following RE in a eumenorrheic, resistance-trained woman but ingestion of 30 g HC with RE augmented the collagen synthetic response at both LF and OM (having its greatest effect at OM). Based on findings from Chapters Three and Four, in which 30 g HC with RE showed greater collagen synthesis response compared to 15 g and 0 g HC, the third (Chapter Five) and fourth (Chapter Six) experimental studies aimed to investigate the effect of 30 g HC with 10 weeks’ soccer training (incorporating resistance/plyometric exercise) on changes in patellar tendon (PT) properties in female soccer players. In Chapter Five, 17 female soccer players from the Under 21s squad of a Football Association (FA) Women’s Super League Football Club were allocated into two groups: HC (COL, n = 8) and placebo (PLA, n = 9). Participants performed three training sessions per week, which comprised bodyweight resistance/plyometric exercise and pitch-based exercise for 10 weeks in-season. COL and PLA consumed 30 g HC and energy matched maltodextrin, respectively, immediately after each training session. COL increased PT stiffness (+18.0 ± 12.2% vs. +5.1 ± 10.4%, P = 0.049) and Young’s modulus (+17.3 ± 11.9% vs. +4.8 ± 10.3% P = 0.035) more than PLA. However, maximum isometric knee extension (KE) torque, vastus lateralis (VL) muscle thickness, the mean PT cross-sectional area (CSA) did not change in either group. The lack of change in PT CSA might have been caused by not enough RE intensity and thus, the aim of Chapter Six was to investigate the effect of including high-intensity RE into soccer training combined with HC or PLA within a FA Women’s Championship first team soccer squad during pre-season. Eleven professional soccer players were allocated into COL (n = 6) and PLA (n = 5). Using the same method as used in Chapter Five, participants consumed 30 g HC or energy matched maltodextrin (PLA) immediately before each training session, which comprised externally loaded resistance exercise (75% – 90% of one-repetition maximum), plus plyometric- and pitch-based exercise three days/week for 10 weeks in the pre-season period. The results from Chapter Six showed that PT stiffness (COL, +15.4 ± 3.1% vs. PLA, +4.6 ± 3.0%, P = 0.002) and Young’s modulus (COL, +14.2 ± 4.0%vs. PLA, +3.4 ± 2.8%, P = 0.004) increased more in COL than in PLA. Although PT CSA increased in both groups (P &lt; 0.05), there was no difference in the percentage change between groups (P &gt; 0.05). So, although the high-intensity RE led to PT hypertrophy, the relatively low frequency of (once a week) was probably insufficient to enable to HC to further augment this hypertrophic effect. 
The aim of the final experimental study (Chapter Seven) was to investigate the effects of 30 g HC ingestion with a shorter (six weeks) period of high-intensity RE on muscle-tendon adaptations in resistance-trained healthy young men. COL (n = 5) and PLA (n = 7) consumed 30 g HC or energy-matched maltodextrin (PLA), respectively, immediately before each training session, which was performed twice a week for six weeks. There were no group differences in the changes in PT properties following six weeks’ resistance training (P &gt; 0.05). However, changes in PT stiffness (+10.1 ± 6.8%; P = 0.019; d = 1.7 vs. +4.5 ± 5.0%; P = 0.061; d = 0.9) and Young’s modulus (+8.7 ± 7.4%; P = 0.085; d = 1.0 vs. +3.3 ± 5.2%; P = 0.151; d = 0.6) were approximately 2.2 times greater in COL than in PLA with large effect sizes for changes in PT stiffness and Young’s modulus in COL compared to PLA, suggesting that the outcome may have been different with a larger sample size and/or a longer training duration. Although both groups increased mean PT CSA, VL muscle thickness, anatomical-cross sectional area and volume (P &lt; 0.05), these changes did not differ between groups (P &gt; 0.05). In summary, this thesis demonstrates a dose-response effect of HC ingestion with a single bout of high-intensity RE on whole body collagen synthesis, and a chronic effect of HC supplementation with exercise training (incorporating muscle-tendon over-load) on changes in tendon properties. For resistance-trained healthy young men, 30 g HC with RE conferred a greater marker of collagen synthesis compared to 15 g and 0 g HC. Further, for a eumenorrheic, resistance-trained woman, the collagen synthetic response was greater when 30 g HC was ingested compared to RE alone, and a lower endogenous oestrogen concentration was associated with a higher whole body collagen synthesis response to RE. Regarding the chronic effect of HC ingestion with RE on muscle-tendon adaptation, 30 g HC ingestion with 10 weeks’ soccer training (incorporating resistance/plyometric exercise) increased tendon stiffness and Young’s modulus in female soccer players. Similarly (although non-significant), 30 g HC ingestion with six weeks’ RE had a positive effect on changes in PT stiffness and Young’s modulus in resistance-trained healthy young men. Future research should investigate if these novel findings might translate to improved athletic performance and/or reduced risk of soft tissue injury in athletic populations.